Pure copper samples were exposed in an environmental chamber for 2, 4, 7, 15, and 30 days at 90% relative humidity, 40 degrees C, and 4 ppm hydrogen sulfide (H2S). Samples were subsequently subjected to microscopy and microanalysis using different techniques: scanning electron microscopy, energy analysis dispersive X-ray spectroscopy, X-ray diffraction, focused ion beam (FIB), and secondary ion mass spectroscopy. The corrosion samples were cross sectioned and the different corrosion layers were imaged using FIB. After 30 days exposure the predominant corrosion products were copper sulfide (Cu2S) and cuprite (Cu2O). Once the Cu2S reached a minimum thickness, the rate of growth of the layer became parabolic due to the limiting Cu+ diffusion through a thickening film. As the layers reach a critical thickness (similar to 1000 nm) internal stresses and defects in the corrosion layer allow virtually free access of H2S and O to the underlying layers, consequently accelerating the film growth. (c) 2007 The Electrochemical Society.