鉄族金属共存下におけるＺｎのＵｎｄｅｒｐｏｔｅｎｔｉａｌ Ｄｅｐｏｓｉｔｉｏｎ

Abstract

Zn underpotential deposition with iron-group metals was studied using a Cu substrate in sulfate or chloride baths containing a small amount of Zn2+ ions at 5 to 80°C under potentiostatic conditions. Underpotential deposition occurs only in the presence of iron-group metals and is facilitated when conditions permit decreased inherent deposition overpotential of iron-group metals such as high temperature and Cl- additive. This is similar to induced alloy deposition, in which the properties of iron-group metals in a metallic state play an important role. This is cleary different, however, from induced because Zn deposition occurs at more noble potentials than its equilibrium. Iron-group metal properties in a metallic state appear responsible for Zn underpotential deposition, although the detailed mechanism is yet unclear. If the codepositing iron-group metal consistently reduces the activity coefficient of Zn deposited on the progressively formed cathode surface, the large amount of underpotential deposition is explainable thermodynamically.