THE CORROSION-RESISTANCE OF ELECTRODEPOSITED ZINC NICKEL-ALLOY COATINGS

The corrosion behaviour of clectrodeposited zinc-nickel (Zn-Ni) alloy coatings has been studied in aqueous chloride environments. The corros ion rates of detached zinc alloys containing up to 25% Ni by weight we re determined using linear polarisation techniques. The corrosion rate of Zn-Ni alloys was found to decrease with increasing Ni content over the compositional range studied. Galvanic corrosion measurements have indicated, however, that Zn-Ni alloy coatings become less sacrificial toward steel as the Ni content is increased. These results are used t o interpret the corrosion behaviour of electroplated steel in a neutra l salt fog environment.