Corrosion Product Film of a Medium-Mn Steel Exposed to Simulated Marine Splash Zone Environment

Abstract

The corrosion behavior of a medium-Mn steel in a simulated marine splash zone was studied by a dry–wet cyclic corrosion experiment and electrochemical experiment. The corrosion products were characterized by corrosion rate calculation, composition detection, morphology observation, element distribution detection, valence analysis, polarization curve, and electrochemical impedance test. The results show that the corrosion products of the sample mainly include γ-FeOOH, FexOy, MnxOy, and a small amount of (Fe,Mn)xOy, and the valence state of iron compounds and manganese compounds in different corrosion stages changed obviously. In the initial corrosion products, Mn is enriched significantly and facilitates the electrochemical reaction of corrosion process. The content of Ni in the inner rust layer is high. The semi-quantitative analysis of the corrosion product elements shows that the atomic concentrations of Cr and Mo increase significantly in later corrosion products, indicating that the dense isolation layer formed by alloy element compounds in the corroded layer is the main factor to improve the protection ability of the rust layer at the end corrosion stage of the sample. With the corrosion durations, the corrosion current density of the sample with the corrosion product film first increases and then decreases, and the corrosion potential first moves negative and then shifts in a positive direction subsequently, indicating that the protective effect of the corrosion product film is gradually significant.

Long-Term Corrosion Behavior of Strong and Ductile High Mn-Low Cr Steel in Acidic Aqueous Environments

“…Except for the very early immersion stages, the oxide layers were formed on the steel surface with a prolonged immersion and the two time constants were contained in an equivalent circuit to fit the Nyquist plots. In contrast to the bare steel, the corrosion scale formed on the steel surface could be measured as another resistance due mainly to its semi-conducting properties [ 15 ]. In this regard, the Nyquist plots with prolonged immersion except for one day of immersion were fitted with an equivalent circuit including two time constants.…”