The Combined Effect of Direct Current Polarization, Ultraviolet Radiation, and Saline Immersion on the Degradation of an Epoxy Coating

The corrosion damage of an epoxy coating/metal system was accelerated by different cyclic tests. Electrochemical impedance spectroscopy (EIS), optical microscopy, laser microscopy, adhesion measurement, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were employed to reveal the degradation processes of the coating/metal system in these tests. The results showed that the test of cyclic polarization in immersion dramatically accelerated the corrosion of the metallic substrate. It is interesting that the alternating simple immersion and UV irradiation could slightly retard the coating damage in the first 15 days, whereas the alternating UV irradiation in air and electrochemical polarization in immersion could speed up the damage, which might better simulate the degradation of the coating/steel system in the marine tidal zone.