Preparation and Characterization of Cerium-Based Conversion Coating on a Fe50Mn30Co10Cr10 Dual-Phase High-Entropy Alloy

Abstract The mechanical properties of the Fe50Mn30Co10Cr10 (at.%) dual-phase high-entropy alloy (DP-HEA) are superior to those of the equiatomic CoCrFeMnNi single-phase HEA. However, poor corrosion resistance due to high manganese content is one of the main factors limiting the potential applications of Fe50Mn30Co10Cr10 DP-HEAs. This study investigated the feasibility of improving the corrosion resistance of Fe50Mn30Co10Cr10 DP-HEAs through the application of a cerium conversion coating to its surface. In addition, this study investigated the effects of bath temperature and the heating process on the formation of the cerium conversion coating. A cerium conversion coating with a thickness of approximately 10–20 nm formed on the DP-HEA surface from cerium conversion baths with various continuous heating processes. The anodic current densities exhibited by the polarization curves decreased, and Tafel extrapolation revealed that the corrosion current densities of the cerium-coated specimens were two to three orders of magnitude lower than that of the untreated DP-HEA. The successful preparation of cerium conversion coatings through continuous bath-heating processes can improve the corrosion resistance of Fe50Mn30Co10Cr10 DP-HEAs. The superior anticorrosion properties of the coating formed by the T70 bath-heating process can be attributed to the increased thickness and large amount of CeO2 in the coating.