Degradation of Polyaspartic Polyurea Coating Under Different Accelerated Weathering Tests

Polyurea coating based on polyaspartic esters(PAE) were prepared from synthesized polyaspartic esters(PAE-F) and hexamethylene diisocyanate(HDI)trimer /amine terminated polyoxypropylene(Jeffamine D2000) prepolymer.The surface topography,structure and morphology and electrochemical impedance spectroscopy(EIS) features of the coating under salt fog exposure and UV/salt fog alternating exposure were investigated through SEM,AFM,FTIR and EIS.The results indicated that the performance of the coating was difference when it was tested in different ways.The surface topography and structure and morphology of the coating changed a little after 25 weeks salt fog exposure.As the result,the coating resistance hold high over the period of 25 weeks.But the performance of the coating under UV/salt fog alternating exposure after the same time was totally different.EIS features of the coating showed a rapid reduction over the period of 25 weeks alternating exposure.FTIR,SEM and AFM showed that the molecule chains of the coating were broken,and the ordered structures of hard segment decreased,which indicated that the structure of the coating was destroyed.At the same time,the surface roughness increased,cracks appeared at soft segment phase,and the shape of hard segment phase changed,showing topography changed severely.The study demonstrates that the PAE coating had good resistance of salt fog corrosion and lost resistance after UV/salt fog alternating corrosion.