Galvanostatic electrodeposition and corrosion behaviour of goldalloy coatings used in jewellery.

Abstract

Au-Cu-Cd alloys have been widely used in jewellery as decorative plating. Nowadays, Au- Cu-In alloys have progressively replaced the first mentioned one due to the high toxicity cadmium presents. In spite of this, there is no knowledge on Au-Cu-Cd in terms of corrosion behaviour, thus information to establish a comparative basis between both alloys is required. The aim of this study is to produce Au-Cu-Cd alloy coating samples by galvanostatic electrodeposition (a purchased alkaline cyanide bath was used for such a purpose) on metal substrates and evaluate their corrosion behaviour via electrochemical measurements. The influence of electrodeposition experimental parameters (current density, rotation speed of working electrode, substrate geometry) in terms of corrosion behaviour and alloy composition is reported as well. It was found out that low negative current densities induce the reduction of larger gold quantity on the substrate, therefore enhancing corrosion resistance. By its part, rotation speed does not seem to affect corrosion behaviour nor the alloy composition. The adaptation of large-scale conditions to lab-scale has been proved to have some limitations: while at industry area is not a determining parameter to obtain 75% Au alloys, only low substrate areas provide alloy coatings with such gold purity approximately under our laboratory conditions.