Electron spectroscopy of corrosion inhibitors: Surface films formed by 2-mercaptobenzothiazole and 2-mercaptobenzimidazole on copper

Abstract

Surface films formed by two structurally related corrosion inhibitors, 2-mercaptobenzothiazole (MBT) and 2-mercaptobenzimidazole (MBIA), on copper have been studied using X-ray photoelectron spectroscopy and X-ray induced Auger spectroscopy. It is shown that under all conditions these corrosion inhibitors form Cu(I) surface films of stoichiometries Cu(MBT) or Cu 2(MBIA). The film thicknesses were found to be closely related to the pH of treatment solutions, which reflects the stability of Cu 2O, and the thickness of the original Cu 2O layer. A precipitation mechanism is suggested for film formation. A study of the oxidation of sulphur present in the surface films revealed that both MBT and MBIA complexes undergo an oxidative-dimerization leading to the formation of Cu(II) and ▪ groups which results in degradation of the surface films.