Electrochemical evaluation of UV aged acrylic polyurethane varnish coatings

An artificial weathering test (UVB radiation condensation) was used for aging testing of acrylic polyurethane varnish coatings. The harrier protection properties of coatings with different exposure times were evaluated using electrochemical impedance spectroscopy (EIS). The results showed that low frequency impedance |Z| at a fixed frequency decreased with the increase of exposure time which and yielded time series function. Fourier transform infrared spectroscopy (FTIR) indicated that degradation had taken place upon exposure to artificial weathering test, and also appearsed to undergo some molecular segments re-association after 12 days exposure which led to the increase of low frequency impedance. Therefore, low frequency impedance could he used as an appropriate parameter to characterize the protective properties of intact organic coatings.