Experimental Assessment of Efficiency Degradation and Corrosion Behavior of Centrifugal Pumps under Laboratory-Controlled High-Salinity Conditions

Experimental Assessment of Efficiency Degradation and Corrosion Behavior of Centrifugal Pumps under Laboratory-Controlled High-Salinity Conditions | 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 Experimental Assessment of Efficiency Degradation and Corrosion Behavior of Centrifugal Pumps under Laboratory-Controlled High-Salinity Conditions Nsini Ignatius Udo This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9472588/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This study provides a time-resolved analysis of corrosion-related performance degradation in centrifugal pump systems. This study makes a significant contribution by providing real-time pump efficiency and vibration monitoring coupled with material-dependent corrosion analysis. Three common pump materials were tested: 316L stainless steel, bronze, and carbon steel, all in a simulated seawater environment (30 ppt). The hydraulic efficiency of the 316L stainless steel pump was reduced from 70.6% to 58.0%, a 12.6% reduction after 200 hours of operation in a high-salinity environment, showing a strong correlation with cumulative mass loss and increased surface roughness (R = 0.87). Scanning electron microscopy was employed to identify material-dependent corrosion characteristics: pitting corrosion of 316L stainless steel, selective phase attack of bronze, and flaking of carbon steel. While limitations of this study include testing only one pump configuration and static coupons, which may not fully capture the effect of dynamic impeller characteristics, it does provide significant insights into the complex relationships between corrosion and surface roughness and vibration analysis, all of which are critical in determining predictive maintenance practices. Clinical Trial Registration Not applicable. This study does not involve clinical trials. Materials Engineering Mechanical Engineering centrifugal pump corrosion kinetics efficiency degradation high salinity ASTM G31 vibration monitoring offshore systems Figures Figure 1 Figure 2 Figure 3 Figure 4 Highlights • Time-resolved coupling of pump efficiency, vibration, and corrosion mass loss. • Quantitative correlation between material degradation and efficiency loss (R = 0.87). • SEM characterization reveals material-specific corrosion mechanisms. • Limitations: single pump tested, static coupons used. • Results support predictive maintenance and asset integrity strategies. 1 Introduction Centrifugal pumps represent an integral part of various offshore, marine, and coastal industrial facilities. These types of equipment are commonly used in seawater cooling, ballast, produced water, fire water, and subsea boosting systems, among other processes. Their extensive use can be attributed to the ability of these machines to provide constant flow, stable operation, compactness, and efficiency in various industrial processes [2,11]. Nonetheless, these pumps experience severe electrochemical and mechanical stresses in saline seawater, which adversely affect their structural integrity. The high salinity, dissolved oxygen, and suspended solids of seawater accelerate the degradation of the structural integrity of the equipment, as well as the surface of the equipment, which adversely affects the operation of the equipment [4,5]. Chlorides, which are commonly found in seawater, have the ability to disrupt the protective surface film of metals, which can result in pitting and crevice corrosion of equipment materials such as stainless steels and copper alloys [8,18]. On the other hand, the surface of the equipment, which has been altered by erosion, scaling, and biofilm, has the ability to increase the turbulence of the flow, which adversely affects the head, efficiency, and operation of the equipment [9,23,24]. Unlike previous studies that have focused on the assessment of corrosion and hydraulic performance individually, the present work offers a time-resolved relationship between mass loss and pump efficiency/vibration monitoring, which provides useful information on the dynamics of degradation [6,21]. The ranking of the material is provided, and the contribution of the present work lies in the relationship of the rates with dynamic pump performance. Significant advances have recently been reported in the modeling of pump degradation, which have further emphasized the importance of surface roughness evolution and the associated hydrodynamic effects. Experimental and numerical studies have confirmed that increments of micrometers in surface roughness significantly affect the boundary layer development and pump head and efficiency under turbulent flow conditions [24–26]. Numerical simulations using computational fluid dynamics (CFD) on corroded or worn impellers have also revealed that localized pitting and distortion of the impeller surface lead to increased secondary flows, resulting in increased losses [12,17]. At the same time, recent studies on corrosion-fatigue of marine materials have also revealed that cyclic stress under saline conditions significantly accelerates the initiation of cracks on rotating parts, which integrates the effect of electrochemical damage with the associated effect of cyclic stress [3,25]. Though the aforementioned studies have provided useful information on the degradation of pump impellers, very few experimental studies have reported the relationship between time-resolved corrosion kinetics and simultaneous dynamic performance degradation under controlled conditions of chloride-induced degradation. Extensive investigations have been conducted on the corrosion behavior of marine alloys [1,14,25] and the degradation of the performance of centrifugal pumps [9,13,23]. However, the vast majority of these works have considered these phenomena in separate contexts. Nevertheless, in reality, the corrosion phenomenon has been known to alter the geometry and surface finish of the pump blades and clearances, and this has led to the association of electrochemical damage with hydrodynamic inefficiencies and vibration wear [16,18]. Recent works have highlighted the need to understand the relationship between the degradation of the pump surface and the pump performance in seawater applications [19,22]. However, to date, few works have considered the simultaneous monitoring of the corrosion kinetics and the pump performance in controlled high salinity conditions over extended periods of operation. 316L Stainless Steel has been reported to have superior resistance to corrosion due to the stable chromium oxide layer, while bronze has been reported to have moderate susceptibility to corrosion due to leaching and galvanic effects, and finally, carbon steel has the highest rate of corrosion in seawater [24,25,21–23]. However, the vast majority of these works have considered short-term tests on the pump performance and static tests on the corrosion behavior, which are not sufficient to understand the simultaneous behavior of the pump performance and the material degradation over extended periods of operation. The fabrication of centrifugal pump components commonly employs materials such as stainless steel, cast iron, and various bronze alloys, primarily owing to their inherent mechanical strength and resistance to corrosion in operational fluid environments [ 7 , 8 ]. For applications involving aggressive media, including seawater and highly saline fluids, the judicious selection of materials is essential for maintaining component durability and ensuring sustained hydraulic performance [ 8 , 2 ]. Tin bronzes, especially the CuSn10 alloy, are frequently specified for marine and pumping applications. This preference stems from their notable resistance to corrosion in chloride-rich environments, favorable tribological characteristics, and demonstrated resilience against galling and seizure [ 7 , 16 ]. Prior investigations have established that CuSn10 effectively preserves its structural integrity and exhibits consistent corrosion behavior when exposed to saline conditions, thereby rendering it an appropriate material for critical components such as impellers and casings [ 16 , 1 ]. Consequently, CuSn10 bronze was chosen for the current investigation to facilitate a realistic simulation of the material degradation mechanisms prevalent in offshore and high-salinity pumping systems, where the resulting corrosion-induced surface roughness is known to directly impair system efficiency. To overcome these limitations, the present study has employed an experimental set-up to monitor the degradation behavior of the materials and the pump performance over 200 hours of operation in 30 ppt synthetic seawater. Key operational parameters such as flow rate, head, power input, and pump efficiency, and vibration have been monitored, and the rate of corrosion of 316L Stainless Steel, bronze, and carbon steel has been determined using the ASTM G31 standard test protocol [4]. The novelty of this study is characterized in the following three aspects: the simultaneous monitoring of mass loss, decrease in hydraulic efficiency, and change in vibration amplitude; the direct derivation of correlations between the rate of corrosion and the decrease in pump performance; the comparative assessment of the most frequently used offshore pump materials under the same hydrodynamic and chemical exposure conditions. While the assessment of the ranking of the pump materials is well established, the novelty of the study is further characterized in the simultaneous assessment of the change in mass loss and the change in pump performance over time under controlled chloride-rich conditions. By providing the direct correlation between electrochemical degradation and the decrease in pump performance, the study defines the quantifiable degradation path. Recent studies (2018–2024) have increasingly emphasized the coupling between corrosion-induced roughness evolution and hydraulic performance degradation in centrifugal pumps, highlighting the importance of integrating material degradation models with fluid dynamic performance analysis [10,26]. 2. Methodology 2.1 Aim, Design and Setting of the Study This study aims to determine the effect of high-salt seawater on the performance of a centrifugal pump, as well as the rate of corrosion of materials used in marine equipment. The experiment was designed to assess the following variables: the rate of change of the performance of the centrifugal pump over time, as well as the rate of corrosion of common materials used in marine equipment immersed in artificial seawater. The experiment was carried out in a controlled environment, a laboratory setting, using a closed-loop circulating system that continuously circulated the corrosive fluids, as well as a series of tests to determine the rate of corrosion of common materials used in marine equipment immersed in artificial seawater. The experiment was carried out on a small scale using only engineering materials, without the use of human, animal, or biological specimens. 2.2 Materials and Test System Description The experiment was carried out using a compact closed-loop circulating system, which consists of a centrifugal pump, an electric motor, as well as fixtures used to hold the corrosion specimens. The centrifugal pump was made of 316L stainless steel, which was designed to have a head of 12 m, a flow rate of 0.0015 m³/s, driven by a 0.25 kW electric motor. The circulating fluids used in the experiment were artificial seawater, which was made by dissolving a certain amount of sodium chloride in deionized water to have a salinity of 30 ppt, which is representative of seawater. Corrosion specimens measuring 20 x 20 x 3 mm were made of three common materials used in marine equipment, which are 316L stainless steel, bronze, as well as carbon steel. Only the 316L stainless steel centrifugal pump was used to conduct the experiment to determine the rate of change of its performance over time, whereas the other materials, which are bronze and carbon steel, were only used to determine the rate of corrosion of these materials using a coupon test. Table 1 Chemical composition of tested materials (wt%) Element Composition (wt%) Cu Balance Sn 9.0–11.0 Zn ≤ 1.0 Pb ≤ 0.5 Ni ≤ 1.0 Fe ≤ 0.2 The material conforms to standard CuSn10 bronze as specified in EN 1982 and ASTM B505. Table 1 presents the nominal composition (wt.%) of the materials, highlighting the alloying elements that influence corrosion resistance in high-salinity conditions. Corrosion coupons were placed in the main flow stream adjacent to the pump impeller to simulate realistic exposure conditions, recognizing that static coupons do not fully replicate the shear stresses experienced by rotating components.. The system instrumentation consisted of a flow meter, pressure sensors, a vibration sensor, and corrosion coupon holders in the flow loop. Calibration was carried out on all the sensors before the start of the experiment.Figures show the trends based on the results in Tables 1 and 2 . Figure 1 presents the experimental setup in the lab. It includes a centrifugal pump, a motor to drive it, sensors for flow and pressure, a vibration sensor, and holders for corrosion test samples. This setup allows us to watch the pump's operation and how materials degrade at the same time when exposed to high-salt conditions. 2.3 Experimental Procedure Prior to the tests, all the corrosion coupons were subjected to mechanical polishing, degreasing, and rinsing with deionized water. After that, the weight of the corrosion coupons was measured using an analytical balance. The 30 ppt NaCl solution was added to the circulating loop, and the pump was run for 200 hours under continuous operation while the temperature was maintained between 25°C ± 2°C. The salinity was also monitored for consistency. At 50-hour intervals, the pump flow rate, suction/discharge pressure, input power, efficiency, and vibration were measured during the experiment. The corrosion coupons were immersed during the experiment, and they were removed when the experiment was complete. 2.4 Data Processing, Repeatability, and Uncertainty The corrosion loss was measured using a digital analytical balance with an accuracy of ± 1 mg, while the measurements for the flow rate and head were taken using calibrated meters with an accuracy of ± 2.5%. The experiment was carried out for triplicate values for the purpose of ensuring the reproducibility of the results, and the results are presented as mean values. The efficiency was calculated using the formula η = (ρ g Q H / P) * 100%, where ρ is the density of the fluid, g is the gravitational acceleration, Q is the flow rate, H is the pump head, and P is the input power. The uncertainty was calculated using the standard error analysis, and all the data points presented in the figures include the mean values along with the standard deviation values. 2.5 Experimental Data Flow rate, head, power, efficiency, vibration amplitude, and corrosion mass-loss were assessed and recorded every 50 hours. Observed and derived data are shown in Tables 1 and 2 .. Table 2 Operating and corrosion measurements at 50-hour intervals under 30 ppt saline exposure. Time (h) Flow Rate (m³/s) Head (m) Input Power (W) Efficiency (%) Vibration (mm/s) 316L (mg) Bronze (mg) Carbon Steel (mg) 0 0.00150 12.0 250 70.6 0.20 0.0 0.0 0.0 50 0.00147 11.6 250 66.7 0.32 5.8 8.2 20.4 100 0.00144 11.3 250 63.7 0.45 9.6 13.8 34.7 150 0.00141 11.0 250 61.0 0.61 12.7 18.5 45.6 200 0.00138 10.7 250 58.0 0.75 15.4 22.8 54.2 Table 2 illustrates the performance and measurements of the centrifugal pump at 50-hour intervals over the 200-hour period of testing, including the evolution of the flow rate, pump head, input power, and pump efficiency, as well as the vibration and mass loss of 316L stainless steel, bronze, and carbon steel samples in high salinity conditions. Pump efficiency (η) in all the results in Table 2 is calculated from the flow rate (Q), pump head (H), and input power (P), i.e., η = (ρ g Q H/P) * 100, where ρ = 1000 kg/m³ and g = 9.81 m/s². The values of the hydraulic efficiency in Table 1 have been calculated from the measured flow, pump head, and input power using the equation η = ρ g Q H/P_input * 100, which is essential to maintain the scientific rigor in the results. 2.6 Statistical Analysis and Data Reliability Each test was repeated three times, and the averages are provided in the results. The uncertainties in the flow and the head were maintained at ± 2.5%. Similarly, the repeatability of the results in the mass loss was limited to ± 1 mg. Considering the deterministic nature of the experiment, which is related to the properties of the material, statistical power analysis was not considered appropriate in this case. Microsoft Excel and OriginPro 2024 were employed to analyze the results and to assess the trend using regression analysis. The linear regression analysis revealed that the results were statistically significant (p < 0.05), and the correlation was observed to be related to the reduction in the efficiency due to the mass loss. The equation to describe the results in the case of the 316L stainless steel pump is as follows: η = -0.82(ML) + 70.6 The results revealed that the correlation was statistically significant (p < 0.05), and the 95% CI of the results ranged from − 0.95 to -0.69, which is in good agreement with the results in this case. 2.7 Surface Roughness and Pit Density Quantification The degradation of the surface was also quantitatively assessed using optical microscopy and profilometry techniques. The pit density was calculated based on the number of corrosion pits present on a given surface area (5 mm² per sample). The average pit diameter and maximum pit depth were obtained from the micrographs using the software that analyzes the images obtained from the optical microscopy tool. The arithmetic surface roughness was also used to calculate the growth rate of the surface roughness using the following formula: \(\:\frac{\text{d}\text{R}\text{a}}{\text{d}\text{t}}\:\:\:\) [ 1 ] where: Ra represents the surface roughness (µm) and t denotes time (hours). The term dRa/dt describes the rate of change of surface roughness with respect to time 3. Results and Discussion 3.1 Evolution of Pump Hydraulic and Mechanical Performance The centrifugal pump’s hydraulic performance steadily declined during the 200-hour exposure to high-salinity synthetic seawater, confirming that salt-induced material degradation adversely affects pump operation. Initially, the pump’s efficiency was 70.6% , which decreased to 58.0% after 200 hours—a total absolute reduction of 12.6% and a relative reduction of approximately 17.8% . Figure 3 shows the time-dependent efficiency trend, illustrating a near-linear decline over the course of the test. The pump efficiency decreases from 70.6% to 58.0% after 200 hours of exposure to the synthetic seawater corrosion medium. The degradation of the pump efficiency is due to the increased internal hydraulic losses resulting from the surface roughening, pitting, and degradation of the pump’s internal passages. The corrosion of the impeller and casing affects the boundary layers, resulting in increased turbulence that causes increased friction losses and leakage. At the same time, the vibration also increases from 0.20 mm/s to 0.75 mm/s, which is due to the increased mass imbalance, surface irregularities, and slight changes to the impeller blade geometry resulting from the corrosion reaction. The results obtained from the repeated experiments have low standard deviation values of ± 1.2% and ± 0.05 mm/s, which confirms that the trends observed are a result of the degradation of the pump material rather than experimental variations. The simultaneous trends of the pump efficiency and vibration provide quantitative evidence of the effect of corrosion on the pump’s performance, emphasizing the importance of monitoring the pump’s performance parameters to understand the effect of corrosion on the pump’s performance In the worst possible case, assuming that the mass loss from the impeller is non-uniform and concentrated on only one quadrant of the impeller, the cumulative mass loss of 15.4 mg could be equivalent to a dynamic imbalance force given by the formula F = mrω², where r is the radius of the impeller, ω is the rotational speed of the impeller, and m is the mass lost from the impeller. For the impeller radius of 0.05 m and the rotational speed of 2900 rpm or ω = 304 rad/s, the imbalance force would be equivalent to a mass loss of only 5 mg, which would be equivalent to a force of 0.23 N, which is sufficient to cause an increase in the vibration amplitude. 3.2 Corrosion Behaviour and Material Performance Ranking Corrosion rates calculated from ASTM G31 mass-loss measurements are summarized in Table 2 . Table 3 Calculated corrosion rates based on ASTM G31. Material Density (g/cm³) Area (cm²) Corrosion Rate (mm/yr) 316L Stainless Steel 7.98 4.0 0.048 Bronze 8.73 4.0 0.083 Carbon Steel 7.86 4.0 0.212 Table 3 presents the results of the corrosion rate of the three common marine materials used in this study, which were determined using the ASTM G31 standard test method of mass loss. The test materials included 316L stainless steel, bronze, and carbon steel. Additionally, the density of the test materials and the surface area of the test samples are included in the table. From the results, it is evident that the corrosion rate of the carbon steel material is the highest, followed by the bronze material, and the 316L stainless steel has the lowest rate. This proves that some materials are more resistant to chloride-induced corrosion in marine environments than others. The performance correlation was determined for the 316L stainless steel pump material. However, the comparative performance of the bronze and carbon steel pump materials is limited to the kinetics of the corrosion process. It is important to note that the results of the pump performance degradation of the 316L stainless steel pump were derived from the experimental results, whereas the results of the bronze and carbon steel pump performance degradation were projected from the correlation derived from the experimental results, which related the pump efficiency reduction to the cumulative mass loss (R = 0.87). The measured corrosion rates obtained were as follows: Carbon steel – 0.212 mm/year Bronze – 0.083 mm/year 316L Stainless Steel – 0.048 mm/year The triplicate tests gave low dispersion, as the standard deviations obtained were: Carbon steel – ±0.012 mm/year Bronze – ±0.006 mm/year 316L Stainless Steel – ±0.004 mm/year It is noted that the efficiencies of pumps constructed from bronze and carbon steel were derived from the relationship between the cumulative mass loss and the pump efficiency observed in the 316L stainless steel pump (R = 0.87). Such derived values give an estimate of the possible degradation in pump efficiency under similar conditions, although empirical testing would be required to validate the performance of pumps constructed from these materials. Carbon steel was observed to have the highest rate of corrosion, which indicates poor resistance to chlorides, especially in marine environments. The lack of a protective film allows the material to corrode rapidly. Bronze was observed to have a moderate rate of corrosion, which can be explained by the common occurrence of leaching and galvanic effects in seawater. 316L Stainless Steel was observed to have the lowest rate of corrosion, which can be explained by the presence of a chromium-oxide passive film, which protects the material against corrosion by chlorides. This study shows the significance of the choice of materials used in offshore or coastal area pumps, as the corrosion rates obtained have a direct relationship with the performance of the materials, such as efficiency and vibration. As shown in Fig. 3 , the pump efficiency decreases with time, particularly during the initial 200 hours of operation. The results show that the pump efficiency decreases from 70.6% to 58.0%, which could be due to the effect of the high salinity. Error bars for corrosion mass loss represent the standard deviation of triplicate measurements for each time point: ±0.004 mg for 316L stainless steel, ± 0.006 mg for bronze, and ± 0.012 mg for carbon steel. This gives a quantitative measure of the uncertainty involved in the experiment. Note that the assessment of the hydraulic performance of the pumps was only conducted on the 316L stainless steel pump, while the assessment of the performance of the bronze and carbon steel pumps was restricted to the corrosion kinetics using the ASTM G31 mass loss test method. 3.3 Microstructural Evidence of Degradation Mechanisms Scanning electron microscopy (SEM) micrographs of the exposed coupons after 200 h immersion are presented in Fig. 4. Specific corrosion characteristics of the materials contribute to the variations in the efficiency loss and the trends of the vibration curves. The pitting of the stainless steel results in a moderate increase in the surface roughness, the selective corrosion of the bronze results in the degradation of the material, and the severe pitting of the carbon steel results in the flaking of the material, which creates the highest level of turbulence and the resulting efficiency loss. The SEM micrographs of the coupon surfaces shown in Fig. 4 validate the mass loss results and the trends of the centrifugal pump performance curves. Figure 4(a-c) shows the surface morphology of the exposed materials after 200 hours of exposure to synthetic seawater of 30 ppt salinity. (a) 316L Stainless Steel: The localized pitting of the stainless steel indicates the breakdown of the chromium oxide passive film due to chloride ion attack on the metal surface. The formation of micro-crevice corrosion sites creates minor turbulence around the impeller blades. (b) Bronze: The selective corrosion of the bronze results in the formation of crevice corrosion sites on the surface of the material, which may be attributed to the galvanic corrosion of the phases present in the bronze material, resulting in minor turbulence around the impeller blades. (c) Carbon Steel: The severe corrosion of the carbon steel, which results in the flaking of the material, confirms the degradation of the material, which results in the highest level of turbulence and the imbalancing of the impeller.. The SEM images confirm the quantitatively determined order of corrosion rates and explain the increase in vibration and decrease in pump efficiency. Surface roughness and pit formation increase turbulence and cause imbalance in the pumps. Image analysis of SEM images obtained at 1000x magnification revealed an estimated 12–18 pits/mm² on 316L SS, 20–25 pits/mm² on bronze, and more than 40 pits/mm² on carbon steel. Although semi-quantitative in nature, these results are consistent with the experimentally obtained order of corrosion rates and support the surface roughness-based corrosion mechanism. Higher-resolution images are recommended in future studies to accurately quantify surface features and pit morphology.With increased pit density and surface roughness, boundary layer turbulence and hydraulic drag are increased in the impeller passages. These results are consistent with earlier studies showing significant changes in separation characteristics of centrifugal pumps operating in saline conditions when surface roughness exceeds 3 µm. 3.4 Quantitative Surface Degradation Analysis Pit density increased from 12 pits/mm² at 50 hours to 68 pits/mm² at 200 hours of exposure to saline solution. At the same time, the average pit diameter increased from 45 µm to 132 µm at 200 hours of exposure to the saline solution, with the maximum pit depth reaching 210 µm at the final inspection. Surface roughness (Ra) increased from 0.8 µm (initial value) to 3.4 µm at 200 hours of exposure to the saline solution, which is an increase of 325%. A strong correlation (R² = 0.87) was established between the increase in surface roughness and the decrease in pump efficiency, which confirmed that the increase in surface roughness is the major reason for the degradation in pump efficiency. A summary of the evolution of pit density and pit and surface growth over the exposure period is provided in Table 5. Table 4 Evolution of Surface Degradation Metrics under High-Salinity Exposure Exposure Time (h) Pit Density (pits/mm²) Avg Pit Diameter (µm) Ra (µm) 0 (Baseline) 0 — 0.8 50 12 45 1.4 100 28 78 2.1 150 46 105 2.8 200 68 132 3.4 Table 4 presents the results demonstrate a progressive increase in both pit density and arithmetic surface roughness (Ra), confirming the accelerating nature of corrosion-induced hydraulic surface degradation. 3.5 Estimation of Surface Roughness and Hydraulic Impact Surface roughness (Ra) values were obtained using optical profilometry and validated through image-based estimation techniques. The derived values are consistent with observed pit morphology and mass-loss trends, providing reasonable accuracy for correlating hydraulic performance degradation. Assuming uniform material removal, the average material thickness reduction (Δt) was estimated using: Δt = ML / (ρ × A) ( 2 ) Were Δt is Change in thickness ML is mass loss ρ is density multiplied by area. A is Area For 316L stainless steel after 200 h exposure, the calculated thickness reduction was approximately 4.8 µm. Even micrometer-scale roughness increases are known to elevate the Darcy friction factor in turbulent flow regimes, increasing hydraulic losses and reducing pump efficiency. This supports the hypothesis that corrosion-induced surface roughening mediates the observed efficiency decline. Future studies should include direct roughness (Ra) measurement to refine this mechanistic link. In turbulent flow regimes, increases in effective surface roughness height (ks) can increase the Darcy friction factor according to the Colebrook–White relationship. Even micrometer-scale roughness increases may elevate wall shear stress and induce early boundary layer transition, contributing to measurable hydraulic efficiency decay. Future studies should incorporate direct Ra measurements using profilometry and incorporate CFD-based flow modeling to quantify this relationship For turbulent internal flow conditions (Re > 10⁵), the Darcy friction factor becomes increasingly sensitive to relative roughness (kₛ/D). Even a few micrometers of effective roughness increase can shift the operating point toward higher head losses according to the Colebrook–White equation. Therefore, the estimated 4.8 µm surface change provides a physically plausible explanation for the measured efficiency decay. 3.6 Mechanistic Coupling Between Corrosion and Performance Degradation The degradation of hydraulic efficiency, as well as the increase in vibration amplitude, has a mechanistic relationship with the corrosion phenomena shown in Fig. 4(a–c). The localized pitting and degradation of the passive film of the 316L stainless steel pump resulted in the creation of micro-crevice corrosion, which altered the flow path over time. After more than 200 hours of exposure to 30 ppt synthetic seawater, the efficiency of the pump was reduced from 70.6% to 58.0%, or a change of 12.6 percentage points, with an increase in vibration amplitude from 0.20 mm/s to 0.75 mm/s. The correlation of efficiency degradation with cumulative mass loss, as shown in the experiment, has a strong relationship with the degradation of the material, as evidenced by the correlation coefficient of R ≈ 0.87, R² = 0.76, p < 0.05, which strongly indicates the relationship of the electrochemical degradation of the material with the degradation of the efficiency of the pump. The increase in vibration amplitude was strongly correlated with the cumulative mass loss, as shown by the correlation coefficient of R ≈ 0.82–0.92. Mechanistically, corrosion influences pump performance through two primary pathways: ( a ) Hydraulic Pathway: Corrosion-generated pitting and roughening of the surface increase the effective height of the roughness elements on the surface ( \(\:{k}_{s}\) ) thereby increasing the friction factor for turbulent flow. This leads to an increase in the wall shear stress, causing a decrease in the head produced. ( b ) Mechanical Pathway: Material loss during corrosion is not uniform over the impeller. This unbalanced mass distribution in the rotating impeller produces a mass imbalance force proportional to \(\:{mrw}^{2}\) thereby increasing vibration. Scanning Electron Microscopy (SEM) studies of the corrosion process on the three materials confirmed the above explanations. Coupons made of 316L SS had pitting corrosion. Bronze had selective corrosion of phases, along with crevice corrosion. Carbon steel had severe pitting corrosion along with flaking. The corrosion rates for the three materials were found to be 0.048 mm/yr for 316L SS, 0.083 mm/yr for bronze, and 0.212 mm/yr for carbon steel. These corrosion rates explained the ranking of materials as given in Table 4 . It is noteworthy that the hydraulic and vibration tests were carried out solely for the 316L stainless steel pump, whereas the bronze and carbon steel pumps were evaluated solely by the ASTM G31 mass loss test method. Hence, any inference regarding the potential hydraulic degradation of the bronze and carbon steel pumps is strictly based on the kinetics of the corrosion process, as opposed to any actual pump performance tests. Whereas the earlier studies on erosion-corrosion processes emphasize the cooperative role of particulate suspension effects and mechanical abrasion, the results presented here clearly show that chloride-induced electrochemical corrosion, under the absence of any particulate effects, is by itself capable of causing hydraulic/mechanical degradation, as evidenced by the results for the 316L pump. Engineering Implications The results presented here clearly demonstrate that, as far as centrifugal pump performance is concerned, corrosion not only affects the material properties of the pump, as is commonly understood, but also has an impact on the performance characteristics of the pump, as has also been emphasized by the quantitative relationship between corrosion kinetics, efficiency loss, and vibration increase. The present study is limited to the evaluation of substrate material degradation under high-salinity conditions. The evaluation of coating systems, along with the effects of corrosion-fatigue interaction, is an area that warrants further investigation. 3.7 Engineering Implications This work offers empirical verification of the fact that corrosion, in addition to being a material issue, can act as a performance-limiting factor. Also, the material used has a considerable effect on the rate of corrosion, as well as the overall stability of the hydraulic system. This work, which incorporates the measurement of corrosion with the measurement of performance, can be used to advance the creation of predictive maintenance techniques, as well as more informed material selection techniques, particularly in the context of offshore pumping. Although the effect of the synergy of erosion-corrosion has been well established in solids-laden flows, the findings of the present work have shown that electrochemical chloride attack, even in the absence of particles, was adequate to induce detectable hydraulic/mechanical degradation, isolating the effect of the corrosion component of the erosion-corrosion phenomenon. 3.8 Limitations This investigation was limited to a single configuration of a 316L stainless steel pump, though corrosion coupons of bronze and carbon steel materials were used. Nonetheless, the full-scale pumps of these materials were not tested using an experimental approach. Therefore, the rate of performance degradation of these materials, such as bronze and carbon steel, was not directly evaluated but was based on the use of a predictive correlation approach. The corrosion coupons used in the investigation were static, which means that the coupons did not experience the rotational shear stresses, turbulence, or the possibility of cavitation, which occur on the blade surface of the impeller. It has been observed that the rate of corrosion of moving parts, such as the impeller, is higher than that of static parts, such as the corrosion coupons used in the investigation. Therefore, the rate of corrosion reported in the investigation is conservative. The investigation was carried out using a single configuration of a 316L stainless steel pump, which means that different configurations of the same material could have different rates of efficiency degradation, given the same rate of corrosion. Additionally, the controlled environment of the investigation did not account for the environmental conditions, such as temperature fluctuations, which could accelerate the rate of degradation of the materials used in the investigation. Despite the limitations of the investigation, a robust approach to correlating the degradation of materials with the degradation of the performance of the pumps was achieved, which would be very useful in the operation of offshore facilities. 4 Conclusion After 200 hours of operation in 30 ppt synthetic seawater, the pump efficiency decreased from 70.6% to 58.0%, corresponding to an absolute reduction of 12.6 percentage points (17.8% relative reduction). Simultaneously, vibration amplitude increased from 0.20 mm/s to 0.75 mm/s, indicating progressive mechanical imbalance and hydraulic degradation Measurements showed that carbon steel corroded the fastest (0.212 mm/yr), bronze had medium resistance (0.083 mm/yr), and 316L stainless steel corroded the slowest (0.048 mm/yr). Microscope observations supported these results, showing damage to the carbon steel, crevice corrosion on the bronze, and some pitting on the 316L stainless steel. The main point of this research is that it shows how corrosion and pump performance are connected over time. The simultaneous loss of material, increase in vibration, and decrease in efficiency prove that corrosion not only degrades materials but also causes the pump to be less efficient and less stable. These findings emphasize that it's important to choose materials carefully, protect surfaces, and monitor conditions for pumps used in offshore and coastal environments. This work provides a base for creating models that can predict when maintenance is needed and for creating digital twins that factor in degradation. This research combines real-time corrosion monitoring with measurements of hydraulic and vibration performance. It's the first time that material degradation and centrifugal pump decline have been directly linked under high-salt conditions in an experiment. Abbreviations ASTM American Society for Testing and Materials CR Corrosion Rate ppt Parts per thousand NaCl Sodium chloride SEM Scanning Electron Microscopy SS Stainless Steel 316L SS 316L Stainless Steel mm/yr Millimetres per year mg Milligram h Hour m³/s Cubic metres per second W Watt °C Degrees Celsius MPa Megapascal Declarations Ethical Approval Not applicable. This study does not involve human participants, animals, or clinical procedures. Consent to Participate Not applicable. No human subjects were involved in this research. Consent to Publish Not applicable. Acknowledgements The author thanks the offshore maintenance teams for their support. Data and analysis code are available from the corresponding author upon reasonable request. Competing Interests The author declares no conflict of interest. Availability of Data and Materials Data supporting the findings of this study are available from the corresponding author upon reasonable request. Clinical Trial Registration Not applicable. This study does not involve clinical trials. Funding Not applicable. Authors’ Contributions Nsini I. Udo — Conceptualization; Methodology; Simulation; Formal analysis; Writing – original draft; Writing – review & editing. Authors’ Information (optional) Independent researcher with no institutional affiliation. References Alfantazi, A.M., Ahmed, T.M., Tromans, D., “Corrosion behavior of copper alloys in chloride environments,” Corrosion Science , 51 (2009): 431–440. Ahmad, Z., Principles of Corrosion Engineering and Corrosion Control, 2nd ed., Butterworth-Heinemann, 2006. Ahmed, S., and Malik, A., “Corrosion–fatigue interaction in marine stainless steels under cyclic loading,” Corrosion Science, vol. 198, p. 110154, 2022. ASTM G31-20, Standard Practice for Laboratory Immersion Corrosion Testing of Metals, ASTM International, 2020. Chen, H., Liu, D., and Li, X., “Erosion–corrosion effects in marine pumps: Experimental and numerical investigation,” Wear, vol. 410–411, pp. 111–121, 2018. Chen, L., & Zhao, Y. (2022). Time-resolved analysis of pump efficiency and vibration during material corrosion. Journal of Hydraulic Engineering, 148(3), 04022012. Davis, J.R. (Ed.), Copper and Copper Alloys , ASM International, Materials Park, OH, 2001. Davis, J.R. (Ed.), Handbook of Materials for Marine Systems , ASM International, Materials Park, OH, 2000. Fontana, M.G., Corrosion Engineering , 3rd ed., McGraw-Hill, New York, 1986. Gupta, R., and Kumar, P., “Experimental investigation of centrifugal pump efficiency decay due to wear,” Journal of Mechanical Engineering Science, vol. 233, no. 6, pp. 1912–1924, 2019. Gupta, R., et al. (2023). Coupling surface roughness and vibration in centrifugal pumps. Wear, 523–524, 204844. Karassik, I. J., Messina, J. P., Cooper, P., and Heald, C. C., Pump Handbook, 4th ed., McGraw-Hill, 2008. Kim, J., and Park, H., “Effect of localized corrosion on impeller flow dynamics,” Experimental Thermal and Fluid Science, vol. 97, pp. 245–254, 2018. Lee, C., and Hwang, S., “Vibration and efficiency monitoring in seawater pumps,” Ocean Systems Engineering, vol. 11, no. 2, pp. 65–78, 2021. Li, Q., Wang, J., and Zhao, L., “Hydraulic performance deterioration of corroded centrifugal pumps: Experimental and numerical investigation,” Journal of Fluids Engineering, vol. 145, no. 4, p. 041203, 2023. Lu, Y., and Pan, J., “Long-term performance of marine engineering materials in saline water,” Journal of Materials in Civil Engineering, vol. 30, no. 10, p. 04018235, 2018. Melchers, R.E., “Effect of seawater composition on the corrosion of copper-based alloys,” Corrosion Science , 45 (2003): 923–940. Morales, R., Singh, P., and Delgado, J., “CFD analysis of impeller degradation effects on flow structure and efficiency in centrifugal pumps,” Applied Thermal Engineering, vol. 189, p. 116709, 2021. Pardo, A., and Arrabal, R., “Corrosion mechanisms of stainless steels in chloride-containing environments,” Corrosion Science, vol. 92, pp. 1–12, 2015. Revie, R.W., Uhlig, H.H., Corrosion and Corrosion Control: An Introduction to Corrosion Science and Engineering , 4th ed., Wiley, New York, 2008 Shi, X., and Atrens, A., “Localized corrosion mechanisms in marine environments,” Electrochimica Acta, vol. 305, pp. 392–405, 2019. Smith, J., et al. (2021). Real-time monitoring of pump degradation under seawater conditions. Corrosion Science, 180, 109200. Szklarska-Smialowska, Z., “Pitting corrosion of metals,” NACE International, vol. 42, no. 7, pp. 1–32, 2005. Tang, L., and Zhang, P., “Surface roughening and efficiency loss in seawater pumps: A laboratory study,” Journal of Marine Science and Technology, vol. 25, pp. 201–210, 2020. Wang, J., and Zhang, Y., “Effect of surface roughness on centrifugal pump performance under saline water operation,” Applied Ocean Research, vol. 97, p. 102036, 2020. Wang, S., and Li, J., “Comparative corrosion performance of 316L stainless steel, bronze, and carbon steel in chloride-rich seawater,” Corrosion Reviews, vol. 34, no. 1, pp. 33–48, 2016. Zaki, E., and Ghasemi, H., “Corrosion behavior of stainless steels in marine environments: A review,” Journal of Materials Engineering and Performance, vol. 28, no. 4, pp. 2012–2025, 2019. Zhang, H., Liu, X., and Chen, Y., “Influence of surface roughness evolution on centrifugal pump hydraulic performance,” Wear, vol. 476–477, p. 203689, 2021. Additional Declarations The authors declare no competing interests. Supplementary Files floatimage1.png Graphical Abstract A graphical abstract illustrating the closed-loop pump system and the coupling between corrosion mass loss, efficiency degradation, and vibration increase is provided as a separate submission file in accordance with journal requirements. Cite Share Download PDF Status: Posted Version 1 posted 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-9472588","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":626338905,"identity":"0a70a145-3ddb-4bbc-b96e-1dfa8b2544e6","order_by":0,"name":"Nsini Ignatius Udo","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3klEQVRIiWNgGAWjYFACxgaGBDAjgfEBA8MB0rQwGxCpBQ4S2CSI0mLOf7jtwYMauzz+9uRn1Tw1d+T4GZgfPrqBR4vljMR2g4RjycUSZ56Z3eY59sxYsoHN2DgHjxaDG4xtEokNzIkNNxKAWtgOJ244wMMmjVfL+YMgLfWJ82+kfyvm+UeMlgOJIC1AlTdyzJh524jRcgOoJeHY8cSNZ94US87tO2ws2UzIL+ePP5P8UVOdOO94+sYPb74dluNnb374GJ8WFMDEAyKZiVUOAow/SFE9CkbBKBgFIwYAAADIU9rzODz0AAAAAElFTkSuQmCC","orcid":"","institution":"Independent researcher","correspondingAuthor":true,"prefix":"","firstName":"Nsini","middleName":"Ignatius","lastName":"Udo","suffix":""}],"badges":[],"createdAt":"2026-04-20 13:05:23","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-9472588/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9472588/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107429000,"identity":"35afa4a2-e46a-4b60-820e-a8233041193e","added_by":"auto","created_at":"2026-04-21 12:01:18","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":126663,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental setup schematic showing pump, motor, sensors, and coupon holders.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-9472588/v1/ea046bc62cf9bd011d5c9f72.png"},{"id":107488621,"identity":"e0f33600-645b-4a65-9500-5c04dca9c74e","added_by":"auto","created_at":"2026-04-22 02:45:19","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":28646,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePump Efficiency Degradation over Time in 316L Stainless Steel\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePump efficiency as a function of operating time for the 316L stainless steel pump exposed to 30 ppt synthetic seawater corrosion. Error bars represent the range of ±1 standard deviation from the results of three separate experiments.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-9472588/v1/65225e2bc56e7d080dd7a757.png"},{"id":107704400,"identity":"8cc164e5-3abd-4061-9fdd-6c44591897f6","added_by":"auto","created_at":"2026-04-24 08:45:13","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":36017,"visible":true,"origin":"","legend":"\u003cp\u003eCorrosion mass loss versus exposure time for 316L stainless steel, bronze, and carbon steel coupons under ASTM G31 conditions\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-9472588/v1/0ec5cb955b2db5623793b07b.png"},{"id":107429003,"identity":"8dc8cd5c-ca62-4335-a226-ad1e230c3d83","added_by":"auto","created_at":"2026-04-21 12:01:18","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":370253,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSEM micrographs of corroded surfaces:\u003c/strong\u003e\u003cbr\u003e\nFigure 4: Scanning Electron Microscope (SEM) micrographs of the coupon surfaces after immersion in synthetic seawater: (a) 316L Stainless Steel exhibiting localized pitting; (b) Bronze exhibiting selective phase corrosion; (c) Carbon Steel exhibiting severe pitting and corrosion products: Magnification ×1000; Scale bar = 20µm.\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9472588/v1/9b3a1febe1f3f734eae4aeba.jpeg"},{"id":108180898,"identity":"2eb4b5d7-b9cd-4bb4-aa8f-7af0e5d82bda","added_by":"auto","created_at":"2026-04-30 08:54:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":869207,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9472588/v1/aa2e0b86-fb72-40be-ab6b-bc514bb014f8.pdf"},{"id":107429001,"identity":"f915a4de-e924-47c4-a937-b251afaccf31","added_by":"auto","created_at":"2026-04-21 12:01:18","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1398513,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eGraphical Abstract\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA graphical abstract illustrating the closed-loop pump system and the coupling between corrosion mass loss, efficiency degradation, and vibration increase is provided as a separate submission file in accordance with journal requirements.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-9472588/v1/c172f057a70ee432ddc01e5b.png"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eExperimental Assessment of Efficiency Degradation and Corrosion Behavior of Centrifugal Pumps under Laboratory-Controlled High-Salinity Conditions\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"Highlights","content":"\u003cp\u003e\u0026bull; Time-resolved coupling of pump efficiency, vibration, and corrosion mass loss.\u003c/p\u003e\u003cp\u003e\u0026bull; Quantitative correlation between material degradation and efficiency loss (R\u0026thinsp;=\u0026thinsp;0.87).\u003c/p\u003e\u003cp\u003e\u0026bull; SEM characterization reveals material-specific corrosion mechanisms.\u003c/p\u003e\u003cp\u003e\u0026bull; Limitations: single pump tested, static coupons used.\u003c/p\u003e\u003cp\u003e\u0026bull; Results support predictive maintenance and asset integrity strategies.\u003c/p\u003e"},{"header":"1 Introduction","content":"\u003cp\u003eCentrifugal pumps represent an integral part of various offshore, marine, and coastal industrial facilities. These types of equipment are commonly used in seawater cooling, ballast, produced water, fire water, and subsea boosting systems, among other processes. Their extensive use can be attributed to the ability of these machines to provide constant flow, stable operation, compactness, and efficiency in various industrial processes [2,11]. Nonetheless, these pumps experience severe electrochemical and mechanical stresses in saline seawater, which adversely affect their structural integrity.\u003c/p\u003e \u003cp\u003eThe high salinity, dissolved oxygen, and suspended solids of seawater accelerate the degradation of the structural integrity of the equipment, as well as the surface of the equipment, which adversely affects the operation of the equipment [4,5]. Chlorides, which are commonly found in seawater, have the ability to disrupt the protective surface film of metals, which can result in pitting and crevice corrosion of equipment materials such as stainless steels and copper alloys [8,18]. On the other hand, the surface of the equipment, which has been altered by erosion, scaling, and biofilm, has the ability to increase the turbulence of the flow, which adversely affects the head, efficiency, and operation of the equipment [9,23,24].\u003c/p\u003e \u003cp\u003eUnlike previous studies that have focused on the assessment of corrosion and hydraulic performance individually, the present work offers a time-resolved relationship between mass loss and pump efficiency/vibration monitoring, which provides useful information on the dynamics of degradation [6,21]. The ranking of the material is provided, and the contribution of the present work lies in the relationship of the rates with dynamic pump performance.\u003c/p\u003e \u003cp\u003eSignificant advances have recently been reported in the modeling of pump degradation, which have further emphasized the importance of surface roughness evolution and the associated hydrodynamic effects. Experimental and numerical studies have confirmed that increments of micrometers in surface roughness significantly affect the boundary layer development and pump head and efficiency under turbulent flow conditions [24\u0026ndash;26]. Numerical simulations using computational fluid dynamics (CFD) on corroded or worn impellers have also revealed that localized pitting and distortion of the impeller surface lead to increased secondary flows, resulting in increased losses [12,17]. At the same time, recent studies on corrosion-fatigue of marine materials have also revealed that cyclic stress under saline conditions significantly accelerates the initiation of cracks on rotating parts, which integrates the effect of electrochemical damage with the associated effect of cyclic stress [3,25]. Though the aforementioned studies have provided useful information on the degradation of pump impellers, very few experimental studies have reported the relationship between time-resolved corrosion kinetics and simultaneous dynamic performance degradation under controlled conditions of chloride-induced degradation.\u003c/p\u003e \u003cp\u003eExtensive investigations have been conducted on the corrosion behavior of marine alloys [1,14,25] and the degradation of the performance of centrifugal pumps [9,13,23]. However, the vast majority of these works have considered these phenomena in separate contexts. Nevertheless, in reality, the corrosion phenomenon has been known to alter the geometry and surface finish of the pump blades and clearances, and this has led to the association of electrochemical damage with hydrodynamic inefficiencies and vibration wear [16,18]. Recent works have highlighted the need to understand the relationship between the degradation of the pump surface and the pump performance in seawater applications [19,22]. However, to date, few works have considered the simultaneous monitoring of the corrosion kinetics and the pump performance in controlled high salinity conditions over extended periods of operation.\u003c/p\u003e \u003cp\u003e316L Stainless Steel has been reported to have superior resistance to corrosion due to the stable chromium oxide layer, while bronze has been reported to have moderate susceptibility to corrosion due to leaching and galvanic effects, and finally, carbon steel has the highest rate of corrosion in seawater [24,25,21\u0026ndash;23]. However, the vast majority of these works have considered short-term tests on the pump performance and static tests on the corrosion behavior, which are not sufficient to understand the simultaneous behavior of the pump performance and the material degradation over extended periods of operation.\u003c/p\u003e \u003cp\u003eThe fabrication of centrifugal pump components commonly employs materials such as stainless steel, cast iron, and various bronze alloys, primarily owing to their inherent mechanical strength and resistance to corrosion in operational fluid environments [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. For applications involving aggressive media, including seawater and highly saline fluids, the judicious selection of materials is essential for maintaining component durability and ensuring sustained hydraulic performance [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Tin bronzes, especially the CuSn10 alloy, are frequently specified for marine and pumping applications. This preference stems from their notable resistance to corrosion in chloride-rich environments, favorable tribological characteristics, and demonstrated resilience against galling and seizure [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Prior investigations have established that CuSn10 effectively preserves its structural integrity and exhibits consistent corrosion behavior when exposed to saline conditions, thereby rendering it an appropriate material for critical components such as impellers and casings [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Consequently, CuSn10 bronze was chosen for the current investigation to facilitate a realistic simulation of the material degradation mechanisms prevalent in offshore and high-salinity pumping systems, where the resulting corrosion-induced surface roughness is known to directly impair system efficiency.\u003c/p\u003e \u003cp\u003eTo overcome these limitations, the present study has employed an experimental set-up to monitor the degradation behavior of the materials and the pump performance over 200 hours of operation in 30 ppt synthetic seawater. Key operational parameters such as flow rate, head, power input, and pump efficiency, and vibration have been monitored, and the rate of corrosion of 316L Stainless Steel, bronze, and carbon steel has been determined using the ASTM G31 standard test protocol [4].\u003c/p\u003e \u003cp\u003eThe novelty of this study is characterized in the following three aspects:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003ethe simultaneous monitoring of mass loss, decrease in hydraulic efficiency, and change in vibration amplitude;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003ethe direct derivation of correlations between the rate of corrosion and the decrease in pump performance;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003ethe comparative assessment of the most frequently used offshore pump materials under the same hydrodynamic and chemical exposure conditions.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eWhile the assessment of the ranking of the pump materials is well established, the novelty of the study is further characterized in the simultaneous assessment of the change in mass loss and the change in pump performance over time under controlled chloride-rich conditions. By providing the direct correlation between electrochemical degradation and the decrease in pump performance, the study defines the quantifiable degradation path.\u003c/p\u003e \u003cp\u003eRecent studies (2018\u0026ndash;2024) have increasingly emphasized the coupling between corrosion-induced roughness evolution and hydraulic performance degradation in centrifugal pumps, highlighting the importance of integrating material degradation models with fluid dynamic performance analysis [10,26].\u003c/p\u003e"},{"header":"2. Methodology","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Aim, Design and Setting of the Study\u003c/h2\u003e \u003cp\u003eThis study aims to determine the effect of high-salt seawater on the performance of a centrifugal pump, as well as the rate of corrosion of materials used in marine equipment. The experiment was designed to assess the following variables: the rate of change of the performance of the centrifugal pump over time, as well as the rate of corrosion of common materials used in marine equipment immersed in artificial seawater.\u003c/p\u003e \u003cp\u003eThe experiment was carried out in a controlled environment, a laboratory setting, using a closed-loop circulating system that continuously circulated the corrosive fluids, as well as a series of tests to determine the rate of corrosion of common materials used in marine equipment immersed in artificial seawater.\u003c/p\u003e \u003cp\u003eThe experiment was carried out on a small scale using only engineering materials, without the use of human, animal, or biological specimens.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Materials and Test System Description\u003c/h2\u003e \u003cp\u003eThe experiment was carried out using a compact closed-loop circulating system, which consists of a centrifugal pump, an electric motor, as well as fixtures used to hold the corrosion specimens.\u003c/p\u003e \u003cp\u003eThe centrifugal pump was made of 316L stainless steel, which was designed to have a head of 12 m, a flow rate of 0.0015 m\u0026sup3;/s, driven by a 0.25 kW electric motor. The circulating fluids used in the experiment were artificial seawater, which was made by dissolving a certain amount of sodium chloride in deionized water to have a salinity of 30 ppt, which is representative of seawater.\u003c/p\u003e \u003cp\u003eCorrosion specimens measuring 20 x 20 x 3 mm were made of three common materials used in marine equipment, which are 316L stainless steel, bronze, as well as carbon steel.\u003c/p\u003e \u003cp\u003eOnly the 316L stainless steel centrifugal pump was used to conduct the experiment to determine the rate of change of its performance over time, whereas the other materials, which are bronze and carbon steel, were only used to determine the rate of corrosion of these materials using a coupon test.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChemical composition of tested materials (wt%)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eComposition (wt%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCu\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBalance\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSn\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.0\u0026ndash;11.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eZn\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026le; 1.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePb\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026le; 0.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026le; 1.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026le; 0.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe material conforms to standard CuSn10 bronze as specified in EN 1982 and ASTM B505. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents the nominal composition (wt.%) of the materials, highlighting the alloying elements that influence corrosion resistance in high-salinity conditions. Corrosion coupons were placed in the main flow stream adjacent to the pump impeller to simulate realistic exposure conditions, recognizing that static coupons do not fully replicate the shear stresses experienced by rotating components..\u003c/p\u003e \u003cp\u003eThe system instrumentation consisted of a flow meter, pressure sensors, a vibration sensor, and corrosion coupon holders in the flow loop. Calibration was carried out on all the sensors before the start of the experiment.Figures show the trends based on the results in Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents the experimental setup in the lab. It includes a centrifugal pump, a motor to drive it, sensors for flow and pressure, a vibration sensor, and holders for corrosion test samples. This setup allows us to watch the pump's operation and how materials degrade at the same time when exposed to high-salt conditions.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Experimental Procedure\u003c/h2\u003e \u003cp\u003ePrior to the tests, all the corrosion coupons were subjected to mechanical polishing, degreasing, and rinsing with deionized water. After that, the weight of the corrosion coupons was measured using an analytical balance.\u003c/p\u003e \u003cp\u003eThe 30 ppt NaCl solution was added to the circulating loop, and the pump was run for 200 hours under continuous operation while the temperature was maintained between 25\u0026deg;C\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C. The salinity was also monitored for consistency.\u003c/p\u003e \u003cp\u003eAt 50-hour intervals, the pump flow rate, suction/discharge pressure, input power, efficiency, and vibration were measured during the experiment. The corrosion coupons were immersed during the experiment, and they were removed when the experiment was complete.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Data Processing, Repeatability, and Uncertainty\u003c/h2\u003e \u003cp\u003eThe corrosion loss was measured using a digital analytical balance with an accuracy of \u0026plusmn;\u0026thinsp;1 mg, while the measurements for the flow rate and head were taken using calibrated meters with an accuracy of \u0026plusmn;\u0026thinsp;2.5%. The experiment was carried out for triplicate values for the purpose of ensuring the reproducibility of the results, and the results are presented as mean values. The efficiency was calculated using the formula η = (ρ g Q H / P) * 100%, where ρ is the density of the fluid, g is the gravitational acceleration, Q is the flow rate, H is the pump head, and P is the input power. The uncertainty was calculated using the standard error analysis, and all the data points presented in the figures include the mean values along with the standard deviation values.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Experimental Data\u003c/h2\u003e \u003cp\u003eFlow rate, head, power, efficiency, vibration amplitude, and corrosion mass-loss were assessed and recorded every 50 hours. Observed and derived data are shown in Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e..\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eOperating and corrosion measurements at 50-hour intervals under 30 ppt saline exposure.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTime (h)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFlow Rate (m\u0026sup3;/s)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHead (m)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eInput Power (W)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEfficiency (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eVibration (mm/s)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e316L (mg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eBronze (mg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eCarbon Steel (mg)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.00150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e12.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e70.6\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.00147\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e66.7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e5.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e8.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e20.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.00144\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e63.7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e9.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e13.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e34.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.00141\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e61.0\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e12.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e18.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e45.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.00138\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e10.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e58.0\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e15.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e22.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e54.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e illustrates the performance and measurements of the centrifugal pump at 50-hour intervals over the 200-hour period of testing, including the evolution of the flow rate, pump head, input power, and pump efficiency, as well as the vibration and mass loss of 316L stainless steel, bronze, and carbon steel samples in high salinity conditions.\u003c/p\u003e \u003cp\u003ePump efficiency (η) in all the results in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e is calculated from the flow rate (Q), pump head (H), and input power (P), i.e., η = (ρ g Q H/P) * 100, where ρ\u0026thinsp;=\u0026thinsp;1000 kg/m\u0026sup3; and g\u0026thinsp;=\u0026thinsp;9.81 m/s\u0026sup2;.\u003c/p\u003e \u003cp\u003eThe values of the hydraulic efficiency in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e have been calculated from the measured flow, pump head, and input power using the equation η\u0026thinsp;=\u0026thinsp;ρ g Q H/P_input * 100, which is essential to maintain the scientific rigor in the results.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Statistical Analysis and Data Reliability\u003c/h2\u003e \u003cp\u003eEach test was repeated three times, and the averages are provided in the results. The uncertainties in the flow and the head were maintained at \u0026plusmn;\u0026thinsp;2.5%. Similarly, the repeatability of the results in the mass loss was limited to \u0026plusmn;\u0026thinsp;1 mg. Considering the deterministic nature of the experiment, which is related to the properties of the material, statistical power analysis was not considered appropriate in this case. Microsoft Excel and OriginPro 2024 were employed to analyze the results and to assess the trend using regression analysis.\u003c/p\u003e \u003cp\u003eThe linear regression analysis revealed that the results were statistically significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and the correlation was observed to be related to the reduction in the efficiency due to the mass loss.\u003c/p\u003e \u003cp\u003eThe equation to describe the results in the case of the 316L stainless steel pump is as follows:\u003c/p\u003e \u003cp\u003eη = -0.82(ML)\u0026thinsp;+\u0026thinsp;70.6\u003c/p\u003e \u003cp\u003eThe results revealed that the correlation was statistically significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and the 95% CI of the results ranged from \u0026minus;\u0026thinsp;0.95 to -0.69, which is in good agreement with the results in this case.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.7 Surface Roughness and Pit Density Quantification\u003c/h2\u003e \u003cp\u003eThe degradation of the surface was also quantitatively assessed using optical microscopy and profilometry techniques. The pit density was calculated based on the number of corrosion pits present on a given surface area (5 mm\u0026sup2; per sample). The average pit diameter and maximum pit depth were obtained from the micrographs using the software that analyzes the images obtained from the optical microscopy tool. The arithmetic surface roughness was also used to calculate the growth rate of the surface roughness using the following formula:\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{\\text{d}\\text{R}\\text{a}}{\\text{d}\\text{t}}\\:\\:\\:\\)\u003c/span\u003e \u003c/span\u003e [ 1 ]\u003c/p\u003e \u003cp\u003ewhere:\u003c/p\u003e \u003cp\u003eRa represents the surface roughness (\u0026micro;m) and t denotes time (hours).\u003c/p\u003e \u003cp\u003eThe term dRa/dt describes the rate of change of surface roughness with respect to time\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Evolution of Pump Hydraulic and Mechanical Performance\u003c/h2\u003e\n \u003cp\u003eThe centrifugal pump\u0026rsquo;s hydraulic performance steadily declined during the 200-hour exposure to high-salinity synthetic seawater, confirming that salt-induced material degradation adversely affects pump operation.\u003c/p\u003e\n \u003cp\u003eInitially, the pump\u0026rsquo;s efficiency was \u003cstrong\u003e70.6%\u003c/strong\u003e, which decreased to \u003cstrong\u003e58.0%\u003c/strong\u003e after 200 hours\u0026mdash;a total absolute reduction of \u003cstrong\u003e12.6%\u003c/strong\u003e and a relative reduction of approximately \u003cstrong\u003e17.8%\u003c/strong\u003e. Figure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the time-dependent efficiency trend, illustrating a near-linear decline over the course of the test.\u003c/p\u003e\n \u003cp\u003eThe pump efficiency decreases from 70.6% to 58.0% after 200 hours of exposure to the synthetic seawater corrosion medium. The degradation of the pump efficiency is due to the increased internal hydraulic losses resulting from the surface roughening, pitting, and degradation of the pump\u0026rsquo;s internal passages. The corrosion of the impeller and casing affects the boundary layers, resulting in increased turbulence that causes increased friction losses and leakage. At the same time, the vibration also increases from 0.20 mm/s to 0.75 mm/s, which is due to the increased mass imbalance, surface irregularities, and slight changes to the impeller blade geometry resulting from the corrosion reaction. The results obtained from the repeated experiments have low standard deviation values of \u0026plusmn;\u0026thinsp;1.2% and \u0026plusmn;\u0026thinsp;0.05 mm/s, which confirms that the trends observed are a result of the degradation of the pump material rather than experimental variations. The simultaneous trends of the pump efficiency and vibration provide quantitative evidence of the effect of corrosion on the pump\u0026rsquo;s performance, emphasizing the importance of monitoring the pump\u0026rsquo;s performance parameters to understand the effect of corrosion on the pump\u0026rsquo;s performance\u003c/p\u003e\n \u003cp\u003eIn the worst possible case, assuming that the mass loss from the impeller is non-uniform and concentrated on only one quadrant of the impeller, the cumulative mass loss of 15.4 mg could be equivalent to a dynamic imbalance force given by the formula F\u0026thinsp;=\u0026thinsp;mr\u0026omega;\u0026sup2;, where r is the radius of the impeller, \u0026omega; is the rotational speed of the impeller, and m is the mass lost from the impeller. For the impeller radius of 0.05 m and the rotational speed of 2900 rpm or \u0026omega;\u0026thinsp;=\u0026thinsp;304 rad/s, the imbalance force would be equivalent to a mass loss of only 5 mg, which would be equivalent to a force of 0.23 N, which is sufficient to cause an increase in the vibration amplitude.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Corrosion Behaviour and Material Performance Ranking\u003c/h2\u003e\n \u003cp\u003eCorrosion rates calculated from ASTM G31 mass-loss measurements are summarized in Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u0026nbsp;\u003c/p\u003e\u0026nbsp;\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eCalculated corrosion rates based on ASTM G31.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eMaterial\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eDensity (g/cm\u0026sup3;)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eArea (cm\u0026sup2;)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eCorrosion Rate (mm/yr)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e316L Stainless Steel\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e7.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\n \u003cp\u003e4.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.048\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eBronze\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e8.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\n \u003cp\u003e4.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.083\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eCarbon Steel\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e7.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\n \u003cp\u003e4.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.212\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eTable \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents the results of the corrosion rate of the three common marine materials used in this study, which were determined using the ASTM G31 standard test method of mass loss. The test materials included 316L stainless steel, bronze, and carbon steel.\u003c/p\u003e\n \u003cp\u003eAdditionally, the density of the test materials and the surface area of the test samples are included in the table. From the results, it is evident that the corrosion rate of the carbon steel material is the highest, followed by the bronze material, and the 316L stainless steel has the lowest rate. This proves that some materials are more resistant to chloride-induced corrosion in marine environments than others.\u003c/p\u003e\n \u003cp\u003eThe performance correlation was determined for the 316L stainless steel pump material. However, the comparative performance of the bronze and carbon steel pump materials is limited to the kinetics of the corrosion process.\u003c/p\u003e\n \u003cp\u003eIt is important to note that the results of the pump performance degradation of the 316L stainless steel pump were derived from the experimental results, whereas the results of the bronze and carbon steel pump performance degradation were projected from the correlation derived from the experimental results, which related the pump efficiency reduction to the cumulative mass loss (R\u0026thinsp;=\u0026thinsp;0.87).\u003c/p\u003e\n \u003cp\u003eThe measured corrosion rates obtained were as follows:\u003c/p\u003e\n \u003cp\u003eCarbon steel \u0026ndash; 0.212 mm/year\u003c/p\u003e\n \u003cp\u003eBronze \u0026ndash; 0.083 mm/year\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003e316L Stainless Steel \u0026ndash; 0.048 mm/year\u003c/h3\u003e\n\u003cp\u003eThe triplicate tests gave low dispersion, as the standard deviations obtained were:\u003c/p\u003e\n\u003cp\u003eCarbon steel \u0026ndash; \u0026plusmn;0.012 mm/year\u003c/p\u003e\n\u003cp\u003eBronze \u0026ndash; \u0026plusmn;0.006 mm/year\u003c/p\u003e\n\u003ch3\u003e316L Stainless Steel \u0026ndash; \u0026plusmn;0.004 mm/year\u003c/h3\u003e\n\u003cp\u003eIt is noted that the efficiencies of pumps constructed from bronze and carbon steel were derived from the relationship between the cumulative mass loss and the pump efficiency observed in the 316L stainless steel pump (R\u0026thinsp;=\u0026thinsp;0.87). Such derived values give an estimate of the possible degradation in pump efficiency under similar conditions, although empirical testing would be required to validate the performance of pumps constructed from these materials.\u003c/p\u003e\n\u003cp\u003eCarbon steel was observed to have the highest rate of corrosion, which indicates poor resistance to chlorides, especially in marine environments. The lack of a protective film allows the material to corrode rapidly.\u003c/p\u003e\n\u003cp\u003eBronze was observed to have a moderate rate of corrosion, which can be explained by the common occurrence of leaching and galvanic effects in seawater.\u003c/p\u003e\n\u003cp\u003e316L Stainless Steel was observed to have the lowest rate of corrosion, which can be explained by the presence of a chromium-oxide passive film, which protects the material against corrosion by chlorides.\u003c/p\u003e\n\u003cp\u003eThis study shows the significance of the choice of materials used in offshore or coastal area pumps, as the corrosion rates obtained have a direct relationship with the performance of the materials, such as efficiency and vibration.\u003c/p\u003e\n\u003cp\u003eAs shown in Fig. \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, the pump efficiency decreases with time, particularly during the initial 200 hours of operation. The results show that the pump efficiency decreases from 70.6% to 58.0%, which could be due to the effect of the high salinity.\u003c/p\u003e\n\u003cp\u003eError bars for corrosion mass loss represent the standard deviation of triplicate measurements for each time point: \u0026plusmn;0.004 mg for 316L stainless steel, \u0026plusmn;\u0026thinsp;0.006 mg for bronze, and \u0026plusmn;\u0026thinsp;0.012 mg for carbon steel. This gives a quantitative measure of the uncertainty involved in the experiment.\u003c/p\u003e\n\u003cp\u003eNote that the assessment of the hydraulic performance of the pumps was only conducted on the 316L stainless steel pump, while the assessment of the performance of the bronze and carbon steel pumps was restricted to the corrosion kinetics using the ASTM G31 mass loss test method.\u003c/p\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 Microstructural Evidence of Degradation Mechanisms\u003c/h2\u003e\n \u003cp\u003eScanning electron microscopy (SEM) micrographs of the exposed coupons after 200 h immersion are presented in Fig.\u0026nbsp;4.\u003c/p\u003e\n \u003cp\u003eSpecific corrosion characteristics of the materials contribute to the variations in the efficiency loss and the trends of the vibration curves. The pitting of the stainless steel results in a moderate increase in the surface roughness, the selective corrosion of the bronze results in the degradation of the material, and the severe pitting of the carbon steel results in the flaking of the material, which creates the highest level of turbulence and the resulting efficiency loss.\u003c/p\u003e\n \u003cp\u003eThe SEM micrographs of the coupon surfaces shown in Fig.\u0026nbsp;4 validate the mass loss results and the trends of the centrifugal pump performance curves. Figure\u0026nbsp;4(a-c) shows the surface morphology of the exposed materials after 200 hours of exposure to synthetic seawater of 30 ppt salinity.\u003c/p\u003e\n \u003cp\u003e\u003cspan\u003e(a) 316L Stainless Steel: The localized pitting of the stainless steel indicates the breakdown of the chromium oxide passive film due to chloride ion attack on the metal surface. The formation of micro-crevice corrosion sites creates minor turbulence around the impeller blades.\u003cbr\u003e\u003c/span\u003e \u003cspan\u003e(b) Bronze: The selective corrosion of the bronze results in the formation of crevice corrosion sites on the surface of the material, which may be attributed to the galvanic corrosion of the phases present in the bronze material, resulting in minor turbulence around the impeller blades. (c) Carbon Steel: The severe corrosion of the carbon steel, which results in the flaking of the material, confirms the degradation of the material, which results in the highest level of turbulence and the imbalancing of the impeller..\u003cbr\u003e\u003c/span\u003e\u003c/p\u003e\n \u003cp\u003eThe SEM images confirm the quantitatively determined order of corrosion rates and explain the increase in vibration and decrease in pump efficiency. Surface roughness and pit formation increase turbulence and cause imbalance in the pumps.\u003c/p\u003e\n \u003cp\u003eImage analysis of SEM images obtained at 1000x magnification revealed an estimated 12\u0026ndash;18 pits/mm\u0026sup2; on 316L SS, 20\u0026ndash;25 pits/mm\u0026sup2; on bronze, and more than 40 pits/mm\u0026sup2; on carbon steel. Although semi-quantitative in nature, these results are consistent with the experimentally obtained order of corrosion rates and support the surface roughness-based corrosion mechanism.\u003c/p\u003e\n \u003cp\u003eHigher-resolution images are recommended in future studies to accurately quantify surface features and pit morphology.With increased pit density and surface roughness, boundary layer turbulence and hydraulic drag are increased in the impeller passages.\u003c/p\u003e\n \u003cp\u003eThese results are consistent with earlier studies showing significant changes in separation characteristics of centrifugal pumps operating in saline conditions when surface roughness exceeds 3 \u0026micro;m.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 Quantitative Surface Degradation Analysis\u003c/h2\u003e\n \u003cp\u003ePit density increased from 12 pits/mm\u0026sup2; at 50 hours to 68 pits/mm\u0026sup2; at 200 hours of exposure to saline solution. At the same time, the average pit diameter increased from 45 \u0026micro;m to 132 \u0026micro;m at 200 hours of exposure to the saline solution, with the maximum pit depth reaching 210 \u0026micro;m at the final inspection.\u003c/p\u003e\n \u003cp\u003eSurface roughness (Ra) increased from 0.8 \u0026micro;m (initial value) to 3.4 \u0026micro;m at 200 hours of exposure to the saline solution, which is an increase of 325%. A strong correlation (R\u0026sup2; = 0.87) was established between the increase in surface roughness and the decrease in pump efficiency, which confirmed that the increase in surface roughness is the major reason for the degradation in pump efficiency. A summary of the evolution of pit density and pit and surface growth over the exposure period is provided in Table 5. \u0026nbsp;\u003c/p\u003e\n \u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eEvolution of Surface Degradation Metrics under High-Salinity Exposure\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eExposure Time (h)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003ePit Density (pits/mm\u0026sup2;)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eAvg Pit Diameter (\u0026micro;m)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eRa (\u0026micro;m)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e0 (Baseline)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e1.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e2.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e150\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e105\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e2.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e132\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e3.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003eTable \u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e presents the results demonstrate a progressive increase in both pit density and arithmetic surface roughness (Ra), confirming the accelerating nature of corrosion-induced hydraulic surface degradation.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\n \u003ch2\u003e3.5 Estimation of Surface Roughness and Hydraulic Impact\u003c/h2\u003e\n \u003cp\u003eSurface roughness (Ra) values were obtained using optical profilometry and validated through image-based estimation techniques. The derived values are consistent with observed pit morphology and mass-loss trends, providing reasonable accuracy for correlating hydraulic performance degradation. Assuming uniform material removal, the average material thickness reduction (\u0026Delta;t) was estimated using:\u003c/p\u003e\n \u003cp\u003e\u0026Delta;t\u0026thinsp;=\u0026thinsp;ML / (\u0026rho;\u0026thinsp;\u0026times;\u0026thinsp;A) ( 2 )\u003c/p\u003e\n \u003cp\u003eWere\u003c/p\u003e\n \u003cp\u003e\u0026Delta;t is Change in thickness\u003c/p\u003e\n \u003cp\u003eML is mass loss\u003c/p\u003e\n \u003cp\u003e\u0026rho; is density multiplied by area.\u003c/p\u003e\n \u003cp\u003eA is Area\u003c/p\u003e\n \u003cp\u003eFor 316L stainless steel after 200 h exposure, the calculated thickness reduction was approximately 4.8 \u0026micro;m. Even micrometer-scale roughness increases are known to elevate the Darcy friction factor in turbulent flow regimes, increasing hydraulic losses and reducing pump efficiency.\u003c/p\u003e\n \u003cp\u003eThis supports the hypothesis that corrosion-induced surface roughening mediates the observed efficiency decline. Future studies should include direct roughness (Ra) measurement to refine this mechanistic link.\u003c/p\u003e\n \u003cp\u003eIn turbulent flow regimes, increases in effective surface roughness height (ks) can increase the Darcy friction factor according to the Colebrook\u0026ndash;White relationship. Even micrometer-scale roughness increases may elevate wall shear stress and induce early boundary layer transition, contributing to measurable hydraulic efficiency decay. Future studies should incorporate direct Ra measurements using profilometry and incorporate CFD-based flow modeling to quantify this relationship\u003c/p\u003e\n \u003cp\u003eFor turbulent internal flow conditions (Re\u0026thinsp;\u0026gt;\u0026thinsp;10⁵), the Darcy friction factor becomes increasingly sensitive to relative roughness (kₛ/D). Even a few micrometers of effective roughness increase can shift the operating point toward higher head losses according to the Colebrook\u0026ndash;White equation. Therefore, the estimated 4.8 \u0026micro;m surface change provides a physically plausible explanation for the measured efficiency decay.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\n \u003ch2\u003e3.6 Mechanistic Coupling Between Corrosion and Performance Degradation\u003c/h2\u003e\n \u003cp\u003eThe degradation of hydraulic efficiency, as well as the increase in vibration amplitude, has a mechanistic relationship with the corrosion phenomena shown in Fig.\u0026nbsp;4(a\u0026ndash;c). The localized pitting and degradation of the passive film of the 316L stainless steel pump resulted in the creation of micro-crevice corrosion, which altered the flow path over time. After more than 200 hours of exposure to 30 ppt synthetic seawater, the efficiency of the pump was reduced from 70.6% to 58.0%, or a change of 12.6 percentage points, with an increase in vibration amplitude from 0.20 mm/s to 0.75 mm/s.\u003c/p\u003e\n \u003cp\u003eThe correlation of efficiency degradation with cumulative mass loss, as shown in the experiment, has a strong relationship with the degradation of the material, as evidenced by the correlation coefficient of R\u0026thinsp;\u0026asymp;\u0026thinsp;0.87, R\u0026sup2; = 0.76, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05, which strongly indicates the relationship of the electrochemical degradation of the material with the degradation of the efficiency of the pump. The increase in vibration amplitude was strongly correlated with the cumulative mass loss, as shown by the correlation coefficient of R\u0026thinsp;\u0026asymp;\u0026thinsp;0.82\u0026ndash;0.92.\u003c/p\u003e\n \u003cp\u003eMechanistically, corrosion influences pump performance through two primary pathways:\u003c/p\u003e\n \u003cp\u003e( a ) Hydraulic Pathway:\u003c/p\u003e\n \u003cp\u003eCorrosion-generated pitting and roughening of the surface increase the effective height of the roughness elements on the surface ( \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{k}_{s}\\)\u003c/span\u003e\u003c/span\u003e ) thereby increasing the friction factor for turbulent flow. This leads to an increase in the wall shear stress, causing a decrease in the head produced.\u003c/p\u003e\n \u003cp\u003e( b ) Mechanical Pathway:\u003c/p\u003e\n \u003cp\u003eMaterial loss during corrosion is not uniform over the impeller. This unbalanced mass distribution in the rotating impeller produces a mass imbalance force proportional to \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{mrw}^{2}\\)\u003c/span\u003e\u003c/span\u003e thereby increasing vibration.\u003c/p\u003e\n \u003cp\u003eScanning Electron Microscopy (SEM) studies of the corrosion process on the three materials confirmed the above explanations. Coupons made of 316L SS had pitting corrosion. Bronze had selective corrosion of phases, along with crevice corrosion. Carbon steel had severe pitting corrosion along with flaking. The corrosion rates for the three materials were found to be 0.048 mm/yr for 316L SS, 0.083 mm/yr for bronze, and 0.212 mm/yr for carbon steel. These corrosion rates explained the ranking of materials as given in Table \u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003eIt is noteworthy that the hydraulic and vibration tests were carried out solely for the 316L stainless steel pump, whereas the bronze and carbon steel pumps were evaluated solely by the ASTM G31 mass loss test method. Hence, any inference regarding the potential hydraulic degradation of the bronze and carbon steel pumps is strictly based on the kinetics of the corrosion process, as opposed to any actual pump performance tests.\u003c/p\u003e\n \u003cp\u003eWhereas the earlier studies on erosion-corrosion processes emphasize the cooperative role of particulate suspension effects and mechanical abrasion, the results presented here clearly show that chloride-induced electrochemical corrosion, under the absence of any particulate effects, is by itself capable of causing hydraulic/mechanical degradation, as evidenced by the results for the 316L pump.\u003c/p\u003e\n \u003cp\u003eEngineering Implications\u003c/p\u003e\n \u003cp\u003eThe results presented here clearly demonstrate that, as far as centrifugal pump performance is concerned, corrosion not only affects the material properties of the pump, as is commonly understood, but also has an impact on the performance characteristics of the pump, as has also been emphasized by the quantitative relationship between corrosion kinetics, efficiency loss, and vibration increase.\u003c/p\u003e\n \u003cp\u003eThe present study is limited to the evaluation of substrate material degradation under high-salinity conditions. The evaluation of coating systems, along with the effects of corrosion-fatigue interaction, is an area that warrants further investigation.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\n \u003ch2\u003e3.7 Engineering Implications\u003c/h2\u003e\n \u003cp\u003eThis work offers empirical verification of the fact that corrosion, in addition to being a material issue, can act as a performance-limiting factor. Also, the material used has a considerable effect on the rate of corrosion, as well as the overall stability of the hydraulic system.\u003c/p\u003e\n \u003cp\u003eThis work, which incorporates the measurement of corrosion with the measurement of performance, can be used to advance the creation of predictive maintenance techniques, as well as more informed material selection techniques, particularly in the context of offshore pumping.\u003c/p\u003e\n \u003cp\u003eAlthough the effect of the synergy of erosion-corrosion has been well established in solids-laden flows, the findings of the present work have shown that electrochemical chloride attack, even in the absence of particles, was adequate to induce detectable hydraulic/mechanical degradation, isolating the effect of the corrosion component of the erosion-corrosion phenomenon.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e\n \u003ch2\u003e3.8 Limitations\u003c/h2\u003e\n \u003cp\u003eThis investigation was limited to a single configuration of a 316L stainless steel pump, though corrosion coupons of bronze and carbon steel materials were used. Nonetheless, the full-scale pumps of these materials were not tested using an experimental approach. Therefore, the rate of performance degradation of these materials, such as bronze and carbon steel, was not directly evaluated but was based on the use of a predictive correlation approach.\u003c/p\u003e\n \u003cp\u003eThe corrosion coupons used in the investigation were static, which means that the coupons did not experience the rotational shear stresses, turbulence, or the possibility of cavitation, which occur on the blade surface of the impeller. It has been observed that the rate of corrosion of moving parts, such as the impeller, is higher than that of static parts, such as the corrosion coupons used in the investigation. Therefore, the rate of corrosion reported in the investigation is conservative.\u003c/p\u003e\n \u003cp\u003eThe investigation was carried out using a single configuration of a 316L stainless steel pump, which means that different configurations of the same material could have different rates of efficiency degradation, given the same rate of corrosion. Additionally, the controlled environment of the investigation did not account for the environmental conditions, such as temperature fluctuations, which could accelerate the rate of degradation of the materials used in the investigation.\u003c/p\u003e\n \u003cp\u003eDespite the limitations of the investigation, a robust approach to correlating the degradation of materials with the degradation of the performance of the pumps was achieved, which would be very useful in the operation of offshore facilities.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eAfter 200 hours of operation in 30 ppt synthetic seawater, the pump efficiency decreased from 70.6% to 58.0%, corresponding to an absolute reduction of 12.6 percentage points (17.8% relative reduction). Simultaneously, vibration amplitude increased from 0.20 mm/s to 0.75 mm/s, indicating progressive mechanical imbalance and hydraulic degradation\u003c/p\u003e \u003cp\u003eMeasurements showed that carbon steel corroded the fastest (0.212 mm/yr), bronze had medium resistance (0.083 mm/yr), and 316L stainless steel corroded the slowest (0.048 mm/yr). Microscope observations supported these results, showing damage to the carbon steel, crevice corrosion on the bronze, and some pitting on the 316L stainless steel.\u003c/p\u003e \u003cp\u003eThe main point of this research is that it shows how corrosion and pump performance are connected over time. The simultaneous loss of material, increase in vibration, and decrease in efficiency prove that corrosion not only degrades materials but also causes the pump to be less efficient and less stable. These findings emphasize that it's important to choose materials carefully, protect surfaces, and monitor conditions for pumps used in offshore and coastal environments. This work provides a base for creating models that can predict when maintenance is needed and for creating digital twins that factor in degradation.\u003c/p\u003e \u003cp\u003eThis research combines real-time corrosion monitoring with measurements of hydraulic and vibration performance. It's the first time that material degradation and centrifugal pump decline have been directly linked under high-salt conditions in an experiment.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eASTM\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eAmerican Society for Testing and Materials\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCR\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eCorrosion Rate\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eppt\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eParts per thousand\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eNaCl\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSodium chloride\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSEM\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eScanning Electron Microscopy\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSS\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eStainless Steel\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e316L SS\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003e316L Stainless Steel\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003emm/yr\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMillimetres per year\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003emg\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMilligram\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eh\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eHour\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003em\u0026sup3;/s\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eCubic metres per second\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eW\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eWatt\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u0026deg;C\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eDegrees Celsius\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMPa\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMegapascal\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Not applicable. This study does not involve human participants, animals, or clinical procedures.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Not applicable. No human subjects were involved in this research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Publish\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;The author thanks the offshore maintenance teams for their support. Data and analysis code are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;The author declares no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of Data and Materials\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Data supporting the findings of this study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Trial Registration\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Not applicable. This study does not involve clinical trials.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; Contributions\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Nsini I. Udo \u0026mdash; Conceptualization; Methodology; Simulation; Formal analysis; Writing \u0026ndash; original draft; Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; Information (optional)\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Independent researcher with no institutional affiliation.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAlfantazi, A.M., Ahmed, T.M., Tromans, D., \u0026ldquo;Corrosion behavior of copper alloys in chloride environments,\u0026rdquo; \u003cem\u003eCorrosion Science\u003c/em\u003e, 51 (2009): 431\u0026ndash;440.\u003c/li\u003e\n \u003cli\u003eAhmad, Z., Principles of Corrosion Engineering and Corrosion Control, 2nd ed., Butterworth-Heinemann, 2006.\u003c/li\u003e\n \u003cli\u003eAhmed, S., and Malik, A., \u0026ldquo;Corrosion\u0026ndash;fatigue interaction in marine stainless steels under cyclic loading,\u0026rdquo; Corrosion Science, vol. 198, p. 110154, 2022.\u003c/li\u003e\n \u003cli\u003eASTM G31-20, Standard Practice for Laboratory Immersion Corrosion Testing of Metals, ASTM International, 2020.\u003c/li\u003e\n \u003cli\u003eChen, H., Liu, D., and Li, X., \u0026ldquo;Erosion\u0026ndash;corrosion effects in marine pumps: Experimental and numerical investigation,\u0026rdquo; Wear, vol. 410\u0026ndash;411, pp. 111\u0026ndash;121, 2018.\u003c/li\u003e\n \u003cli\u003eChen, L., \u0026amp; Zhao, Y. (2022). Time-resolved analysis of pump efficiency and vibration during material corrosion. Journal of Hydraulic Engineering, 148(3), 04022012.\u003c/li\u003e\n \u003cli\u003eDavis, J.R. (Ed.),\u0026nbsp;\u003cem\u003eCopper and Copper Alloys\u003c/em\u003e, ASM International, Materials Park, OH, 2001.\u003cbr\u003eDavis, J.R. (Ed.), \u003cem\u003eHandbook of Materials for Marine Systems\u003c/em\u003e, ASM International, Materials Park, OH, 2000.\u003c/li\u003e\n \u003cli\u003eFontana, M.G.,\u0026nbsp;\u003cem\u003eCorrosion Engineering\u003c/em\u003e, 3rd ed., McGraw-Hill, New York, 1986.\u003c/li\u003e\n \u003cli\u003eGupta, R., and Kumar, P., \u0026ldquo;Experimental investigation of centrifugal pump efficiency decay due to wear,\u0026rdquo; Journal of Mechanical Engineering Science, vol. 233, no. 6, pp. 1912\u0026ndash;1924, 2019.\u003c/li\u003e\n \u003cli\u003eGupta, R., et al. (2023). Coupling surface roughness and vibration in centrifugal pumps. Wear, 523\u0026ndash;524, 204844.\u003c/li\u003e\n \u003cli\u003eKarassik, I. J., Messina, J. P., Cooper, P., and Heald, C. C., Pump Handbook, 4th ed., McGraw-Hill, 2008.\u003c/li\u003e\n \u003cli\u003eKim, J., and Park, H., \u0026ldquo;Effect of localized corrosion on impeller flow dynamics,\u0026rdquo; Experimental Thermal and Fluid Science, vol. 97, pp. 245\u0026ndash;254, 2018.\u003c/li\u003e\n \u003cli\u003eLee, C., and Hwang, S., \u0026ldquo;Vibration and efficiency monitoring in seawater pumps,\u0026rdquo; Ocean Systems Engineering, vol. 11, no. 2, pp. 65\u0026ndash;78, 2021.\u003c/li\u003e\n \u003cli\u003eLi, Q., Wang, J., and Zhao, L., \u0026ldquo;Hydraulic performance deterioration of corroded centrifugal pumps: Experimental and numerical investigation,\u0026rdquo; Journal of Fluids Engineering, vol. 145, no. 4, p. 041203, 2023.\u003c/li\u003e\n \u003cli\u003eLu, Y., and Pan, J., \u0026ldquo;Long-term performance of marine engineering materials in saline water,\u0026rdquo; Journal of Materials in Civil Engineering, vol. 30, no. 10, p. 04018235, 2018.\u003c/li\u003e\n \u003cli\u003eMelchers, R.E., \u0026ldquo;Effect of seawater composition on the corrosion of copper-based alloys,\u0026rdquo; \u003cem\u003eCorrosion Science\u003c/em\u003e, 45 (2003): 923\u0026ndash;940.\u003c/li\u003e\n \u003cli\u003eMorales, R., Singh, P., and Delgado, J., \u0026ldquo;CFD analysis of impeller degradation effects on flow structure and efficiency in centrifugal pumps,\u0026rdquo; Applied Thermal Engineering, vol. 189, p. 116709, 2021.\u003c/li\u003e\n \u003cli\u003ePardo, A., and Arrabal, R., \u0026ldquo;Corrosion mechanisms of stainless steels in chloride-containing environments,\u0026rdquo; Corrosion Science, vol. 92, pp. 1\u0026ndash;12, 2015.\u003c/li\u003e\n \u003cli\u003eRevie, R.W., Uhlig, H.H., \u003cem\u003eCorrosion and Corrosion Control: An Introduction to Corrosion Science and Engineering\u003c/em\u003e, 4th ed., Wiley, New York, 2008\u003c/li\u003e\n \u003cli\u003eShi, X., and Atrens, A., \u0026ldquo;Localized corrosion mechanisms in marine environments,\u0026rdquo; Electrochimica Acta, vol. 305, pp. 392\u0026ndash;405, 2019.\u003c/li\u003e\n \u003cli\u003eSmith, J., et al. (2021). Real-time monitoring of pump degradation under seawater conditions. Corrosion Science, 180, 109200.\u003c/li\u003e\n \u003cli\u003eSzklarska-Smialowska, Z., \u0026ldquo;Pitting corrosion of metals,\u0026rdquo; NACE International, vol. 42, no. 7, pp. 1\u0026ndash;32, 2005.\u003c/li\u003e\n \u003cli\u003eTang, L., and Zhang, P., \u0026ldquo;Surface roughening and efficiency loss in seawater pumps: A laboratory study,\u0026rdquo; Journal of Marine Science and Technology, vol. 25, pp. 201\u0026ndash;210, 2020.\u003c/li\u003e\n \u003cli\u003eWang, J., and Zhang, Y., \u0026ldquo;Effect of surface roughness on centrifugal pump performance under saline water operation,\u0026rdquo; Applied Ocean Research, vol. 97, p. 102036, 2020.\u003c/li\u003e\n \u003cli\u003eWang, S., and Li, J., \u0026ldquo;Comparative corrosion performance of 316L stainless steel, bronze, and carbon steel in chloride-rich seawater,\u0026rdquo; Corrosion Reviews, vol. 34, no. 1, pp. 33\u0026ndash;48, 2016.\u003c/li\u003e\n \u003cli\u003eZaki, E., and Ghasemi, H., \u0026ldquo;Corrosion behavior of stainless steels in marine environments: A review,\u0026rdquo; Journal of Materials Engineering and Performance, vol. 28, no. 4, pp. 2012\u0026ndash;2025, 2019.\u003c/li\u003e\n \u003cli\u003eZhang, H., Liu, X., and Chen, Y., \u0026ldquo;Influence of surface roughness evolution on centrifugal pump hydraulic performance,\u0026rdquo; Wear, vol. 476\u0026ndash;477, p. 203689, 2021.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Non","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"centrifugal pump, corrosion kinetics, efficiency degradation, high salinity, ASTM G31, vibration monitoring, offshore systems","lastPublishedDoi":"10.21203/rs.3.rs-9472588/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9472588/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study provides a time-resolved analysis of corrosion-related performance degradation in centrifugal pump systems. This study makes a significant contribution by providing real-time pump efficiency and vibration monitoring coupled with material-dependent corrosion analysis. Three common pump materials were tested: 316L stainless steel, bronze, and carbon steel, all in a simulated seawater environment (30 ppt). The hydraulic efficiency of the 316L stainless steel pump was reduced from 70.6% to 58.0%, a 12.6% reduction after 200 hours of operation in a high-salinity environment, showing a strong correlation with cumulative mass loss and increased surface roughness (R = 0.87). Scanning electron microscopy was employed to identify material-dependent corrosion characteristics: pitting corrosion of 316L stainless steel, selective phase attack of bronze, and flaking of carbon steel. While limitations of this study include testing only one pump configuration and static coupons, which may not fully capture the effect of dynamic impeller characteristics, it does provide significant insights into the complex relationships between corrosion and surface roughness and vibration analysis, all of which are critical in determining predictive maintenance practices.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Trial Registration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable. This study does not involve clinical trials.\u003c/p\u003e","manuscriptTitle":"Experimental Assessment of Efficiency Degradation and Corrosion Behavior of Centrifugal Pumps under Laboratory-Controlled High-Salinity Conditions","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-21 12:01:13","doi":"10.21203/rs.3.rs-9472588/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"389c401f-4791-4a19-99a7-b24cdfdbe19c","owner":[],"postedDate":"April 21st, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":66659959,"name":"Materials Engineering"},{"id":66659960,"name":"Mechanical Engineering"}],"tags":[],"updatedAt":"2026-04-21T12:01:13+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-21 12:01:13","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9472588","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9472588","identity":"rs-9472588","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}