The effects of chloride and sulphate on the growth of sulphide films on copper in anoxic sulphide solutions

Abstract

AbstractThe corrosion of copper in chloride‐ and sulphate‐containing solutions containing sulphide (ranging from 5 × 10−5 M to 10−3 M) was studied by electrochemical impedance spectroscopy and the structure and physical properties of the copper sulphide deposits (Cu2S) were analysed by scanning electron microscopy. At low [SH−], a porous and non‐protective deposit was formed, and the low corrosion rates were limited by sulphide transport, partially within the deposit and partially in the bulk of the solution. At higher [SH−], the corrosion rates were much higher and initially more rapid in chloride‐containing than in sulphate‐containing solutions, suggesting a direct role for chloride in the interfacial corrosion process. When the copper sulphide deposit thickened, the rate became limited by CuI transport within the more compact and more crystalline deposit formed. Changes in the morphology of the deposit suggest that chloride adsorption on the surfaces of the deposit inhibited the incorporation of Cu3S3 clusters, transported from the corroding copper surface, into the growing crystals.