Copper corrosion originated by propionic acid vapors (CH3CH2COOH), ranging from 10 to 300 ppm, at 100% relative humidity, was studied. At 300 ppm pollutant level, the copper corrosion rate was 3.3 mg/dm(2) day. The cathodic reduction technique showed that the amount of corrosion products grew with both exposure time and pollutant level. Corrosion products were also characterized using X-ray diffraction and Fourier transform infrared techniques, and their morphology was observed by scanning electron microscope methodology. The main compounds identified were cuprite (Cu2O), copper hydroxide [Cu(OH)(2)], and a copper propionate compound. Important amounts of an organic copper compound were observed at propionic acid vapor concentrations higher than 50 ppm. (C) 2003 The Electrochemical Society.