Significantly improves the mechanical strength of aluminum alloy adhesive joint through electrochemical pretreatment in environmentally friendly medium

Adhesive bonding of aluminum alloys is extensively practiced to achieve optimum lightweight and reliable structures in the aerospace, automobile, and maritime industries. This paper represents the inaugural attempt to use neutral salt solutions as electrolytes for the electrochemical pretreatment of aluminum alloy bonding surfaces, with the aim of achieving high-performance bonding. The NaNO3 and NaCl solutions were selected carefully due to their non-toxic, easy to obtain, and inexpensive. Comprehensive experiments were conducted, and the specimen surfaces were characterized by advanced characterization methods before and after electrochemical treatment. The results demonstrated that the surface morphology of the treated aluminum alloy exhibited notable alterations, and the wettability, roughness, and chemical composition were effectively improved. Subsequently, aluminum alloy single lap joints were subjected to detailed examination in order to evaluate the effectiveness of the pretreatments on the bonding strength and fracture resistance. The results showed that under the condition of 5 A and 1 min, the specimen treated with NaCl solution demonstrated a notable enhancement in bonding performance, and its bonding strength increased by more than 200 % that of the untreated specimen joints. Moreover, this study integrates the characterization and experimental findings to provide a comprehensive analysis of the mechanisms underlying the deterioration or improvement of the bonding performances under different pretreatment conditions. This study demonstrates not only the extremely friendly characteristics to operators and environment, but also the technical advantages of low cost, high efficiency and good bonding performance.