Inhibition of corrosion of copper in acids by norfloxacin

Purpose - This paper aims to evaluate the inhibition efficiency of norfloxacin on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions. Design/methodology/approach - Evaluation was carried out by electrochemical techniques such as electrochemical impedance spectroscopy and potentiodynamic polarization studies. Scanning electron microscopy was used, and it finally confirmed the existence of the adsorbed film. Findings -The electrochemical measurements showed that norfloxacin has good inhibition efficiency on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions. The inhibition action of norfloxacin in both of the corrosive media was observed to be of mixed type but with more of cathodic nature. The temperature dependence of the corrosion rate was studied in the temperature range from 35 to 55 degrees C and the activation energy (E-a) was calculated. The adsorption of norfloxacin molecules on copper surface obeyed Langmuir adsorption isotherm. Studies on the potential of zero charge have been carried out to establish the mechanism of adsorption of the inhibitor onto the metal surface. The thermodynamic parameters such as the adsorption equilibrium constant (K-ads) and the free energy of adsorption (Delta G(ads)) were calculated. The value of free energy of adsorption very close to -40 kJmol(-1) indicates that the adsorption is through electrostatic coulombic attraction and chemisorption. The decrease in value of Ea with the addition of inhibitor also shows the chemisorption of the inhibitor on the metal surface. Originality/value - This paper indicates that norfloxacin can act as a good inhibitor for the corrosion of copper in both the acid media.