Effect of Small Content of Chromium on Wet–Dry Acid Corrosion Behavior of Low Alloy Steel

Effect of small content of chromium (Cr) on wet–dry acid corrosion behavior of low alloy steels has been investigated. The results show that the corrosion resistance of the steels increased with increasing Cr content from 0.10 to 0.50 wt%. Higher content of Cr promotes initial corrosion and accelerates the formation of dense and protective rust in long-term corrosion. The enhanced protectiveness of the rust is closely related to its composition. High content of Cr increases the content of amorphous phases and decreases the content of γ-FeOOH in the rust, resulting in the high compactness of the rust and low electrochemical activity in acid condition. Cr dopes in rust and depresses the transformation from amorphous phases to α-FeOOH, as well as the growth process of FeOOH particles, which is responsible for the enhanced compactness of rust in long-term corrosion.