Corrosion Behavior of E690 High-Strength Steel in Alternating Wet-Dry Marine Environment with Different pH Values

The corrosion behavior and mechanism of E690 high-strength steel in marine environment with different pH values were studied through electrochemical technology and long-term alternating wet-dry cycle experiments combined with SEM and XRD. Results showed that the corrosion current density of E690 high-strength steel gradually increased with decreased pH. After long-term tests in alternating wet-dry marine environment with various pH values, uniform corrosion mainly occurred on E690 steel, accompanied by vast corrosion pitting. Weight loss analysis demonstrated that corrosion rate decreased with increased pH. Moreover, corrosion mechanism varied with pH, and hydrogen-evolution reaction greatly increased the E690 steel corrosion rate at low pH. Meanwhile, the compositions of corrosion products slightly differed with pH; these products consisted of Fe₃O₄, Fe₂O₃, α-FeOOH, β-FeOOH, γ-FeOOH, and amorphous substances. However, the rust-layer density varied. Cr in the rust layer promoted the densification of rust layer and improved the decay resistance of E690 steel.