ELECTRODEPOSITION BEHAVIOR OF ZN-IRON-GROUP METAL-ALLOYS FROM SULFATE AND CHLORIDE BATHS

Electrodeposition of Zn-iron-group metal binary alloys, which has been applied in the production of highly corrosion-resistant alloy plated steel sheet, was conducted from sulfate and chloride baths and the alloy deposition behavior was compared between two types of baths. The current density-dependence of alloy composition showed a typical feature of an anomalous codeposition in the sulfate baths. In the chloride baths, the deposition behavior was shifted gradually from an anomalous to a regular type with increasing chloride ion concentration. On the basis of the factors determining the characteristic current density at which Zn deposition began, the alloy deposition behavior was discussed with the particular reference to the effect of catalytic chloride ions for iron-group metal deposition.