Process Optimization, Morphology, Structure, and Adhesive Strength of Electrodeposited Ni–Fe–Graphene Composite Coating on the 7075 Aluminum Alloy

Abstract

The process parameters of electrodeposited Ni–Fe–graphene composite coating on the 7075 aluminum alloy were optimized by the orthogonal experiment. The optimized process parameters were determined as follows: graphene concentration of 1 g L−1, current density of 9 A dm−2, agitation speed of 250 r min−1, and temperature of 60 °C, on the basis of hardness and friction coefficient. The Ni–Fe–graphene composite coating shows an increment of 393.0% in hardness and a decrement of 55.9% in friction coefficient in comparison with 7075 aluminum alloy substrate. The Ni–Fe–graphene composite coating binds tightly to 7075 aluminum alloy with adhesion strength of higher than 6.895 MPa. These make contributions to provide effective protection for aluminum alloys. Surface morphology and corrosion morphology, as well as morphology of the side bound to the substrate, were characterized. The scattered asperities on the surface were proven to be graphene nanoplatelets being wrapped by Ni–Fe, which comprehensively reveals the formation of asperities.