The role of codeposited elements in gold plated contacts

Summary

The most widely favoured gold electrolyte for sliding wear, electrical contact application is undoubtedly the acid cyanide family of solutions with additions of cobalt, nickel or iron salts. It is known that the resultant deposit contains not only the additive metal but also small quantities of carbon, nitrogen and potassium. Connector contacts have been high speed selectively gold plated and Hull cell panels have been plated in a proprietary cobalt-bearing electrolyte and the composition of the gold deposits determined using electron microprobe analysis. The effect of cobalt content of the electrolyte and also cathode current density of the Hull cell panels on cobalt and potassium content is reported. It is shown that cobalt content of the deposit is proportional to the cobalt in solution, but that potassium in the deposit shows a maxim. The work is shown to correlate well with previous work and an attempt is made to propose a relationship between deposit composition and wear resistance.