Corrosion inhibition of aluminum – silicon alloy in hydrochloric acid solution using carbamidic thioanhydride derivatives

The corrosion inhibition of Al–Si alloy in 1 M HCl solution using some carbamidic thioanhydride derivatives at various concentrations has been studied using potentiodynamic polarization, electrochemical impedance spectroscopy, electrochemical frequency modulation, and hydrogen evolution techniques. Results obtained indicate that the inhibition efficiency (% g) reached 94 % at 2 9 10^-5 M concentration and was found to increase with increasing the inhibitor concentrations.

% g decreased with increasing the temperature. Potentiodynamic polarization curves showed that the investigated derivatives were mixed-type inhibitors. Some activation and adsorption thermodynamic parameters (DH, DG, and DS) were calculated and discussed. The adsorption of these derivatives on the alloy surface was found to obey Langmuir adsorption isotherm. The electrochemical results are in good agreement with the calculated quantum chemical HOMO and LUMO energies of the tested molecules.