Diaza-adamantane derivatives as corrosion inhibitor for copper in nitric acid medium

Abstract

The effect of newly synthesized 6-hydroxy-5,7-diphenyl-1,3-diazaadamantane (HDDA) and 5,7-diphenyl-1,3-diazaadamantan-6-one (DDA) against the corrosion of copper in 1 M HNO3 solution was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. These measurements show that the inhibition efficiency (IE %) obtained by these compounds increased by increasing their concentrations, and maximum IE % to 90.84 % for HDDA and 89.87 % for DDA were found at 300 ppm. Data obtained from EIS studies were analyzed by an equivalent circuit model. EIS plots indicated that the inhibitor performance depends on the adsorption of the molecules on the metal surface. Polarization measurements showed that both HDDA and DDA are mixed-type but predominantly cathodic in 1 M HNO3 solution. The adsorption of inhibitors on the copper surface from the nitric acid follows the Langmuir adsorption isotherm with a negative value of free energy, and these values indicated that adsorption of both HDDA and DDA molecules adsorbs physically on the copper surface. The surface morphology was examined by scanning electron microscope and atomic force microscope. Further, theoretical calculations were carried out and relationships between computed parameters and experimental IE % were discussed. All the results confirmed that e HDDA showed better efficiency in 1 M HNO3 compared to DDA.