Surface Analysis of Inhibitor Films Formed in Hydrogen Sulfide Medium

Abstract

Steel samples exposed to a 5% sodium chloride (NaCl) solution containing 0.5% acetic acid (CH3COOH) saturated with hydrogen sulfide (H2S), with and without imidazole (C3H4N2) as an inhibitor, were analyzed by x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The metal surface was covered initially by a layer of iron sulfide or oxide. This layer, in turn, was covered by layers in which Fe was bonded to bisulfide and C3H4N2 groups. Corrosion protection probably resulted from the iron sulfide or oxide formed on the metal which was prevented from going into solution and recrystallization by the thin upper layer containing C3H4N2.