Development of vanadium impregnated flat absorber composite PEO coating on AA6061

Abstract The formation of black plasma electrolytic oxidation (PEO) coating on aluminium alloy using vanadyl sulphate as additive in a silicate-based electrolyte is investigated. A brief discussion on the mechanism of incorporation of vanadium in PEO coating starting with a cationic species of vanadium (i.e., VO2+) in solution is attempted. The coating formation with respect to morphology and composition is systematically studied as a function of process time. With increase in process time, incorporation of vanadium ions in the coating increases and the formation of black colour is attributed to the presence of V3+ and V4+ species in the coating. A 55 ± 5 μm thick flat absorber black coating with high solar absorptance (0.92) and high infrared emittance (0.88) is obtained with a process time of 10 min.