CORROSION EVALUATION OF CN AND NON-CN ZINC COATINGS USING ELECTROCHEMICAL POLARIZATION

Electrochemical techniques can rapidly evaluate the quality of electro plated finishes relatively faster than the conventional long-term neut ral salt spray test. In addition to quantifying the corrosion, they al so yield mechanistic information about the corrosion process. One such application of these techniques to evaluate the corrosion resistance of zinc coatings is discussed. Comparison of two zinc coatings shows t hat deposits from a non-cyanide zinc bath provide excellent corrosion resistance in contrast to those from a cyanide zinc bath. Of the three types of chromate coatings tested, the least protection is provided b y the blue chromate; the most protection is from olive green chromate passivation.