Abstract
The influences of Al3+ ion on the nickel deposition from nickel-aluminum ammonium sulfate bath (Ni2+ 0.15mol/l, Al3+ 0.15mol/l) containing citric acid were studied by means of galvanostatic/potentiostatic electrolysis, pH titration, and cathode polarization methods with respect to the feasibility of Ni-Al codeposition. If the amount of citric acid added was less than 30g/l and powdery or peeling deposits including aluminum were obtained at pH3, but when added citric acid was more than 30g/l, stable Al-citrate complexes were formed and uniform bright nickel deposits without containing aluminum were deposited. Cathode polarization curves were found to shift at a current density where powdery or peeling deposits began to appear. The cathodic decomposition potential for powdery or peeling deposition was more noble than for uniform bright deposition.
