Copper corrosion initiated by butyric acid vapors [CH3(CH2)(2)COOH] ranging from 0.1 to 100 ppm at 100% relative humidity was studied. The copper corrosion rate at 0.1 and 100 ppm pollutant levels was 8.5 and 630 mg m(-2) d(-2), respectively. Corrosion products were characterized using X-ray diffraction and X-ray photoelectron spectroscopy analyses and their morphology was observed by scanning electron microscopy (SEM). The main compounds identified were cuprite and a copper butyrate compound. The amount of cuprite decreased as the pollution level increased. Copper butyrate was observed from the lowest concentrations, and its amount increased with the butyric acid vapor concentration. The patina formed was very porous and provided little protection to the underlying copper. (C) 2004 The Electrochemical Society.