STUDY OF THE INTERFACIAL CHEMISTRY OF POLY(VINYL CHLORIDE) PAINT ON STEEL EXPOSED TO THE ULTRAVIOLET-WATER CONDENSATION TEST

The effect of exposure to the UVCON (humidity and UV radiation) accele rated corrosion test of a poly(vinyl chloride) paint applied over clea ned, abraded, and pre-rusted mild steel substrates has been investigat ed from the interfacial chemistry and adhesion standpoints. The X-ray photoelectron spectroscopy (XPS) data reveal significant differences i n the locus and mode of adhesion loss, which depend on the time of exp osure and the initial presence of a rust layer on the mild steel. The adhesion values obtained with the pre-rusted mild steel were greater t han those obtained with the cleaned and abraded mild steel before expo sure. After 15 days of exposure, it was observed that changes in the i nterfacial surface composition of the PVC/cleaned and abraded mild ste el systems might have important positive effects on the adhesion stren gth values. The XPS data suggest the oxidation of both interfacial sur faces, incorporating polar C-O and C=O species, which would be expecte d to enhance the adhesion of paint to metal. In contrast, the PVC pain t/pre-rusted mild steel system showed no change in adhesion values or interfacial surface composition over the entire period of exposure.