Zinc-nickel alloys obtained from an alkaline bath were passivated with a black, silver-free, chromate conversion coating (CCC). The attack of the chromate solution on the coatings changed most of their characteristics. The CCC modified the composition, thickness, structure, roughness, and stress level of the alloys. Since most of the accelerated corrosion tests include a heat-treatment prior to the measurements, the chromated coatings were subjected to this treatment and their characteristics were evaluated again. We observed that while most of the coating properties were unaffected by the heat-treatment, the corrosion resistance was improved. Scanning force microscopy was finally used to find the differences that could explain this change in the corrosion behavior of the coatings. (C) 2003 The Electrochemical Society.