Effects of cathodic hydrogen evolution on electrodeposited Au-Cu-Cd alloys

Hydrogen can be incorporated into electrodeposited Au alloys either during electrodeposition or by cathodic charging. Incorporated hydrogen in these alloys generally impairs their mechanical properties. In this work, we present results of a study of electrochemical, structural, surface composition, and morphological effects of cathodic charging of Au-Cu-Cd alloys electrodeposited from a cyanoalkaline bath. Different kinds of linear sweep voltammetric behaviors are observed for alloys with different compositions and for repeated scans, which is related to a loss of electrocatalytic activity for high Cu content alloys and prolonged cathodic charging. The surface composition of alloys is altered by cathodic charging, resulting in a decrease in Au content. The surface morphology, as observed by scanning electron and atomic force microscopies, is modified by cathodic charging: large crystallites are attacked and globular features appear on Bat deposits. The crystallographic structure of the alloys is affected by prolonged hydrogen evolution; the original preferred orientation is disrupted and a Cu-rich phase appears. (C) 2001 The Electrochemical Society.