Influence of 1-methyl 2-mercapto imidazole on corrosion inhibition of carbon steel in 0.5 M H2SO4

Purpose - To evaluate the inhibition efficiency of 1-methyl 2-mercapto imidazole (MMI) in controlling the corrosion of carbon steel in sulphuric acid and to study its action mechanism. Design/methodology/approach - The effect of concentration, immersion time and temperature on the behaviour of this inhibitor has been studied using weight loss, d.c. polarisation and a.c. polarisation techniques. Findings - The results show that MMI is a mixed type inhibitor. Changes in impedance parameters (charge transfer resistance, R-t; and double layer capacitance, C-dl) were indicative of adsorption of MMI on the metal surface, leading to the formation of a protective film that grew with the increasing exposure time. Adsorption of MMI on the carbon steel is found to obey the Langmuir adsorption isotherm. The inhibition efficiency of MMI is temperature-independent and its addition leads to a small increase in activation corrosion energy. Research limitations/implications - Surface analytical techniques such as X-ray photoelectron spectroscopy and Auger spectroscopy can enlighten more on the mechanism of corrosion inhibition. Originality/value - A survey of literature has shown that no work using electrochemical techniques has yet been done on MMI as corrosion inhibitor for carbon steel in sulfuric acid.