UV ageing characterisation of organic anticorrosion coatings by dynamic mechanical analysis, Vickers microhardness, and infra-red analysis

To monitor the UV degradation of organic anticorrosion coatings, different kinds of information provided by different characterisation methods are compared. Vickers microhardness (HV) results are correlated with T-g measurements, by the pin point method. This technique is investigated during UV-A artificial ageing taking into account the influence of coating thickness and mineral pigments. After verifying the high quality and accuracy of the Tg information, the HV data are corrected, to prevent distortion of the measurements by thickness and pigment concentration. A corrective method is discussed and checked. The chemical degradation and mechanisms, identified by FT-IR spectroscopy, are also correlated to Tg changes. This has allowed us to validate the previous method. The main interest of this study is a correlation the mechanical modifications of the top-coat which are macroscopic consequences of the UV ageing, with photochemical degradations which directly correspond to the molecular modifications induced by UV radiation. For that the T-g measurements are of great interest. (C) 2001 Elsevier Science Ltd. All rights reserved.