Inhibition of acidic iron corrosion by γ-irradiated 2-mercaptobenzimidazole

The authors report on the corrosion inhibition of St 3 steel in hydrochloric acid by 2-mercaptobenzimidazole previously gamma-irradiated from a cobalt 60 source over an absorbed dose range of 0.25-50 MGy. The electrochemical corrosion characteristics of the steel inhibited by both irradiated and unirradiated quantities of the inhibitor were determined under controlled conditions. The possible effects of gamma radiation on the inhibitor molecules was explored by taking their ultraviolet and infrared spectra. The authors postulate that the gamma radiation can split the -SH group from the molecule to form free sulfur in the inhibitor solution and alter the inhibitor from the thiol to the thione form. The radiation-induced accumulation of the thione form, whose inhibitive action is due to highly negative pi-electron population density at the sulfur atom, gives the irradiated imidazole consistently good inhibitive properties