A laboratory study of the effect of sub-ppm levels of H2S and NO2 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 H2S/NO2 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 H2S adsorbed on the ZnS surface. NO2 acts as a cathodic depolarizer, forming HNO2(g), resulting in a strongly increased rate of zinc sulfidation.