“Barrier-Adhesion” Principle for Corrosion Protection

Abstract

Abstract The “barrier-adhesion” principle for corrosion protection of aluminum alloys is presented. Corrosion that occurs in a coated aluminum alloy can be viewed as pertaining to one of the two following corrosion modes: corrosion that occurs at and in the vicinity of a damaged coating (damaged surface corrosion, such as that associated with scribed corrosion testing) and corrosion that occurs under an undamaged coating, which often appears as many small pits (pitting corrosion). The damaged surface corrosion has been found to be a consequence of corrosion-induced delamination of the coating, which enhances the propagation of corrosion from the damaged site. With a coating system that contains corrosion inhibitors, the corrosion at the damaged site is suppressed to prevent delamination. It was found that if a good barrier is adhered to the metal surface by the tenacious water-insensitive adhesion, the corrosion-induced delamination can be prevented without corrosion inhibitors in the primer. Pitting corr...