Electrochemical investigation of di-phosphonic acid on corrosion inhibition behavior of copper in hydrochloric acid medium

The inhibitory performance of the Methylene bis[(2-hydroxy-5,1-phenylene)methylene] bis phosphonic acid (DPA) on corrosion of copper in 0.5 M HCl has been studied experimentally and theoretically. The inhibition was investigated by electrochemical tests (electrochemical impedance, potentiodynamic polarization), weight loss methods and surface morphology analysis. The parameters obtained by density functional theory (DFT) were calculated and discussed. Impedance spectroscopy results showed that the R-t values are increased but the values of CPE are decreased with decrease in DPA concentration. Potentiodynamic polarization measurements indicate that DPA inhibits both the anodic and cathodic reactions of copper. Thus, they refer to the mixed-type corrosion inhibitor. The adsorption of inhibitor on the copper surface follows Frumkin adsorption isotherm. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed that DPA forms a dense film on the copper surface. The results obtained showed that DPA reveals good anti-corrosion capacity.