Inhibition of copper corrosion by p-hydroxybenzoic acid in NaCl solution

The inhibitive action of p-hydroxybenzoic acid (p-HBA) on the corrosion behaviour of copper was investigated in a 0.5 M NaCl solution. The results of polarization measurements indicate that the p-HBA acts as a mixed-type inhibitor. The values of standard free energy of adsorption, as calculated from the Freundlich adsorption isotherm, indicate that p-HBA adsorbs on copper by the physical adsorption mechanism. The impedance spectra performed at open circuit potential are determined by two time constants, the first one relating to the charge transfer process while the second one includes mass transport of copper ions through the surface layer. The thickness and protective properties of the surface layer increase with the increase of inhibition concentration and immersion time.