Study on Corrosion and Mechanical Property Degradation Behavior of NiCrMoV Steel Under Laboratory‐Simulated Low‐Temperature Seawater Conditions

Abstract

To elucidate the corrosion behavior and mechanical property degradation mechanisms of NiCrMoV steel under laboratory‐simulated low‐temperature seawater conditions, this study conducts systematic experiments under three static temperature conditions and two freezing‐thawing conditions. The results indicate that low temperature significantly inhibits the corrosion behavior of this steel. The rust layer primarily consists of α‐FeOOH, β‐FeOOH, γ‐FeOOH, and Fe 3 O 4 /γ‐Fe 2 O 3 . Although evident cracks exist within the rust layer, the accumulated rust may partially hinder the transport of ions to the substrate. Elevated temperature effectively promotes the development of corrosion pits in both lateral and vertical directions, whereas high Cl − concentration only promotes pit development in the longitudinal direction. A small pit width‐to‐depth ratio deteriorates the mechanical properties severely. Within the present dataset, the degradation of mechanical properties exhibits a quadratic trend with the pit width‐to‐depth ratio, which is associated with the reduction in effective load‐bearing area and increased stress concentration. The occurrence of pitting corrosion causes a more pronounced degradation in elongation than in strength.