Cobalt layer prepared on copper using galvanic replacement as an alternative to palladium for activating electroless Ni-P plating

Cobalt layer prepared on copper using galvanic replacement as an alternative to palladium for activating electroless Ni-P plating | 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 Research Article Cobalt layer prepared on copper using galvanic replacement as an alternative to palladium for activating electroless Ni-P plating Guanqun Hu, Rupeng Li, Wanda Liao, Changning Bai, Xingkai Zhang, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4291415/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 21 Jul, 2024 Read the published version in Journal of Applied Electrochemistry → Version 1 posted 11 You are reading this latest preprint version Abstract Electroless nickel-phosphorus (Ni-P) plating is a widely used surface treatment method due to its excellent corrosion and wear resistance properties. However, the inertness of copper to hypophosphite oxidation necessitates a palladium activation process for the preparation of Ni-P coating on copper. In this study, we present a convenient approach for the deposition of a cobalt layer on copper using galvanic replacement, facilitated by the special complexing ability of iodide. The results demonstrated that the actual potential of copper could be adjusted to be lower than that of cobalt in a solution containing 8 mol/L NaI, enabling the deposition of a cobalt layer on copper in 15 minutes at 90°C. Furthermore, the deposition rate of the cobalt layer was found to increase with the concentration of CoCl 2 in the NaI solution. Importantly, the Ni-P coating obtained through cobalt layer activation exhibited morphology, structure, and corrosion resistance, friction resistance similar to the Ni-P coating obtained using the common palladium activation. Therefore, the cobalt layer prepared on copper through galvanic replacement may serve as a viable alternative to palladium for activating electroless Ni-P plating. cobalt galvanic replacement electroless Ni-P plating activation corrosion resistance tribology performance 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 1. Introduction The surface treatment process plays a key role in printed circuit board (PCB) reliability as the copper circuit is prone to be oxidated and corroded [ 1 , 2 ] . Electroless nickel electroless palladium immersion gold (ENEPIG) is commonly used as the ideal surface treatment process of PCB for its advantages of good flatness, solderability, corrosion and wear resistance [ 3 , 4 ] . The ENEPIG process mainly uses the electroless plating method to prepare nickel-phosphorus (Ni-P) coating on the surface of copper circuits first, and then uses galvanic replacement plating or electroless plating to deposit palladium and gold coatings on the Ni-P coating to further improve the corrosion resistance, wear resistance and solderability [ 5 , 6 ] . Electroless Ni-P plating can’t proceed on copper circuits in PCB unless an activation process is conducted on copper first owing to the high energy potential barrier of copper to the oxidation of hypophosphite [ 7 , 8 ] . Depositing palladium film on copper circuits by galvanic replacement is commonly adopted as the activation process for PCB owing to the excellent activation ability of palladium [ 9 ] . However, because the copper circuit in PCB becomes finer and the space between copper circuits is narrower, it is easy to generate Ni-P coatings outside the copper circuits, that is, the phenomenon of overflow plating, resulting in PCB failure due to short circuits [ 10 , 11 ] . The reason is that the palladium activation process can lead to the activation of the polymer substrate between the copper circuits, and Ni-P coating will be deposited outside the copper circuits [ 12 , 13 ] . In addition, the rising price of palladium leads to the increasingly high cost of the palladium activation process. Therefore, it is needed to develop a low-cost, high-activity, and easy-to-scale palladium-free activation treatment for PCB copper circuits. In addition to palladium, cobalt can significantly reduce the catalytic oxidation potential of hypophosphite [ 14 , 15 ] , and therefore it also has a good activation ability for electroless Ni-P and Co-P plating. Lin et al. reduced cobalt ions adsorbed on the surface of polypyrrole membrane using sodium borohydride, and then prepared a Ni-Sn-P coating on the surface of polypyrrole membrane by cobalt-activated electroless plating, which significantly improved the hydrophilic separation of the membrane by improving its hydrophilicity significantly [ 16 ] . Zhang et al. prepared Co activators on WC powders by soaking WC powders in a mixed solution of cobalt sulfate heptahydrate and sodium hypophosphite and then heat treated at 220°C, and then achieved electroless cobalt plating on their surface [ 17 , 18 ] . Xu et al. used the ion-exchange reaction to chelate Co 2+ or Ni 2+ cations on the modified Tencel fabric samples and then prepared Co and Ni activators using potassium borohydride solution reduction [ 19 , 20 ] . They compared the activation ability of Co and Ni to deposit Co-Ni-P coating on Tencel fabric surfaces, and the comparison study revealed that the Co-Ni-P plating prepared using Co as the activator has better conductivity and magnetic properties [ 19 ] . The above research indicated that cobalt had a good activation ability for electroless Ni-P coating, but how to prepare cobalt activation layer on copper surface efficiently becomes a problem. Galvanic replacement is one of the convenient methods to prepare metal nanostructures and layers [ 20 , 21 ] . However, since the standard electrode potential of cobalt (Co 2+/Co , − 0.277 V) is lower than that of copper (Cu 2+/Cu , 0.337 V), galvanic replacement deposition of cobalt on copper is generally not possible [ 22 ] . According to the Nernst equation, the actual potential of a metal varies with ion concentration, complexing agent, and temperature. The change in actual potential may reverse the direction of replacement deposition. For example, tin and nickel could be obtained on copper by galvanic replacement when using particular complexing agents [ 23 , 24 ] . In this work, we achieved the galvanic replacement deposition of cobalt on the copper based on the fact that a high concentration of iodine ions in the solution could significantly reduce the actual potential of copper [ 25 ] . With a fixed concentration of NaI, the concentration of cobalt ions had a significant effect on the replacement deposition of cobalt on copper. The cobalt layer obtained by galvanic replacement was able to act as an activator to initiate the electroless Ni-P plating on copper. The morphology, structure, corrosion resistance, and tribology performance of the Ni-P coating obtained on the as-prepared cobalt layer and common palladium layer were characterized to compare the activation ability of the cobalt layer and palladium layer prepared on copper by galvanic replacement. The results showed that the cobalt layer had comparable activation ability for electroless Ni-P plating, and it could serve as an alternative to palladium for activating electroless Ni-P plating. 2. Materials and methods 2.1. Preparation of cobalt and palladium lays on copper Pure copper substrates (99.9%) were first ultrasonically cleaned in hydrochloric acid solution (5 wt.%) for 5 min to remove surface oxides and contaminants, then washed with deionized water and alcohol. The cobalt immersion plating solutions containing 0.05, 0.1, 0.2, 0.4, and 0.8 mol/L CoCl 2 were prepared by adding CoCl 2 ·6H 2 O in 8 mol/L NaI solution. The cleaned copper substrates were then immersed into the above solutions separately, and the immersion plating of cobalt layers on copper was carried out at 90°C for 15 min. For comparison, the conventional palladium layer was prepared on copper substrates by immersion plating in a solution containing 15 g/L NH 4 Cl and 1 g/L PdCl 2 with a pH value of 2.5 for 1 min at 20°C. 2.2. Preparation of Ni-P plating on cobalt and palladium layers The copper substrates with cobalt or palladium immersion layer were placed in acidic or alkaline electroless Ni-P plating baths to prepare Ni-P coating: the commercial acidic plating bath (Atotech 1151, pH = 4.5); the alkaline plating bath containing 50 g/L C 6 H 5 O 7 (NH 4 ) 3 , 10 g/L NH 4 Cl, 30 g/L NiSO 4 ·6H 2 O and 20 g/L NaH 2 PO 2 ·H 2 O (pH = 10.5, adjusted by 40 g/L NaOH solution). The deposition temperature was 85°C and the deposition time was 30 min. After the deposition process, complete and bright Ni-P coatings were obtained on both cobalt and palladium layers. The weight gain of Ni-P coating was used to evaluate the deposition rate of electroless Ni-P plating. 2.3. Characterization of the samples The surface morphology of cobalt layers and Ni-P coatings on cobalt or palladium layers were characterized by scanning electron microscope (FIB-SEM, Crossbeam 540, Zeiss). The elemental composition of the cobalt layers and Ni-P coatings were determined by energy dispersive X-ray spectrometry (EDS, Oxford) and X-ray photoelectron spectrometry (XPS, ESCALAB 250Xi, Thermo Fisher Scientific). The structure of Ni-P coatings was characterized by X-ray diffractometer (XRD, Empyrean, Panalytical) with a grazing angle of 1°. The thickness of the Ni-P coating was determined by optical microscopy (Olympus, PD73). 2.4. Electrochemical measurements Electrochemical experiments were performed using an electrochemistry workstation (µAutolab Ш, Metrohm). An Ag/AgCl electrode (in saturated KCl solution) and a Pt plate (1×1 cm 2 ) were used as reference and counter electrodes, respectively. To evaluate the possibility of replacement deposition of cobalt on copper, the open circuit potential (OCP) of pure copper and cobalt sheets in 0.4 mol/L CoCl 2 ·6H 2 O aqueous solution, 8 mol/L NaI solution or 8 mol/L NaI solution containing 0.4 mol/L CoCl 2 ·6H 2 O were measured at room temperature. To evaluate the corrosion resistance of Ni-P coatings activated by cobalt and palladium layers, potentiodynamic polarization tests were performed in a 3.5 wt.% NaCl solution with a scan rate of 5 mV/s after 30 min of OCP measurements. 2.5. Tribological performance test Before the friction experiment, the surface of the sample was wiped with a dust-free cloth, and the counterface balls was ultrasonically cleaned in ethanol for 5 min to remove surface impurities, and then dried with a hair dryer. Then, the sample and the counterface balls were installed and fixed. When conducting the experiment, three experiments were performed on the same sample under the same conditions, and the three experimental results data were averaged to draw the friction curve. After the friction experiment, the wear track of the Ni-P coatings was first cleaned by ultrasonic in ethanol for 5 min to remove the wear debris on the surface, and then cleaned and dried with deionized water, and then observed by the optical microscope (Olympus, PD73). 3. Results and discussion 3.1. Deposition of cobalt layer on copper by galvanic replacement As shown in Fig. 1 a, the actual potential of cobalt sheet in 0.4 mol/L CoCl 2 solution was − 0.427 V, which was lower than that of copper sheet (− 0.163 V), complying with the metal activity series. Therefore, it was impossible to deposit a cobalt layer on copper by galvanic replacement in CoCl 2 solution. However, the actual potential of copper sheet significantly decreased to − 0.610 V in 8 mol/L NaI solution, while the actual potential of cobalt sheet slightly increased to − 0.195 V. The actual potential of cobalt sheet was higher than that of copper sheet in high concentration NaI solution. That was mainly because of the strong copper complexation and weak cobalt complexation ability of I − . In addition, the actual potential of cobalt sheet (− 0.173 V) was still higher than that of copper sheet (− 0.577 V) in 8 mol/L NaI solution containing 0.4 mol/L CoCl 2 , indicating that copper was likely to react with cobalt ions in this solution. The special complexation ability of I − made the deposition of cobalt layer on copper by galvanic replacement possible. The effect of cobalt ion concentration in NaI solution on depositing cobalt layers on the copper substrate by galvanic replacement was explored. The morphological, compositional and structural characterization results shown in Fig. 2 indicated that the cobalt ion concentration had a significant effect on the galvanic replacement reaction rate between copper substrate and cobalt ions in NaI solution. When the concentration of cobalt ion was 0.05 mol/L, a cobalt layer could be obtained on copper, but there were several cracks and pores, which was the typical phenomenon of galvanic replacement deposition. The cobalt layer was mainly composed of nanoparticles with a size of less than 100 nm, suggesting the fast nucleation process of galvanic replacement reaction. The cobalt content in the sample was 7.23 at.%, indicating that only little cobalt could be deposited on the copper surface. When the concentration of cobalt ion increased to 0.1 mol/L and 0.2 mol/L, the cobalt content in the sample increased to 11.43 at.% and 12.28 at.%, and relatively complete cobalt layers could be obtained. However, there were still a few pores in the cobalt layers. When the concentration of cobalt ions continued to raise to 0.4 mol/L and 0.8 mol/L, complete cobalt layers could be obtained on copper and the cobalt content was increased to 17.06 at.% and 19.72 at.%, respectively. The galvanic replacement deposition rate of cobalt layer was increased with the increase of CoCl 2 concentration in the NaI solution. It could also be found that there was some content of iodine element (less than 1 at.%) in all samples, which was generated owing to the high concentration of iodide in the deposition solution. The diffraction pattern for the cobalt layer obtained from the solution containing 0.4 mol/L Co 2+ was shown in Fig. 2 f. It can be found that there were obvious diffraction peaks of the copper substrate at 43.5°, 50.4°, 74.0°, 89.9° and 95.6° because of the limited thickness of cobalt layer. In addition, the diffraction peak of the cobalt layer at 44.4° was overlayed with the diffraction peak of copper substrate at 43.5°. The diffraction peaks of the cobalt layer at 51.6° was overlayed with the diffraction peak of the copper substrate at 50.4°. The XPS survey showed the existence of Co, Cu, and I elements in the cobalt layer, which was in good agreement with the EDS analysis results. Figure 3 a and 3 b presented the high-resolution 2p spectra in the Co (2p) and I (2p) regions for the as-prepared Co layer from the solution containing 0.4 mol/L Co 2+ . The peaks appearing at 780.5 eV and 796.6 eV in Fig. 3 a were attributed to Co2p3/2 and Co2p1/2, respectively, which corresponded well to metallic Co, confirming the replacement deposition of cobalt on copper. The satellite peaks at 786.2 eV and 804.5 eV and the corresponding oscillation peaks could be attributed to divalent cobalt owing to the oxidation of cobalt. The distinct I3d5/2 and I3d3/2 peaks at 619.0 eV and 630.7 eV presented in Fig. 3 b indicated that partial iodide was generated in the cobalt layers during the replacement deposition of cobalt on copper. Figure 4 a and 4 d show the cross-sectional morphology of the cobalt layer. It can be found that a thin cobalt layer with a thickness of about 200 nm had been deposited on the copper substrate, as verified by the element distribution map shown in Fig. 4 b and 4 c. An obvious interface and some pore defects could be found between the cobalt layer and copper substrate. The pore defects were generated owing to the result of obvious corrosion of the copper substrate caused by the galvanic replacement reaction between the copper substrate and cobalt ions. The cobalt layer was deposited on copper according to the following reactions: Anodic reaction: Cu + 2I − → [CuI 2 ] − + e − (1) Cathodic reaction: Co 2+ + 2e − → Co (2) Copper was eroded in the high concentration I − solution and [CuI 2 ] − was generated because of the strong complexing ability of iodide to copper. Meanwhile, the cobalt ions could be reduced to cobalt and form a compact cobalt layer on copper substrate. This reaction process could be roughly illustrated by Fig. 5 . In order to verify the activation ability of deposited cobalt lay to electroless Ni-P plating, the cobalt layers on copper obtained from 8 mol/L NaI solutions with different Co 2+ concentrations were immersed in the acidic and alkaline electroless Ni-P plating baths, respectively. Figure 6 a shows the weight gain of Ni-P coatings obtained on cobalt layer from acidic or alkaline electroless Ni-P plating bath at 90°C for 30 min. It can be seen that there was no Ni-P coating on the cobalt layer obtained from 0.05 mol/L and 0.1 mol/L CoCl 2 owing to the limited cobalt deposition. When the CoCl 2 concentration increased to 0.2 mol/L, obvious Ni-P could be obtained from both acidic and alkaline electroless plating bath. The weight gain of Ni-P coating (26 mg) in alkaline electroless plating bath was higher than that (14 mg) in acidic electroless plating bath. With the increasing of CoCl 2 concentration in the deposition solution, the weight gain of Ni-P coatings from alkaline electroless plating bath was firstly increased to 36 mg and then decreased to 30 mg. However, the weight gain of Ni-P coating from acidic electroless plating bath was relatively stable. The above results suggested that the sufficient cobalt layer had enough activation ability to initiate electroless Ni-P plating. The morphology, composition and performance of Ni-P coating on cobalt layer obtained from solution containing 0.4 mol/L was characterized and compared with the Ni-P coating on the traditional palladium layer. 3.2 Morphology, composition of Ni-P coatings on cobalt and palladium layers As shown in Fig. 7 , the acidic Ni-P coating obtained on both cobalt and palladium layers was homogeneous and dense, and the EDS results indicated that the phosphorus content in the Ni-P coatings were 19.80 at.% and 18.80 at.%, respectively. The phosphorus content in the Ni-P coating by cobalt layer activation was a little higher than that of the Ni-P coating by palladium layer activation. The crystal structures of the acidic Ni-P coatings prepared on the surfaces of the nickel and palladium layers were characterized by XRD, and it was observed that the acidic Ni-P coating on the surface of the cobalt and palladium layers had similar structures and both were semi-amorphous. There was a main broad peak with 2θ angular range of about 37–55° which corresponds to the nickel plane. The detailed composition of the acidic Ni-P coatings on cobalt and palladium layers obtained from acidic electroless plating solution were analyzed by XPS, and the high-resolution spectra of Ni and P elements were shown in Fig. 8 . It can be found that both Ni-P coatings showed similar nickel and phosphorus spectra, indicating comparable activation ability of cobalt and palladium. As shown in the Ni 2p spectra (Fig. 8 a and Fig. 8 c), most of the cobalt corresponded to nickel metal with binding energies of 851.8 eV and 868.9 eV. Also, there were two other major peaks at 855.5 eV and 873.3 eV and their nearby satellite peaks at binding energies of 858.5 eV and 875.9 eV. This indicated the presence of other nickel-containing compounds due to the oxidation and phosphorylation of nickel [ 26 ] . The spectra of phosphorus (Fig. 8 b and Fig. 8 d) expressed that the peaks at 128.6 eV and 129.4 eV corresponded to P2p3/2 and P2p1/2 of phosphorus in the Ni-P plating [ 27 ] . In addition, the peak positioned at 132.0 eV could be recognized as the hypophosphites or phosphorus in its intermediate chemical states as the solid solution in Ni-P coatings. The binding energy of the two peaks of phosphorus in the Ni-P coating activated by the cobalt layer was lower than that of the phosphorus peak in the Ni-P coating activated by the palladium layer, which might be due to the fact that the phosphorus content in the Ni-P coating activated by the cobalt layer was higher than that in the Ni-P coating activated by the palladium layer. As shown in Fig. 9 , the surface morphology of the Ni-P coatings on cobalt and palladium layers obtained from alkaline electroless plating solution indicated both Ni-P coatings were uniform and dense. The phosphorus content of Ni-P coating activated by the cobalt layer was 7.50%, which was lower than the phosphorus content of Ni-P coating activated by the traditional palladium layer (9.14%). The crystal structures of the Ni-P coatings on cobalt and palladium layers were characterized by XRD, and the two Ni-P coatings had a similar amorphous structure. There was an obvious broad peak between 44.4° and 51.6° could be indexed to the combination of (111) and (200) planes. The other weak and broad peaks at 76.1° and 92.1° could be indexed to (220) and (311) plane of nickel. Figure 10 presents the XPS spectra of Ni-P coatings on cobalt layer and palladium layer obtained from alkaline electroless plating solution, and it can be found that the Ni2p and P2p fine spectra of Ni-P coating activated by cobalt and palladium layers are similar, indicating that the activation capacities of cobalt and palladium are equivalent. From the Ni2p fine spectra (Fig. 10 a and Fig. 10 c), it can be seen that most of the elemental nickel in the Ni-P coating corresponded to metallic nickel with binding energies of 852.00 eV and 869.1 eV, respectively. Also, the remaining two main peaks at 855.6 eV and 873.4 eV, respectively, as well as the nearby satellite peaks at 858.3 eV and 874.8 eV, indicated that other nickel-containing compounds were generated during the oxidation and phosphorylation of nickel in the alkaline Ni-P coating. The spectra of phosphorus (Fig. 10 b and 10 d) show that the peaks at 129.0 eV and 129.8 eV corresponded to P2p3/2 and P2p1/2 of phosphorus in the Ni-P plating, while the other peaks of phosphorus at ~ 132.4 eV were more heterogeneous, with a variety of phosphorus oxides produced during the electroless plating of Ni-P and the oxidation of the surface in air. It can be seen from the cross-sectional morphology of Ni-P coatings on cobalt and palladium layers that all the coatings were compact and bonded well to the copper substrate. Both the Ni-P coatings obtained from the acidic electroless plating bath were thicker than the coatings obtained from the alkaline electroless plating bath. The Ni-P coating on cobalt layer obtained from acidic electroless plating bath had a thickness of 14.6 µm, which was smaller than the Ni-P coating on palladium layer with a thickness of 15.4 µm. The thickness of Ni-P coating on cobalt layer obtained from alkaline electroless plating bath (6.7 µm) was also lower than that of Ni-P coating on palladium layer under the same reaction conditions and reaction time. Although the smaller thickness of Ni-P coatings on cobalt layer suggested that the activation ability of cobalt layer was a littler weaker than that of palladium layer, cobalt layer could still serve as the activation layer to initiate electroless Ni-P plating. 3.3 Corrosion and tribological performance of Ni-P coating on cobalt and palladium layers The corrosion resistance of Ni-P coatings on cobalt and palladium layers obtained from acidic and alkaline electroless plating bath were compared by electrochemical methods in 3.5 wt.% NaCl solutions. As shown in Fig. 12 a, compared with Ni-P coating on palladium layer with the corrosion potential (E corr ) of − 0.483 V and the corresponding corrosion current density (i corr ) of 0.94 µA·cm − 2 , the E corr of Ni-P coating on cobalt layer was decreased to − 0.519 V, and its i corr was increased to 1.63 µA·cm − 2 . The corrosion resistance of Ni-P coating on cobalt layer was a little weaker than that of Ni-P coating on palladium layer. As shown in Fig. 12 b, compared with Ni-P coating on palladium layer obtained from alkaline electroless plating bath with the corrosion potential (E corr ) of − 0.568 V and the corresponding corrosion current density (i corr ) of 1.64 µA·cm − 2 , the E corr of Ni-P coating on cobalt layer was increased to − 0.564 V, and its i corr was decreased to 1.16 µA·cm − 2 . The above results indicated that Ni-P coating on cobalt and palladium layer exhibited similar corrosion resistance, indicating that the activation ability of cobalt and palladium is comparable. The dynamic friction coefficients of the Ni-P coatings measured in reciprocating mode are shown in Fig. 13 a and 13 b. From Fig. 13 a, it can be seen from the friction curves of the acidic Ni-P coating activated by cobalt and palladium that the friction coefficients began stable after the 1000 s wear period, and the friction coefficient after stabilization was 0.178. The friction coefficients of the Ni-P coatings obtained from acidic bath were basically the same, indicating that cobalt and palladium had the same activation effect. From Fig. 13 b, it can be seen that the friction curves of cobalt and palladium activated Ni-P coatings obtained from alkaline bath. The friction coefficient of cobalt activated Ni-P coatings remained stable throughout the friction period, and the friction coefficient after stabilization was 0.038. While the friction coefficient of palladium activated Ni-P coating increased slowly and steadily throughout the friction period. From Fig. 13 c and 13 d, it was obvious that the both cobalt and palladium activated Ni-P coating obtained from acidic bath was severely worn, and an obvious wide wear tract could be found. As can be seen from Fig. 13 e and 13 f, the wear of Ni-P coatings obtained from alkaline bath showed a smaller wear, and the wear tracks were narrow and discontinuous. Although the palladium activated Ni-P coating showed a little slighter were when compared with the cobalt activated Ni-P coating, the cobalt and palladium activated acidic and alkaline Ni-P coating had similar tribological performance. 4. Conclusions In this study, a cobalt layer was deposited on a copper substrate using galvanic replacement from a high concentration of sodium iodide solution containing cobalt chloride. The presence of a high concentration of iodide ions reduces the actual potential of the copper substrate, enabling cobalt ions to react with the substrate and form a cobalt layer on the copper surface. The deposition rate of the cobalt layer was observed to increase with increasing CoCl 2 concentration in the NaI solution. Nickel-phosphorus (Ni-P) coatings could be obtained on the cobalt and palladium layers using acidic and alkaline electroless plating baths. The obtained Ni-P coatings exhibited similar morphology, composition, structure, corrosion resistance, and tribological performance. This finding suggests that the cobalt layer deposited on copper by galvanic replacement can serve as a viable alternative to palladium for activating electroless Ni-P plating on copper substrates. The results of this study also highlight the potential use of galvanic replacement to deposit less noble metallic films. Declarations Author Contribution Guanqun Hu: Investigation, Visualization. Rupeng Li: Investigation, Visualization. Wanda Liao: Investigation, Visualization. Changning Bai: Investigation, Visualization, Writing - review & editing. Xingkai Zhang: Conceptualization, Funding acquisition, Supervision, Writing - original draft. Qiuping Zhao: Supervision, Writing - review & editing. Junyan Zhang: Supervision, Writing - review & editing. Acknowledgement This work was supported by National Natural Science Foundation of China [U22A20180]; Industrial Technology Development Program [JCKY2021130B038]; Lanzhou Youth Science and Technology Talent Innovation Project [2023-QN-82]. References Tseng TH, Wu AT (2019) Corrosion on automobile printed circuit broad. Microelectron Reliab 98:19–23. https://doi.org/10.1016/j.microrel.2019.04.012 Xiao K, Bai Z, Yan L, Yi P, Dong C, Wu J, Hu Y, Xiong R, Li X (2018) Microporous corrosion behavior of gold-plated printed circuit boards in an atmospheric environment with high salinity. J Mater Sci-Mater El 29:8877–8885. https://doi.org/10.1007/s10854-018-8905-7 Ratzker M, Pearl A, Osterman M, Pecht M, Milad G (2014) Review of capabilities of the ENEPIG surface finish. J Electron 43:3885–3897. https://doi.org/10.1007/s11664-014-3322-z Tian R, Tian Y, Huang Y, Yang D, Chen C, Sun H (2021) Comparative study between the Sn–Ag–Cu/ENIG and Sn–Ag–Cu/ENEPIG solder joints under extreme temperature thermal shock. J Mater Sci-Mater El 32:6890–6899. https://doi.org/10.1007/s10854-021-05395-7 Kim J, Jung SB, Yoon JW (2021) Effect of Ni (P) thickness in Au/Pd/Ni (P) surface finish on the electrical reliability of Sn–3.0 Ag–0.5 Cu solder joints during current-stressing. J Alloys Compd 850:156729. https://doi.org/10.1016/j.jallcom.2020.156729 Chi P, Li Y, Pan H, Wang Y, Chen N, Li M, Gao L (2021) Effect of Ni (P) Layer Thickness on Interface Reaction and Reliability of Ultrathin ENEPIG Surface Finish. Mater 14(24):7874. https://doi.org/10.3390/ma14247874 Lin J, Wang C, Wang S, Chen Y, He W, Xiao D (2016) Initiation electroless nickel plating by atomic hydrogen for PCB final finishing. Chem Eng J 306:117–123. https://doi.org/10.1016/j.cej.2016.07.033 Lee HB, Chen KL, Su JW, Lee CY (2020) The use of surfactants and supercritical CO2 assisted processes in the electroless nickel plating of printed circuit board with blind via. Mater Chem Phys 241:122418. https://doi.org/10.1016/j.matchemphys.2019.122418 Wang W, Zhang W, Wang Y, Mitsuzak N, Chen Z (2016) Ductile electroless Ni–P coating onto flexible printed circuit board. Appl Surf Sci 367:528–532. https://doi.org/10.1016/j.apsusc.2016.01.254 Liu D, Tian H, Lin L, Shi W (2019) Improved uniformity of Ni/Au coating on circuits by electroless plating. Surf Eng 35(10):913–918. https://doi.org/10.1080/02670844.2018.1548537 Nothdurft P, Riess G, Kern W (2019) Copper/epoxy joints in printed circuit boards: Manufacturing and interfacial failure mechanisms. Mater 12(3):550. https://doi.org/10.3390/ma12030550 Schlesinger M (2000) Electroless deposition of nickel. Mod electroplating 4:667–684 O'Sullivan EJ, Schrott AG, Paunovic M, Sambucetti CJ, Marino JR, Bailey PJ, Kaja S, Semkow KW (1998) Electrolessly deposited diffusion barriers for microelectronics. Ibm J Res Dev 42(5):607–620. https://doi.org/10.1147/rd.425.0607 Ohno I, Wakabayashi O, Haruyama S (1985) Anodic oxidation of reductants in electroless plating. J Electrochem Soc 132(10):2323. https://doi.org/10.1149/1.2113572 Prins R, Bussell ME (2012) Metal phosphides: preparation, characterization and catalytic reactivity. Catal Lett 142:1413–1436. https://doi.org/10.1007/s10562-012-0929-7 Chen B, Xie H, Shen L, Xu Y, Zhang M, Yu H, Li R, Lin H (2021) Electroless Ni–Sn–P plating to fabricate nickel alloy coated polypropylene membrane with enhanced performance. J Membrane Sci 640:119820. https://doi.org/10.1016/j.memsci.2021.119820 Tong J, Zhang J, Wang Y, Min F, Wang X, Zhang H (2019) Jichang Ma Preparation of Co-plated WC powders by a non-precious-Co-activation triggered electroless plating strategy. Adv Powder Technol 30(10):2311–2319. https://doi.org/10.1016/j.apt.2019.07.012 Guo L, Xiao L, Zhao X, Song Y, Cai Z, Wang H (2017) CB Liu Preparation of WC/Co composite powders by electroless plating. Ceram Int 43(5):4076–4082. https://doi.org/10.1016/j.ceramint.2016.11.220 Bi S, Zhao H, Hou L, Lu Y (2017) Comparative study of electroless Co-Ni-P plating on Tencel fabric by Co0-based and Ni0-based activation for electromagnetic interference shielding. Appl Surf Sci 419:465–475. https://doi.org/10.1016/j.apsusc.2017.04.176 Sarkar S, Baranwal RK, Biswas C (2019) Gautam Majumdar1 and Julfikar Haider Optimization of process parameters for electroless Ni–Co–P coating deposition to maximize micro-hardness. Mater Res Express 6(4):046415. https://doi.org/10.1088/2053-1591/aafc47 Xia X, Wang Y, Ruditskiy A, Xia Y (2013) 25th anniversary article: galvanic replacement: a simple and versatile route to hollow nanostructures with tunable and well-controlled properties. Adv Mater 25(44):6313–6333. https://doi.org/10.1002/adma.201302820 Larson JW, Cerutti P, Garber HK, Hepler LG (1968) Electrode potentials and thermodynamic data for aqueous ions. Copper, zinc, cadmium, iron, cobalt, and nickel. ACS Publications 72(8):2902–2907. https://doi.org/10.1021/j100854a037 Chen Y, Wang Y, Wan C (2007) Microstructural characteristics of immersion tin coatings on copper circuitries in circuit boards. Surf Coat Tech 202(3):417–424. https://doi.org/10.1016/j.surfcoat.2007.06.004 Hu G, Huang R, Wang H, Zhao Q, Zhang X (2022) Facile galvanic replacement deposition of nickel on copper substrate in deep eutectic solvent and its activation ability for electroless Ni–P plating. J Solid State Electr 26(5):1313–1322. https://doi.org/10.1007/s10008-022-05172-4 Zhao Q, Hu G, Huang R, Qiang L, Zhang X (2022) Iodide-induced galvanic replacement of nickel film on copper as activator for electroless nickel-phosphorus plating. Mater Lett 314:131833. https://doi.org/10.1016/j.matlet.2022.131833 Farhan M, Fayyaz O, Nawaz M, Radwan AB, Shakoor RA (2022) Synthesis and properties of electroless Ni–P-HfC nanocomposite coatings. Mater Chem Phys 291:126696. https://doi.org/10.1016/j.matchemphys.2022.126696 Huang H, Xiao Q, Wang J, Yu X, Wang H, Zhang H, Chu P (2017) Black phosphorus: a two-dimensional reductant for in situ nanofabrication. Npj 2d Mater Appl 1(1):20. https://doi.org/10.1038/s41699-017-0022-6 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 21 Jul, 2024 Read the published version in Journal of Applied Electrochemistry → Version 1 posted Editorial decision: Revision requested 16 Jun, 2024 Reviews received at journal 11 Jun, 2024 Reviews received at journal 10 Jun, 2024 Reviews received at journal 01 Jun, 2024 Reviewers agreed at journal 23 May, 2024 Reviewers agreed at journal 21 May, 2024 Reviewers agreed at journal 20 May, 2024 Reviewers invited by journal 19 May, 2024 Editor assigned by journal 20 Apr, 2024 Submission checks completed at journal 20 Apr, 2024 First submitted to journal 19 Apr, 2024 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-4291415","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":293540495,"identity":"25b68778-7159-442f-b2e3-f2ef8d048f0c","order_by":0,"name":"Guanqun Hu","email":"","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Guanqun","middleName":"","lastName":"Hu","suffix":""},{"id":293540496,"identity":"b20fa146-bff8-4abb-8006-2f0dbdc1af0b","order_by":1,"name":"Rupeng Li","email":"","orcid":"","institution":"Lanzhou University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Rupeng","middleName":"","lastName":"Li","suffix":""},{"id":293540497,"identity":"1b80ec5d-2fb2-4379-8669-356090912f08","order_by":2,"name":"Wanda Liao","email":"","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Wanda","middleName":"","lastName":"Liao","suffix":""},{"id":293540498,"identity":"b66fab77-b3b5-48f4-9a07-48788b14c463","order_by":3,"name":"Changning Bai","email":"","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Changning","middleName":"","lastName":"Bai","suffix":""},{"id":293540499,"identity":"b91a8fbc-d690-4b97-857b-b32e1da6d599","order_by":4,"name":"Xingkai Zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABCElEQVRIiWNgGAWjYDACZgYGxgYGCQYDEOdDgQSJWhhnGBCjhQGshQGshZnHgAjlBsd5D7+cUWNhb85+9vBrGwMLeXMG5ocffzDY5eHSItnMl2a54ZgEs2VPXpp1joGE4c4GNmNpHobkYlxa+Jl5zAwfsEmwGRzIMTMGakkwOMDDIM3AcCCxAYcWNrCWfxI8BuffmBlbQLQw//yBRwvQFuOHG9skJAxu5Bg/ZoBoYZPgwaNFspnHjHFmn4SBwY03Zow9IL80s5lZ8xgk49RicP6M8ceeb3X2BudzjD/8qKiTN2dvfnzzR4UdTi0g70igMAyYwSRu9UDA/AGFQUxsjoJRMApGwcgCALB7THXINRJiAAAAAElFTkSuQmCC","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":true,"prefix":"","firstName":"Xingkai","middleName":"","lastName":"Zhang","suffix":""},{"id":293540500,"identity":"3a92191f-3c01-40bc-957c-138254a462e6","order_by":5,"name":"Qiuping Zhao","email":"","orcid":"","institution":"Lanzhou University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Qiuping","middleName":"","lastName":"Zhao","suffix":""},{"id":293540501,"identity":"74e2b248-14fe-4fb6-8483-8731c90a7adf","order_by":6,"name":"Junyan Zhang","email":"","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Junyan","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2024-04-19 07:05:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4291415/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4291415/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10800-024-02177-x","type":"published","date":"2024-07-22T00:33:59+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":55221592,"identity":"63b7059a-aad4-4364-97ab-5ac690024c2b","added_by":"auto","created_at":"2024-04-24 09:17:34","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":102483,"visible":true,"origin":"","legend":"\u003cp\u003eOCP of copper and cobalt in different solutions: (a) CoCl\u003csub\u003e2\u003c/sub\u003e solution; (b) NaI solution; (c) CoCl\u003csub\u003e2\u003c/sub\u003e+NaI solution.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/c79a88198779b376311cfd4f.png"},{"id":55222142,"identity":"64b839b9-145a-4518-8bd6-998826e64f8a","added_by":"auto","created_at":"2024-04-24 09:25:34","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1001203,"visible":true,"origin":"","legend":"\u003cp\u003eSurface morphology and elemental composition of cobalt layers deposited on copper by galvanic replacement in solutions with different Co\u003csup\u003e2+\u003c/sup\u003e concentrations: (a) 0.05 mol/L, (b) 0.1 mol/L, (c) 0.2 mol/L, (d) 0.4 mol/L, (d) 0.8 mol/L. (f) typical XRD pattern of cobalt layer obtained from solution containing 0.4 mol/L Co\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/415d9b4ce154306ae4479f2e.png"},{"id":55222140,"identity":"99ec51ab-42bf-4635-b857-0ad19cf2ace1","added_by":"auto","created_at":"2024-04-24 09:25:34","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":139745,"visible":true,"origin":"","legend":"\u003cp\u003eHigh-resolution XPS patterns of (a) Co, (b) I of Co layer obtained from the solution containing 0.4 mol/L Co\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/cfcb94add33eb6f307e0a942.png"},{"id":55221596,"identity":"437503c6-e85b-4949-91b9-f9b98718be40","added_by":"auto","created_at":"2024-04-24 09:17:34","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":752419,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Cross-sectional morphology of cobalt layers deposited on copper by galvanic replacement n solutions with Co\u003csup\u003e2+\u003c/sup\u003e concentrations of 0.4 mol/L, (b)-(c) the corresponding elemental distribution map. (d) the magnified cross-sectional morphology of cobalt layers.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/7d747de2f09f2ac86dc229fd.png"},{"id":55221600,"identity":"ed8e7757-9b74-4ce0-9239-53bc006ebd58","added_by":"auto","created_at":"2024-04-24 09:17:34","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":700499,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of copper replacement by cobalt ions in solution\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/c7cdaf7e8ff7d04a4352dc9c.png"},{"id":55221594,"identity":"2d5c1353-4af9-4681-9c0c-df43bc8a96b7","added_by":"auto","created_at":"2024-04-24 09:17:34","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":88994,"visible":true,"origin":"","legend":"\u003cp\u003eThe weight gain of Ni-P coatings obtained on cobalt layer from (a) acidic and (b) alkaline electroless plating bath.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/27cfca3b768164118d4c805c.png"},{"id":55222829,"identity":"1f928c43-d672-47f2-8a77-be02176f74e9","added_by":"auto","created_at":"2024-04-24 09:33:34","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":389869,"visible":true,"origin":"","legend":"\u003cp\u003e(a) SEM morphology, (b) EDS energy spectrum and (c) XRD of Ni-P coating on cobalt layer obtained from acidic electroless plating solution. (d) SEM morphology, (e) EDS energy spectrum and (f) XRD of Ni-P coating on palladium layer obtained from acidic electroless plating solution.\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/a75b58a5dbe0509d16ecd6c0.png"},{"id":55221606,"identity":"9b87c6b8-4db1-44af-88cf-00b24d860a6c","added_by":"auto","created_at":"2024-04-24 09:17:34","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":225544,"visible":true,"origin":"","legend":"\u003cp\u003eHigh-resolution XPS spectra of Ni-P coatings on cobalt layer and palladium layer obtained from acidic electroless plating solution. (a) and (c) High-resolution XPS spectra of Ni 2P of Ni-P coatings on cobalt layer; (b) and (d) High-resolution XPS spectra of P2P of Ni-P coatings on palladium layer.\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/20fc6164ce86ed570f7a956b.png"},{"id":55221604,"identity":"200a5364-5e52-4bc8-b002-db4c1f2eb22b","added_by":"auto","created_at":"2024-04-24 09:17:34","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":364746,"visible":true,"origin":"","legend":"\u003cp\u003e(a) SEM morphology, (b) EDS energy spectrum and (c) XRD of Ni-P coating on cobalt layer obtained from alkaline electroless plating solution. (d) SEM morphology, (e) EDS energy spectrum and (f) XRD of Ni-P coating on palladium layer obtained from alkaline electroless plating solution.\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/7bf87514578456f11407e242.png"},{"id":55221603,"identity":"d5905149-2eea-4169-83c5-91cc19e3f0ab","added_by":"auto","created_at":"2024-04-24 09:17:34","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":281781,"visible":true,"origin":"","legend":"\u003cp\u003eHigh-resolution XPS spectra of Ni-P coatings on cobalt layer and palladium layer obtained from alkaline electroless plating solution. (a) and (c) High-resolution XPS spectra of Ni 2P of Ni-P coatings on cobalt layer; (b) and (d) High-resolution XPS spectra of P2P of Ni-P coatings on palladium layer.\u003c/p\u003e","description":"","filename":"image10.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/be6edfd75893fb19620c232f.png"},{"id":55221607,"identity":"bfe7a116-b0f4-4867-b9fa-1efb88b97ab6","added_by":"auto","created_at":"2024-04-24 09:17:34","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":1099849,"visible":true,"origin":"","legend":"\u003cp\u003eCross-sectional morphology of Ni-P coatings on cobalt and palladium layers obtained from alkaline and acidic electroless plating bath. (a) Ni-P coating on cobalt layer and (b) Ni-P coating on palladium layer obtained from alkaline electroless plating bath; (c) Ni-P coating on cobalt layer and (d) Ni-P coating on palladium layer obtained from acidic electroless plating bath.\u003c/p\u003e","description":"","filename":"image11.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/cfc1776d3615457ec82c7d57.png"},{"id":55222143,"identity":"9e2c0898-be08-403c-9466-a7e62d8ba5bd","added_by":"auto","created_at":"2024-04-24 09:25:34","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":106882,"visible":true,"origin":"","legend":"\u003cp\u003eThe potentiodynamic polarization plots of Ni-P coatings on cobalt and palladium layers obtained from (a) acidic electroless plating bath and (b) alkaline electroless plating bath.\u003c/p\u003e","description":"","filename":"image12.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/bdf680adba42b77e44419f87.png"},{"id":55221602,"identity":"2bfa84e4-44c6-48f0-a19f-4043dc37f95f","added_by":"auto","created_at":"2024-04-24 09:17:34","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":681672,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Friction coefficient graphs and (b) wear track micrographs of Ni-P coatings obtained from acidic and alkaline baths. (c) Ni-P coatings on cobalt layer and (d) Ni-P coatings on palladium layer obtained from acidic bath; (e) Ni-P coatings on cobalt layer and (f) Ni-P coatings on palladium layer obtained from alkaline bath.\u003c/p\u003e","description":"","filename":"image13.png","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/969bdf76044b0d5cdf39ff35.png"},{"id":60858373,"identity":"1dd7f978-1751-4340-a4ee-ce652e9ac1fc","added_by":"auto","created_at":"2024-07-23 00:34:07","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":7140643,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4291415/v1/83f74f84-b091-4de1-aec6-732532775410.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Cobalt layer prepared on copper using galvanic replacement as an alternative to palladium for activating electroless Ni-P plating","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe surface treatment process plays a key role in printed circuit board (PCB) reliability as the copper circuit is prone to be oxidated and corroded \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. Electroless nickel electroless palladium immersion gold (ENEPIG) is commonly used as the ideal surface treatment process of PCB for its advantages of good flatness, solderability, corrosion and wear resistance \u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. The ENEPIG process mainly uses the electroless plating method to prepare nickel-phosphorus (Ni-P) coating on the surface of copper circuits first, and then uses galvanic replacement plating or electroless plating to deposit palladium and gold coatings on the Ni-P coating to further improve the corrosion resistance, wear resistance and solderability \u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eElectroless Ni-P plating can\u0026rsquo;t proceed on copper circuits in PCB unless an activation process is conducted on copper first owing to the high energy potential barrier of copper to the oxidation of hypophosphite \u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. Depositing palladium film on copper circuits by galvanic replacement is commonly adopted as the activation process for PCB owing to the excellent activation ability of palladium \u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. However, because the copper circuit in PCB becomes finer and the space between copper circuits is narrower, it is easy to generate Ni-P coatings outside the copper circuits, that is, the phenomenon of overflow plating, resulting in PCB failure due to short circuits \u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. The reason is that the palladium activation process can lead to the activation of the polymer substrate between the copper circuits, and Ni-P coating will be deposited outside the copper circuits \u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e. In addition, the rising price of palladium leads to the increasingly high cost of the palladium activation process. Therefore, it is needed to develop a low-cost, high-activity, and easy-to-scale palladium-free activation treatment for PCB copper circuits.\u003c/p\u003e \u003cp\u003eIn addition to palladium, cobalt can significantly reduce the catalytic oxidation potential of hypophosphite \u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e, and therefore it also has a good activation ability for electroless Ni-P and Co-P plating. Lin et al. reduced cobalt ions adsorbed on the surface of polypyrrole membrane using sodium borohydride, and then prepared a Ni-Sn-P coating on the surface of polypyrrole membrane by cobalt-activated electroless plating, which significantly improved the hydrophilic separation of the membrane by improving its hydrophilicity significantly \u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. Zhang et al. prepared Co activators on WC powders by soaking WC powders in a mixed solution of cobalt sulfate heptahydrate and sodium hypophosphite and then heat treated at 220\u0026deg;C, and then achieved electroless cobalt plating on their surface \u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e. Xu et al. used the ion-exchange reaction to chelate Co\u003csup\u003e2+\u003c/sup\u003e or Ni\u003csup\u003e2+\u003c/sup\u003e cations on the modified Tencel fabric samples and then prepared Co and Ni activators using potassium borohydride solution reduction\u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. They compared the activation ability of Co and Ni to deposit Co-Ni-P coating on Tencel fabric surfaces, and the comparison study revealed that the Co-Ni-P plating prepared using Co as the activator has better conductivity and magnetic properties \u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e .\u003c/p\u003e \u003cp\u003eThe above research indicated that cobalt had a good activation ability for electroless Ni-P coating, but how to prepare cobalt activation layer on copper surface efficiently becomes a problem. Galvanic replacement is one of the convenient methods to prepare metal nanostructures and layers \u003csup\u003e[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e. However, since the standard electrode potential of cobalt (Co\u003csub\u003e2+/Co\u003c/sub\u003e, \u0026minus;\u0026thinsp;0.277 V) is lower than that of copper (Cu\u003csub\u003e2+/Cu\u003c/sub\u003e, 0.337 V), galvanic replacement deposition of cobalt on copper is generally not possible \u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAccording to the Nernst equation, the actual potential of a metal varies with ion concentration, complexing agent, and temperature. The change in actual potential may reverse the direction of replacement deposition. For example, tin and nickel could be obtained on copper by galvanic replacement when using particular complexing agents \u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e. In this work, we achieved the galvanic replacement deposition of cobalt on the copper based on the fact that a high concentration of iodine ions in the solution could significantly reduce the actual potential of copper \u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e. With a fixed concentration of NaI, the concentration of cobalt ions had a significant effect on the replacement deposition of cobalt on copper. The cobalt layer obtained by galvanic replacement was able to act as an activator to initiate the electroless Ni-P plating on copper. The morphology, structure, corrosion resistance, and tribology performance of the Ni-P coating obtained on the as-prepared cobalt layer and common palladium layer were characterized to compare the activation ability of the cobalt layer and palladium layer prepared on copper by galvanic replacement. The results showed that the cobalt layer had comparable activation ability for electroless Ni-P plating, and it could serve as an alternative to palladium for activating electroless Ni-P plating.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Preparation of cobalt and palladium lays on copper\u003c/h2\u003e \u003cp\u003ePure copper substrates (99.9%) were first ultrasonically cleaned in hydrochloric acid solution (5 wt.%) for 5 min to remove surface oxides and contaminants, then washed with deionized water and alcohol. The cobalt immersion plating solutions containing 0.05, 0.1, 0.2, 0.4, and 0.8 mol/L CoCl\u003csub\u003e2\u003c/sub\u003e were prepared by adding CoCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO in 8 mol/L NaI solution. The cleaned copper substrates were then immersed into the above solutions separately, and the immersion plating of cobalt layers on copper was carried out at 90\u0026deg;C for 15 min. For comparison, the conventional palladium layer was prepared on copper substrates by immersion plating in a solution containing 15 g/L NH\u003csub\u003e4\u003c/sub\u003eCl and 1 g/L PdCl\u003csub\u003e2\u003c/sub\u003e with a pH value of 2.5 for 1 min at 20\u0026deg;C.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Preparation of Ni-P plating on cobalt and palladium layers\u003c/h2\u003e \u003cp\u003eThe copper substrates with cobalt or palladium immersion layer were placed in acidic or alkaline electroless Ni-P plating baths to prepare Ni-P coating: the commercial acidic plating bath (Atotech 1151, pH\u0026thinsp;=\u0026thinsp;4.5); the alkaline plating bath containing 50 g/L C\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e(NH\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e, 10 g/L NH\u003csub\u003e4\u003c/sub\u003eCl, 30 g/L NiSO\u003csub\u003e4\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO and 20 g/L NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e2\u003c/sub\u003e\u0026middot;H\u003csub\u003e2\u003c/sub\u003eO (pH\u0026thinsp;=\u0026thinsp;10.5, adjusted by 40 g/L NaOH solution). The deposition temperature was 85\u0026deg;C and the deposition time was 30 min. After the deposition process, complete and bright Ni-P coatings were obtained on both cobalt and palladium layers. The weight gain of Ni-P coating was used to evaluate the deposition rate of electroless Ni-P plating.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Characterization of the samples\u003c/h2\u003e \u003cp\u003eThe surface morphology of cobalt layers and Ni-P coatings on cobalt or palladium layers were characterized by scanning electron microscope (FIB-SEM, Crossbeam 540, Zeiss). The elemental composition of the cobalt layers and Ni-P coatings were determined by energy dispersive X-ray spectrometry (EDS, Oxford) and X-ray photoelectron spectrometry (XPS, ESCALAB 250Xi, Thermo Fisher Scientific). The structure of Ni-P coatings was characterized by X-ray diffractometer (XRD, Empyrean, Panalytical) with a grazing angle of 1\u0026deg;. The thickness of the Ni-P coating was determined by optical microscopy (Olympus, PD73).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Electrochemical measurements\u003c/h2\u003e \u003cp\u003eElectrochemical experiments were performed using an electrochemistry workstation (\u0026micro;Autolab Ш, Metrohm). An Ag/AgCl electrode (in saturated KCl solution) and a Pt plate (1\u0026times;1 cm\u003csup\u003e2\u003c/sup\u003e) were used as reference and counter electrodes, respectively. To evaluate the possibility of replacement deposition of cobalt on copper, the open circuit potential (OCP) of pure copper and cobalt sheets in 0.4 mol/L CoCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO aqueous solution, 8 mol/L NaI solution or 8 mol/L NaI solution containing 0.4 mol/L CoCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO were measured at room temperature. To evaluate the corrosion resistance of Ni-P coatings activated by cobalt and palladium layers, potentiodynamic polarization tests were performed in a 3.5 wt.% NaCl solution with a scan rate of 5 mV/s after 30 min of OCP measurements.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Tribological performance test\u003c/h2\u003e \u003cp\u003eBefore the friction experiment, the surface of the sample was wiped with a dust-free cloth, and the counterface balls was ultrasonically cleaned in ethanol for 5 min to remove surface impurities, and then dried with a hair dryer. Then, the sample and the counterface balls were installed and fixed. When conducting the experiment, three experiments were performed on the same sample under the same conditions, and the three experimental results data were averaged to draw the friction curve. After the friction experiment, the wear track of the Ni-P coatings was first cleaned by ultrasonic in ethanol for 5 min to remove the wear debris on the surface, and then cleaned and dried with deionized water, and then observed by the optical microscope (Olympus, PD73).\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Deposition of cobalt layer on copper by galvanic replacement\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea, the actual potential of cobalt sheet in 0.4 mol/L CoCl\u003csub\u003e2\u003c/sub\u003e solution was \u0026minus;\u0026thinsp;0.427 V, which was lower than that of copper sheet (\u0026minus;\u0026thinsp;0.163 V), complying with the metal activity series. Therefore, it was impossible to deposit a cobalt layer on copper by galvanic replacement in CoCl\u003csub\u003e2\u003c/sub\u003e solution. However, the actual potential of copper sheet significantly decreased to \u0026minus;\u0026thinsp;0.610 V in 8 mol/L NaI solution, while the actual potential of cobalt sheet slightly increased to \u0026minus;\u0026thinsp;0.195 V. The actual potential of cobalt sheet was higher than that of copper sheet in high concentration NaI solution. That was mainly because of the strong copper complexation and weak cobalt complexation ability of I\u003csup\u003e\u0026minus;\u003c/sup\u003e. In addition, the actual potential of cobalt sheet (\u0026minus;\u0026thinsp;0.173 V) was still higher than that of copper sheet (\u0026minus;\u0026thinsp;0.577 V) in 8 mol/L NaI solution containing 0.4 mol/L CoCl\u003csub\u003e2\u003c/sub\u003e, indicating that copper was likely to react with cobalt ions in this solution. The special complexation ability of I\u003csup\u003e\u0026minus;\u003c/sup\u003e made the deposition of cobalt layer on copper by galvanic replacement possible.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe effect of cobalt ion concentration in NaI solution on depositing cobalt layers on the copper substrate by galvanic replacement was explored. The morphological, compositional and structural characterization results shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e indicated that the cobalt ion concentration had a significant effect on the galvanic replacement reaction rate between copper substrate and cobalt ions in NaI solution. When the concentration of cobalt ion was 0.05 mol/L, a cobalt layer could be obtained on copper, but there were several cracks and pores, which was the typical phenomenon of galvanic replacement deposition. The cobalt layer was mainly composed of nanoparticles with a size of less than 100 nm, suggesting the fast nucleation process of galvanic replacement reaction. The cobalt content in the sample was 7.23 at.%, indicating that only little cobalt could be deposited on the copper surface. When the concentration of cobalt ion increased to 0.1 mol/L and 0.2 mol/L, the cobalt content in the sample increased to 11.43 at.% and 12.28 at.%, and relatively complete cobalt layers could be obtained. However, there were still a few pores in the cobalt layers. When the concentration of cobalt ions continued to raise to 0.4 mol/L and 0.8 mol/L, complete cobalt layers could be obtained on copper and the cobalt content was increased to 17.06 at.% and 19.72 at.%, respectively. The galvanic replacement deposition rate of cobalt layer was increased with the increase of CoCl\u003csub\u003e2\u003c/sub\u003e concentration in the NaI solution. It could also be found that there was some content of iodine element (less than 1 at.%) in all samples, which was generated owing to the high concentration of iodide in the deposition solution.\u003c/p\u003e \u003cp\u003eThe diffraction pattern for the cobalt layer obtained from the solution containing 0.4 mol/L Co\u003csup\u003e2+\u003c/sup\u003e was shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef. It can be found that there were obvious diffraction peaks of the copper substrate at 43.5\u0026deg;, 50.4\u0026deg;, 74.0\u0026deg;, 89.9\u0026deg; and 95.6\u0026deg; because of the limited thickness of cobalt layer. In addition, the diffraction peak of the cobalt layer at 44.4\u0026deg; was overlayed with the diffraction peak of copper substrate at 43.5\u0026deg;. The diffraction peaks of the cobalt layer at 51.6\u0026deg; was overlayed with the diffraction peak of the copper substrate at 50.4\u0026deg;.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe XPS survey showed the existence of Co, Cu, and I elements in the cobalt layer, which was in good agreement with the EDS analysis results. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb presented the high-resolution 2p spectra in the Co (2p) and I (2p) regions for the as-prepared Co layer from the solution containing 0.4 mol/L Co\u003csup\u003e2+\u003c/sup\u003e. The peaks appearing at 780.5 eV and 796.6 eV in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea were attributed to Co2p3/2 and Co2p1/2, respectively, which corresponded well to metallic Co, confirming the replacement deposition of cobalt on copper. The satellite peaks at 786.2 eV and 804.5 eV and the corresponding oscillation peaks could be attributed to divalent cobalt owing to the oxidation of cobalt. The distinct I3d5/2 and I3d3/2 peaks at 619.0 eV and 630.7 eV presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb indicated that partial iodide was generated in the cobalt layers during the replacement deposition of cobalt on copper.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed show the cross-sectional morphology of the cobalt layer. It can be found that a thin cobalt layer with a thickness of about 200 nm had been deposited on the copper substrate, as verified by the element distribution map shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec. An obvious interface and some pore defects could be found between the cobalt layer and copper substrate. The pore defects were generated owing to the result of obvious corrosion of the copper substrate caused by the galvanic replacement reaction between the copper substrate and cobalt ions. The cobalt layer was deposited on copper according to the following reactions:\u003c/p\u003e \u003cp\u003eAnodic reaction: Cu\u0026thinsp;+\u0026thinsp;2I\u003csup\u003e\u0026minus;\u003c/sup\u003e \u0026rarr; [CuI\u003csub\u003e2\u003c/sub\u003e]\u003csup\u003e\u0026minus;\u003c/sup\u003e + e\u003csup\u003e\u0026minus;\u003c/sup\u003e (1)\u003c/p\u003e \u003cp\u003eCathodic reaction: Co\u003csup\u003e2+\u003c/sup\u003e + 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e \u0026rarr; Co (2)\u003c/p\u003e \u003cp\u003eCopper was eroded in the high concentration I\u003csup\u003e\u0026minus;\u003c/sup\u003e solution and [CuI\u003csub\u003e2\u003c/sub\u003e]\u003csup\u003e\u0026minus;\u003c/sup\u003e was generated because of the strong complexing ability of iodide to copper. Meanwhile, the cobalt ions could be reduced to cobalt and form a compact cobalt layer on copper substrate. This reaction process could be roughly illustrated by Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn order to verify the activation ability of deposited cobalt lay to electroless Ni-P plating, the cobalt layers on copper obtained from 8 mol/L NaI solutions with different Co\u003csup\u003e2+\u003c/sup\u003e concentrations were immersed in the acidic and alkaline electroless Ni-P plating baths, respectively. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea shows the weight gain of Ni-P coatings obtained on cobalt layer from acidic or alkaline electroless Ni-P plating bath at 90\u0026deg;C for 30 min. It can be seen that there was no Ni-P coating on the cobalt layer obtained from 0.05 mol/L and 0.1 mol/L CoCl\u003csub\u003e2\u003c/sub\u003e owing to the limited cobalt deposition. When the CoCl\u003csub\u003e2\u003c/sub\u003e concentration increased to 0.2 mol/L, obvious Ni-P could be obtained from both acidic and alkaline electroless plating bath. The weight gain of Ni-P coating (26 mg) in alkaline electroless plating bath was higher than that (14 mg) in acidic electroless plating bath. With the increasing of CoCl\u003csub\u003e2\u003c/sub\u003e concentration in the deposition solution, the weight gain of Ni-P coatings from alkaline electroless plating bath was firstly increased to 36 mg and then decreased to 30 mg. However, the weight gain of Ni-P coating from acidic electroless plating bath was relatively stable. The above results suggested that the sufficient cobalt layer had enough activation ability to initiate electroless Ni-P plating.\u003c/p\u003e \u003cp\u003eThe morphology, composition and performance of Ni-P coating on cobalt layer obtained from solution containing 0.4 mol/L was characterized and compared with the Ni-P coating on the traditional palladium layer.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Morphology, composition of Ni-P coatings on cobalt and palladium layers\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, the acidic Ni-P coating obtained on both cobalt and palladium layers was homogeneous and dense, and the EDS results indicated that the phosphorus content in the Ni-P coatings were 19.80 at.% and 18.80 at.%, respectively. The phosphorus content in the Ni-P coating by cobalt layer activation was a little higher than that of the Ni-P coating by palladium layer activation. The crystal structures of the acidic Ni-P coatings prepared on the surfaces of the nickel and palladium layers were characterized by XRD, and it was observed that the acidic Ni-P coating on the surface of the cobalt and palladium layers had similar structures and both were semi-amorphous. There was a main broad peak with 2θ angular range of about 37\u0026ndash;55\u0026deg; which corresponds to the nickel plane.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe detailed composition of the acidic Ni-P coatings on cobalt and palladium layers obtained from acidic electroless plating solution were analyzed by XPS, and the high-resolution spectra of Ni and P elements were shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. It can be found that both Ni-P coatings showed similar nickel and phosphorus spectra, indicating comparable activation ability of cobalt and palladium.\u003c/p\u003e \u003cp\u003eAs shown in the Ni 2p spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea and Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec), most of the cobalt corresponded to nickel metal with binding energies of 851.8 eV and 868.9 eV. Also, there were two other major peaks at 855.5 eV and 873.3 eV and their nearby satellite peaks at binding energies of 858.5 eV and 875.9 eV. This indicated the presence of other nickel-containing compounds due to the oxidation and phosphorylation of nickel \u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. The spectra of phosphorus (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb and Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ed) expressed that the peaks at 128.6 eV and 129.4 eV corresponded to P2p3/2 and P2p1/2 of phosphorus in the Ni-P plating \u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e. In addition, the peak positioned at 132.0 eV could be recognized as the hypophosphites or phosphorus in its intermediate chemical states as the solid solution in Ni-P coatings. The binding energy of the two peaks of phosphorus in the Ni-P coating activated by the cobalt layer was lower than that of the phosphorus peak in the Ni-P coating activated by the palladium layer, which might be due to the fact that the phosphorus content in the Ni-P coating activated by the cobalt layer was higher than that in the Ni-P coating activated by the palladium layer.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, the surface morphology of the Ni-P coatings on cobalt and palladium layers obtained from alkaline electroless plating solution indicated both Ni-P coatings were uniform and dense. The phosphorus content of Ni-P coating activated by the cobalt layer was 7.50%, which was lower than the phosphorus content of Ni-P coating activated by the traditional palladium layer (9.14%). The crystal structures of the Ni-P coatings on cobalt and palladium layers were characterized by XRD, and the two Ni-P coatings had a similar amorphous structure. There was an obvious broad peak between 44.4\u0026deg; and 51.6\u0026deg; could be indexed to the combination of (111) and (200) planes. The other weak and broad peaks at 76.1\u0026deg; and 92.1\u0026deg; could be indexed to (220) and (311) plane of nickel.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e presents the XPS spectra of Ni-P coatings on cobalt layer and palladium layer obtained from alkaline electroless plating solution, and it can be found that the Ni2p and P2p fine spectra of Ni-P coating activated by cobalt and palladium layers are similar, indicating that the activation capacities of cobalt and palladium are equivalent. From the Ni2p fine spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ea and Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ec), it can be seen that most of the elemental nickel in the Ni-P coating corresponded to metallic nickel with binding energies of 852.00 eV and 869.1 eV, respectively. Also, the remaining two main peaks at 855.6 eV and 873.4 eV, respectively, as well as the nearby satellite peaks at 858.3 eV and 874.8 eV, indicated that other nickel-containing compounds were generated during the oxidation and phosphorylation of nickel in the alkaline Ni-P coating. The spectra of phosphorus (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003eb and \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ed) show that the peaks at 129.0 eV and 129.8 eV corresponded to P2p3/2 and P2p1/2 of phosphorus in the Ni-P plating, while the other peaks of phosphorus at ~\u0026thinsp;132.4 eV were more heterogeneous, with a variety of phosphorus oxides produced during the electroless plating of Ni-P and the oxidation of the surface in air.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIt can be seen from the cross-sectional morphology of Ni-P coatings on cobalt and palladium layers that all the coatings were compact and bonded well to the copper substrate. Both the Ni-P coatings obtained from the acidic electroless plating bath were thicker than the coatings obtained from the alkaline electroless plating bath. The Ni-P coating on cobalt layer obtained from acidic electroless plating bath had a thickness of 14.6 \u0026micro;m, which was smaller than the Ni-P coating on palladium layer with a thickness of 15.4 \u0026micro;m. The thickness of Ni-P coating on cobalt layer obtained from alkaline electroless plating bath (6.7 \u0026micro;m) was also lower than that of Ni-P coating on palladium layer under the same reaction conditions and reaction time. Although the smaller thickness of Ni-P coatings on cobalt layer suggested that the activation ability of cobalt layer was a littler weaker than that of palladium layer, cobalt layer could still serve as the activation layer to initiate electroless Ni-P plating.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Corrosion and tribological performance of Ni-P coating on cobalt and palladium layers\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe corrosion resistance of Ni-P coatings on cobalt and palladium layers obtained from acidic and alkaline electroless plating bath were compared by electrochemical methods in 3.5 wt.% NaCl solutions. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003ea, compared with Ni-P coating on palladium layer with the corrosion potential (E\u003csub\u003ecorr\u003c/sub\u003e) of \u0026minus;\u0026thinsp;0.483 V and the corresponding corrosion current density (i\u003csub\u003ecorr\u003c/sub\u003e) of 0.94 \u0026micro;A\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, the E\u003csub\u003ecorr\u003c/sub\u003e of Ni-P coating on cobalt layer was decreased to \u0026minus;\u0026thinsp;0.519 V, and its i\u003csub\u003ecorr\u003c/sub\u003e was increased to 1.63 \u0026micro;A\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. The corrosion resistance of Ni-P coating on cobalt layer was a little weaker than that of Ni-P coating on palladium layer. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003eb, compared with Ni-P coating on palladium layer obtained from alkaline electroless plating bath with the corrosion potential (E\u003csub\u003ecorr\u003c/sub\u003e) of \u0026minus;\u0026thinsp;0.568 V and the corresponding corrosion current density (i\u003csub\u003ecorr\u003c/sub\u003e) of 1.64 \u0026micro;A\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, the E\u003csub\u003ecorr\u003c/sub\u003e of Ni-P coating on cobalt layer was increased to \u0026minus;\u0026thinsp;0.564 V, and its i\u003csub\u003ecorr\u003c/sub\u003e was decreased to 1.16 \u0026micro;A\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. The above results indicated that Ni-P coating on cobalt and palladium layer exhibited similar corrosion resistance, indicating that the activation ability of cobalt and palladium is comparable.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe dynamic friction coefficients of the Ni-P coatings measured in reciprocating mode are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003ea and \u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003eb. From Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003ea, it can be seen from the friction curves of the acidic Ni-P coating activated by cobalt and palladium that the friction coefficients began stable after the 1000 s wear period, and the friction coefficient after stabilization was 0.178. The friction coefficients of the Ni-P coatings obtained from acidic bath were basically the same, indicating that cobalt and palladium had the same activation effect. From Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003eb, it can be seen that the friction curves of cobalt and palladium activated Ni-P coatings obtained from alkaline bath. The friction coefficient of cobalt activated Ni-P coatings remained stable throughout the friction period, and the friction coefficient after stabilization was 0.038. While the friction coefficient of palladium activated Ni-P coating increased slowly and steadily throughout the friction period. From Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003ec and \u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003ed, it was obvious that the both cobalt and palladium activated Ni-P coating obtained from acidic bath was severely worn, and an obvious wide wear tract could be found. As can be seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003ee and \u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003ef, the wear of Ni-P coatings obtained from alkaline bath showed a smaller wear, and the wear tracks were narrow and discontinuous. Although the palladium activated Ni-P coating showed a little slighter were when compared with the cobalt activated Ni-P coating, the cobalt and palladium activated acidic and alkaline Ni-P coating had similar tribological performance.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn this study, a cobalt layer was deposited on a copper substrate using galvanic replacement from a high concentration of sodium iodide solution containing cobalt chloride. The presence of a high concentration of iodide ions reduces the actual potential of the copper substrate, enabling cobalt ions to react with the substrate and form a cobalt layer on the copper surface. The deposition rate of the cobalt layer was observed to increase with increasing CoCl\u003csub\u003e2\u003c/sub\u003e concentration in the NaI solution. Nickel-phosphorus (Ni-P) coatings could be obtained on the cobalt and palladium layers using acidic and alkaline electroless plating baths. The obtained Ni-P coatings exhibited similar morphology, composition, structure, corrosion resistance, and tribological performance. This finding suggests that the cobalt layer deposited on copper by galvanic replacement can serve as a viable alternative to palladium for activating electroless Ni-P plating on copper substrates. The results of this study also highlight the potential use of galvanic replacement to deposit less noble metallic films.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eGuanqun Hu: Investigation, Visualization. Rupeng Li: Investigation, Visualization. Wanda Liao: Investigation, Visualization. Changning Bai: Investigation, Visualization, Writing - review \u0026amp; editing. Xingkai Zhang: Conceptualization, Funding acquisition, Supervision, Writing - original draft. Qiuping Zhao: Supervision, Writing - review \u0026amp; editing. Junyan Zhang: Supervision, Writing - review \u0026amp; editing.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e \u003cp\u003eThis work was supported by National Natural Science Foundation of China [U22A20180]; Industrial Technology Development Program [JCKY2021130B038]; Lanzhou Youth Science and Technology Talent Innovation Project [2023-QN-82].\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eTseng TH, Wu AT (2019) Corrosion on automobile printed circuit broad. Microelectron Reliab 98:19\u0026ndash;23. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.microrel.2019.04.012\u003c/span\u003e\u003cspan address=\"10.1016/j.microrel.2019.04.012\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXiao K, Bai Z, Yan L, Yi P, Dong C, Wu J, Hu Y, Xiong R, Li X (2018) Microporous corrosion behavior of gold-plated printed circuit boards in an atmospheric environment with high salinity. J Mater Sci-Mater El 29:8877\u0026ndash;8885. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10854-018-8905-7\u003c/span\u003e\u003cspan address=\"10.1007/s10854-018-8905-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRatzker M, Pearl A, Osterman M, Pecht M, Milad G (2014) Review of capabilities of the ENEPIG surface finish. J Electron 43:3885\u0026ndash;3897. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11664-014-3322-z\u003c/span\u003e\u003cspan address=\"10.1007/s11664-014-3322-z\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTian R, Tian Y, Huang Y, Yang D, Chen C, Sun H (2021) Comparative study between the Sn\u0026ndash;Ag\u0026ndash;Cu/ENIG and Sn\u0026ndash;Ag\u0026ndash;Cu/ENEPIG solder joints under extreme temperature thermal shock. J Mater Sci-Mater El 32:6890\u0026ndash;6899. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10854-021-05395-7\u003c/span\u003e\u003cspan address=\"10.1007/s10854-021-05395-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim J, Jung SB, Yoon JW (2021) Effect of Ni (P) thickness in Au/Pd/Ni (P) surface finish on the electrical reliability of Sn\u0026ndash;3.0 Ag\u0026ndash;0.5 Cu solder joints during current-stressing. J Alloys Compd 850:156729. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jallcom.2020.156729\u003c/span\u003e\u003cspan address=\"10.1016/j.jallcom.2020.156729\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChi P, Li Y, Pan H, Wang Y, Chen N, Li M, Gao L (2021) Effect of Ni (P) Layer Thickness on Interface Reaction and Reliability of Ultrathin ENEPIG Surface Finish. Mater 14(24):7874. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/ma14247874\u003c/span\u003e\u003cspan address=\"10.3390/ma14247874\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLin J, Wang C, Wang S, Chen Y, He W, Xiao D (2016) Initiation electroless nickel plating by atomic hydrogen for PCB final finishing. Chem Eng J 306:117\u0026ndash;123. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.cej.2016.07.033\u003c/span\u003e\u003cspan address=\"10.1016/j.cej.2016.07.033\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee HB, Chen KL, Su JW, Lee CY (2020) The use of surfactants and supercritical CO2 assisted processes in the electroless nickel plating of printed circuit board with blind via. Mater Chem Phys 241:122418. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.matchemphys.2019.122418\u003c/span\u003e\u003cspan address=\"10.1016/j.matchemphys.2019.122418\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang W, Zhang W, Wang Y, Mitsuzak N, Chen Z (2016) Ductile electroless Ni\u0026ndash;P coating onto flexible printed circuit board. Appl Surf Sci 367:528\u0026ndash;532. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.apsusc.2016.01.254\u003c/span\u003e\u003cspan address=\"10.1016/j.apsusc.2016.01.254\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu D, Tian H, Lin L, Shi W (2019) Improved uniformity of Ni/Au coating on circuits by electroless plating. Surf Eng 35(10):913\u0026ndash;918. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/02670844.2018.1548537\u003c/span\u003e\u003cspan address=\"10.1080/02670844.2018.1548537\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNothdurft P, Riess G, Kern W (2019) Copper/epoxy joints in printed circuit boards: Manufacturing and interfacial failure mechanisms. Mater 12(3):550. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/ma12030550\u003c/span\u003e\u003cspan address=\"10.3390/ma12030550\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchlesinger M (2000) Electroless deposition of nickel. Mod electroplating 4:667\u0026ndash;684\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eO'Sullivan EJ, Schrott AG, Paunovic M, Sambucetti CJ, Marino JR, Bailey PJ, Kaja S, Semkow KW (1998) Electrolessly deposited diffusion barriers for microelectronics. Ibm J Res Dev 42(5):607\u0026ndash;620. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1147/rd.425.0607\u003c/span\u003e\u003cspan address=\"10.1147/rd.425.0607\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOhno I, Wakabayashi O, Haruyama S (1985) Anodic oxidation of reductants in electroless plating. J Electrochem Soc 132(10):2323. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1149/1.2113572\u003c/span\u003e\u003cspan address=\"10.1149/1.2113572\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePrins R, Bussell ME (2012) Metal phosphides: preparation, characterization and catalytic reactivity. Catal Lett 142:1413\u0026ndash;1436. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10562-012-0929-7\u003c/span\u003e\u003cspan address=\"10.1007/s10562-012-0929-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen B, Xie H, Shen L, Xu Y, Zhang M, Yu H, Li R, Lin H (2021) Electroless Ni\u0026ndash;Sn\u0026ndash;P plating to fabricate nickel alloy coated polypropylene membrane with enhanced performance. J Membrane Sci 640:119820. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.memsci.2021.119820\u003c/span\u003e\u003cspan address=\"10.1016/j.memsci.2021.119820\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTong J, Zhang J, Wang Y, Min F, Wang X, Zhang H (2019) Jichang Ma Preparation of Co-plated WC powders by a non-precious-Co-activation triggered electroless plating strategy. Adv Powder Technol 30(10):2311\u0026ndash;2319. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.apt.2019.07.012\u003c/span\u003e\u003cspan address=\"10.1016/j.apt.2019.07.012\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGuo L, Xiao L, Zhao X, Song Y, Cai Z, Wang H (2017) CB Liu Preparation of WC/Co composite powders by electroless plating. Ceram Int 43(5):4076\u0026ndash;4082. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.ceramint.2016.11.220\u003c/span\u003e\u003cspan address=\"10.1016/j.ceramint.2016.11.220\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBi S, Zhao H, Hou L, Lu Y (2017) Comparative study of electroless Co-Ni-P plating on Tencel fabric by Co0-based and Ni0-based activation for electromagnetic interference shielding. Appl Surf Sci 419:465\u0026ndash;475. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.apsusc.2017.04.176\u003c/span\u003e\u003cspan address=\"10.1016/j.apsusc.2017.04.176\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSarkar S, Baranwal RK, Biswas C (2019) Gautam Majumdar1 and Julfikar Haider Optimization of process parameters for electroless Ni\u0026ndash;Co\u0026ndash;P coating deposition to maximize micro-hardness. Mater Res Express 6(4):046415. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1088/2053-1591/aafc47\u003c/span\u003e\u003cspan address=\"10.1088/2053-1591/aafc47\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXia X, Wang Y, Ruditskiy A, Xia Y (2013) 25th anniversary article: galvanic replacement: a simple and versatile route to hollow nanostructures with tunable and well-controlled properties. Adv Mater 25(44):6313\u0026ndash;6333. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/adma.201302820\u003c/span\u003e\u003cspan address=\"10.1002/adma.201302820\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLarson JW, Cerutti P, Garber HK, Hepler LG (1968) Electrode potentials and thermodynamic data for aqueous ions. Copper, zinc, cadmium, iron, cobalt, and nickel. ACS Publications 72(8):2902\u0026ndash;2907. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/j100854a037\u003c/span\u003e\u003cspan address=\"10.1021/j100854a037\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen Y, Wang Y, Wan C (2007) Microstructural characteristics of immersion tin coatings on copper circuitries in circuit boards. Surf Coat Tech 202(3):417\u0026ndash;424. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.surfcoat.2007.06.004\u003c/span\u003e\u003cspan address=\"10.1016/j.surfcoat.2007.06.004\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHu G, Huang R, Wang H, Zhao Q, Zhang X (2022) Facile galvanic replacement deposition of nickel on copper substrate in deep eutectic solvent and its activation ability for electroless Ni\u0026ndash;P plating. J Solid State Electr 26(5):1313\u0026ndash;1322. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10008-022-05172-4\u003c/span\u003e\u003cspan address=\"10.1007/s10008-022-05172-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhao Q, Hu G, Huang R, Qiang L, Zhang X (2022) Iodide-induced galvanic replacement of nickel film on copper as activator for electroless nickel-phosphorus plating. Mater Lett 314:131833. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.matlet.2022.131833\u003c/span\u003e\u003cspan address=\"10.1016/j.matlet.2022.131833\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFarhan M, Fayyaz O, Nawaz M, Radwan AB, Shakoor RA (2022) Synthesis and properties of electroless Ni\u0026ndash;P-HfC nanocomposite coatings. Mater Chem Phys 291:126696. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.matchemphys.2022.126696\u003c/span\u003e\u003cspan address=\"10.1016/j.matchemphys.2022.126696\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuang H, Xiao Q, Wang J, Yu X, Wang H, Zhang H, Chu P (2017) Black phosphorus: a two-dimensional reductant for in situ nanofabrication. Npj 2d Mater Appl 1(1):20. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41699-017-0022-6\u003c/span\u003e\u003cspan address=\"10.1038/s41699-017-0022-6\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\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":"journal-of-applied-electrochemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jach","sideBox":"Learn more about [Journal of Applied Electrochemistry](http://link.springer.com/journal/10800)","snPcode":"10800","submissionUrl":"https://submission.nature.com/new-submission/10800/3","title":"Journal of Applied Electrochemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"cobalt, galvanic replacement, electroless Ni-P plating, activation, corrosion resistance, tribology performance","lastPublishedDoi":"10.21203/rs.3.rs-4291415/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4291415/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eElectroless nickel-phosphorus (Ni-P) plating is a widely used surface treatment method due to its excellent corrosion and wear resistance properties. However, the inertness of copper to hypophosphite oxidation necessitates a palladium activation process for the preparation of Ni-P coating on copper. In this study, we present a convenient approach for the deposition of a cobalt layer on copper using galvanic replacement, facilitated by the special complexing ability of iodide. The results demonstrated that the actual potential of copper could be adjusted to be lower than that of cobalt in a solution containing 8 mol/L NaI, enabling the deposition of a cobalt layer on copper in 15 minutes at 90\u0026deg;C. Furthermore, the deposition rate of the cobalt layer was found to increase with the concentration of CoCl\u003csub\u003e2\u003c/sub\u003e in the NaI solution. Importantly, the Ni-P coating obtained through cobalt layer activation exhibited morphology, structure, and corrosion resistance, friction resistance similar to the Ni-P coating obtained using the common palladium activation. Therefore, the cobalt layer prepared on copper through galvanic replacement may serve as a viable alternative to palladium for activating electroless Ni-P plating.\u003c/p\u003e","manuscriptTitle":"Cobalt layer prepared on copper using galvanic replacement as an alternative to palladium for activating electroless Ni-P plating","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-24 09:17:29","doi":"10.21203/rs.3.rs-4291415/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-06-16T18:58:35+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-06-12T00:18:03+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-06-11T03:03:15+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-06-01T12:21:35+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"280225704812385630655862376462925380199","date":"2024-05-23T09:04:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"293993418995506839881206510703902107884","date":"2024-05-21T16:13:36+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"242227921832826579385391668456220504601","date":"2024-05-20T06:32:08+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-05-19T16:09:46+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-04-20T17:01:46+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-04-20T12:57:03+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Applied Electrochemistry","date":"2024-04-19T07:02:42+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-applied-electrochemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jach","sideBox":"Learn more about [Journal of Applied Electrochemistry](http://link.springer.com/journal/10800)","snPcode":"10800","submissionUrl":"https://submission.nature.com/new-submission/10800/3","title":"Journal of Applied Electrochemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"bd5dddd4-d8d9-4a44-b4c9-08a04115eeb1","owner":[],"postedDate":"April 24th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-07-23T00:33:59+00:00","versionOfRecord":{"articleIdentity":"rs-4291415","link":"https://doi.org/10.1007/s10800-024-02177-x","journal":{"identity":"journal-of-applied-electrochemistry","isVorOnly":false,"title":"Journal of Applied Electrochemistry"},"publishedOn":"2024-07-22 00:33:59","publishedOnDateReadable":"July 22nd, 2024"},"versionCreatedAt":"2024-04-24 09:17:29","video":"","vorDoi":"10.1007/s10800-024-02177-x","vorDoiUrl":"https://doi.org/10.1007/s10800-024-02177-x","workflowStages":[]},"version":"v1","identity":"rs-4291415","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4291415","identity":"rs-4291415","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}