Synergistic accelerated corrosion of ultraviolet irradiation on epoxy coating aging behavior

The structure component, surface topography and electrochemical impedance spectroscopy features of the epoxy coating under two synergistic accelerated corrosions (moist heat-salt spray-fatigue and moist heat-ultraviolet-salt spray-fatigue) were investigated through FTIR, SEM and EIS. The surface topography of inter coating under synergistic accelerated corrosion without ultraviolet has no significant change. After 8 cycles, the edge of coating has fracture and corrosion on the base metal occurs under the coating. In the process of synergistic accelerated corrosion with ultraviolet, the surface roughness of the coating increase and produce powder and loss of light phenomenon after ultraviolet irradiation. Along with the accelerating period extension, coating surface has crackle and the quantity of coating surface crack increase. The results of FTIR indicate that the coating structure is unchanged under synergistic accelerated corrosion without irradiation. But the coating structure is changed obviously under synergistic accelerated corrosion with irradiation. The polymer chains rupture and keys O-H, C-H, C=C and benzene ring disappear. After 8 cycles, the electrochemical impedance value of synergistic accelerated corrosion with ultraviolet was only 1/2 of synergistic accelerated corrosion without ultraviolet.