Experimental and theoretical investigation on the effect of N-substituent position on the inhibition performance ofl-lysine derivatives for carbon steel in H(2)SO(4)solution

摘要

The inhibitive effect and inhibition mechanism ofl-lysine derivatives, namely alpha-N-benzyloxycarbonyl-l-lysine (alpha-NL) and epsilon-N-benzyloxycarbonyl-l-lysine (epsilon-NL), on the corrosion of carbon steel in 0.5 M H(2)SO(4)solution were investigated by electrochemical technique, weightlessness test, scanning electron microscope, atomic force microscope, infrared attenuated reflectance spectroscopy and quantum chemical calculation. The results showed that alpha-NL and epsilon-NL as moderate cathodic inhibitors mainly inhibited the cathodic reaction of carbon steel in 0.5 M H(2)SO(4)solution, and the terminal substituted epsilon-NL showed better corrosion inhibition than the alpha-N-benzyloxycarbonyl protected alpha-NL. Their inhibition efficiencies increased with the increase in inhibitor concentration, and the inhibition efficiency of alpha-NL and epsilon-NL with concentration of 10 mmol can reach 53.4% and 61.5%, respectively, but decreased with rising temperature. The adsorption of investigated inhibitors on the surface of carbon steel obeyed the modified Langmuir isotherm and El-Awady thermodynamic-kinetic model, and the thermodynamic and kinetic parameters were determined to discuss the mechanism of inhibition of alpha-NL and epsilon-NL. Moreover, Quantum chemical calculation gave further insight into the inhibition mechanism of alpha-NL and epsilon-NL and was employed to reveal the reasons for their differences in inhibition performance.