Corrosion behaviour of oil well casing steel in H2S saturated NACE solution

Abstract

The corrosion behaviour of oil well casing steel in H₂S saturated NACE solution (5 wt-%NaCl+0·5 wt-%CH₃COOH) was investigated by means of electrochemical methods, X-ray photoelectron spectroscopy and scanning electron microscopy. It was found that the investigated oil well casing steel can react with hydrogen sulphide in the H₂S saturated NACE solution at 25°C. During the reaction, corrosion films of mackinawite (FeS) form on the steel surface and the hydrogen atoms diffuse into steel matrix. The further corrosion of iron with H₂S can be retarded, and hydrogen permeation flux decreased, by the presence of the mackinawite film, which acts as a protective barrier provided it remains intact.