Modified AC-DC-AC method for evaluation of corrosion damage of acrylic varnish paint coating/Q215 steel system.

To improve the alternating current-direct current-alternating current (AC-DC-AC) coating evaluation technique, the single DC step in the AC-DC-AC method was replaced with a combination of cathodic and anodic polarization in this work. The modified alternate anodic and cathodic AC-DC-AC method experimentally proved to more reliably evaluate the protection performance of an acrylic varnish paint coating than the conventional AC-DC-AC test, as it could more rationally accelerate the coating degradation process without changing the mechanism of the coating corrosion damage. The corrosion damage and mechanism of the acrylic varnish paint coating/Q215 steel system was discussed in detail based on the results obtained from the modified AC-DC-AC tests. • Conventional AC-DC-AC test accelerates the corrosion damage of an organic coating system differently from that in natural exposure. • The combination of the anodic and cathodic polarization in the DC step of the AC-DC-AC cycle reasonably speeds up the corrosion damage. [ABSTRACT FROM AUTHOR]