Surface Modification Originated Multifunctionalization of Aluminum Alloys Using Steam

Al alloys, especially Al-Mg-Si alloys and Al-Zn-Mg alloys, have been used as advanced structural materials in automobile industries because of the excellent physical and mechanical properties such as low density, high specific strength and ductility. Their low corrosion resistance, however, hinders their use in the corrosive environment. To improve the corrosion resistance of the Al alloys, the development of a novel coating technology has been highly desirable. Steam coating is a novel environmentally-friendly coating method, where only pure water is required. Conventional coating methods for Aluminum alloys, anodization and chemical conversion treatments, could be replaced by steam coating. Steam coating was applied to a couple systems of Aluminum alloys. The anticorrosive film was generated with a chemical reaction of steam and Aluminum during steam coating. In this article, the mechanism of steam coating was interpreted from the chemical reaction of Aluminum alloys with steam as well as the induced precipitation behavior in substrate by a thermal energy of steam. The surfaces morphology of the specimens subjected to steam coating process was found to be significantly unique and changed depend on the process condition. These surfaces are expected to be utilized to enhance adhesion and jointing strength.