Comparative Study on Corrosion Behavior of Two Novel Ni-Cr-Mo-V Steels in Simulated Seawater Environment
The corrosion behavior of two novel Ni-Cr-Mo-V steels(steel A and steel B)in a simulat-ed seawater environment was comparatively investigated by means of immersion test,electrochemical test,and microscopic observation.The results indicate that the cathodic and anodic electrochemical pro-cesses in the corrosion process of the two steels are consistent,while the steel B shows a more positive corrosion potential and lower corrosion current density.The main inclusions in steel A is CaS-MgO-Al2O3 with sizes ranging from 3 to 5 μm,which act as active sites of localized corrosion initiation;in comparison,the Al2O3 inclusions in steel B with sizes ranging from 1 μm to 3 μm,the tendency of localized corrosion in-duced by which is relatively light.After long-term corrosion for 42 d,the two steels all show uniform corro-sion with bilayered corrosion product scale composed of a dense inner rust layer and a loose outer rust layer.However,the thickness of the rust scale of steel A was greater than that of steel B.Besides,there existed longitudinal cracks in the inner rust layer of steel A,which may deteriorate the protective property of the rust scale.
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