Corrosion inhibition of zinc in 0.1 M hydrochloric acid medium with clotrimazole: Experimental, theoretical and quantum studies

Clotrimazole an antifungal drug was investigated for its corrosion inhibition action on zinc metal in 0.1 M HCl solution. Corrosion rate was determined by weight loss, potentiodynamic polarization and impedance spectroscopic techniques. Electrochemical methods (EIS and polarization) have reported inhibition efficiency of up to 90% for 500 ppm concentration of clotrimazole. Data obtained from both chemical and electrochemical studies showed that the corrosion rate of Zn decreased with increase in inhibitor concentration and also with temperature. Tafel polarization measurements showed that clotrimazole acts as mixed type of corrosion inhibitor and its adsorption on the zinc surface obeys Langmuir isotherm. Thermodynamic activation and quantum chemical parameters were calculated and discussed to describe the mechanism of adsorption. These results were supported by FTIR spectral study of corrosion product formed on the zinc surface in the presence of clotrimazole. Contact angle measurements show increased hydrophobicity of zinc surface, while SEM images of zinc surface confirmed considerable decrease of surface inhomogenities in the presence of clotrimazole.