Integrated Electrochemical and Long‐Term Crevice Corrosion Assessment of Inconel X750 for Offshore Valve Applications

ABSTRACT

The corrosion performance of Inconel X750 was systematically investigated in aggressive chloride‐containing environments representative of service conditions encountered in aerospace and offshore systems. Electrochemical techniques, including open circuit potential (OCP) monitoring, linear and potentiodynamic polarization, cyclic polarization, and galvanic coupling, were employed in combination with long‐term immersion and crevice corrosion testing. The results show that Inconel X750 exhibits excellent corrosion resistance in both acidic and brine solutions, maintaining stable electrochemical behavior over exposure periods of up to 12 months. Potentiodynamic polarization measurements showed corrosion current densities on the order of 10 nA, corresponding to a corrosion rate of approximately 0.054 mil/year. Cyclic polarization tests showed no significant susceptibility to pitting or localized corrosion. In addition, crevice corrosion evaluations confirmed the absence of measurable attack under both parallel and angled crevice configurations. Galvanic coupling experiments further indicated that Inconel X750 demonstrated excellent corrosion resistance with minimal degradation risk. Although Inconel X750 behaved anodically relative to Hastelloy C276 during galvanic coupling, the measured galvanic current remained very low, indicating negligible galvanic corrosion. The superior corrosion resistance is attributed to the formation of a stable, chromium‐rich passive oxide layer with strong repassivation capability, which effectively limits metal dissolution and suppresses localized corrosion processes. These findings highlight the robustness of Inconel X750 in chloride‐rich environments and demonstrate its suitability for critical applications requiring long‐term corrosion resistance, including components such as offshore valve springs and related mechanical systems.