L-Methionine Methyl Ester Hydrochloride as a Corrosion Inhibitor of Iron in Acid Chloride Solution

Some aminoester organic compounds were tested as corrosion inhibitors for iron in molar hydrochloric acid (HCl) by mass-loss and electrochemical polarization methods. Both techniques gave the same order of inhibition. Comparison of results among those aminoesters showed L-methionine methyl ester (METOCH₃) was the best inhibitor. Its inhibition efficiency (E%) reached a maximum value of 95% at 10^–2 M. Polarization measurements indicated METOCH₃ acted as a cathodic inhibitor without changing the mechanism of the hydrogen evolution reaction. METOCH₃ was adsorbed on the iron surface according to a Frumkin isotherm model. The effect of temperature indicated that E% of METOCH₃ increased with increasing temperature in the range of20°C to 50°C.