Combined Treatment on an Al Surface to Improve the Metal-Polymer Adhesion Strength

The development of mobile industries and urban transportation today requires nanotechnology for research and processing of metallic surfaces. Here, aluminum alloys (Al) are the most common material with the best physical properties that need to be treated. The advantages of Al in manufacturing are obvious; however, the Al surface is sensitive to the presence of acid or base, and thus protecting the Al surface is mandatory. In this study, Al surfaces have been subjected to a new surface treatment process that includes sandblasting, anodizing, and subsequent post-etching steps. The treated surfaces are evaluated by surface morphology including contact angle measurement and polymer adhesion strength. The adhesion strength of blasted Al-polymer assemblies with and without an anodizing step have been performed with a single lap shear test. This clearly shows the profound effect of the combined treatment process. The results reveal that a combination of high surface roughness and area as well as a thick Al₂O₃ layer with micro-cavities created by a post-etch step can significantly improve the adhesion strength of the Al-polymer. This, in turn, enhances the quality of and longevity of Al surface in production and application.