The effect of 1-(2-pyridylazo)-2-naphthol on the corrosion of cold rolled steel in acid media

The corrosion inhibition of 1-(2-pyridylazo)-2-naphthol (PAN) on the corrosion of cold rolled steel in 1.0 M hydrochloric acid (HCl) was studied using weight loss method and potentiodynamic polarization method. Results obtained revealed that PAN is an effective inhibitor. It was found that the adsorption of PAN could prevent steel from weight loss and the adsorption accorded with the Langmuir adsorption isotherm. Potentiodynamic polarization studies showed that PAN is of the mixed-type but act as an anodic inhibitor for steel in 1.0 M HCl. Thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy were obtained from experimental data of the temperature studies of the inhibition process at four temperatures ranging from 35 to 50 °C. The most suitable range of inhibitor concentration was discussed. The kinetic data such as apparent activation energies and pre-exponential factors at different concentrations of the inhibitor were calculated, and the effect of the apparent activation energies and pre-exponential factors on the corrosion rates of cold rolled steel was discussed. The inhibitive action was satisfactorily explained by using both thermodynamic and kinetic models. Synergism between chloride ion and PAN was proposed. The results obtained from weight loss and potentiodynamic polarization were in good agreement.