Effect of Citric and Boric Acids on the Electrodeposition of Copper-Nickel Alloys from Sulfate Baths.

The bath used contains 0. 4 mol/liter of each metal sulfate and of boric and citric acids. The citric acid serves as a complex-forming agent, while boric acid serves as a buffer. Citrate complexes of copper are very stable at high current densities and high pH's. As a result, the deposition potential of of copper is shifted in the direction of the nickel potential, thus making codeposition possible. Boric acid suppresses hydrolysis and ensures favorable deposition conditions. The brightest coatings are obtained at a pH of 6. 2, a current density of 3. 2 A/dm**2, a temperature of 40 degree C, and an electrolysis time of 15 min.