Influence of cementite coarsening on the corrosion resistance of high strength low alloy steel

The impact of heat treatment on the initiation and progression of localized corrosion in E690 steel in a simulated marine environment was investigated systematically. The primary cause of localized corrosion was the presence of inclusions, which led to the dissolution of the distorted matrix surrounding them. In the initial stages of corrosion, localized corrosion resulting from inclusions was the predominant form. The chemical and electrochemical mechanisms underlying matrix deformation and localized corrosion caused by inclusions were meticulously elucidated. As the immersion time was extended, the galvanic contributions at the ferrite-austenite interfaces, as well as the coarsened carbides, reduced the polarization resistance in the annealed specimen, accelerating the corrosion rate compared to the lath martensite in the as-received specimen. Consequently, the heat-treated sample promoted a transition from localized to uniform corrosion. Finally, a model was established to describe the corrosion behavior of E690 steel in the marine environment.