Studies on the Corrosion Inhibition of Copper in Nitric Acid Solution Using Some Pharmaceutical Compounds

Abstract

The inhibition effect of some pharmaceutical compounds, on copper corrosion in 2 M HNO3 at 30°C was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrical frequency modulation (EFM) techniques as well as weight loss measurements. Tafel polarization studies have shown that these compounds suppress both the cathodic and anodic processes and thus these compounds act as mixed-type inhibitors. The results of EIS indicate that the presence of these compounds in the corrosive solutions decreases the double layer capacitance, increases the charge transfer resistance and inhibition efficiency. EFM can be used as a rapid and non destructive technique for corrosion rate measurements without prior knowledge of Tafel constants. The adsorption of these compounds on copper surface was found follows the Temkin’s adsorption isotherm. The effect of temperature on corrosion inhibition has been studied and the thermodynamic activation and adsorption parameters were calculated to elaborate the mechanism of corrosion inhibition. The relationships between the inhibition efficiency and some quantum chemical parameters have been discussed.