Inhibition Effects of Methionine and Tyrosine on Corrosion of Iron in HCl Solution: Electrochemical, FTIR, and Quantum-Chemical Study

The inhibiting effect of methionine and tyrosine on the corrosion of iron is researched electrochemically in 0.1M HCl, Quantum chemical calculations were performed. The level of HF with the 6-311G(d,p) basis set for methionine and tyrosine. Corrosion current density has been determined by polarization measures and the inhibition effect was calculated. With an increase in the concentration of inhibitor, the effectiveness of inhibition increases. The highest inhibition is determined as 97.8% at 100 ppm methionine. The effect of temperature is determined by chronoammetric measures. Surface analysis is performed with FTIR spectroscopy. Methionine and tyrosine adsorb on the iron surface according to Langmiur isotherm. The highest occupied and the lowest unoccupied molecular orbital energy, as well as Mulliken and atomic charges with hydrogens summed into heavy atoms of C, N, O, S atoms and of methionine, tyrosine, and protonated forms have been examined.