Self-Healing Coatings with Double-Layered Structure for Corrosion Protection of Aluminum Alloys

Abstract

Surface treatments of Al alloys are generally performed to protect them from corrosion before they are used as many kinds of industrial product. However, corrosion protection abilities of the surface layers formed by the surface treatment are lost by unexpected physical damages because the metal substrate is exposed to corrosive environments at the damaged area. From the viewpoint described above, surface films with self-healing properties should be developed to keep corrosion protection abilities high for long periods without any maintenance. In this study, double-layered films with self-healing abilities were formed on Al alloys by the combination of anodizing and organic coating. Corrosion tests in Cl⁻/Cu²⁺ solutions after physical damaging were carried out to compare corrosion protection abilities of the double-layered films formed by three processes: formation of film including 1) no healing agent in the outer and inner layers, 2) healing agents only in the inner layer, and 3) healing agents both in the outer and inner layers. The double-layered film including healing agents in both layers showed much higher self-healing ability than other coatings.