The influence of electrolysis parameters on the composition and morphologyof Co-Ni alloys

The influence of cathodic current density, the concentration of Co2+ ions i n the electrolyte, and additional substances (saccharin and sodium lauryl s ulfate) on the composition and morphology of Co-Ni alloys were investigated . Research was carried out in a Watts-type bath in the presence of boric ac id, as a buffer substance. The circulation speed of the electrolyte was 40 dm(3) h(-1). Cathodic polarisation curves were determined for parent metals and the Co-Ni alloy, it was established that the presence of additives shi fts the cathodic potential of alloy deposition towards more negative values . An increase in the cobalt content in the alloy was observed with decreasi ng of the cathodic current density and increasing of the Co2+ ions concentr ation in the bath. Results obtained confirmed the anomalous character of de position of the Co-Ni alloy. The cathodic current efficiency is dependent m ainly on the current density applied, but the direction of changes has nut been precisely determined, for it depends on the composition of the electro lyte. Using diffractional X-ray and micro X-ray analyses, it was determined that single-phase deposits with an fcc lattice for the whole investigated range of current density and electrolyte composition were obtained. Ln the presence of additives there were obtained fine-grained, bright alloys which adhered well to the substrate. (C) 2000 Elsevier Science B.V. All rights r eserved.