Abstract
Corrosion resistance of Zn alloy electroplated steel sheets was investigated using the salt spray test. Unpainted Zn-Ni electroplated steel sheet showed a higher resistance to red rusting than unpainted Zn and Zn-Fe electroplated steel sheets. The corrosion products of Zn-Ni were more stable than those of Zn and Zn-Fe.
The corrosion resistance of painted Zn-Fe and Zn-Ni electroplated steel sheets was affected by the composition and the structure of their electrodeposits. The crystal structure of Zn-Fe electrodeposits changed with the composition of electrodeposits and electroplating conditions such as the kind of electroplating solution and current density. The electrodeposit of the small, granular crystals had better corrosion resistance against blistering than the electrodeposit of the big, dendrite crystals. The difference is considered to come from that between the corrosion resistances against OH-ions formed by the cathodic reaction under the paint film.
