Corrosion behavior of zinc-nickel alloy electrodeposited coatings

Various types of zinc-electrocoated steel sheets are used to improve the du rability of car bodies. Among these coatings, the Zn-Ni alloy has higher co rrosion resistance than pure Zn, as well as better welding and painting pro perties. The corrosion mechanism of the Zn-Ni alloy has been investigated m ainly on the basis of accelerated tests and electrochemical measurements. T here are few data about long-term corrosion tests. In the present study, th e behavior of unpainted Zn-Ni alloy coated steel was studied during 3 years of exposure in industrial and marine environments. Electrochemical impedan ce spectroscopy (EIS) and surface analysis (scanning electron microscopy [S EM] and Auger electron spectroscopy [AESI] were the experimental techniques used Long-term atmospheric corrosion mechanism of Zn-Ni coatings was discu ssed and compared with that proposed based on shortterm tests.