SKP as a tool to study the physicochemical interaction at buried metal–coating interfaces

The scanning Kelvin probe (SKP) was used as a tool to receive information about the interfacial interaction strength between coatings and oxide surfaces. Potential shifts induced by the application of two polymer films (polyurethane and epoxy‐amide) on differently treated steel substrates were measured as a function of the physicochemical condition of the oxide surface (hydroxyl fraction and surface energy). The results showed that, in the case of strong interfacial acid‐base interactions, a direct correlation exists between the Volta potential drop and the adhesion strength of the coating. This phenomenon indicated that the interface dipoles formed by oxide‐coating acid‐base interactions were reflected in the SKP potential shifts and that these dipoles could be detected, even when they were covered by a thick coating.