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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]

• Salt crystallization accelerates the degradation of epoxy in the surface layer. • UVA irradiation further exacerbates the salt crystallization effect. • There is a possible synergistic effect on epoxy degradation between the UVA irradiation and the NaCl solution wet-dry cycling. • The salt-accelerated UVA degradation may be employed to rapidly evaluate the performance of an epoxy resin coating. Epoxy resin samples were cyclically exposed to ultraviolet A (UVA) and a 5 wt% salt solution in a specially designed marine environment simulation system. Surface analyses indicated that UVA irradiation could accelerate the degradation of the epoxy surface and the dissolution of the degraded products, while the salt crystallization in the drying process could further accelerate the chalking and peeling of the degraded products. A possible synergistic effect between the UVA irradiation and salt crystallization was proposed to interpret the degradation, which may provide a new insight into the damage of organic polymer materials in marine environments. [ABSTRACT FROM AUTHOR]