Electrodeposition Behaviours of Silver-Palladium Alloy from Cyanide Solution and Effects of Arsenic

Abstract

Electrodeposition of silver-palladium alloy from cyanide solutions with addition of NaAsO₂ has been investigated. It was found that the arsenic ions have marked effects that made deposition potentials of silver, palladium and silver-palladium alloy more noble and limiting current higher. The silver-palladium alloy appears to be deposited under the diffusion control of silver ions. Palladium content in the alloy tended to increase with an increase of NaAsO₂ or palladium content in electrolytes and decreased with an increase of solution temperature. Further, a decrease in the current density or an increase in the magnitude of stirring yielded alloy coatings with lower palladium content. The cathode current efficiency was found to be lowered, at a high current density by the evolution of hydrogen. SEM photographs showed that crystal grains became globular as the current density was enhanced, and alloy films with less than 10% palladium had smooth and fine surfaces.