Long-term corrosion of copper in a dilute anaerobic sulfide solution

• DOI: 10.1016/j.electacta.2011.04.086
• Publication Date: 2011-07-23T12:25:03Z
• Authors: J. Chen; Z. Qin; D.W. Shoesmith
• Keywords: Copper sulfide; Energy-dispersive X-ray spectroscopy; Anaerobic corrosion

Abstract The mechanism of corrosion of oxygen-free copper has been studied in stagnant aqueous sulfide solutions using corrosion potential and electrochemical impedance spectroscopy (EIS) measurements. Film structure and composition were examined on surfaces and on cross-sections prepared by focused ion beam (FIB) milling using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Experiments were conducted in anaerobic 5 × 10 −5 mol dm −3 Na 2 S + 0.1 mol dm −3 NaCl solutions for exposure periods up to 4000 h (∼167 days) to mimic (at least partially) the conditions that could develop on a copper nuclear fuel waste container in a deep geologic repository. The corrosion film formed was a single cellular Cu 2 S layer with a non-uniform thickness. The film thickness increased approximately linearly with immersion time, which implied that the sulfide film formed on the Cu surface is non-protective under these conditions up to this exposure time. The film growth process was controlled by HS − diffusion partially in the aqueous solution in the pores in the cellular sulfide film and partially in the bulk of the aqueous solution.