Microstructural Development of Copper Sulfide on Copper Exposed to Humid H[sub 2]S

Abstract

Pure copper samples were exposed in an environmental chamber for 2, 4, 7, 15, and at 90% relative humidity, , and hydrogen sulfide (). 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 exposure the predominant corrosion products were copper sulfide and cuprite . Once the reached a minimum thickness, the rate of growth of the layer became parabolic due to the limiting diffusion through a thickening film. As the layers reach a critical thickness internal stresses and defects in the corrosion layer allow virtually free access of and O to the underlying layers, consequently accelerating the film growth.