Monitoring of degradation process in automotive-multilayer coatings using photooxidation index

The photooxidative degradation of e-coats in different automotive multilayer coating systems was investigated by performing photooxidation index (POI) measurements using a FT-IR-microscopic device. For the photoxidation index measurements a special flat cutting was developed and the measurements were performed on the original and the corresponding weathered multicoat systems. The obtained POl results were compared with the corresponding UV-VIS-NIR transmittance and absorption data and finally the influencing parameters of photochemical degradation processes were discussed. The obtained results prove that the transmittance of UV-light is not the only important parameter which influences the degradation stability of the e-coat and thermocatalytic effects, which accelerate the photooxidation process, should be regarded.