The corrosion behavior of zinc with a chromate conversion coating containing ~ 0.02 g/m2 Cr(VI) was investigated. X-ray photoelectron spectroscopy (XPS) showed Cr(VI) was located in layers near the surface of the coating. Corrosion current densities and Cr(VI) content in the coating decreased with immersion time. An electrochemical reduction of Cr(VI) to Cr(III) parallel to oxygen (O2) reduction in the first stages of immersion was reviewed. Inhibition of the corrosion rate proceeded simultaneously with dissolution of the conversion coating. It was concluded that the thickness of the coating was not the most important factor to hinder O2 reduction. Corrosion inhibition was attributed to zinc surface passivation byproducts of ionization.

Subject
Zinc rich coatings, Coatings, Corrosion rate, Metal surfaces, Chromium, Sodium chloride, Sodium chloride solution, Chromate conversion coatings, Immersion, Zinc, Risk reduction, Chemical conversion coatings, Electrodes
Keywords:
Auger electron spectroscopy, chromate conversion coatings, chromium, corrosion current, corrosion rate, ionization, passivaton, sodium chloride and solutions, x-ray photoelectron spectroscopy, zinc
NACE International
1997
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