A major factor determining the ability of a surface coating to prevent corrosion of the substrate is the adhesion of the coating to the substrate and its sensitivity to the ingress of moisture. Diffusion of water through a coating may dissolve low molecular weight organic residues from an incompletely cured resin and transport them to the interface or it may alternatively dissolve inorganic contaminants left on the substrate as a result of imperfect surface preparation. In either case a small volume of aqueous solution is formed at the coating/substrate interface and the resultant osmotic processes can lead to the formation of blisters. The equilibrium radius of a blister is controlled by a combination of the pressure developed within it, the adhesive fracture surface energy of the substrate/coating interface and the mechanical properties of the coating. From the dimensions of the blister and its mechanical properties it is possible to calculate the pressure within it and an analysis of its contents reveals the origin of the solutes that are responsible for the osmotic forces.
|Number of pages||6|
|Journal||Corrosion and Materials|
|Publication status||Published - Aug 2011|