Microstructure and Corrosion Properties of AlxFeCoCrNiCu (x=0.25, 0.5, 1.0) Thin Coatings on Steel Substrates Deposited by Electron Beam Evaporation

High entropy alloy (HEA) thin coatings have been deposited on steel substrate of a mixed alloy power made of high purity elemental aluminium, cobalt, chromium, copper, iron and nickel by electron beam evaporation and effects of the Al content of the coating on its structure, surface morphology and electrical properties were investigated. The results of X-ray diffraction (XRD) show that coatings are typical dendrite and interdendrite structures with different aluminum contents. The coatings' surface chemical components are basically similar to originally designed alloys by electron probe micro-analyzer (EPMA). Atomic force microscopy (AFM) results indicate that the modified surface of all coatings are very smooth and uniform. HEA coatings exhibit wide passive regions>700 mV in aqueous solutions of H2SO4 and NaCl. A large corrosion potential (−129 mV) and a small corrosion current density (≈2.2×10−6 A/cm2) clearly reveals that the corrosion resistance of the Al0.5FeCoCrNiCu coating is superior to that of the coatings.