Development of Anti-cathodic Disbonding Epoxy Coating

Abstract An epoxy coating with excellent cathodic disbondment resistance performance is developed in this paper. Bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin and C9 petroleum resin were used as the resin system of coating. The orthogonal test of four factors at four levels was applied to select the amount of each resin. The mixed curing agent of polyamide and modified phenolic amine showed good performance. When the ratio of polyamide and modified phenolic amine was 2:1, the anti-cathodic disbonding performance of the coatings was the best. The optimized ratio of pigment to resin (pigment/binder ratio) is 1:1, which was concluded from the correlation between P/B (pigment/binder) ratio (0.75:1~1.5:1) and cathodic disbonding resistance performance. The final epoxy coating formulation with optimized resin, curing agent and pigment/binder ratio has excellent cathodic disbonding performance, which is only 3 mm of cathodic disbonding equivalent diameter after 48 hours cathodic disbondment test (-1.5V (vs. SCE), 65°C seawater).