Interfacial chemistry of humidity-induced adhesion loss of chlorinated rubber on rusted steel substrates

The effect of the exposure to the humidity of a chlorinated rubber coating applied to pre-rusted mild steel has been investigated from the interfacial chemistry and adhesion point of view. X-ray photoelectron spectroscopy (XPS) data suggest that the locus of failure changes with the time of exposure to the humidity. The adhesion strength values are strongly dependent on the time of exposure. The presence of a pre-rusted layer on the mild steel has a detrimental effect on the formation of bonds between the metallic substrate and the coating after the curing process. After 1 day of exposure, the adhesion values increase nearly twice compared to the non-exposed system, XPS data suggest the presence of an important coating residue on the interfacial substrate surface. The locus of adhesion loss is probably within the coating closest to the substrate. After 30-60 days of exposure, adhesion again shows low values, the locus of adhesion loss being now inside the transformed pre-corroded layer. (C) 1997 Elsevier Science S.A.