Alkyd Coated Laser-Induced Graphene Patches For Corrosion Resistance of Metal Substrates

Alkyd Coated Laser-Induced Graphene Patches For Corrosion Resistance of Metal Substrates | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Alkyd Coated Laser-Induced Graphene Patches For Corrosion Resistance of Metal Substrates Mir Mehdi Hashemi, Farzane Hasheminia, Sadegh Sadeghzadeh This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6234092/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 26 Aug, 2025 Read the published version in Scientific Reports → Version 1 posted 10 You are reading this latest preprint version Abstract Corrosion can severely degrade surfaces and materials, impacting functionality and safety. Laser-induced graphene (LIG) offers substantial corrosion resistance, making it ideal for protecting metals like carbon steel. This study developed adhesive, corrosion-resistant LIG patches on polyimide (PI) layers, enhanced with an alkyd resin coating, and applied to pretreated aluminum surfaces. LIG was synthesized using laser powers of 6, 8, 10, and 12 W, followed by alkyd coating for improved performance. Results of EDS, SEM, TGA, XRD, Raman spectroscopy and surface-wetting properties are studied. SEM and XRD analyses revealed that lower laser power (6 W) produced uniform, crystalline LIG, while higher power (12 W) caused defects and porosity. Corrosion tests in an alkaline environment showed that the A-LIG6@PI patch had the best structural integrity, with minimal pitting after 96 hours, outperforming other samples. The electrochemical analysis demonstrated a corrosion inhibition efficiency of 98.36% for A-LIG6@PI, with a corrosion current density of 0.11 µA/cm² and polarization resistance (Rp) of 8.51×10⁶ Ω·cm². Contact angle measurements confirmed enhanced hydrophobicity, with A-LIG6@PI showing an 88° angle compared to 58° for bare LIG. These results emphasize the potential of lower laser power for creating durable, corrosion-resistant graphene-based coatings suitable for flexible electronics and protective applications. Physical sciences/Chemistry Physical sciences/Chemistry/Electrochemistry Physical sciences/Materials science/Materials for energy and catalysis Physical sciences/Materials science/Nanoscale materials Laser-Induced Graphene Alkyd Resin Corrosion Resistance Patches Metal Substrates Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 1 Introduction Corrosion poses a significant threat to the integrity and lifespan of metal structures, making it essential to implement effective mitigation strategies to maintain their functional properties[ 1 ]. Various methods have been developed to address corrosion, including anodic and cathodic protection, corrosion inhibitors, and advanced waterproofing techniques. Among these, the application of coatings has become a popular and straightforward method for preventing corrosion[ 2 ]. The wide range of coating formulations enables customized protective solutions that improve the performance and reparability of metal surfaces. Coatings primarily work by providing a physical barrier that blocks the pathways for corrosive agents like oxygen and moisture, thereby greatly diminishing the electrochemical reactions that result in deterioration. A deeper understanding of coating materials and application methods continues to foster advancements in corrosion protection strategies, ultimately aiming to prolong the service life of metal components across various environments[ 3 , 4 ]. The effectiveness of protective coatings is significantly affected by their thermal stability, especially at high temperatures, where changes in thermal conductivity and expansion can create considerable thermal stresses, potentially leading to early failure. This issue is especially critical in various industries, including civil engineering, aerospace, marine sectors, and the chemical industry, where materials like steel and aluminum are commonly used. The widespread problem of corrosion greatly compromises the structural integrity of these metals, negatively influencing their mechanical properties, load-bearing capabilities, overall safety, and the lifespan of different infrastructures. The topic of metal corrosion remains a key area of research, highlighted by its substantial financial impact; corrosion-related damages cost the industrial sector around 276 billion US dollars annually, creating a significant economic burden for both government and industry [ 5 ]. To address these challenges, it is crucial to implement effective corrosion management strategies to reduce associated costs. Research indicates that improving corrosion resistance through surface modification techniques is a practical solution, particularly for carbon steel[ 6 , 7 ]. Protective coatings have received notable attention among the various approaches examined due to their effective preparation methods. Numerous types of coatings, such as traditional coatings [ 8 , 9 ], superhydrophobic coatings [ 10 , 11 ], conductive polymer coatings[ 12 , 13 ], polymer nanocomposites, and hybrid inorganic-organic compounds [ 14 ]have emerged as promising options for preventing corrosion. This variety in coating technologies reflects the field's ongoing advancements, which aim to enhance the durability and performance of metal substrates in corrosive environments. Alongside the previously mentioned factors, the ability of protective coatings to withstand environmental degradation is crucial for reducing corrosion. Thus, evaluating adhesion strength becomes a key factor in determining the effectiveness of organic coatings on metal surfaces. For example, adhesives are commonly used in aluminum alloys for critical applications in the aerospace and automotive sectors, as they allow for even load distribution and help reduce manufacturing costs. A major challenge in this area is finding more efficient and environmentally friendly surface treatment methods that improve bonding performance. The adhesive and substrate interface is vital in transferring loads between structural components. Critchlow and Brewis' research highlights that surface treatments' main goal is to enhance the inherent properties of aluminum alloys, reducing contamination and improving adhesion [ 15 , 16 ]. Changes in surface texture can significantly boost hydrolytic stability by creating rougher surfaces with better wettability, which is vital for forming strong adhesive bonds [ 17 ]. Given the considerations outlined above, protective coatings are crucial in situations requiring exceptional wear resistance, chemical deterioration, and severe environmental conditions. Although these coatings typically provide excellent insulation and moisture retention, their effectiveness in preventing corrosion can be limited. A significant challenge is finding cost-effective alternatives to protect important metal substrates. Various techniques, such as immersion methods, electroless plating, the sol-gel process, and electrodeposition, have created superhydrophobic coatings. These advanced coatings can achieve impressive water contact angles between 145 and 165 degrees, demonstrating their potential for superior water repellency [ 18 , 19 ]. Furthermore, recent research has investigated the use of soft lithography with polydimethylsiloxane (PDMS) molds to develop nanostructured superhydrophobic surfaces [ 20 ]. Despite the significant progress in creating superhydrophobic coatings with anti-corrosive properties, most of these developments are still limited to controlled laboratory environments. As a result, there are considerable challenges in adapting them for widespread industrial application. The production processes for these coatings are often complex, costly, and inefficient, making them unsuitable for on-site use. Therefore, developing an optimized coating solution that integrates excellent water repellency, durability, strong adhesion, cost-effectiveness, and simple manufacturing methods is essential to enable practical application across various industries. Graphene is a groundbreaking material that is expected to drive numerous technological innovations. It features a distinctive two-dimensional lattice structure composed of sp² hybridized carbon atoms arranged in a hexagonal formation. This unique structure grants graphene outstanding mechanical properties and excellent electrical and thermal conductivities, making it a promising option for corrosion protection applications. Various graphene-based coatings, from unmodified to functionalized types, have been created, demonstrating effective passivation abilities that considerably reduce electrochemical activity. These coatings' natural mechanical strength and flexibility enable them to withstand significant stress, reducing the likelihood of cracking and subsequent corrosion. [ 21 – 23 ] For instance, Yuwei et al. [ 24 ] developed graphene sheets with a porous polyhedral oligomeric silsesquioxane framework for self-healing organic coatings. These sheets were loaded with the corrosion inhibitor benzotriazole and incorporated into an epoxy coating. Results showed that the coating's protective effects were attributed to the graphene acting as a physical barrier, significantly reducing the penetration of corrosion-causing substances. In-situ grown graphene offers superior corrosion resistance compared to transferred graphene. Research by Prasa et al.[ 25 ] demonstrated that nickel coated with a chemically vapour-deposited graphene film corroded 20 times slower than nickel coated with four layers of mechanically transferred graphene. This enhanced corrosion resistance of in-situ graphene may be attributed to its structural integrity and stronger interfacial adhesion, which enhance both electrochemical and mechanical stability. This underscores the importance of developing in-situ graphene growth methods for anti-corrosion applications. Misyura et al. [ 26 ] examined the wettability, evaporation of droplets, and corrosion characteristics of textured copper samples with graphene and smooth copper samples with fluorographene. Textured graphene surfaces achieved a maximum contact angle of 93° and exhibited a more stable contact line than smooth graphene surfaces. Fluorination increased surface roughness by 2.6 to 2.7 times. Although the laser-textured copper sample with multiple layers of graphene demonstrated anti-corrosion performance, the challenges of scaling such textured surfaces for industrial applications could significantly hinder the practical use of these groundbreaking findings. Kumar et al. [ 27 ] investigated the enhanced cavitation-corrosion resistance of graphene-coated WC-Co-Cr applied to a steel substrate through high-velocity oxygen fuel spraying, utilizing surface texturing as a pre-coating preparation method. The results indicated a significant reduction in the corrosion rate. However, the sprayed WC-Co-Cr-graphene exhibited micron-sized uniformity issues, particularly concerning the distribution of graphene within the matrix. Zhang et al. [ 21 ] electrodeposition process, by varying the duty cycle, the deposited Ni-Gr functionally graded realized graphene content gradient in the grain size thickness and increased the coating. The results show that the corrosion current density of functionally graded Ni-Gr coating is one and three orders of magnitude lower than that of uniform Ni-Gr composite coating and low-carbon steel. Meshram and Punith Kumar et al. [ 22 , 23 ] studied electrodeposition to prepare dense Ni-P-graphene and ZnNiFe-graphene composite coatings in the presence of graphene. The results show that both have a significant protective effect on steel substrates. By electrodeposition, Bagherzadeh et al. [ 24 ] directly deposited reduced graphene oxide nanosheets (RGON) on carbon steel. Results show that the coating composition provides adequate barrier protection for the steel substrate. As a manufacturing tool of the high-energy beam, the laser has apparent advantages in micro-nano manufacturing. Various methods have been reported, including the preparation of laser-based coating graphene. All the studies reported above demonstrate the potential of graphene as a protective coating. However, in most reported works, graphene is commonly used as an additive [ 20 – 23 ], and the obtained results cannot fully showcase graphene's superiority. Only when graphene is used as an independent surface coating can it protect metals and improve their electrical and thermal properties to the highest level. Chemical vapour deposition (CVD) is the most common method for producing large-area graphene on metal foils [ 24 – 26 ]. In another study conducted by Jiangtong et al.[ 28 ] the researchers prepared a graphene/CoCrFeMo0.5NiTi0.5 high-entropy alloy composite coating on the surfaces of curved parts using both high-speed and low-speed laser cladding techniques. The low-speed laser processing resulted in a smoother and more uniform surface, achieving an average microhardness 1.49 times higher than the high-speed processed coatings. While both cladding layers demonstrated abrasive wear, it was noted that the wear rate for the low-speed laser-processed coating was approximately 3.06 times higher than that of the high-speed processed counterpart. Furthermore, the study identified a correlation between increased oxygen content and wear rates, which may indicate potential challenges in maintaining the performance of coatings in oxidizing environments. Zesen et al. [ 29 ] employed electrophoretic deposition to prepare graphene coatings on titanium alloys. This method facilitates the deposition of materials from a colloidal suspension under the influence of an electric field, resulting in dense and uniformly distributed coatings, even on substrates with complex shapes. The coatings demonstrated an impressive corrosion current density of only 0.06 µA/cm², indicating a significant enhancement in corrosion resistance. However, certain defect levels in the electrophoretic deposition process led to increased permeability of corrosive media, which consequently accelerated the corrosion of the titanium substrate in areas where these defects were present. Anti-corrosion treatments using chemical vapour-deposited graphene on nickel and copper significantly improved corrosion resistance by nearly three orders of magnitude in aggressive acidic conditions[ 30 ]. The graphene-TiO2 nanohybrid on an aluminium substrate, created via laser powder bed fusion, showed strong anti-corrosion properties due to a synergistic interaction between graphene and TiO 2 [ 31 ]. However, the scalability of these fabrication processes for industrial applications needs evaluation. Scalable laser treatments, such as the laser-induced graphene (LIG) coating[ 32 , 33 ], offer efficient production methods and can maintain desired material properties. LIG converts carbon-rich materials into a nanostructured graphene layer using high-energy laser pulses, providing excellent conductivity and mechanical properties. However, the use of LIG for the development of graphene-based anti-corrosive coatings has not been extensively studied. Wanli et al.[ 34 ] examined the corrosion resistance of a graphene layer applied to carbon steel through a combination of electroplated nickel and laser-induced graphene techniques. Their results demonstrated that the graphene coating had lower corrosion rates than pure nickel coatings and untreated carbon steel, as evidenced by polarization curves and electrochemical impedance spectroscopy. Their process requires substrate materials with carbon atoms to enable graphene induction via laser treatment. The methodology is complex and expensive, relying on electroplating and laser preparation, which could limit its scalability for industrial use. The findings also revealed that while the graphene coating has high hardness and strength, these properties are significantly lower than those of nickel coatings and pure carbon steel. Ye and colleagues[ 35 ] have also presented a new method for fixing damaged areas of graphene using a laser. This technique entails placing carbon sources under a nickel coating, which are then transferred to the surface when activated by the laser. By fine-tuning the laser parameters, this technology can effectively repair graphene layers in the compromised regions and shows great potential for protecting metals against corrosion, wear, and friction. Xiaohui Ye et al. [ 36 ] have introduced a novel technique for producing graphene on carbon steel by incorporating nickel via laser alloying. This method forms a Ni/Fe alloy catalyst that facilitates the growth of multilayer graphene on the carbon steel surface. The graphene layers achieved a resistance comparable to that of stainless steel alongside a minimal corrosion rate. Additionally, the exceptional characteristics of graphene, such as its impermeability and excellent adhesion, greatly enhanced the corrosion resistance of carbon steel, rendering it highly durable in challenging environments. This paper suggests a more accessible method for creating three-dimensional porous graphene films by directly transforming commercially available polyimide (PI) polymer films using a CO 2 infrared laser and adhering them to a metallic substrate. This single-step technique can be utilized on any metal surface, promoting the creation of LIG@PI anti-corrosion coatings. Adhesive bonding is the most common technique for attaching polymers to metals, and polymers have considerable capacity for forming strong bonds with metals[ 37 ]. In our LIG@PI case, PI film is commercially provided with adhesive, which can be bonded to any metal part. The metallic part (aluminium in our study) and LIG@PI can be prepared separately and then joined together (LIG@PI/Al), which provides the repair concepts for the method. Moreover, multi-layer LIG@PI can be set up for better coating performance. Previously, it has been shown that polyimide can significantly enhance the anti-corrosion capabilities of Mg alloy by sealing micro-defects, improving corrosion resistance, and providing self-lubricating properties, all while maintaining stability under high temperatures[ 38 ]The laser parameters significantly impact the structure of LIG@PI protective coatings. This relationship is systematically investigated through characterization techniques, static corrosion analyses, and potentiodynamic polarization studies. We propose enhancing graphene-based layers on commercially available polyimide coupled with robust adhesive bonding to metal substrates. The effectiveness of these coatings in preventing corrosion is intrinsically linked to the quality of the formed graphene layer and the strength of the adhesion between the polyimide and the metallic substrate. By leveraging the protective attributes of graphene and polyimide alongside resilient adhesive bonding, we can effectively tackle the challenges currently facing the corrosion protection landscape. After applying LIG, a coating of alkyd resin is added, serving as a barrier layer that further strengthens the structure against environmental damage. Alkyd resins are recognized for their strong adhesion, flexibility, and moisture resistance, making them ideal for harsh environments. The combined effect of the LIG surface treatment and the protective alkyd resin results in a composite material patch with outstanding performance, thereby improving the durability and reliability of components exposed to corrosive conditions. This innovative approach showcases the potential for enhancing corrosion resistance and illustrates the effectiveness of merging advanced material processing techniques with traditional polymer coatings in creating next-generation protective materials. 2 Characterizations The surface morphology and structure of the LIG-coated patches were examined using Scanning Electron Microscopy (SEM) on a VEGA3 system. Raman spectroscopy was employed to assess the samples' chemical composition and molecular structure using a Raman spectrometer (Ram-532-004). The crystallinity and phase composition of the LIG were further analyzed through X-ray Diffraction (XRD) with an XPert Pro diffractometer. Thermogravimetric analysis (TGA) and elemental identification analysis (Energy-Dispersive X-ray Spectroscopy (EDS)) were performed using TGA STA6000 and MAPPING Vega2 instruments. A CAG-20 device studied the surface-wetting properties of samples. Potentiodynamic Polarization Electrochemical analysis was conducted using a three-electrode electrochemical test system in a 3.5% sodium chloride solution for corrosion resistance evaluation. 3 Materials Kapton tape (a polyimide film from DuPont), Sodium hydroxide (NaOH) pellets from Merk, and sodium carbonate monohydrate (Na 2 CO 3 ·H 2 O) from Merk were employed. Various sandpapers with grits of #200, #400, #600, #800, and #1000 were utilized for surface preparations. Aluminium foil was incorporated as a metallic substrate for the experiment, and Vako transparent spray was employed to coat the alkyd resin without further purification. A polyethylene (PE) substrate was used as the Kapton tape's support in LIG processes. The hydrogen peroxide (H 2 O 2 ) used to prepare an alkaline aggressive solution in the immersion test section was 30% Pro Analysis Merck. 4 Experimental 4.1 Preparation of Samples 4.1.1 Metal substrate Aluminium foils are meticulously cut into squares. Figure 1a shows the preparation steps of the untreated metal substrate. Initially, the cut pieces undergo an acetone wash and a thorough rinse in a cleanroom environment. Subsequently, they are subjected to an alkaline degreasing process for 10 minutes, utilizing a diluted 0.1M solution of sodium hydroxide (NaOH) pellets dissolved in deionized water. Upon completion of the degreasing protocol, the metal surfaces are mechanically treated through grinding procedures. This is succeeded by a final chemical treatment conducted at room temperature, wherein the aluminium pieces are immersed in two distinct alkaline solutions: a 20-second immersion in a one wt% NaOH solution, followed by a 30-second immersion in an aqueous solution containing five wt% sodium carbonate monohydrate. It is essential to note that between each stage of surface treatment, the aluminium pieces are rinsed with deionized water to ensure the removal of residual contaminants. In the mechanical treatment phase, the aluminium pieces are dry-ground utilizing sandpapers of grits #200, #400, #600, #800, and #1000, each applied ten times in succession. This meticulous grinding process enhances the subsequent polyimide layer's adhesion properties and achieves a smoother surface finish. 4.1.2 Fabrication of LIG patches Kapton Polyimide (PI) adhesive is used as the substrate of laser-induced graphene. Polyethylene, by having lower surface energy, ensures a smoother surface for adhesion of tapes. Also, less adhesive will be lost, and more will remain on Kapton tape. Two CO 2 lasers with 60 and 100-watt tubes generate LIG on PI. The laser parameters are set to a speed of 100mm/s with a distance of 6 cm from the head of the laser to the substrate. After the surfaces are subjected to laser, a black graphene layer is produced on PI. With the laser beam’s spot diameter of ~ 100 µm and 50% overlap ratio, uniform graphene coating is achieved on the substrates. Using CAD drawing software, scanning lines are set to 0.05 mm distance to obtain 50% overlap. 6-8-10-12 W laser powers have been adopted in the preparation of LIG. Figure 1b shows the schematic of the implementation steps of the LIG, which is placed on the metal substrate after the induction of graphene. Figure 2 shows elemental EDS analyses performed on bare PI and LIG surfaces to study the quality of purchased tape and the synthesized graphene layer. According to EDS results, carbon is the most abundant element in the bare PI layer Fig. 2(a-f) and constitutes 49.09% of the weight, followed by O and N elements (Fig. 2(c)). After the direct laser scribing process (Fig. 2(g-l)), the carbon content of the resulting LIG has increased to 82.22% of the weight (Fig. 2(i)), which is due to the removed amount of the C-O and C-N bonds as exhaust gas during the process, leaving behind solid C-C bonds. Carbon bonds can contribute to a more resilient surface toward corrosion by reducing electrochemical reactions and improving mechanical properties. 4.1.3 Coating Alkyd Resin Since LIG is subjected to environmental degradation, according to presented schematic in Fig. 1(c), unmodified commercial alkyd resin is sprayed on the surface of LIG6@PI, LIG8@PI, LIG10@PI, and LIG12@PI, through spraying. This ensures that the functional properties of the graphene material are untouched to obtain adhesion, durability, and protective finish. For an even distribution of the alkyd resin, complete spray coverage of the surface is done by spraying at a distance of 20 cm. As the alkyd resin cures, a robust, flexible layer on LIG is archived. A combination of alkyd resin and LIG can be particularly beneficial for applications in flexible electronics, sensors, and composite materials, where both the conductivity of graphene and the protective qualities of the alkyd resin are crucial for performance and longevity. Figure 3 represents a schematic structure of an adhesion-bonded anti-corrosion patch after the final alkyd resin spray coating. Following the alkyd coating process, a thermogravimetric study used TGA to study decomposition patterns. Figure 4 shows alkyd-coated LIG12@PI (A-LIG12@PI) weight loss while increasing temperature from 25°C to 800°C. Initial weight loss of 2-3wt% is observed at about 33–100°C for A-LIG12@PI, which is attributed to removing moisture, volatiles, and ashes within the material. The onset of degradation for alkyd resin and PI starts from 150–200°C and 500–600°C, respectively[ 39 , 40 ]. Also, the total weight loss for alkyd resin is at 350–400°C, where the TGA plot for A-LIG12@PI increases its weight loss[ 39 ]. PI's total weight loss value is at 650–700°C, as observed from the TGA plot of PI. All the while, LIG maintains thermal stability at up to 700°C. Increasing temperature up to 800°C, the remaining ash components after TGA are 19.34% and 45.56% for PI and A-LIG12@PI, respectively. 5 Results and Discussion 5.1 Characterizations of Samples 5.1.1 SEM analysis Figure 5(a-d( presents scanning electron microscopy (SEM) images of porous laser-induced graphene (LIG) synthesized at power levels of 6, 8, 10, and 12 watts, respectively. For lower power levels (i.e., 6 W and 8 W), a 60-watt tube laser is employed, while a 100-watt tube laser is utilized for higher power levels (i.e., 10 W and 12 W). The LIG produced at lower power levels exhibits a more uniform structure characterized by flake-like graphene. In contrast, higher power levels induce a more fibrous morphology in the LIG. The graphenization process is predominantly influenced by the overlapping laser scanning parameters, especially at lower power levels. In this context, carbonization primarily occurs due to the inherent carbon content in the polyimide (PI) backbone, which facilitates controlled and uniform graphene generation. Conversely, at power levels of 10 W and 12 W, graphenization appears to be augmented by introducing additional carbon-rich sources generated from the previously induced graphene and the PI substrate itself. Notably, at 12 W, the fibrous clusters exhibit uncontrolled growth, resulting in significant thickness variations across the LIG surface. Regardless of the power applied, the bundles formed via laser radiation intertwine to create a network of porous structures. Regarding the dimensional characteristics of LIG, as illustrated in Fig. 6(a), the thickness of LIG increases linearly with laser power, demonstrating a steep slope. At the same time, the remaining PI beneath the porous LIG structure diminishes at a comparatively slower rate, as depicted in Fig. 6(b). This observation suggests that at higher power levels, the LIG utilizes both the carbon source from the PI and the residual carbon from the previous scanning lines, thereby leaving more PI on the substrate[ 41 ]. 5.1.2 XRD spectroscopy The X-ray diffraction (XRD) patterns presented in Fig. 7reveal a pronounced peak at an angle of approximately 27.2 degrees (2θ) for A-LIG8@PI, A-LIG10@PI, and A-LIG12@PI and 26.5 for A-LIG6@PI, which can correspond to the (002) plane of LIG. Notably, the peaks exhibit increased sharpness with the lowering power of the laser, suggesting more entangled porous structures, potentially attributed to the aggregation of the graphene sheets inside the LIG layer. Moreover, variations in the peak positions are likely attributed to the interactions between the graphene matrix of LIG and coated alkyd resin. The wider spectrum observed at the (002) plane of LIG for A-LIG12@PI likely indicates an increase in disorder due to the thermal stress and rapid cooling at higher powers and a broader range of crystal phases. The shift in the 2θ peak from 26.5° for A-LIG6@PI to approximately 27.2° for A-LIG8@PI, A-LIG10@PI, and A-LIG12@PI likely suggests changes in the crystallinity. The uniform peak around 27.2° may indicate that the increase in power leads to comparable structural transformations in the LIG, resulting in consistent peak positions. A more uniform surface morphology of LIG6@PI compared to other samples (Figure) 5a() and its better crystalline structure with a closer peak-to-origin of LIG (2theta = 26.5°) might promote better chemical bonding of alkyd to graphene and reduce the probability of corrosion pathways between the coating and substrate. In other words, LIG6@PI has an optimal graphenization condition with a denser, more crystalline structure, which may provide improved protection against moisture and corrosive species, leading to better corrosion resistance when coated with alkyd resin. 5.1.3 Raman Spectroscopy Raman spectroscopy in Fig. 8)a( provides crucial insight into the structural quality of alkyd-coated laser-induced graphene (LIG) fabricated at varying laser powers. It specifically examines the D, G, and 2D peaks that characterize graphene materials and interactions of coated material. According to Fig. 8)a(, all D, G and 2D peaks are observed at lower frequencies 1084cm -1 , 1331cm -1 and 2478cm -1 , respectively (For LIG, the G band is at 1580cm -1 , D band is at 1350cm -1 , and 2D band is at 2700 cm -1 [ 42 ]). These shifts suggest interfacial interaction between the alkyd matrix and graphene-conjugated aromatic rings. Also, sample A-LIG6@PI shows additional peaks at 1175cm -1 and 1580cm -1 which can be related to the carboxylated groups of alkyd material creating efficient interfacial bonds of C-C and -COO- with LIG[ 43 ]. The G peak is a fundamental indicator of the presence of sp² carbon networks within the LIG structure. A strong G peak signifies ordered graphitic domains and is associated with the inplane vibration of sp²-bonded carbon atoms. Across the samples, the A-LIG6@PI shows the most pronounced G peak, indicating optimal graphitization at this power level. In contrast, LIG samples fabricated at 8W, 10W, and 12W exhibit a slightly diminished G peak intensity, suggesting an increase in structural disorder as the laser power increases. The D peak arises due to the vibration modes and is associated with defects in the carbon lattice. Higher D/G ratios generally imply greater structural imperfections[ 44 ]. In this study, the 6W sample demonstrates a relatively low D/G intensity ratio compared to the other samples, highlighting a lower defect density (Fig. 6)b(). Also, by increasing laser power, the D/G intensity ratio exhibits a wider range, introducing non-uniform structural properties and scattered defect density. As the laser power rises to 8W, 10W, and 12W, the D peak becomes more prominent, indicating that higher laser power introduces more defects into the graphene structure, potentially due to excessive energy causing lattice distortions[ 45 ]. The 2D peak is particularly significant in distinguishing between single-layer and multi-layer graphene[ 46 ]. A sharp, symmetric 2D peak suggests high-quality, few-layer graphene, while a broader or shifted 2D peak can indicate a greater layer count or increased disorder. All LIG samples exhibit broadened 2D peaks, implying the porous multi-layer structure of all samples. 5.1.4 Corrosion behavior A one-liter deionized water-based aggressive alkaline solution containing 3.1 g of hydrogen peroxide and 59 g of sodium chloride was employed for the static corrosion analyses of all samples. The samples, specifically A-LIG6@PI, A-LIG8@PI, A-LIG10@PI, and A-LIG12@PI, were immersed in this solution, with the pH of the environment carefully maintained at 9.3. Scanning electron microscopy (SEM) images of samples subjected to corrosion for 24 hours, 48 hours, and 96 hours were analyzed to investigate the pitting and cracking phenomena across all samples. Figure 9(a-l) displays the SEM images of the surfaces of A-LIG6@PI (a,b,c), A-LIG8@PI (d,e,f), A-LIG10@PI (g,h,i), and A-LIG12@PI (j,k,l) following immersion for 24 hours (a,d,g,j), 48 hours (b,e,h,k), and 96 hours (c,f, i,l). For the A-LIG6@PI sample, minimal pitting and cracking were observed after 24 hours of immersion. Conversely, for the A-LIG12@PI sample, significant pitting and cracking emerged within the first 24 hours of exposure to the alkaline solution, characterized by notable crack lengths and interconnected pits. With prolonged immersion in the solution, the mechanisms of pitting and cracking were activated, exhibiting a slower rate for A-LIG6@PI, while A-LIG8@PI, A-LIG10@PI, and A-LIG12@PI demonstrated a more rapid corrosion rate. These observations indicate that A-LIG6@PI exhibits enhanced resistance to corrosion under identical testing conditions. Figure 10 shows a polarization test to investigate the anti-corrosion ability of LIG@PI and A-LIG@PI patches after covering a 2cm×2cm aluminium foil with each patch. All samples are tested by immersion in 3.5 wt% NaCl for 3 hours. The findings provide valuable insights into the anti-corrosion capabilities of these materials. LIG12@PI exhibits superior corrosion resistance compared to LIG10@PI, which continues sequentially down to LIG6@PI. The reasons can be attributed to several factors, as discussed below. Firstly, the structural characteristics of the LIG@PI patches play a pivotal role in their corrosion resistance. The patch with the highest porous medium structure, LIG12@PI, likely facilitates enhanced barrier properties against corrosive ions from the surrounding environment. A more porous structure may allow for effective load distribution and better physical interlocking, improving the patch's adhesion to the aluminium substrate and reducing the likelihood of corrosion. Secondly, the thickness of the LIG graphene film in each sample directly influences their protective capabilities. Thicker films typically provide a more effective and continuous barrier against corrosive species. In the series of samples tested, it can be inferred that LIG12@PI, having the thickest film (Fig. 5(d)), would exhibit a reduced permeation rate of chloride ions, leading to lower corrosion rates than thinner films found in LIG10@PI, LIG8@PI, and LIG6@PI. Additionally, the intrinsic properties of the LIG itself should be considered. Higher graphene content in LIG12@PI may result in superior electrical conductivity, reducing localized corrosion processes, such as pitting. This property and the morphology of the patches could contribute to the overall enhanced performance observed in the polarization test results. Furthermore, the interface quality between the patch and the aluminium substrate is crucial. If LIG12@PI demonstrates better adhesion due to its structural properties, it could diminish the likelihood of delamination, a common precursor to corrosion in layered materials[ 47 ]. The mechanical stability provided by such a robust interface would enhance the longevity of the protective layer. The differences in corrosion resistance between alkyd resin sprayed LIG, which is synthesized at various power levels, and between bare PI and a LIG12@PI sample are illustrated in Fig. 11. These differences can stem from how the laser power affects the structural and chemical properties of the laser-induced graphene and the integrity of the LIG and alkyd interface. The A-LIG6@PI sample has a more controlled graphitization process with a denser, more uniform, and stable microstructure (Fig. 5(a)) with an alkyd material. Bare LIG6@PI does not create a tighter barrier to prevent corrosive agents from penetrating the treated aluminium substrate (Fig. 9). Still, it can provide better interaction sites with alkyd, as discussed in Raman spectroscopy for LIG6@PI in Fig. 8. The pronounced interfacial bonds of alkyd carboxylated groups with LIG6@PI are due to the uniformity and less defect density of LIG at lower powers. Increasing laser power LIG generation increases the degree of ablation, which can lead to a more diffectfull porous graphene structure (Fig. 5(b-d)). This less uniformity reduces the effectiveness of the LIG and alkyd interaction as a barrier and allows for greater electrolyte penetration, decreasing corrosion resistance. At higher laser powers, there is also a greater likelihood of thermal decomposition or partial oxidation of the LIG surface, which introduces defects and reduces the integrity of the graphene layer. The A-LIG6@PI coating benefits most from a combination of optimal graphitization of LIG at lower powers, better alkyd interfacial properties, and uniform graphene layers. Lower-power LIG forms a smoother, less porous substrate that allows the alkyd to have an effective, consistent coating. Additionally, the corrosion resistance of bare PI is lower than that of all A-LIG@PI samples, which can be why PI lacks the barrier properties provided by the LIG’s conductive, impermeable structure. This is while bare PI exhibits better corrosion resistance due to having a thicker polyimide layer than uncoated LIG samples. LIG is more susceptible to environmental degradation, which weakens its barrier against corrosion. To evaluate the corrosion resistance of treated aluminium, corrosion potential (E corr ), corrosion current density (i corr ), anodic and cathodic Tafel slopes (b a and b c ), polarization resistance (R p ), and inhibition efficiency (η) were analyzed as shown in Table 1[ 48 ]. Treated aluminum displayed high corrosion susceptibility with an E corr of -0.656 V and i corr of 7.02 µA/cm². In comparison, PI without LIG improved resistance, shifting E corr to -0.532 V and reducing i corr to 1.95 µA/cm², with R p at 5.32×10⁵ Ω·cm² and an η of 72.15%. Modifying PI with LIG at 6 W (LIG6@PI) gave moderate corrosion resistance, with an E corr of -0.672 V, i corr of 4.24 µA/cm², R p of 4.11×10⁵ Ω·cm², and η of 39.59%. At 8 W (LIG8@PI), i corr dropped to 3.00 µA/cm², R p increased to 4.48×10⁵ Ω·cm², and η rose to 57.24%, suggesting improved barrier properties. With a laser power of 10 W (LIG10@PI), corrosion resistance further improved (E corr -0.666 V, i corr 2.74 µA/cm², R p 5.14×10⁵ Ω·cm², η 61.01%). At 12 W (LIG12@PI), the highest R p (6.51×10⁵ Ω·cm²) and an i corr of 2.33 µA/cm² gave an η of 66.81%. Alkyd-coated LIG samples (A-LIG@PI) performed exceptionally. A-LIG6@PI with 6W power showed an E corr of -0.456 V, very low i corr of 0.11 µA/cm², R p of 8.51×10⁶ Ω·cm², and η of 98.36%. Similarly, A-LIG8@PI and A-LIG10@PI samples maintained high efficiencies of 97.79% and 95.70%, with optimized LIG and coating qualities. The A-LIG12@PI, though slightly lower at 86.62% efficiency, still showed strong protection, indicating alkyd with 8–10 W laser powers offered the best corrosion resistance. Table 1. Electrochemical polarization parameters of treated aluminium substrate and different adhesion bonded anti-corrosion patches after 3 h of immersion in 3.5 wt% NaCl solution Samples E corr (v) i corr (µA/cm 2 ) b a b c R p (Ωcm 2 ) η (%) Treated Al -0.656 7.02 15.7 14.6 - - PI -0.532 1.95 6.8 3.7 5.32E + 05 72.15 LIG6@PI -0.672 4.24 5.6 14.2 4.11E + 05 39.59 LIG8@PI -0.668 3.00 4.3 11.1 4.48E + 05 57.24 LIG10@PI -0.666 2.74 5.2 8.6 5.14E + 05 61.01 LIG12@PI -0.664 2.33 5.5 9.6 6.51E + 05 66.81 A-LIG6@PI -0.456 0.11 3.3 7.1 8.51E + 06 98.36 A-LIG8@PI -0.504 0.15 6.3 7.6 9.65E + 06 97.79 A-LIG10@PI -0.512 0.30 4.6 8.2 4.23E + 06 95.70 A-LIG12@PI -0.518 0.94 5.6 5.3 1.26E + 06 86.62 E corr : Corrosion voltage. I corr : Corrosion current density. b a : Anodic tafel slope. b c : Cathodic tafel slope. R p : Polarization resistance The electrochemical stability of alkyd-coated LIG-modified PI samples (A-LIG@PI) on aluminum was evaluated by measuring corrosion current density (i corr ) and corrosion potential (E corr ) after 48 and 96 hours of exposure (Fig. 12). The A-LIG6@PI sample demonstrated a low initial i corr of 4×10⁻⁹ A/cm² after 48 hours (Fig. 13(a)), with a relatively stable E corr of -0.67 V, indicating good corrosion resistance (Fig. 13(b)). However, after 96 hours, i corr increased to 3.675×10⁻⁸ A/cm², and E corr shifted slightly to -0.632 V, suggesting minor degradation over time. This increase in i corr reflects a gradual decline in the protective efficiency of the LIG layer, though the sample still maintained a reasonable level of corrosion resistance. For A-LIG8@PI, i corr was higher at 1.475×10⁻⁸ A/cm² after 48 hours with an E corr of -0.616 V, showing slightly lower corrosion resistance than A-LIG6@PI (Fig. 13). After 96 hours, i corr increased to 4×10⁻⁸ A/cm², with a shift in E corr to -0.65 V. These changes indicate that while A-LIG8@PI initially provides moderate protection, the increase in i corr over time points to some loss in coating performance. The A-LIG10@PI sample exhibited a significantly higher i corr of 3.55×10⁻⁷ A/cm² after 48 hours, coupled with an E corr of -0.668 V. This initial high i corr suggests that, despite the more intense laser power, the corrosion resistance may be compromised initially due to possible structural imperfections in the LIG layer at this power level. However, after 96 hours, i corr dropped to 5.25×10⁻⁸ A/cm² with a slightly more negative E corr of -0.684 V, suggesting some stabilization in the coating’s protective capability over time. The A-LIG12@PI sample initially showed a moderate i corr of 4.575×10⁻⁸ A/cm² and an E corr of -0.642 V after 48 hours. After 96 hours, i corr was relatively stable at 4.75×10⁻⁸ A/cm², with E corr shifting to -0.624 V. This stability in i corr and E corr suggests that the LIG layer formed at 12 W provides consistent protection over the tested period, likely due to an optimized LIG structure that better resists environmental degradation (Fig. 13). It can be concluded that while the A-LIG6@PI and A-LIG12@PI samples maintain more stable corrosion resistance, the performance of A-LIG8@PI and A-LIG10@PI shows greater fluctuation over time, and A-LIG6@PI and A-LIG12@PI are offering better long-term corrosion protection on aluminum. 6 Contact angle measurements Figure 14describes water contact angle measurements for the LIG-modified PI and alkyd-coated LIG-modified PI samples subjected to varying laser powers (6, 8, 10, and 12 W), which reveal critical insights into their wetting properties and surface hydrophobicity. Wetting properties directly impact corrosion resistance patches. Higher contact angles suggest increased hydrophobicity, which minimizes water adsorption and enhances corrosion resistance. Contact angles for the LIG@PI samples (Fig. 14(a)) are notably lower, ranging from around 46° to 58° across samples treated with different laser powers (6, 8, 10, and 12 W). Specifically, LIG6@PI and LIG8@PI exhibit slightly higher average contact angles, around 54–55°, compared to LIG10@PI and LIG12@PI, which have average values closer to 48–49°. These relatively low contact angles indicate that the untreated LIG-modified surfaces are somewhat hydrophilic, allowing more moisture interaction with the surface. This hydrophilicity may make them more susceptible to corrosion, as water can readily penetrate and initiate corrosion processes. In contrast, the A-LIG@PI samples in Fig. 14(b), which were further coated with alkyd, show a significant increase in contact angles, indicating enhanced hydrophobicity. For A-LIG6@PI and A-LIG8@PI, contact angles range from approximately 92° to 105°, averaging around 98–100°. This high hydrophobicity is associated with the protective alkyd layer that limits water contact and thus helps prevent corrosion. The A-LIG10@PI and A-LIG12@PI samples have slightly lower average contact angles, around 89–96°, suggesting a slight reduction in hydrophobicity at higher laser powers, potentially due to changes in the LIG layer’s surface structure. For the A-LIG6@PI sample, contact angles ranged from 92.2° to 105.5°, averaging around 98.0°. This relatively high and consistent hydrophobicity suggests that the laser power of 6 W optimally supports a dense, uniform LIG layer on the PI surface. The resulting hydrophobic surface prevents water molecules and delays the onset of corrosion, correlating with the high corrosion resistance observed in electrochemical testing for this sample. The A-LIG8@PI sample showed contact angles between 90° and 104°, averaging approximately 97.7°. While slightly variable, the angles still indicate high hydrophobicity, suggesting an effective barrier against moisture. The strong water resistance and the robust LIG structure formed at 8W may explain this sample's stable corrosion resistance over time. The increased contact angles in A-LIG@PI samples correlate well with improved corrosion resistance, as evidenced by their reduced corrosion current densities (i corr ) in electrochemical tests. The higher hydrophobicity of A-LIG6@PI and A-LIG8@PI reflects a robust barrier against moisture, thereby limiting the electrochemical reactions that drive corrosion. Conversely, the moderate decrease in contact angles observed in A-LIG10@PI and A-LIG12@PI may correspond to slightly lower corrosion resistance, as minor variations in surface uniformity at higher laser powers can affect wetting properties. The water contact angle measurements for the (a) LIG-modified PI and (b) alkyd-coated LIG-modified PI laser powers 6, 8, 10, and 12 W. 7 Conclusion This research highlights the significant advancements in applying laser-induced graphene (LIG) as a protective material for aluminum substrates, particularly when coupled with alkyd resin coatings. A clear relationship was established between laser power, graphene quality, and corrosion resistance by systematically analyzing the effects of varying laser powers on LIG's structural, morphological, and electrochemical properties. Lower laser power settings, particularly 6W, yielded a highly uniform, crystalline LIG structure with minimal defects, which was instrumental in forming strong interfacial bonds with the alkyd resin coating. This combination enhanced corrosion resistance, reduced defect density, and improved hydrophobicity, making A-LIG6@PI stand out in this study. The comprehensive characterizations, including SEM, XRD, Raman spectroscopy, and electrochemical polarization tests, revealed that the protective capabilities of LIG and alkyd coatings are influenced by the structural properties of graphene and their interactions with the polymer matrix. The findings showed that the synergistic effects of optimized graphitization at lower laser powers and the alkyd resin's chemical compatibility significantly enhance the protective layer's durability and efficiency. Notably, A-LIG6@PI demonstrated superior resistance to moisture and corrosive agents, with minimal pitting and cracking observed after prolonged exposure to aggressive environments. Higher laser powers, resulting in thicker LIG layers, introduced greater structural defects and less uniform graphene morphology, reducing the effectiveness of the alkyd-LIG barrier. The decrease in hydrophobicity and the increase in defect density at higher powers underscore the importance of optimizing laser parameters to achieve the desired balance between material thickness and structural integrity. These insights pave the way for tailoring LIG-based coatings for specific applications, particularly in environments that demand high-performance anti-corrosion solutions. The study also emphasized the role of hydrophobicity in enhancing corrosion resistance. Water contact angle measurements revealed that alkyd-coated LIG samples exhibited significantly higher hydrophobicity than bare LIG-modified PI, with A-LIG6@PI and A-LIG8@PI achieving the highest levels. This improvement in surface hydrophobicity is directly correlated with lower corrosion current densities and higher polarization resistance, demonstrating the effectiveness of the alkyd resin in complementing the protective properties of LIG. In summary, this research provides a framework for designing advanced anti-corrosion materials that integrate the unique properties of graphene with polymer-based coatings. The optimal conditions identified for LIG fabrication, particularly at 6W laser power, offer a blueprint for achieving superior performance in adhesion, durability, and resistance to environmental degradation. These findings hold immense promise for applications in flexible electronics, sensors, structural materials, and industries requiring robust and long-lasting anti-corrosion solutions. Future studies should explore scalable manufacturing processes to broaden the applicability of LIG-alkyd coatings. Additionally, investigating the long-term stability of these materials under varied environmental conditions and their potential integration with other functional coatings could open new avenues for innovation. 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Cite Share Download PDF Status: Published Journal Publication published 26 Aug, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 27 May, 2025 Reviews received at journal 14 May, 2025 Reviews received at journal 03 May, 2025 Reviewers agreed at journal 29 Apr, 2025 Reviewers agreed at journal 23 Apr, 2025 Reviewers invited by journal 21 Mar, 2025 Editor assigned by journal 21 Mar, 2025 Editor invited by journal 21 Mar, 2025 Submission checks completed at journal 20 Mar, 2025 First submitted to journal 15 Mar, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6234092","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":433636064,"identity":"e07f8032-310d-4f58-9b5b-5bfeb42ce75f","order_by":0,"name":"Mir Mehdi Hashemi","email":"","orcid":"","institution":"Iran University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Mir","middleName":"Mehdi","lastName":"Hashemi","suffix":""},{"id":433636065,"identity":"bdd513d2-9e6b-42e3-af03-3ca27d6a39ca","order_by":1,"name":"Farzane Hasheminia","email":"","orcid":"","institution":"Iran University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Farzane","middleName":"","lastName":"Hasheminia","suffix":""},{"id":433636066,"identity":"a3103b7c-ffe1-449a-be72-0ea361e652a3","order_by":2,"name":"Sadegh Sadeghzadeh","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+UlEQVRIiWNgGAWjYHACAwbGBiB1gIfxQQJMLAGXYjQtzAZAlRIkaWEDKZcg6Cr59sMbH37dUSfPd7z3WMXDtro6BvbDDxge7sFjxZm0YmPZM2yGM8+cS7uR2HZYgoEnzYAh4Rk+V+WYSUu28TBuuJFjBtRyAOiwHKBfDuBxWP8b89+SbRL2G+6/MStIbKuTYOB/g18LA9Bwxo9tBokbbvCYMSS2MUswSBCwxeDGs2JpxraE5JlncowlEs4dBtr4zOAAfoclb/z4s63Otu/4GcOPP8rq+Pn5kx8+/IHPYUDAzIPMYwNiAhoYGBh/EFIxCkbBKBgFIxsAAFeCVPSEIuW3AAAAAElFTkSuQmCC","orcid":"","institution":"Iran University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Sadegh","middleName":"","lastName":"Sadeghzadeh","suffix":""}],"badges":[],"createdAt":"2025-03-15 17:08:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6234092/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6234092/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-17456-6","type":"published","date":"2025-08-26T15:58:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":79575837,"identity":"d044da59-762d-493f-a1a1-8709ec8e493f","added_by":"auto","created_at":"2025-03-31 11:17:20","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":242324,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Steps of fabrication for LIG patches consist of lamination on PE and graphene induction at laser powers of 6, 8, 10, 10, 12 W. Schematic diagram for steps of (b) degreasing, grinding, and chemical treatment of the untreated metal substrate followed by (c) adhesion bonding of different anti-corrosion alkyd resin coated LIG patches to metal substrates.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/2f3d7e0faace44f541334686.png"},{"id":79577394,"identity":"55352ec2-412a-4220-9e84-7f8763eb959e","added_by":"auto","created_at":"2025-03-31 11:25:20","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":615469,"visible":true,"origin":"","legend":"\u003cp\u003eEDS Elemental identification analyses for (a-f) bare PI and (g-l) LIG. Distribution of N, O and C atoms in selected areas of (a,b) PI surface and (g,h) LIG surface. Quantitative values and spectrum of the constituent elements for (c) PI and (i) LIG. Mapping pattern of N, O and C elements for (d,e,f) PI and (j,k,l) LIG, respectively.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/8337dfd01edeffa0c29250c2.png"},{"id":79575839,"identity":"dbc4ca8f-7f28-4a4f-8639-efb7b1051ffa","added_by":"auto","created_at":"2025-03-31 11:17:20","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":192255,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic layout of final adhesion bonded and alkyd resin coated LIG patch on a metal substrate\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/06fe860e37a3ea127909b16d.png"},{"id":79575838,"identity":"b675624b-83ac-48c0-aaaa-7da5945a7969","added_by":"auto","created_at":"2025-03-31 11:17:20","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":90107,"visible":true,"origin":"","legend":"\u003cp\u003eThermogravimetric analysis plots show weight loss versus temperature for PI and alkyd-coated LIG synthesized on PI at 12 W laser power.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/56c67faa51f7a9414f7e36ea.png"},{"id":79575855,"identity":"23497eb1-055e-4840-a94e-5eb81c08c953","added_by":"auto","created_at":"2025-03-31 11:17:20","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":205173,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of synthesized LIG samples at different powers (a) 6W, (b) 8W, (c) 10W, and (d) 12W\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/f880a1d89b47a026b7f3eead.png"},{"id":79575840,"identity":"2085a2c1-6ed6-4640-aa8b-8474cca4192d","added_by":"auto","created_at":"2025-03-31 11:17:20","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":124511,"visible":true,"origin":"","legend":"\u003cp\u003eDimensional characteristics of LIG (a) schematic illustration of dimensions for synthesized graphene and remaining PI after laser radiation, (b) dependence of LIG's dimensions characteristics on laser power.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/98191b43cb0ccbfc454728b7.png"},{"id":79575877,"identity":"d45872bb-efc2-4168-ae10-2a96ade63c29","added_by":"auto","created_at":"2025-03-31 11:17:21","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":54782,"visible":true,"origin":"","legend":"\u003cp\u003eXRD diffraction spectra of A-LIG6@PI, A-LIG8@PI, A-LIG10@PI, and A-LIG12@PI showing 2theta angle of ~26.5degree matching to d spacing of 3.36Å\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/099110c91b0f0de4ed7aee4b.png"},{"id":79577406,"identity":"0adb0182-533a-4399-98a1-c52cfd2f9ec1","added_by":"auto","created_at":"2025-03-31 11:25:21","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":128989,"visible":true,"origin":"","legend":"\u003cp\u003eRaman analyses of samples, (a) Raman spectra of A-LIG6@PI, A-LIG8@PI, A-LIG10@PI, and A-LIG12@PI, (b) analysis of D and G peak intensities.\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/5bc362976c149c755a3f1e4f.png"},{"id":79575869,"identity":"cf197f06-70f0-468a-825a-37592c58afbb","added_by":"auto","created_at":"2025-03-31 11:17:21","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":643695,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images showing pitting and cracking corrosion attack of (a, b, c) A-LIG6@PI, (d, e, f) A-LIG8@PI, (g, h, i) A-LIG10@PI, and (j, k, l) A-LIG12@PI for 24, 48, and 96 hours. Patches are immersed in an aggressive alkaline solution of NaCl+H2O2 with pH controlled at 9.3\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/072f69e28d900d93388736e8.png"},{"id":79577410,"identity":"79184200-5265-401f-b46b-0a563bce602d","added_by":"auto","created_at":"2025-03-31 11:25:21","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":119519,"visible":true,"origin":"","legend":"\u003cp\u003ePotentiodynamic polarization curves of treated Al and LIG@PI samples after immersion in 3.5 wt% NaCl solution for 3 h.\u003c/p\u003e","description":"","filename":"image10.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/af2bf519b1545b2b47b8ff4b.png"},{"id":79575847,"identity":"39ee5d43-db6b-46ee-8902-ca1b1c5b1fd0","added_by":"auto","created_at":"2025-03-31 11:17:20","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":102561,"visible":true,"origin":"","legend":"\u003cp\u003ePotentiodynamic polarization curves of treated Al, LIG12@PI, and A-LIG@PI samples after immersion in 3.5 wt% NaCl solution for 3 h.\u003c/p\u003e","description":"","filename":"image11.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/69c4190fbe9cacda3215da79.png"},{"id":79577398,"identity":"949d4143-80cd-4afa-b28b-d328f0743f89","added_by":"auto","created_at":"2025-03-31 11:25:20","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":106219,"visible":true,"origin":"","legend":"\u003cp\u003ePotentiodynamic polarization curves of A-LIG@PI patches immersed in 3.5 wt% NaCl solution for 48 h and 96 h.\u003c/p\u003e","description":"","filename":"image12.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/8886625074ef6d450961242d.png"},{"id":79578378,"identity":"cea3a69e-5cf2-435e-8153-357468e42a66","added_by":"auto","created_at":"2025-03-31 11:33:21","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":51263,"visible":true,"origin":"","legend":"\u003cp\u003ePotentiodynamic polarization (a) corrosion current and (b) corrosion potential of A-LIG@PI patches after 3, 48, and 96 test hours.\u003c/p\u003e","description":"","filename":"image13.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/b58421063ca38e6f9e277fab.png"},{"id":79575853,"identity":"6c283f1b-3e98-4287-9e93-099091b05237","added_by":"auto","created_at":"2025-03-31 11:17:20","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":127910,"visible":true,"origin":"","legend":"\u003cp\u003eThe water contact angle measurements for the (a) LIG-modified PI and (b) alkyd-coated LIG-modified PI laser powers 6, 8, 10, and 12 W.\u003c/p\u003e","description":"","filename":"image14.png","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/13aaa2c88c5da7788bc914ff.png"},{"id":90345010,"identity":"9682c167-684e-4699-b8d2-318666c9b5a6","added_by":"auto","created_at":"2025-09-01 16:09:13","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3616642,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6234092/v1/23048464-60c2-40ad-955d-c46e9703471b.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Alkyd Coated Laser-Induced Graphene Patches For Corrosion Resistance of Metal Substrates","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eCorrosion poses a significant threat to the integrity and lifespan of metal structures, making it essential to implement effective mitigation strategies to maintain their functional properties[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Various methods have been developed to address corrosion, including anodic and cathodic protection, corrosion inhibitors, and advanced waterproofing techniques. Among these, the application of coatings has become a popular and straightforward method for preventing corrosion[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The wide range of coating formulations enables customized protective solutions that improve the performance and reparability of metal surfaces. Coatings primarily work by providing a physical barrier that blocks the pathways for corrosive agents like oxygen and moisture, thereby greatly diminishing the electrochemical reactions that result in deterioration. A deeper understanding of coating materials and application methods continues to foster advancements in corrosion protection strategies, ultimately aiming to prolong the service life of metal components across various environments[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe effectiveness of protective coatings is significantly affected by their thermal stability, especially at high temperatures, where changes in thermal conductivity and expansion can create considerable thermal stresses, potentially leading to early failure. This issue is especially critical in various industries, including civil engineering, aerospace, marine sectors, and the chemical industry, where materials like steel and aluminum are commonly used. The widespread problem of corrosion greatly compromises the structural integrity of these metals, negatively influencing their mechanical properties, load-bearing capabilities, overall safety, and the lifespan of different infrastructures. The topic of metal corrosion remains a key area of research, highlighted by its substantial financial impact; corrosion-related damages cost the industrial sector around 276\u0026nbsp;billion US dollars annually, creating a significant economic burden for both government and industry [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTo address these challenges, it is crucial to implement effective corrosion management strategies to reduce associated costs. Research indicates that improving corrosion resistance through surface modification techniques is a practical solution, particularly for carbon steel[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Protective coatings have received notable attention among the various approaches examined due to their effective preparation methods. Numerous types of coatings, such as traditional coatings [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], superhydrophobic coatings [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], conductive polymer coatings[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], polymer nanocomposites, and hybrid inorganic-organic compounds [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]have emerged as promising options for preventing corrosion. This variety in coating technologies reflects the field's ongoing advancements, which aim to enhance the durability and performance of metal substrates in corrosive environments.\u003c/p\u003e \u003cp\u003eAlongside the previously mentioned factors, the ability of protective coatings to withstand environmental degradation is crucial for reducing corrosion. Thus, evaluating adhesion strength becomes a key factor in determining the effectiveness of organic coatings on metal surfaces. For example, adhesives are commonly used in aluminum alloys for critical applications in the aerospace and automotive sectors, as they allow for even load distribution and help reduce manufacturing costs. A major challenge in this area is finding more efficient and environmentally friendly surface treatment methods that improve bonding performance. The adhesive and substrate interface is vital in transferring loads between structural components. Critchlow and Brewis' research highlights that surface treatments' main goal is to enhance the inherent properties of aluminum alloys, reducing contamination and improving adhesion [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Changes in surface texture can significantly boost hydrolytic stability by creating rougher surfaces with better wettability, which is vital for forming strong adhesive bonds [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eGiven the considerations outlined above, protective coatings are crucial in situations requiring exceptional wear resistance, chemical deterioration, and severe environmental conditions. Although these coatings typically provide excellent insulation and moisture retention, their effectiveness in preventing corrosion can be limited. A significant challenge is finding cost-effective alternatives to protect important metal substrates. Various techniques, such as immersion methods, electroless plating, the sol-gel process, and electrodeposition, have created superhydrophobic coatings. These advanced coatings can achieve impressive water contact angles between 145 and 165 degrees, demonstrating their potential for superior water repellency [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Furthermore, recent research has investigated the use of soft lithography with polydimethylsiloxane (PDMS) molds to develop nanostructured superhydrophobic surfaces [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Despite the significant progress in creating superhydrophobic coatings with anti-corrosive properties, most of these developments are still limited to controlled laboratory environments. As a result, there are considerable challenges in adapting them for widespread industrial application. The production processes for these coatings are often complex, costly, and inefficient, making them unsuitable for on-site use. Therefore, developing an optimized coating solution that integrates excellent water repellency, durability, strong adhesion, cost-effectiveness, and simple manufacturing methods is essential to enable practical application across various industries.\u003c/p\u003e \u003cp\u003eGraphene is a groundbreaking material that is expected to drive numerous technological innovations. It features a distinctive two-dimensional lattice structure composed of sp\u0026sup2; hybridized carbon atoms arranged in a hexagonal formation. This unique structure grants graphene outstanding mechanical properties and excellent electrical and thermal conductivities, making it a promising option for corrosion protection applications. Various graphene-based coatings, from unmodified to functionalized types, have been created, demonstrating effective passivation abilities that considerably reduce electrochemical activity. These coatings' natural mechanical strength and flexibility enable them to withstand significant stress, reducing the likelihood of cracking and subsequent corrosion. [\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eFor instance, Yuwei et al. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] developed graphene sheets with a porous polyhedral oligomeric silsesquioxane framework for self-healing organic coatings. These sheets were loaded with the corrosion inhibitor benzotriazole and incorporated into an epoxy coating. Results showed that the coating's protective effects were attributed to the graphene acting as a physical barrier, significantly reducing the penetration of corrosion-causing substances.\u003c/p\u003e \u003cp\u003eIn-situ grown graphene offers superior corrosion resistance compared to transferred graphene. Research by Prasa et al.[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] demonstrated that nickel coated with a chemically vapour-deposited graphene film corroded 20 times slower than nickel coated with four layers of mechanically transferred graphene. This enhanced corrosion resistance of in-situ graphene may be attributed to its structural integrity and stronger interfacial adhesion, which enhance both electrochemical and mechanical stability. This underscores the importance of developing in-situ graphene growth methods for anti-corrosion applications.\u003c/p\u003e \u003cp\u003eMisyura et al. [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] examined the wettability, evaporation of droplets, and corrosion characteristics of textured copper samples with graphene and smooth copper samples with fluorographene. Textured graphene surfaces achieved a maximum contact angle of 93\u0026deg; and exhibited a more stable contact line than smooth graphene surfaces. Fluorination increased surface roughness by 2.6 to 2.7 times. Although the laser-textured copper sample with multiple layers of graphene demonstrated anti-corrosion performance, the challenges of scaling such textured surfaces for industrial applications could significantly hinder the practical use of these groundbreaking findings.\u003c/p\u003e \u003cp\u003eKumar et al. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] investigated the enhanced cavitation-corrosion resistance of graphene-coated WC-Co-Cr applied to a steel substrate through high-velocity oxygen fuel spraying, utilizing surface texturing as a pre-coating preparation method. The results indicated a significant reduction in the corrosion rate. However, the sprayed WC-Co-Cr-graphene exhibited micron-sized uniformity issues, particularly concerning the distribution of graphene within the matrix.\u003c/p\u003e \u003cp\u003eZhang et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] electrodeposition process, by varying the duty cycle, the deposited Ni-Gr functionally graded realized graphene content gradient in the grain size thickness and increased the coating. The results show that the corrosion current density of functionally graded Ni-Gr coating is one and three orders of magnitude lower than that of uniform Ni-Gr composite coating and low-carbon steel.\u003c/p\u003e \u003cp\u003eMeshram and Punith Kumar et al. [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] studied electrodeposition to prepare dense Ni-P-graphene and ZnNiFe-graphene composite coatings in the presence of graphene. The results show that both have a significant protective effect on steel substrates.\u003c/p\u003e \u003cp\u003eBy electrodeposition, Bagherzadeh et al. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] directly deposited reduced graphene oxide nanosheets (RGON) on carbon steel. Results show that the coating composition provides adequate barrier protection for the steel substrate. As a manufacturing tool of the high-energy beam, the laser has apparent advantages in micro-nano manufacturing. Various methods have been reported, including the preparation of laser-based coating graphene.\u003c/p\u003e \u003cp\u003eAll the studies reported above demonstrate the potential of graphene as a protective coating. However, in most reported works, graphene is commonly used as an additive [\u003cspan additionalcitationids=\"CR21 CR22\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], and the obtained results cannot fully showcase graphene's superiority. Only when graphene is used as an independent surface coating can it protect metals and improve their electrical and thermal properties to the highest level. Chemical vapour deposition (CVD) is the most common method for producing large-area graphene on metal foils [\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn another study conducted by Jiangtong et al.[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] the researchers prepared a graphene/CoCrFeMo0.5NiTi0.5 high-entropy alloy composite coating on the surfaces of curved parts using both high-speed and low-speed laser cladding techniques. The low-speed laser processing resulted in a smoother and more uniform surface, achieving an average microhardness 1.49 times higher than the high-speed processed coatings. While both cladding layers demonstrated abrasive wear, it was noted that the wear rate for the low-speed laser-processed coating was approximately 3.06 times higher than that of the high-speed processed counterpart. Furthermore, the study identified a correlation between increased oxygen content and wear rates, which may indicate potential challenges in maintaining the performance of coatings in oxidizing environments.\u003c/p\u003e \u003cp\u003eZesen et al. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] employed electrophoretic deposition to prepare graphene coatings on titanium alloys. This method facilitates the deposition of materials from a colloidal suspension under the influence of an electric field, resulting in dense and uniformly distributed coatings, even on substrates with complex shapes. The coatings demonstrated an impressive corrosion current density of only 0.06 \u0026micro;A/cm\u0026sup2;, indicating a significant enhancement in corrosion resistance. However, certain defect levels in the electrophoretic deposition process led to increased permeability of corrosive media, which consequently accelerated the corrosion of the titanium substrate in areas where these defects were present.\u003c/p\u003e \u003cp\u003eAnti-corrosion treatments using chemical vapour-deposited graphene on nickel and copper significantly improved corrosion resistance by nearly three orders of magnitude in aggressive acidic conditions[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. The graphene-TiO2 nanohybrid on an aluminium substrate, created via laser powder bed fusion, showed strong anti-corrosion properties due to a synergistic interaction between graphene and TiO\u003csub\u003e2\u003c/sub\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. However, the scalability of these fabrication processes for industrial applications needs evaluation. Scalable laser treatments, such as the laser-induced graphene (LIG) coating[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], offer efficient production methods and can maintain desired material properties. LIG converts carbon-rich materials into a nanostructured graphene layer using high-energy laser pulses, providing excellent conductivity and mechanical properties. However, the use of LIG for the development of graphene-based anti-corrosive coatings has not been extensively studied.\u003c/p\u003e \u003cp\u003eWanli et al.[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] examined the corrosion resistance of a graphene layer applied to carbon steel through a combination of electroplated nickel and laser-induced graphene techniques. Their results demonstrated that the graphene coating had lower corrosion rates than pure nickel coatings and untreated carbon steel, as evidenced by polarization curves and electrochemical impedance spectroscopy. Their process requires substrate materials with carbon atoms to enable graphene induction via laser treatment. The methodology is complex and expensive, relying on electroplating and laser preparation, which could limit its scalability for industrial use. The findings also revealed that while the graphene coating has high hardness and strength, these properties are significantly lower than those of nickel coatings and pure carbon steel.\u003c/p\u003e \u003cp\u003eYe and colleagues[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e] have also presented a new method for fixing damaged areas of graphene using a laser. This technique entails placing carbon sources under a nickel coating, which are then transferred to the surface when activated by the laser. By fine-tuning the laser parameters, this technology can effectively repair graphene layers in the compromised regions and shows great potential for protecting metals against corrosion, wear, and friction.\u003c/p\u003e \u003cp\u003eXiaohui Ye et al. [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] have introduced a novel technique for producing graphene on carbon steel by incorporating nickel via laser alloying. This method forms a Ni/Fe alloy catalyst that facilitates the growth of multilayer graphene on the carbon steel surface. The graphene layers achieved a resistance comparable to that of stainless steel alongside a minimal corrosion rate. Additionally, the exceptional characteristics of graphene, such as its impermeability and excellent adhesion, greatly enhanced the corrosion resistance of carbon steel, rendering it highly durable in challenging environments.\u003c/p\u003e \u003cp\u003eThis paper suggests a more accessible method for creating three-dimensional porous graphene films by directly transforming commercially available polyimide (PI) polymer films using a CO\u003csub\u003e2\u003c/sub\u003e infrared laser and adhering them to a metallic substrate. This single-step technique can be utilized on any metal surface, promoting the creation of LIG@PI anti-corrosion coatings. Adhesive bonding is the most common technique for attaching polymers to metals, and polymers have considerable capacity for forming strong bonds with metals[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn our LIG@PI case, PI film is commercially provided with adhesive, which can be bonded to any metal part. The metallic part (aluminium in our study) and LIG@PI can be prepared separately and then joined together (LIG@PI/Al), which provides the repair concepts for the method. Moreover, multi-layer LIG@PI can be set up for better coating performance. Previously, it has been shown that polyimide can significantly enhance the anti-corrosion capabilities of Mg alloy by sealing micro-defects, improving corrosion resistance, and providing self-lubricating properties, all while maintaining stability under high temperatures[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]The laser parameters significantly impact the structure of LIG@PI protective coatings. This relationship is systematically investigated through characterization techniques, static corrosion analyses, and potentiodynamic polarization studies.\u003c/p\u003e \u003cp\u003eWe propose enhancing graphene-based layers on commercially available polyimide coupled with robust adhesive bonding to metal substrates. The effectiveness of these coatings in preventing corrosion is intrinsically linked to the quality of the formed graphene layer and the strength of the adhesion between the polyimide and the metallic substrate. By leveraging the protective attributes of graphene and polyimide alongside resilient adhesive bonding, we can effectively tackle the challenges currently facing the corrosion protection landscape.\u003c/p\u003e \u003cp\u003eAfter applying LIG, a coating of alkyd resin is added, serving as a barrier layer that further strengthens the structure against environmental damage. Alkyd resins are recognized for their strong adhesion, flexibility, and moisture resistance, making them ideal for harsh environments. The combined effect of the LIG surface treatment and the protective alkyd resin results in a composite material patch with outstanding performance, thereby improving the durability and reliability of components exposed to corrosive conditions. This innovative approach showcases the potential for enhancing corrosion resistance and illustrates the effectiveness of merging advanced material processing techniques with traditional polymer coatings in creating next-generation protective materials.\u003c/p\u003e"},{"header":"2 Characterizations","content":"\u003cp\u003eThe surface morphology and structure of the LIG-coated patches were examined using Scanning Electron Microscopy (SEM) on a VEGA3 system. Raman spectroscopy was employed to assess the samples' chemical composition and molecular structure using a Raman spectrometer (Ram-532-004). The crystallinity and phase composition of the LIG were further analyzed through X-ray Diffraction (XRD) with an XPert Pro diffractometer. Thermogravimetric analysis (TGA) and elemental identification analysis (Energy-Dispersive X-ray Spectroscopy (EDS)) were performed using TGA STA6000 and MAPPING Vega2 instruments. A CAG-20 device studied the surface-wetting properties of samples. Potentiodynamic Polarization Electrochemical analysis was conducted using a three-electrode electrochemical test system in a 3.5% sodium chloride solution for corrosion resistance evaluation.\u003c/p\u003e"},{"header":"3 Materials","content":"\u003cp\u003eKapton tape (a polyimide film from DuPont), Sodium hydroxide (NaOH) pellets from Merk, and sodium carbonate monohydrate (Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e\u0026middot;H\u003csub\u003e2\u003c/sub\u003eO) from Merk were employed. Various sandpapers with grits of #200, #400, #600, #800, and #1000 were utilized for surface preparations. Aluminium foil was incorporated as a metallic substrate for the experiment, and Vako transparent spray was employed to coat the alkyd resin without further purification. A polyethylene (PE) substrate was used as the Kapton tape's support in LIG processes. The hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) used to prepare an alkaline aggressive solution in the immersion test section was 30% Pro Analysis Merck.\u003c/p\u003e"},{"header":"4 Experimental","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e4.1 Preparation of Samples\u003c/h2\u003e\n \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\n \u003ch2\u003e4.1.1 Metal substrate\u003c/h2\u003e\n \u003cp\u003eAluminium foils are meticulously cut into squares. Figure 1a shows the preparation steps of the untreated metal substrate. Initially, the cut pieces undergo an acetone wash and a thorough rinse in a cleanroom environment. Subsequently, they are subjected to an alkaline degreasing process for 10 minutes, utilizing a diluted 0.1M solution of sodium hydroxide (NaOH) pellets dissolved in deionized water. Upon completion of the degreasing protocol, the metal surfaces are mechanically treated through grinding procedures. This is succeeded by a final chemical treatment conducted at room temperature, wherein the aluminium pieces are immersed in two distinct alkaline solutions: a 20-second immersion in a one wt% NaOH solution, followed by a 30-second immersion in an aqueous solution containing five wt% sodium carbonate monohydrate. It is essential to note that between each stage of surface treatment, the aluminium pieces are rinsed with deionized water to ensure the removal of residual contaminants.\u003c/p\u003e\n \u003cp\u003eIn the mechanical treatment phase, the aluminium pieces are dry-ground utilizing sandpapers of grits #200, #400, #600, #800, and #1000, each applied ten times in succession. This meticulous grinding process enhances the subsequent polyimide layer\u0026apos;s adhesion properties and achieves a smoother surface finish.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e\n \u003ch2\u003e4.1.2 Fabrication of LIG patches\u003c/h2\u003e\n \u003cp\u003eKapton Polyimide (PI) adhesive is used as the substrate of laser-induced graphene. Polyethylene, by having lower surface energy, ensures a smoother surface for adhesion of tapes. Also, less adhesive will be lost, and more will remain on Kapton tape. Two CO\u003csub\u003e2\u003c/sub\u003e lasers with 60 and 100-watt tubes generate LIG on PI. The laser parameters are set to a speed of 100mm/s with a distance of 6 cm from the head of the laser to the substrate. After the surfaces are subjected to laser, a black graphene layer is produced on PI. With the laser beam\u0026rsquo;s spot diameter of ~\u0026thinsp;100 \u0026micro;m and 50% overlap ratio, uniform graphene coating is achieved on the substrates. Using CAD drawing software, scanning lines are set to 0.05 mm distance to obtain 50% overlap. 6-8-10-12 W laser powers have been adopted in the preparation of LIG. Figure 1b shows the schematic of the implementation steps of the LIG, which is placed on the metal substrate after the induction of graphene. Figure 2 shows elemental EDS analyses performed on bare PI and LIG surfaces to study the quality of purchased tape and the synthesized graphene layer. According to EDS results, carbon is the most abundant element in the bare PI layer Fig. 2(a-f) and constitutes 49.09% of the weight, followed by O and N elements (Fig. 2(c)). After the direct laser scribing process (Fig. 2(g-l)), the carbon content of the resulting LIG has increased to 82.22% of the weight (Fig. 2(i)), which is due to the removed amount of the C-O and C-N bonds as exhaust gas during the process, leaving behind solid C-C bonds. Carbon bonds can contribute to a more resilient surface toward corrosion by reducing electrochemical reactions and improving mechanical properties.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e\n \u003ch2\u003e4.1.3 Coating Alkyd Resin\u003c/h2\u003e\n \u003cp\u003eSince LIG is subjected to environmental degradation, according to presented schematic in Fig.\u0026nbsp;1(c), unmodified commercial alkyd resin is sprayed on the surface of LIG6@PI, LIG8@PI, LIG10@PI, and LIG12@PI, through spraying. This ensures that the functional properties of the graphene material are untouched to obtain adhesion, durability, and protective finish. For an even distribution of the alkyd resin, complete spray coverage of the surface is done by spraying at a distance of 20 cm. As the alkyd resin cures, a robust, flexible layer on LIG is archived. A combination of alkyd resin and LIG can be particularly beneficial for applications in flexible electronics, sensors, and composite materials, where both the conductivity of graphene and the protective qualities of the alkyd resin are crucial for performance and longevity. Figure\u0026nbsp;3 represents a schematic structure of an adhesion-bonded anti-corrosion patch after the final alkyd resin spray coating. Following the alkyd coating process, a thermogravimetric study used TGA to study decomposition patterns. Figure\u0026nbsp;4 shows alkyd-coated LIG12@PI (A-LIG12@PI) weight loss while increasing temperature from 25\u0026deg;C to 800\u0026deg;C. Initial weight loss of 2-3wt% is observed at about 33\u0026ndash;100\u0026deg;C for A-LIG12@PI, which is attributed to removing moisture, volatiles, and ashes within the material. The onset of degradation for alkyd resin and PI starts from 150\u0026ndash;200\u0026deg;C and 500\u0026ndash;600\u0026deg;C, respectively[\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e]. Also, the total weight loss for alkyd resin is at 350\u0026ndash;400\u0026deg;C, where the TGA plot for A-LIG12@PI increases its weight loss[\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e]. PI\u0026apos;s total weight loss value is at 650\u0026ndash;700\u0026deg;C, as observed from the TGA plot of PI. All the while, LIG maintains thermal stability at up to 700\u0026deg;C. Increasing temperature up to 800\u0026deg;C, the remaining ash components after TGA are 19.34% and 45.56% for PI and A-LIG12@PI, respectively.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"5 Results and Discussion","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e5.1 Characterizations of Samples\u003c/h2\u003e\n \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n \u003ch2\u003e5.1.1 SEM analysis\u003c/h2\u003e\n \u003cp\u003eFigure 5(a-d( presents scanning electron microscopy (SEM) images of porous laser-induced graphene (LIG) synthesized at power levels of 6, 8, 10, and 12 watts, respectively. For lower power levels (i.e., 6 W and 8 W), a 60-watt tube laser is employed, while a 100-watt tube laser is utilized for higher power levels (i.e., 10 W and 12 W). The LIG produced at lower power levels exhibits a more uniform structure characterized by flake-like graphene. In contrast, higher power levels induce a more fibrous morphology in the LIG.\u003c/p\u003e\n \u003cp\u003eThe graphenization process is predominantly influenced by the overlapping laser scanning parameters, especially at lower power levels. In this context, carbonization primarily occurs due to the inherent carbon content in the polyimide (PI) backbone, which facilitates controlled and uniform graphene generation. Conversely, at power levels of 10 W and 12 W, graphenization appears to be augmented by introducing additional carbon-rich sources generated from the previously induced graphene and the PI substrate itself.\u003c/p\u003e\n \u003cp\u003eNotably, at 12 W, the fibrous clusters exhibit uncontrolled growth, resulting in significant thickness variations across the LIG surface. Regardless of the power applied, the bundles formed via laser radiation intertwine to create a network of porous structures.\u003c/p\u003e\n \u003cp\u003eRegarding the dimensional characteristics of LIG, as illustrated in Fig.\u0026nbsp;6(a), the thickness of LIG increases linearly with laser power, demonstrating a steep slope. At the same time, the remaining PI beneath the porous LIG structure diminishes at a comparatively slower rate, as depicted in Fig.\u0026nbsp;6(b). This observation suggests that at higher power levels, the LIG utilizes both the carbon source from the PI and the residual carbon from the previous scanning lines, thereby leaving more PI on the substrate[\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003e5.1.2 XRD spectroscopy\u003c/h2\u003e\n \u003cp\u003eThe X-ray diffraction (XRD) patterns presented in Fig.\u0026nbsp;7reveal a pronounced peak at an angle of approximately 27.2 degrees (2\u0026theta;) for A-LIG8@PI, A-LIG10@PI, and A-LIG12@PI and 26.5 for A-LIG6@PI, which can correspond to the (002) plane of LIG. Notably, the peaks exhibit increased sharpness with the lowering power of the laser, suggesting more entangled porous structures, potentially attributed to the aggregation of the graphene sheets inside the LIG layer.\u003c/p\u003e\n \u003cp\u003eMoreover, variations in the peak positions are likely attributed to the interactions between the graphene matrix of LIG and coated alkyd resin. The wider spectrum observed at the (002) plane of LIG for A-LIG12@PI likely indicates an increase in disorder due to the thermal stress and rapid cooling at higher powers and a broader range of crystal phases.\u003c/p\u003e\n \u003cp\u003eThe shift in the 2\u0026theta; peak from 26.5\u0026deg; for A-LIG6@PI to approximately 27.2\u0026deg; for A-LIG8@PI, A-LIG10@PI, and A-LIG12@PI likely suggests changes in the crystallinity. The uniform peak around 27.2\u0026deg; may indicate that the increase in power leads to comparable structural transformations in the LIG, resulting in consistent peak positions. A more uniform surface morphology of LIG6@PI compared to other samples (Figure) 5a() and its better crystalline structure with a closer peak-to-origin of LIG (2theta\u0026thinsp;=\u0026thinsp;26.5\u0026deg;) might promote better chemical bonding of alkyd to graphene and reduce the probability of corrosion pathways between the coating and substrate. In other words, LIG6@PI has an optimal graphenization condition with a denser, more crystalline structure, which may provide improved protection against moisture and corrosive species, leading to better corrosion resistance when coated with alkyd resin.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e5.1.3 Raman Spectroscopy\u003c/h2\u003e\n \u003cp\u003eRaman spectroscopy in Fig.\u0026nbsp;8)a( provides crucial insight into the structural quality of alkyd-coated laser-induced graphene (LIG) fabricated at varying laser powers. It specifically examines the D, G, and 2D peaks that characterize graphene materials and interactions of coated material.\u003c/p\u003e\n \u003cp\u003eAccording to Fig.\u0026nbsp;8)a(, all D, G and 2D peaks are observed at lower frequencies 1084cm\u003csup\u003e-1\u003c/sup\u003e, 1331cm\u003csup\u003e-1\u003c/sup\u003e and 2478cm\u003csup\u003e-1\u003c/sup\u003e, respectively (For LIG, the G band is at 1580cm\u003csup\u003e-1\u003c/sup\u003e, D band is at 1350cm\u003csup\u003e-1\u003c/sup\u003e, and 2D band is at 2700 cm\u003csup\u003e-1\u003c/sup\u003e [\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e]). These shifts suggest interfacial interaction between the alkyd matrix and graphene-conjugated aromatic rings. Also, sample A-LIG6@PI shows additional peaks at 1175cm\u003csup\u003e-1\u003c/sup\u003e and 1580cm\u003csup\u003e-1\u003c/sup\u003e which can be related to the carboxylated groups of alkyd material creating efficient interfacial bonds of C-C and -COO- with LIG[\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003eThe G peak is a fundamental indicator of the presence of sp\u0026sup2; carbon networks within the LIG structure. A strong G peak signifies ordered graphitic domains and is associated with the inplane vibration of sp\u0026sup2;-bonded carbon atoms. Across the samples, the A-LIG6@PI shows the most pronounced G peak, indicating optimal graphitization at this power level. In contrast, LIG samples fabricated at 8W, 10W, and 12W exhibit a slightly diminished G peak intensity, suggesting an increase in structural disorder as the laser power increases.\u003c/p\u003e\n \u003cp\u003eThe D peak arises due to the vibration modes and is associated with defects in the carbon lattice. Higher D/G ratios generally imply greater structural imperfections[\u003cspan class=\"CitationRef\"\u003e44\u003c/span\u003e]. In this study, the 6W sample demonstrates a relatively low D/G intensity ratio compared to the other samples, highlighting a lower defect density (Fig.\u0026nbsp;6)b(). Also, by increasing laser power, the D/G intensity ratio exhibits a wider range, introducing non-uniform structural properties and scattered defect density. As the laser power rises to 8W, 10W, and 12W, the D peak becomes more prominent, indicating that higher laser power introduces more defects into the graphene structure, potentially due to excessive energy causing lattice distortions[\u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003eThe 2D peak is particularly significant in distinguishing between single-layer and multi-layer graphene[\u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e]. A sharp, symmetric 2D peak suggests high-quality, few-layer graphene, while a broader or shifted 2D peak can indicate a greater layer count or increased disorder. All LIG samples exhibit broadened 2D peaks, implying the porous multi-layer structure of all samples.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n \u003ch2\u003e5.1.4 Corrosion behavior\u003c/h2\u003e\n \u003cp\u003eA one-liter deionized water-based aggressive alkaline solution containing 3.1 g of hydrogen peroxide and 59 g of sodium chloride was employed for the static corrosion analyses of all samples. The samples, specifically A-LIG6@PI, A-LIG8@PI, A-LIG10@PI, and A-LIG12@PI, were immersed in this solution, with the pH of the environment carefully maintained at 9.3. Scanning electron microscopy (SEM) images of samples subjected to corrosion for 24 hours, 48 hours, and 96 hours were analyzed to investigate the pitting and cracking phenomena across all samples. Figure\u0026nbsp;9(a-l) displays the SEM images of the surfaces of A-LIG6@PI (a,b,c), A-LIG8@PI (d,e,f), A-LIG10@PI (g,h,i), and A-LIG12@PI (j,k,l) following immersion for 24 hours (a,d,g,j), 48 hours (b,e,h,k), and 96 hours (c,f, i,l).\u003c/p\u003e\n \u003cp\u003eFor the A-LIG6@PI sample, minimal pitting and cracking were observed after 24 hours of immersion. Conversely, for the A-LIG12@PI sample, significant pitting and cracking emerged within the first 24 hours of exposure to the alkaline solution, characterized by notable crack lengths and interconnected pits. With prolonged immersion in the solution, the mechanisms of pitting and cracking were activated, exhibiting a slower rate for A-LIG6@PI, while A-LIG8@PI, A-LIG10@PI, and A-LIG12@PI demonstrated a more rapid corrosion rate. These observations indicate that A-LIG6@PI exhibits enhanced resistance to corrosion under identical testing conditions.\u003c/p\u003e\n \u003cp\u003eFigure 10 shows a polarization test to investigate the anti-corrosion ability of LIG@PI and A-LIG@PI patches after covering a 2cm\u0026times;2cm aluminium foil with each patch. All samples are tested by immersion in 3.5 wt% NaCl for 3 hours. The findings provide valuable insights into the anti-corrosion capabilities of these materials. LIG12@PI exhibits superior corrosion resistance compared to LIG10@PI, which continues sequentially down to LIG6@PI. The reasons can be attributed to several factors, as discussed below.\u003c/p\u003e\n \u003cp\u003eFirstly, the structural characteristics of the LIG@PI patches play a pivotal role in their corrosion resistance. The patch with the highest porous medium structure, LIG12@PI, likely facilitates enhanced barrier properties against corrosive ions from the surrounding environment. A more porous structure may allow for effective load distribution and better physical interlocking, improving the patch\u0026apos;s adhesion to the aluminium substrate and reducing the likelihood of corrosion.\u003c/p\u003e\n \u003cp\u003eSecondly, the thickness of the LIG graphene film in each sample directly influences their protective capabilities. Thicker films typically provide a more effective and continuous barrier against corrosive species. In the series of samples tested, it can be inferred that LIG12@PI, having the thickest film (Fig.\u0026nbsp;5(d)), would exhibit a reduced permeation rate of chloride ions, leading to lower corrosion rates than thinner films found in LIG10@PI, LIG8@PI, and LIG6@PI.\u003c/p\u003e\n \u003cp\u003eAdditionally, the intrinsic properties of the LIG itself should be considered. Higher graphene content in LIG12@PI may result in superior electrical conductivity, reducing localized corrosion processes, such as pitting. This property and the morphology of the patches could contribute to the overall enhanced performance observed in the polarization test results. Furthermore, the interface quality between the patch and the aluminium substrate is crucial. If LIG12@PI demonstrates better adhesion due to its structural properties, it could diminish the likelihood of delamination, a common precursor to corrosion in layered materials[\u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e]. The mechanical stability provided by such a robust interface would enhance the longevity of the protective layer.\u003c/p\u003e\n \u003cp\u003eThe differences in corrosion resistance between alkyd resin sprayed LIG, which is synthesized at various power levels, and between bare PI and a LIG12@PI sample are illustrated in Fig.\u0026nbsp;11. These differences can stem from how the laser power affects the structural and chemical properties of the laser-induced graphene and the integrity of the LIG and alkyd interface. The A-LIG6@PI sample has a more controlled graphitization process with a denser, more uniform, and stable microstructure (Fig.\u0026nbsp;5(a)) with an alkyd material. Bare LIG6@PI does not create a tighter barrier to prevent corrosive agents from penetrating the treated aluminium substrate (Fig.\u0026nbsp;9). Still, it can provide better interaction sites with alkyd, as discussed in Raman spectroscopy for LIG6@PI in Fig.\u0026nbsp;8. The pronounced interfacial bonds of alkyd carboxylated groups with LIG6@PI are due to the uniformity and less defect density of LIG at lower powers. Increasing laser power LIG generation increases the degree of ablation, which can lead to a more diffectfull porous graphene structure (Fig.\u0026nbsp;5(b-d)). This less uniformity reduces the effectiveness of the LIG and alkyd interaction as a barrier and allows for greater electrolyte penetration, decreasing corrosion resistance. At higher laser powers, there is also a greater likelihood of thermal decomposition or partial oxidation of the LIG surface, which introduces defects and reduces the integrity of the graphene layer. The A-LIG6@PI coating benefits most from a combination of optimal graphitization of LIG at lower powers, better alkyd interfacial properties, and uniform graphene layers. Lower-power LIG forms a smoother, less porous substrate that allows the alkyd to have an effective, consistent coating.\u003c/p\u003e\n \u003cp\u003eAdditionally, the corrosion resistance of bare PI is lower than that of all A-LIG@PI samples, which can be why PI lacks the barrier properties provided by the LIG\u0026rsquo;s conductive, impermeable structure. This is while bare PI exhibits better corrosion resistance due to having a thicker polyimide layer than uncoated LIG samples. LIG is more susceptible to environmental degradation, which weakens its barrier against corrosion.\u003c/p\u003e\n \u003cp\u003eTo evaluate the corrosion resistance of treated aluminium, corrosion potential (E\u003csub\u003ecorr\u003c/sub\u003e), corrosion current density (i\u003csub\u003ecorr\u003c/sub\u003e), anodic and cathodic Tafel slopes (b\u003csub\u003ea\u003c/sub\u003e and b\u003csub\u003ec\u003c/sub\u003e), polarization resistance (R\u003csub\u003ep\u003c/sub\u003e), and inhibition efficiency (\u0026eta;) were analyzed as shown in Table\u0026nbsp;1[\u003cspan class=\"CitationRef\"\u003e48\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003eTreated aluminum displayed high corrosion susceptibility with an E\u003csub\u003ecorr\u003c/sub\u003e of -0.656 V and i\u003csub\u003ecorr\u003c/sub\u003e of 7.02 \u0026micro;A/cm\u0026sup2;. In comparison, PI without LIG improved resistance, shifting E\u003csub\u003ecorr\u003c/sub\u003e to -0.532 V and reducing i\u003csub\u003ecorr\u003c/sub\u003e to 1.95 \u0026micro;A/cm\u0026sup2;, with R\u003csub\u003ep\u003c/sub\u003e at 5.32\u0026times;10⁵ Ω\u0026middot;cm\u0026sup2; and an \u0026eta; of 72.15%.\u003c/p\u003e\n \u003cp\u003eModifying PI with LIG at 6 W (LIG6@PI) gave moderate corrosion resistance, with an E\u003csub\u003ecorr\u003c/sub\u003e of -0.672 V, i\u003csub\u003ecorr\u003c/sub\u003e of 4.24 \u0026micro;A/cm\u0026sup2;, R\u003csub\u003ep\u003c/sub\u003e of 4.11\u0026times;10⁵ Ω\u0026middot;cm\u0026sup2;, and \u0026eta; of 39.59%. At 8 W (LIG8@PI), i\u003csub\u003ecorr\u003c/sub\u003e dropped to 3.00 \u0026micro;A/cm\u0026sup2;, R\u003csub\u003ep\u003c/sub\u003e increased to 4.48\u0026times;10⁵ Ω\u0026middot;cm\u0026sup2;, and \u0026eta; rose to 57.24%, suggesting improved barrier properties. With a laser power of 10 W (LIG10@PI), corrosion resistance further improved (E\u003csub\u003ecorr\u003c/sub\u003e -0.666 V, i\u003csub\u003ecorr\u003c/sub\u003e 2.74 \u0026micro;A/cm\u0026sup2;, R\u003csub\u003ep\u003c/sub\u003e 5.14\u0026times;10⁵ Ω\u0026middot;cm\u0026sup2;, \u0026eta; 61.01%). At 12 W (LIG12@PI), the highest R\u003csub\u003ep\u003c/sub\u003e (6.51\u0026times;10⁵ Ω\u0026middot;cm\u0026sup2;) and an i\u003csub\u003ecorr\u003c/sub\u003e of 2.33 \u0026micro;A/cm\u0026sup2; gave an \u0026eta; of 66.81%.\u003c/p\u003e\n \u003cp\u003eAlkyd-coated LIG samples (A-LIG@PI) performed exceptionally. A-LIG6@PI with 6W power showed an E\u003csub\u003ecorr\u003c/sub\u003e of -0.456 V, very low i\u003csub\u003ecorr\u003c/sub\u003e of 0.11 \u0026micro;A/cm\u0026sup2;, R\u003csub\u003ep\u003c/sub\u003e of 8.51\u0026times;10⁶ Ω\u0026middot;cm\u0026sup2;, and \u0026eta; of 98.36%. Similarly, A-LIG8@PI and A-LIG10@PI samples maintained high efficiencies of 97.79% and 95.70%, with optimized LIG and coating qualities. The A-LIG12@PI, though slightly lower at 86.62% efficiency, still showed strong protection, indicating alkyd with 8\u0026ndash;10 W laser powers offered the best corrosion resistance.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1.\u003c/strong\u003e Electrochemical polarization parameters of treated aluminium substrate and different adhesion bonded anti-corrosion patches after 3 h of immersion in 3.5 wt% NaCl solution\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv class=\"colspec\"\u003e\n \u003ctable id=\"Taba\" border=\"1\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSamples\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eE\u003csub\u003ecorr\u003c/sub\u003e (v)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ei\u003csub\u003ecorr\u003c/sub\u003e (\u0026micro;A/cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eb\u003csub\u003ea\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eb\u003csub\u003ec\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eR\u003csub\u003ep\u003c/sub\u003e (Ωcm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u0026eta; (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTreated Al\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.656\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.532\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.32E\u0026thinsp;+\u0026thinsp;05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e72.15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLIG6@PI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.672\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.11E\u0026thinsp;+\u0026thinsp;05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e39.59\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLIG8@PI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.668\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.48E\u0026thinsp;+\u0026thinsp;05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e57.24\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLIG10@PI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.666\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.14E\u0026thinsp;+\u0026thinsp;05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e61.01\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLIG12@PI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.664\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.51E\u0026thinsp;+\u0026thinsp;05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e66.81\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eA-LIG6@PI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.456\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.51E\u0026thinsp;+\u0026thinsp;06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e98.36\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eA-LIG8@PI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.504\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.65E\u0026thinsp;+\u0026thinsp;06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e97.79\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eA-LIG10@PI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.512\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.23E\u0026thinsp;+\u0026thinsp;06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e95.70\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eA-LIG12@PI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.518\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.26E\u0026thinsp;+\u0026thinsp;06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e86.62\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"7\"\u003e\n \u003cp\u003eE\u003csub\u003ecorr\u003c/sub\u003e: Corrosion voltage.\u003c/p\u003e\n \u003cp\u003eI\u003csub\u003ecorr\u003c/sub\u003e: Corrosion current density.\u003c/p\u003e\n \u003cp\u003eb\u003csub\u003ea\u003c/sub\u003e: Anodic tafel slope.\u003c/p\u003e\n \u003cp\u003eb\u003csub\u003ec\u003c/sub\u003e: Cathodic tafel slope.\u003c/p\u003e\n \u003cp\u003eR\u003csub\u003ep\u003c/sub\u003e: Polarization resistance\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eThe electrochemical stability of alkyd-coated LIG-modified PI samples (A-LIG@PI) on aluminum was evaluated by measuring corrosion current density (i\u003csub\u003ecorr\u003c/sub\u003e) and corrosion potential (E\u003csub\u003ecorr\u003c/sub\u003e) after 48 and 96 hours of exposure (Fig.\u0026nbsp;12). The A-LIG6@PI sample demonstrated a low initial i\u003csub\u003ecorr\u003c/sub\u003e of 4\u0026times;10⁻⁹ A/cm\u0026sup2; after 48 hours (Fig. 13(a)), with a relatively stable E\u003csub\u003ecorr\u003c/sub\u003e of -0.67 V, indicating good corrosion resistance (Fig. 13(b)). However, after 96 hours, i\u003csub\u003ecorr\u003c/sub\u003e increased to 3.675\u0026times;10⁻⁸ A/cm\u0026sup2;, and E\u003csub\u003ecorr\u003c/sub\u003e shifted slightly to -0.632 V, suggesting minor degradation over time. This increase in i\u003csub\u003ecorr\u003c/sub\u003e reflects a gradual decline in the protective efficiency of the LIG layer, though the sample still maintained a reasonable level of corrosion resistance.\u003c/p\u003e\n \u003cp\u003eFor A-LIG8@PI, i\u003csub\u003ecorr\u003c/sub\u003e was higher at 1.475\u0026times;10⁻⁸ A/cm\u0026sup2; after 48 hours with an E\u003csub\u003ecorr\u003c/sub\u003e of -0.616 V, showing slightly lower corrosion resistance than A-LIG6@PI (Fig. 13). After 96 hours, i\u003csub\u003ecorr\u003c/sub\u003e increased to 4\u0026times;10⁻⁸ A/cm\u0026sup2;, with a shift in E\u003csub\u003ecorr\u003c/sub\u003e to -0.65 V. These changes indicate that while A-LIG8@PI initially provides moderate protection, the increase in i\u003csub\u003ecorr\u003c/sub\u003e over time points to some loss in coating performance.\u003c/p\u003e\n \u003cp\u003eThe A-LIG10@PI sample exhibited a significantly higher i\u003csub\u003ecorr\u003c/sub\u003e of 3.55\u0026times;10⁻⁷ A/cm\u0026sup2; after 48 hours, coupled with an E\u003csub\u003ecorr\u003c/sub\u003e of -0.668 V. This initial high i\u003csub\u003ecorr\u003c/sub\u003e suggests that, despite the more intense laser power, the corrosion resistance may be compromised initially due to possible structural imperfections in the LIG layer at this power level. However, after 96 hours, i\u003csub\u003ecorr\u003c/sub\u003e dropped to 5.25\u0026times;10⁻⁸ A/cm\u0026sup2; with a slightly more negative E\u003csub\u003ecorr\u003c/sub\u003e of -0.684 V, suggesting some stabilization in the coating\u0026rsquo;s protective capability over time.\u003c/p\u003e\n \u003cp\u003eThe A-LIG12@PI sample initially showed a moderate i\u003csub\u003ecorr\u003c/sub\u003e of 4.575\u0026times;10⁻⁸ A/cm\u0026sup2; and an E\u003csub\u003ecorr\u003c/sub\u003e of -0.642 V after 48 hours. After 96 hours, i\u003csub\u003ecorr\u003c/sub\u003e was relatively stable at 4.75\u0026times;10⁻⁸ A/cm\u0026sup2;, with E\u003csub\u003ecorr\u003c/sub\u003e shifting to -0.624 V. This stability in i\u003csub\u003ecorr\u003c/sub\u003e and E\u003csub\u003ecorr\u003c/sub\u003e suggests that the LIG layer formed at 12 W provides consistent protection over the tested period, likely due to an optimized LIG structure that better resists environmental degradation (Fig. 13). It can be concluded that while the A-LIG6@PI and A-LIG12@PI samples maintain more stable corrosion resistance, the performance of A-LIG8@PI and A-LIG10@PI shows greater fluctuation over time, and A-LIG6@PI and A-LIG12@PI are offering better long-term corrosion protection on aluminum.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"6 Contact angle measurements","content":"\u003cp\u003eFigure 14describes water contact angle measurements for the LIG-modified PI and alkyd-coated LIG-modified PI samples subjected to varying laser powers (6, 8, 10, and 12 W), which reveal critical insights into their wetting properties and surface hydrophobicity. Wetting properties directly impact corrosion resistance patches. Higher contact angles suggest increased hydrophobicity, which minimizes water adsorption and enhances corrosion resistance.\u003c/p\u003e \u003cp\u003eContact angles for the LIG@PI samples (Fig.\u0026nbsp;14(a)) are notably lower, ranging from around 46\u0026deg; to 58\u0026deg; across samples treated with different laser powers (6, 8, 10, and 12 W). Specifically, LIG6@PI and LIG8@PI exhibit slightly higher average contact angles, around 54\u0026ndash;55\u0026deg;, compared to LIG10@PI and LIG12@PI, which have average values closer to 48\u0026ndash;49\u0026deg;. These relatively low contact angles indicate that the untreated LIG-modified surfaces are somewhat hydrophilic, allowing more moisture interaction with the surface. This hydrophilicity may make them more susceptible to corrosion, as water can readily penetrate and initiate corrosion processes.\u003c/p\u003e \u003cp\u003eIn contrast, the A-LIG@PI samples in Fig.\u0026nbsp;14(b), which were further coated with alkyd, show a significant increase in contact angles, indicating enhanced hydrophobicity. For A-LIG6@PI and A-LIG8@PI, contact angles range from approximately 92\u0026deg; to 105\u0026deg;, averaging around 98\u0026ndash;100\u0026deg;. This high hydrophobicity is associated with the protective alkyd layer that limits water contact and thus helps prevent corrosion. The A-LIG10@PI and A-LIG12@PI samples have slightly lower average contact angles, around 89\u0026ndash;96\u0026deg;, suggesting a slight reduction in hydrophobicity at higher laser powers, potentially due to changes in the LIG layer\u0026rsquo;s surface structure.\u003c/p\u003e \u003cp\u003eFor the A-LIG6@PI sample, contact angles ranged from 92.2\u0026deg; to 105.5\u0026deg;, averaging around 98.0\u0026deg;. This relatively high and consistent hydrophobicity suggests that the laser power of 6 W optimally supports a dense, uniform LIG layer on the PI surface. The resulting hydrophobic surface prevents water molecules and delays the onset of corrosion, correlating with the high corrosion resistance observed in electrochemical testing for this sample.\u003c/p\u003e \u003cp\u003eThe A-LIG8@PI sample showed contact angles between 90\u0026deg; and 104\u0026deg;, averaging approximately 97.7\u0026deg;. While slightly variable, the angles still indicate high hydrophobicity, suggesting an effective barrier against moisture. The strong water resistance and the robust LIG structure formed at 8W may explain this sample's stable corrosion resistance over time.\u003c/p\u003e \u003cp\u003eThe increased contact angles in A-LIG@PI samples correlate well with improved corrosion resistance, as evidenced by their reduced corrosion current densities (i\u003csub\u003ecorr\u003c/sub\u003e) in electrochemical tests. The higher hydrophobicity of A-LIG6@PI and A-LIG8@PI reflects a robust barrier against moisture, thereby limiting the electrochemical reactions that drive corrosion. Conversely, the moderate decrease in contact angles observed in A-LIG10@PI and A-LIG12@PI may correspond to slightly lower corrosion resistance, as minor variations in surface uniformity at higher laser powers can affect wetting properties.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe water contact angle measurements for the (a) LIG-modified PI and (b) alkyd-coated LIG-modified PI laser powers 6, 8, 10, and 12 W.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"7 Conclusion","content":"\u003cp\u003eThis research highlights the significant advancements in applying laser-induced graphene (LIG) as a protective material for aluminum substrates, particularly when coupled with alkyd resin coatings. A clear relationship was established between laser power, graphene quality, and corrosion resistance by systematically analyzing the effects of varying laser powers on LIG's structural, morphological, and electrochemical properties. Lower laser power settings, particularly 6W, yielded a highly uniform, crystalline LIG structure with minimal defects, which was instrumental in forming strong interfacial bonds with the alkyd resin coating. This combination enhanced corrosion resistance, reduced defect density, and improved hydrophobicity, making A-LIG6@PI stand out in this study.\u003c/p\u003e \u003cp\u003eThe comprehensive characterizations, including SEM, XRD, Raman spectroscopy, and electrochemical polarization tests, revealed that the protective capabilities of LIG and alkyd coatings are influenced by the structural properties of graphene and their interactions with the polymer matrix. The findings showed that the synergistic effects of optimized graphitization at lower laser powers and the alkyd resin's chemical compatibility significantly enhance the protective layer's durability and efficiency. Notably, A-LIG6@PI demonstrated superior resistance to moisture and corrosive agents, with minimal pitting and cracking observed after prolonged exposure to aggressive environments.\u003c/p\u003e \u003cp\u003eHigher laser powers, resulting in thicker LIG layers, introduced greater structural defects and less uniform graphene morphology, reducing the effectiveness of the alkyd-LIG barrier. The decrease in hydrophobicity and the increase in defect density at higher powers underscore the importance of optimizing laser parameters to achieve the desired balance between material thickness and structural integrity. These insights pave the way for tailoring LIG-based coatings for specific applications, particularly in environments that demand high-performance anti-corrosion solutions.\u003c/p\u003e \u003cp\u003eThe study also emphasized the role of hydrophobicity in enhancing corrosion resistance. Water contact angle measurements revealed that alkyd-coated LIG samples exhibited significantly higher hydrophobicity than bare LIG-modified PI, with A-LIG6@PI and A-LIG8@PI achieving the highest levels. This improvement in surface hydrophobicity is directly correlated with lower corrosion current densities and higher polarization resistance, demonstrating the effectiveness of the alkyd resin in complementing the protective properties of LIG.\u003c/p\u003e \u003cp\u003eIn summary, this research provides a framework for designing advanced anti-corrosion materials that integrate the unique properties of graphene with polymer-based coatings. The optimal conditions identified for LIG fabrication, particularly at 6W laser power, offer a blueprint for achieving superior performance in adhesion, durability, and resistance to environmental degradation. These findings hold immense promise for applications in flexible electronics, sensors, structural materials, and industries requiring robust and long-lasting anti-corrosion solutions.\u003c/p\u003e \u003cp\u003eFuture studies should explore scalable manufacturing processes to broaden the applicability of LIG-alkyd coatings. Additionally, investigating the long-term stability of these materials under varied environmental conditions and their potential integration with other functional coatings could open new avenues for innovation. By addressing these challenges, the full potential of LIG-based technologies can be harnessed to create transformative solutions in materials science and engineering.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eM.M.H.: Conceptualization, Methodology, Experiment, Writing- Original draft preparation. F.H.: Methodology, Experiment. S.S.: Visualization, Investigation, Supervision\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analysed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eXu, H. \u0026amp; Zhang, Y. 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Emerging layered materials and their applications in the corrosion protection of metals and alloys. \u003cem\u003eSustainability\u003c/em\u003e \u003cb\u003e14\u003c/b\u003e (7), 4079 (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAnita, N. et al. \u003cem\u003eLinear polarization resistance (LPR) technique for corrosion measurements, in Electrochemical and Analytical Techniques for Sustainable Corrosion Monitoring\u003c/em\u003ep. 59\u0026ndash;80 (Elsevier, 2023).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Laser-Induced Graphene, Alkyd Resin, Corrosion Resistance Patches, Metal Substrates","lastPublishedDoi":"10.21203/rs.3.rs-6234092/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6234092/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCorrosion can severely degrade surfaces and materials, impacting functionality and safety. Laser-induced graphene (LIG) offers substantial corrosion resistance, making it ideal for protecting metals like carbon steel. This study developed adhesive, corrosion-resistant LIG patches on polyimide (PI) layers, enhanced with an alkyd resin coating, and applied to pretreated aluminum surfaces. LIG was synthesized using laser powers of 6, 8, 10, and 12 W, followed by alkyd coating for improved performance. Results of EDS, SEM, TGA, XRD, Raman spectroscopy and surface-wetting properties are studied. SEM and XRD analyses revealed that lower laser power (6 W) produced uniform, crystalline LIG, while higher power (12 W) caused defects and porosity. Corrosion tests in an alkaline environment showed that the A-LIG6@PI patch had the best structural integrity, with minimal pitting after 96 hours, outperforming other samples. The electrochemical analysis demonstrated a corrosion inhibition efficiency of 98.36% for A-LIG6@PI, with a corrosion current density of 0.11 \u0026micro;A/cm\u0026sup2; and polarization resistance (Rp) of 8.51\u0026times;10⁶ Ω\u0026middot;cm\u0026sup2;. Contact angle measurements confirmed enhanced hydrophobicity, with A-LIG6@PI showing an 88\u0026deg; angle compared to 58\u0026deg; for bare LIG. These results emphasize the potential of lower laser power for creating durable, corrosion-resistant graphene-based coatings suitable for flexible electronics and protective applications.\u003c/p\u003e","manuscriptTitle":"Alkyd Coated Laser-Induced Graphene Patches For Corrosion Resistance of Metal Substrates","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-31 11:17:15","doi":"10.21203/rs.3.rs-6234092/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-05-27T10:30:04+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-14T10:51:21+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-03T07:38:40+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"71371008832294774434680992718836259536","date":"2025-04-29T06:53:44+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"260964717961472429377306066957184877235","date":"2025-04-23T07:19:04+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-03-21T11:55:46+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-03-21T11:50:21+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-03-21T10:41:37+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-03-20T11:32:29+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-03-15T17:05:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"4acd99fd-ceee-4423-a25b-cb916d385d84","owner":[],"postedDate":"March 31st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":46172074,"name":"Physical sciences/Chemistry"},{"id":46172075,"name":"Physical sciences/Chemistry/Electrochemistry"},{"id":46172076,"name":"Physical sciences/Materials science/Materials for energy and catalysis"},{"id":46172077,"name":"Physical sciences/Materials science/Nanoscale materials"}],"tags":[],"updatedAt":"2025-09-01T16:05:22+00:00","versionOfRecord":{"articleIdentity":"rs-6234092","link":"https://doi.org/10.1038/s41598-025-17456-6","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-08-26 15:58:00","publishedOnDateReadable":"August 26th, 2025"},"versionCreatedAt":"2025-03-31 11:17:15","video":"","vorDoi":"10.1038/s41598-025-17456-6","vorDoiUrl":"https://doi.org/10.1038/s41598-025-17456-6","workflowStages":[]},"version":"v1","identity":"rs-6234092","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6234092","identity":"rs-6234092","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}