Relationship between Microstructure and Corrosion Behavior in Dual‐Phase Steels with Various Si Content

Abstract

The objective herein is to evaluate the effect of silicon on the corrosion behavior of dual‐phase steels. For this purpose, five different steels with various Si content ranging from 0.34 to 2.26 wt% are intercritically annealed at 780 °C for 15 min. It is clarified that the mechanism of the effect of Si on the corrosion behavior of dual‐phase steels is a mutual mechanism. The increase in Si content (from 0.34% to 0.91%) initially reduces corrosion resistance due to a decrease in the volume fraction of martensite. However, according to microcapillary studies, a further increase in Si content (from 0.91% to 2.26%) reduces the potential difference between ferrite and martensite and, as a result, reduces the galvanic couple between them. Therefore, corrosion resistance improves by increasing Si content in the range of 0.91%–2.26%. It is also shown that in the corroded surface of the low‐silicon sample, γ‐FeOOH is mainly formed, whereas with an increase in Si content, this compound reduces and α‐FeOOH rises. Also, β‐FeOOH, silicon oxide and Fe3O4 are formed in the high‐silicon sample. The study of the corroded surface topography depicts that surface roughness in a high‐Si sample is less than low‐Si sample.