Failure process of epoxy zinc yellow primer/acrylic polyurethane coating system on aluminum alloy substrate was studied under simulated ocean atmosphere environment. By comparative evaluation at cyclic acceleration

UV/condensation and neutral salt spray conditions

effects on failure modes of epoxy primer

polyurethane topcoat and composite coating were assessed. Results showed that UV/condensation had strong destructive effect on acrylic polyurethane topcoat

but had little effect on impedance change of overall composite coating. During UV/condensation process

experimental temperature within glass transition temperature of topcoat and UV damage on carbamate group were main reasons for topcoat destruction. Salt spray had minimal effect on change of gloss loss and color difference

whereas consistent salt spray infiltration obviously accelerated impedance decrease of the coating system and caused significant reduction of adhesion between primer and substrate. Compared to UV/condensation or salt spray test alone

cyclic accelerated tests considered influences of different environmental factors such as strong solar radiation

high temperature and humidity

high salinity and temperature difference in ocean atmosphere of the South Sea

which can more accurately reflect failure process of the coating system in the region.