<p>FeCoNiCr_x (<i>x</i> = 0, 0.5, 0.6, 0.7, 0.8) high-entropy alloy (HEA) cladding layers were prepared using the plasma cladding method, to study the corrosion resistance of FeCoNiCr_x high-entropy alloy cladding layers. This article investigates the effect of Cr content on the phase structure, microstructure, and corrosion resistance of FeCoNi-based high-entropy alloys. The results indicate that the FeCoNiCr_x high-entropy alloy cladding layer prepared by plasma melting is an FCC solid solution with uniform composition and defect-free microstructure. When the Cr content increases, the corrosion resistance of the high-entropy alloy cladding layer exhibits a development pattern that first increases and then decreases. The corrosion morphology changes from uniform corrosion of FeCoNi to localized pitting corrosion of FeCoNiCr_x. The FeCoNiCr_0.7 coating has the best corrosion resistance, with the lowest corrosion current density (5.702 nA/cm²) and the highest breakdown potential (− 0.152 <i>V</i>_Ag/AgCl). The results indicate that there is an optimal critical value for the Cr element in the FeCoNiCr_x cladding layer. When the Cr content is low, the density of the oxide film is poor due to the lack of Cr³⁺. When the content of Cr exceeds the optimal level, Cr-O-based oxide segregation can lead to uneven composition in the passivation film, thereby disrupting the continuity of the oxide film and reducing corrosion resistance.</p>