Abstract

A laboratory study of the effect of sub‐ppm levels of and on the atmospheric corrosion of zinc in humid air is reported. Each sample was exposed individually to a synthetic atmosphere with careful control of pollutant concentrations, relative humidity, and flow conditions. Corrosion products were analyzed by grazing angle x‐ray diffraction and x‐ray photoelectron spectroscopy. Ion chromatography was employed to identify water soluble anions. The interaction of the pollutants with zinc metal was studied using trace gas analysis in real time. A strong synergism was observed. The main solid product was zinc blende (ZnS), accompanied by small amounts of sulfate. The optically smooth zinc sulfide film was shown to grow by solid‐state diffusion of ions, the rate controlling step being the deprotonation of adsorbed on the ZnS surface. acts as a cathodic depolarizer, forming , resulting in a strongly increased rate of zinc sulfidation.

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