Corrosion Performance of Graphene-Strengthened CoCrFeNiMo0.2 High-Entropy Alloy in Simulated Acid Rain Prepared by Laser Cladding

We study the graphene (Gr)-strengthened CoCrFeNiMo_0.2 high-entropy alloys (HEAs) prepared by laser cladding. The corrosion properties of the alloys under simulated acid rain conditions are studied through rainfall experiments, electrochemical experiments, and immersion experiments. The experimental results show that the microstructure of the Gr-strengthened CoCrFeNiMo_0.2 HEAs mainly including three morphologies. Mo element occurs segregation. Gr concentrates on the alloy surface during melting. The alloy has a face centered cubic (FCC) single-phase structure. With increase in the rainfall and immersion period, the corrosion resistance of the Gr-strengthened HEAs decreases. With increase in the pH, the corrosion resistance of the alloys increase. The corrosion current densities of Gr-strengthened CoCrFeNiMo_0.2 HEAs are small, indicating that the alloys have excellent corrosion resistance. Electrochemical impedance spectroscopy (EIS) shows that as the pH increases, the capacitance arc radius, impedance modulus, and phase angle show increasing trend. The reason for excellent corrosion resistance are as follows: the Gr enriched on the surface plays a shielding role during alloy melting, Gr reacts with alloy elements to form a passive film on the alloy surface, the lattice distortion and grain refinement are caused by Gr, providing the single-phase structure of the alloy.