Metal-adhesive interface, formation products

The interfacial chemistry of corrosion-induced failure on galvanized steel has been investigated (2) adhesion of a polyurethane coating was not found to involve chemical transformations detectable by XPS, but exposure to Kesternich aging caused zinc diffusion into the coating. Similar results were obtained with an alkyd coating. Adhesion loss was proposed to be due to formation of a weak boundary layer of zinc soaps or water-soluble zinc corrosion products at the paint metal Interface. 

In BPDA-PDA, the only hydrolysis observed was of anhydride. If the samples are cured to at least 400 °C to minimize the residual anhydride, the bulk polymer should be quite stable to hydrolysis. In this material, then, the major remaining concerns about hydrolytic stability center on the polymer-substrate interfaces whether possible polymer-metal interactions could result in the formation of hydrolytically unstable products and whether or not agents used to promote adhesion will retain their efficacy under humid aging. 

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