Various types of zinc-electrocoated steel sheets are used to improve the durability of car bodies. Among these coatings, the Zn-Ni alloy has higher corrosion resistance than pure Zn, as well as better welding and painting properties. The corrosion mechanism of the Zn-Ni alloy has been investigated mainly on the basis of accelerated tests and electrochemical measurements. There are few data about long-term corrosion tests. In the present study, the behavior of unpainted Zn-Ni alloy coated steel was studied during 3 years of exposure in industrial and marine environments. Electrochemical impedance spectroscopy (EIS) and surface analysis (scanning electron microscopy [SEM] and Auger electron spectroscopy [AES]) were the experimental techniques used. Long-term atmospheric corrosion mechanism of Zn-Ni coatings was discussed and compared with that proposed based on short-term tests.

Subject
Scanning electron microscopy, Zinc nickel coatings, Zinc rich coatings, Nickel based alloys, Atmosphere, Impedance, Corrosion cracking, Corrosion detection, Corrosion products, Sodium chloride solution, Maritime, Alloys, Samples
Keywords:
atmospheric corrosion, Auger electron spectroscopy, coatings, electrochemical impedance, nickel, scanning electron microscopy, steel, zinc
NACE International
1999
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