Experimental and theoretical investigation on the effect of N-substituent position on the inhibition performance ofl-lysine derivatives for carbon steel in H2SO4solution

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.

Automated summary

The study investigated the inhibitive effect and mechanism of l-lysine derivatives on the corrosion of carbon steel in sulfuric acid solution. It found that the derivatives acted as cathodic inhibitors and their inhibition efficiency increased with inhibitor concentration. Adsorption studies and quantum chemical calculations provided insights into the inhibition mechanism of the derivatives.