| 2024 aluminum alloy is widely used in the aerospace industry,automotive industry and other applications due to its light weight and reliable mechanical properties.Due to the strong oxygen affinity of the aluminum alloy,it is easy to form a natural oxide film on the surface,which can not provide adequate protection against aggressive ions.Therefore,the surface treatment of aluminum alloys is extremely necessary to improve the corrosion resistance.At present,the most widely used anti-corrosion technology of aluminium alloy surface at home and abroad is the anodic oxidation method.The anodic oxidation film of aluminium alloy is composed of barrier layer and porous layer,unfortunately,the porous layer may provide a channel for the entry of corrosive medium and reduce the corrosion resistance of aluminium alloy.Therefore,the sealing treatment after anodic oxidation is necessary to seal the pores and improve the corrosion resistance of aluminium alloy.In this paper,2024 aluminium alloy was anodized with oxalic acid solution,and then the effect of NaAlO2 sealing on corrosion resistance of anodic oxide film was studied.The best sealing conditions and mechanism of NaAlO2 sealing were studied by polarization curves,electrochemical impedance spectroscopy?EIS?,scanning electron microscopy?SEM?and X-ray photoelectron spectroscopy?XPS?.The experimental results show that the unsealed anodic oxide film of aluminium alloy is a porous structure with poor corrosion resistance.However,when the sample was immersed in 0.2 mol/L NaAlO2 solution with the PH of 7,the solution temperature of 85?and the sealing time of 5 minutes,the pore on the sample surface was filled and the surface became smooth,therefore the corrosion resistance was greatly improved.It is also found that the corrosion resistance of the anodic alumina alloy after sealing with NaAlO2 is better than that of the boiling water sealing,because more AlOOH is produced in the process of NaAlO2 sealing. |
PDF Full Text Request