Development of Zn–Ni–Cd coatings by pulse electrodeposition process

A pulse electrodeposition process was developed for the synthesis of Zn–Ni–Cd alloys with cadmium contents between 2 and 7 wt.%. The alloy was deposited from an alkaline bath (pH = 9.3). The results indicated that the average current density and pulse current on time (Ton) control the corrosion potential and the composition of the resultant alloys. An increase in average current density resulted in a decrease in both nickel and cadmium content in the alloy. At lower Ton time (0.5 ms), higher percentages of zinc and cadmium were deposited. The barrier properties of Zn–Ni–Cd alloys plated using different average current densities were evaluated by using mechanical, electrochemical and ASTM B117 salt spray tests and compared with commercial Zn–Ni and Cd deposits. The results indicated that Zn–Ni–Cd alloys exhibit superior barrier properties when compared to Cd or Zn–Ni coatings.