Copper corrosion originated by propionic acid vapors ranging from 10 to 300 ppm, at 100% relative humidity, was studied. At 300 ppm pollutant level, the copper corrosion rate was 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 copper hydroxide and a copper propionate compound. Important amounts of an organic copper compound were observed at propionic acid vapor concentrations higher than 50 ppm. © 2003 The Electrochemical Society. All rights reserved.