Effects of surface treatment on bonding properties and corrosion resistance of al-Li alloy

The paper aims to improve the strength and corrosion resistance of aluminum-lithium alloy bonded joints. Surface treatments including sandpaper polishing, sandblasting and phosphoric acid anodizing were applied to Al-Li alloy. After surface treatment, a layer of FM94 adhesive was laid on the substrate and pressurized to cure to obtain a single lap joint. The surface properties of alloy samples including surface morphology, surface roughness, surface free energy and surface chemical composition were analyzed. The strength of the bonded joints before and after hot-humid exposure was tested, respectively to reveal the effects of different surface treatment methods on the strength and corrosion resistance of the bonded joints. Compared with sandpaper polished alloy samples, sandblasting and phosphoric acid anodizing treatments could significantly improve the surface roughness and surface free energy of aluminum-lithium alloy samples. At the same time, it was found by EDS analysis that the surface of the anodized alloy samples had a large amount of oxygen. The joint strength of anodized and sandblasted joints was 37.0 MPa and 26.8 MPa, respectively. However, that of sandpaper polished joints was only 16.4 MPa. After hot-humid exposure, the strength of phosphoric acid anodized joints was only decreased by 12.2%. However, the strength of joints after sandblasting and sanding treatment was decreased by 30.6% and 19.5%, respectively. Both anodizing and sand blasting surface treatments could increase the strength of the Al-li alloy bonded joint; however, the anodizing effect is better. The anodizing treatment can significantly enhance the corrosion resistance of the joint. However, the sandblasting treatment does not significantly improve the corrosion resistance of the joint. © 2019, Chongqing Wujiu Periodicals Press. All rights reserved.