Key Takeaways & Executive Findings
- •• • V2O5 at 0.05 mol/L achieved inhibition efficiencies of 79.90% for 316L SS and 89.58% for 2205 DSS in 6.0 mol/L NaOH + 2.0 mol/L NaCl at 90 °C, demonstrating its superior performance in extreme alkaline chloride environments; this translates to a potential 5–10× extension of component service life in industrial electrolyzers, reducing maintenance downtime and replacement costs. • • Na3PO4 delivered 83.33% inhibition efficiency for 2205 DSS, positioning it as a viable secondary option; however, its performance on 316L SS was lower, indicating alloy-specific compatibility that must be considered in material selection for electrolyzer components. • • EIS data for 316L SS with 0.05 mol/L V2O5 showed Rct = 29,770 Ω·cm² and Rf = 923.50 Ω·cm², with CPEf parameter Y0 at its lowest and n = 1, signifying a dense, uniform film with minimal dispersion; this directly correlates with reduced charge-transfer kinetics and a more effective barrier against corrosive species. • • XPS analysis detected V4+ and V5+ states in the V2O5 system and PO4³− in the Na3PO4 system, confirming the formation of a vanadium/phosphate composite film that modifies the Fe 2p binding energy and suppresses metal dissolution; this mechanistic insight enables the design of tailored inhibitor formulations for specific stainless steel grades.
China Advanced Materials & Deep-Tech Radar
Get verified English translations, SEM micrographs & open-access PDF alerts from China's leading state key laboratories delivered to your inbox every Monday at 08:00 EST.
Abstract
Alkaline seawater electrolysis for hydrogen production imposes severe corrosion on structural stainless steels, particularly in high-temperature, highly alkaline, chloride-rich electrolytes. This study evaluates four inorganic inhibitors—sodium molybdate (Na2MoO4), sodium tungstate (Na2WO4), sodium phosphate (Na3PO4), and vanadium pentoxide (V2O5)—for 316L austenitic stainless steel (316L SS) and 2205 duplex stainless steel (2205 DSS) in a simulated electrolytic seawater environment (6.0 mol/L NaOH, 2.0 mol/L NaCl, 90 °C). Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and 14-day immersion tests quantified inhibition efficiency (IE). Surface morphology and film chemistry were characterized by SEM, optical profilometry (OP), and XPS. V2O5 exhibited the highest IE, reaching 79.90% for 316L SS and 89.58% for 2205 DSS at 0.05 mol/L, followed by Na3PO4 (83.33% for 2205 DSS). Na2MoO4 and Na2WO4 were least effective. EIS fitting revealed that V2O5 markedly increased film resistance (Rf) and charge-transfer resistance (Rct) (e.g., Rct = 29,770 Ω·cm², Rf = 923.50 Ω·cm² for 316L SS), indicating suppressed interfacial charge transfer. XPS confirmed the incorporation of V4+/V5+ and PO4³− species into the surface film, forming a dense, barrier-type vanadium/phosphate composite layer that mitigates corrosion. These findings establish V2O5 and Na3PO4 as promising inhibitors for stainless steel in harsh alkaline electrolytic seawater systems.
1. Introduction
Alkaline seawater electrolysis for hydrogen production operates under aggressive conditions—6.0 mol/L NaOH, 2.0 mol/L NaCl, and 90 °C—that accelerate corrosion of stainless steel components, leading to premature failure and unplanned downtime. Conventional corrosion mitigation strategies, such as increasing alloy grade or applying protective coatings, often prove insufficient or cost-prohibitive in these high-chloride, high-pH environments. The lack of effective, scalable inhibitors that can withstand such extremes has stalled the widespread adoption of seawater electrolysis as a viable industrial hydrogen source.
This study addresses the bottleneck by systematically evaluating four inorganic inhibitors—Na2MoO4, Na2WO4, Na3PO4, and V2O5—on 316L SS and 2205 DSS. Through a combination of electrochemical testing, long-term immersion, and surface analysis, the work identifies V2O5 and Na3PO4 as high-performance candidates that form protective composite films, thereby extending the operational envelope of stainless steels in electrolytic seawater systems. The findings provide a mechanistic foundation for inhibitor selection and optimization, directly impacting the reliability and economics of industrial hydrogen production.
Loading authentic research manuscript (Pages 1–5)...
LIU Zhirong, LI Shiyu, ZHANG Huiyu, ZHANG Hailong, LIN Bing, TANG Junlei (2026). Corrosion Inhibition Mechanism of Typical Inorganic Inhibitors on Stainless Steel in a Simulated Electrolytic Seawater Environment. Surface Technology (表面技术). https://doi.org/10.16490/j.cnki.issn.1001-3660.2026.10.004
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntelare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoTechIntel claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the primary failure mechanism of 316L SS and 2205 DSS in the simulated electrolytic seawater environment without inhibitors?
Without inhibitors, 316L SS undergoes uniform corrosion with a thick, porous corrosion product layer, while 2205 DSS is susceptible to pitting corrosion. The high chloride concentration (2.0 mol/L) and elevated temperature (90 °C) in 6.0 mol/L NaOH accelerate breakdown of the passive film, leading to localized attack and increased surface roughness.
How does the inhibition efficiency of V2O5 compare to Na3PO4, and what are the underlying mechanistic differences?
V2O5 outperforms Na3PO4, achieving 79.90% (316L SS) and 89.58% (2205 DSS) inhibition efficiency at 0.05 mol/L, versus 83.33% for Na3PO4 on 2205 DSS. Mechanistically, V2O5 incorporates V4+ and V5+ species into the surface film, forming a dense vanadium-rich layer that significantly increases Rct (29,770 Ω·cm² for 316L SS) and Rf (923.50 Ω·cm²). Na3PO4 forms a phosphate composite film (PO4³−) that also enhances barrier properties but with lower efficacy on 316L SS.
What are the scalability and cost implications of using V2O5 as an inhibitor in industrial electrolyzers?
V2O5 is a relatively low-cost industrial chemical, and its effective concentration (0.05 mol/L) is moderate, making it economically feasible for large-scale electrolyte systems. However, vanadium toxicity and environmental regulations may require containment and recovery measures, adding to operational complexity. Na3PO4, while less effective, is environmentally benign and cheaper, offering a trade-off between performance and regulatory compliance.
Can these inhibitors be used in dynamic flow conditions typical of industrial electrolyzers, or does the static immersion test overestimate performance?
The 14-day static immersion tests provide a baseline for film formation and stability, but dynamic flow can erode protective films and reduce inhibitor efficiency. The composite films formed by V2O5 and Na3PO4 are chemically bonded to the surface, suggesting moderate resistance to shear, but further testing under flow velocities >1 m/s is required to validate performance. The high Rf values indicate robust films that may withstand moderate flow, but localized breakdown at welds or crevices remains a risk.
What are the long-term stability and replenishment requirements for V2O5 and Na3PO4 in continuous operation?
The study demonstrates film formation over 14 days, but continuous operation may consume inhibitor through precipitation or incorporation into corrosion products. V2O5 showed stable performance at 0.05 mol/L, but periodic monitoring of vanadium concentration in the electrolyte is recommended to maintain threshold levels. Na3PO4 may deplete faster due to phosphate precipitation with hardness ions; dosage control and filtration are advised. Long-term (>6 months) pilot testing is needed to establish replenishment schedules.
Related Chinese Research & Cross-Citations
Research Progress and Prospects of Corrosion-resistant High-entropy Alloy Coatings
Marine environments impose combined electrochemical, microbiological, and cavitation erosion degradation on metallic infrastructure, shortening service intervals and inflating maintenance expenditure. High-entropy alloy (HEA) coatings mitigate these failure modes through simple solid-solution or amorphous microstructures that suppress galvanic coupling and promote dense passive film formation. This review systematically examines corrosion-resistant HEA coatings from single-factor to multi-factor coupling perspectives, covering classification and compositional design, fabrication routes, and corrosion behavior under complex marine conditions. Key coating systems include FeCoCrNiMn, AlCoCrFeNi, FeCrNiCoAl, and (FeCoCrNi)75B15Si10 amorphous alloys deposited by atmospheric plasma spraying, high-velocity oxy-fuel spraying, and wire arc spraying. Elemental additions of Cr, Al, and Mo enhance passivation; B and Si promote amorphous phase formation. The review identifies core engineering bottlenecks: compositional design, process optimization, and service performance validation. A multi-scale simulation, process-structure optimization, and in-situ characterization framework is proposed to accelerate coating deployment. These findings provide theoretical and technical guidance for next-generation corrosion-resistant coatings in marine equipment.
Effect of Sodium Hypochlorite Concentration and Medium Temperature on Corrosion of 45# Steel in Artificial Seawater and Simulated Concrete Pore Solution
Seawater discharged during LNG regasification carries residual chlorine, predominantly sodium hypochlorite (NaClO), and low temperature, posing a dual corrosion threat to carbon steel components and adjacent reinforced concrete. This study systematically evaluates the corrosion behavior of 45# steel in artificial seawater (AS) and simulated concrete pore solution (SCPS, pH≈10) under NaClO concentrations of 0, 1, 10, and 100 mg/L at 10 °C and 25 °C. Electrochemical impedance spectroscopy, potentiodynamic polarization, weight-loss measurements, and localized corrosion-depth analysis were combined with SEM, EDS, XPS, and XRD to resolve corrosion kinetics, morphology, and product composition. In AS at 25 °C, increasing NaClO from 0 to 100 mg/L decreased charge transfer and film resistance (Rct + Rf) from 2266 to 1207 Ω·cm² and increased corrosion current density (Jcorr) from 11.48 to 18.29 μA/cm². Weight-loss rates remained 0.108 mm/a at 0 and 1 mg/L NaClO, rose slightly to 0.123 mm/a at 10 mg/L (+13%), and sharply to 0.202 mm/a at 100 mg/L (+87%). Corrosion morphology shifted from localized to uniform, with reduced pit depth. In SCPS at 25 °C, the alkaline environment suppressed NaClO-induced acceleration: Rct + Rf decreased from 2922 to 2266 Ω·cm², and weight-loss rates increased only 8% (0.0937 mm/a) at 10 mg/L and 25% (0.108 mm/a) at 100 mg/L relative to the 0.0865 mm/a control. However, 100 mg/L NaClO in SCPS significantly deepened localized pits. At 10 °C, both media exhibited reduced corrosion current density, thinner product layers, and shallower pits. Under standard discharge conditions (residual chlorine ≤0.2 mg/L), the additional corrosion risk from cold discharge water is negligible.
Influence of Temperature on Diffusion Behavior and Infiltration Layer Structure of Sherardizing on Structural Steel
Powder sherardizing on Q235 structural steel was conducted in a 70wt.% Zn–0.8wt.% NH4Cl–29.2wt.% α-Al2O3 activated pack at 340–400 °C for 2–10 h to establish the temperature-dependent growth kinetics, phase evolution, and corrosion performance of Zn–Fe intermetallic layers. Cross-sectional SEM/EDS and XRD show that all layers consist of δ and Γ phases, with Γ concentrated near the substrate; excessive Γ at 340 °C initiates interfacial cracking. Layer thickness increases monotonically with temperature and time, rising from 10.80 μm at 340 °C to 43.90 μm at 400 °C after 6 h, and from 12.10 μm at 2 h to 81.60 μm at 10 h at 380 °C. The Zn/Fe ratio and δ-phase fraction increase with temperature, yielding denser layers and improved corrosion resistance; at 380–400 °C, corrosion current densities fall to 1.16×10⁻⁶–9.78×10⁻⁷ A/cm². The diffusion coefficient at 380 °C is 2.341×10⁻¹³ m²/s. Prolonged holding beyond 6 h produces through-thickness cracks. DSC and microstructural evidence support a three-stage growth mechanism: formation of active Zn atoms via ZnCl2 decomposition, bidirectional Zn/Fe interdiffusion along substrate defects, and continuous inward advancement of the Zn–Fe intermetallic front. The optimal processing window is 380 °C for 6 h, yielding a ~36.1 μm crack-free layer with 84.1% δ phase and superior corrosion resistance.
Research Progress and Problem Analysis on Corrosion Prediction of Supercritical CO2 Transport Pipelines
Pipeline transport is the core of large-scale CO2 delivery in CCUS projects, and supercritical pipeline transport is the most economical and feasible method. However, inherent multicomponent impurities and complex aqueous phase precipitation make corrosion control difficult and costly. This review assesses corrosion mechanisms and prediction technologies for supercritical CO2 transport pipelines, focusing on numerical analysis, supporting experiments, and field application within comprehensive mechanistic models. Current understanding has clarified the effects of individual impurities (H2O, H2S, O2, SO2, N2O, N2, H2, CH4) and operating parameters, but synergistic mechanisms of mixed gases remain unresolved, lacking systematic quantitative description. Existing prediction models are limited in applicability to corrosion conditions, morphological matching, and comprehensiveness of factors. Experimental methods suffer from insufficient reliability, particularly in precise metering and replenishment of corrosive media under low water content and multicomponent impurity synergy. Field application faces challenges in rational model use and accurate extraction of field data. Future directions include: deepening research on synergistic effects of impurity gases and quantifying them via theoretical analysis to establish mapping between impurity concentration and corrosion rate; accelerating development of aqueous phase precipitation and distribution models, multicomponent impurity water chemistry models, thermodynamic and kinetic models for multicomponent reactions, and competitive formation/growth models for multiple product films; strengthening experimental techniques for precise metering and replenishment under low water and multicomponent synergy; and improving field application by understanding model parameter physical meanings, applicability boundaries, and ensuring reasonable input parameters and accurate field data extraction.
Research on Wear Resistance and Wear Mechanism of NM500 Steel in a Wide Temperature Range
The tribological behavior of NM500 wear-resistant steel was systematically evaluated across a wide temperature range from −50 to 600 °C to elucidate the influence of temperature on wear resistance and to provide a theoretical basis for service life extension. Friction and wear tests were conducted using a high-temperature tribometer under a normal load of 150 N, rotational speed of 354 r/min, wear track diameter of 15 mm, and test duration of 60 minutes. The microstructure was characterized by SEM and EBSD, while worn surfaces were analyzed using XRD, SEM, and 3D laser confocal microscopy. NM500 steel exhibits a fine lath martensitic structure with a grain size of 7.08 μm, conferring high hardness and superior wear resistance. At cryogenic temperatures (−50, −25, 0 °C), the wear mechanism is predominantly abrasive wear, with a wear rate of only 1.29×10−6 mm3/(N·m). As temperature increases, oxide formation on the worn surface intensifies, friction coefficient decreases to a minimum of 0.3 (50% lower than at low temperature), and wear rate increases significantly: 18×10−6, 22.7×10−6, 46.7×10−6, and 128×10−6 mm3/(N·m) at 100, 200, 300, and 600 °C, respectively. The dominant wear mechanism transitions from abrasive wear at low temperatures to oxidative wear with adhesive wear at elevated temperatures. At 600 °C, thermal softening, reduced texture strength, and oxide film delamination exacerbate material loss, shifting the mechanism to oxidative wear as the primary mode with adhesive wear as secondary.
Effect of Ni Content on the Microstructure and Tribological Properties of NiTi Alloy Coatings
Plasma arc cladding was employed to fabricate NiTi coatings with varying Ni contents (60, 63, 65, 67, and 70 wt.%) on TC4 titanium alloy to enhance surface wear resistance. Microstructural characterization via SEM, OM, and XRD revealed that coatings with 60–67 wt.% Ni were dense and defect-free, whereas the 70 wt.% Ni coating exhibited through-thickness cracks. All coatings exceeded 1.2 mm in thickness and comprised a NiTi toughening phase and Ti2Ni strengthening phase. Increased dilution ratio with higher Ni content reduced actual Ni in the coating, maximizing Ti2Ni fraction (78.6%) in the 67NiTi coating, which achieved a peak hardness of 677.41 HV0.2 (2.05 times that of the TC4 substrate). Tribological testing under 5–20 N loads showed that the average wear rate of all coatings decreased significantly, following a V-shaped trend with Ni content. The 67NiTi coating exhibited the lowest wear rate (2.74×10⁻⁴ mm³/(N·m)) at 20 N, a 65% improvement over the substrate, with wear mechanisms dominated by mild abrasive and adhesive wear. These findings demonstrate that optimized Ni content in plasma-clad NiTi coatings effectively mitigates the poor wear resistance of titanium alloys, offering a viable surface engineering solution for load-bearing applications.