The acetic acid and acetaldehyde-induced atmospheric corrosion of a zinc surface was investigated by in situ infrared reflection-absorption spectroscopy. Independent of the relative humidity, both corrosive gases yielded zinc oxide and zinc acetate as reaction products. However, faster kinetics for the acetate formation was observed for acetic acid, which was attributed to an acetate-induced zinc dissolution mechanism as the rate determining step, and a more complicated reaction path for acetaldehyde to form the zinc-acetate surface species. Additionally, the rate varied significantly with the relative humidity, and an enhanced corrosion rate was observed under more humid conditions, when the water adlayer that always covers a metal surface is thicker. Scanning electron microscopy revealed the formation of radial growth of corrosion products in the case of acetic acid and filiform corrosion for acetaldehyde. By X-ray diffraction of the powderlike corrosion products, solely zinc oxide was detected. This implies a minute production of zinc acetate in comparison to zinc oxide, or a noncrystalline phase of the acetate. Reaction paths for acetic acid and acetaldehyde were proposed. (c) 2006 The Electrochemical Society.