Inhibition of copper corrosion in sodium nitrate solutions with nontoxic inhibitors

The influence of the concentration of purine (PU) and adenine (AD) on the corrosion and spontaneous dissolution of copper in 0.5 M NaNO₃ solutions of pH 3.0 was studied. The investigations involved electrochemical polarization methods and gravimetric measurements as well as quartz crystal microbalance (QCM) techniques and scanning microscopy (SEM). The inhibition efficiency increases with an increase in the concentration of PU and AD. Adherent layers of inhibitors were postulated to account for the protective effect. The adsorptions of inhibitors were found to occur on the surface of copper according to the Langmuir isotherm. The values of standard free energies of adsorption suggest the chemical adsorption of PU and AD on the copper surface.