Tailored AlCoCrNiMo0.3 High Entropy Alloy Coatings for Advanced Corrosion Protection

This study reports the synthesis and corrosion performance of a non‐equiatomic AlCoCrNiMo 0.3 high‐entropy alloy (HEA) coating, developed via mechanical alloying and deposited onto SS316 substrates using high‐velocity oxy‐fuel (HVOF) spraying. X‐ray diffraction confirmed the formation of a single‐phase body‐centered cubic (BCC) solid solution after 20 h of milling, while FESEM‐EDS analysis revealed a dense and homogeneously distributed microstructure. Electrochemical characterization in 3.5 wt% NaCl solution demonstrated that the AlCoCrNiMo 0.3 coating exhibited superior corrosion resistance, with a lower corrosion current density ( i corr = 0.45 µA/cm 2 ) and a more noble corrosion potential E corr = −320 mV versus SCE compared to equiatomic AlCoCrNiMo and WC–CoCr coatings. Post‐corrosion analysis confirmed the formation of a Cr/Mo‐rich passive layer responsible for localized corrosion inhibition. The optimized Mo addition avoided the formation of brittle secondary phases, maintaining structural integrity. These results establish AlCoCrNiMo 0.3 as a promising candidate for corrosion‐resistant coatings in chloride‐rich environments.