Quantitative determination of the synergistic effects between UV irradiation and corrosion using the coating impedance index

The synergistic effect between irradiation and corrosion in atmospheric environments resulted in the complex failure mechanism of an organic coating protective system with many types of failure modes. In this study, the coating impedance index (CI) was defined to quantitatively evaluate the degradation degree of an organic coating protective system and the calculation formula of the synergistic effect (ΔCI) was proposed to study the synergistic effect. And that based on the values of the coating impedance index (CI), the levels of consequences, which were generated by UV irradiation, corrosion and their synergistic effect, were determined, respectively. The failure mechanism of two kinds of organic coating protective systems in an urban and a plateau atmospheric simulating environments were quantitatively studied using accelerated tests in conjunction with electrochemical impedance spectroscopy (EIS) on the basis of the coating impedance index (CI) and the quantitative calculation of the synergistic effect (ΔCI). It was found that the synergistic effect between irradiation and corrosion played a major role in the failure of these two kinds of organic coating protective systems.