The production of nickel–alumina composite coating via electroplating

A series of electroplating works have been conducted to investigate the best condition for the coelectrodeposition of nickel–alumina (Ni/α–Al 2 O 3 ) composite coating. Co-electrodeposition was done onto mild steel as cathode at ambient temperature (27°C) with current density of 30 mA/cm 2 under α-Al 2 O 3 concentration of 2 g/l and various agitation speeds of 50, 100, 150, 200, and 250 rpms. The cross-section of the composite coatings portrayed α-Al 2 O 3 particles was co-deposited. Under field emission scanning electron microscopy analysis, the coating shows a coarse surface morphology, while cross-sectional microstructures shows a compact embedding of α-Al 2 O 3 particle in the Ni matrix. Elemental analysis by EDX detected the presence of Ni and α-Al 2 O 3 . Vickers microhardness testing shows that the coating hardness increases almost 60% at the highest agitation speed, i.e., 250 rpm.