The electrodeposition behavior of Ni-Mo alloy from a gluconate bath was investigated by a Hull cell test. The Mo content and deposition current efficiency of the Ni-Mo alloy were also measured as a function of the plating conditions of bath pH, deposition current density and bath ingredient concentrations.
Smooth and bright Ni-Mo alloy was deposited at a relatively high deposition current efficiency (about 60%) from an ammonium-gluconate bath of above pH9. The higher the molybdate concentration in the bath, the higher the Mo content of the deposits. On the other hand, the Mo content of the deposits decreased with an increase in deposition current density and bath pH. The current efficiency of the Ni-Mo alloy deposits decreased linearly with Mo content.
SEM observation revealed that the alloy deposits from the gluconate bath were smooth and compact with no cracks. Polarization curve measuremants and immersion tests of Ni-Mo alloy deposits were carreid out in solutions of both 1N HCl and 1N H2
. The results indicated that the Ni-Mo alloy had a higher self-passivation ability and lower corrosion rate than the conventional Cr plating deposits. A salt spray test showed the better corrosion resistance of the alloy deposits with the higher Mo content.