Effect of Pretreatment on Surface Micro-Characteristics and Filiform Corrosion Resistance of 6063 Aluminum Alloy

Different pretreatment methods were applied to modify the 6063 aluminum alloy surface, and scanning electrion microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and atomic force microscopy (AFM) were respectively used to study the micro-morphology, composition and potential distribution of the aluminum alloy surface, in addition, potentiodynamic polarization curve and electrochemical impendence spectroscopy (EIS) were also used to compare the filiform corrosion rate of the different surface-pretreated 6063 aluminum alloy. It was found that the pretreatment in the F- containing acid solution after etching in the alkaline solution could decrease the second phase amount in the alloy surface and make a devotion to improve the corrosion resistance. As a result of surface modification in the optimized solutions, the fillform corrosion current was lowered, and the painted aluminium alloy had the minimum double-layer capacitance (Cdl) and maximum electronic transfer resistance (Rct) in the EIS, while pretreatment in the mixed acid solution was unable to decrease the fillform corrosion rate.