Investigation On Corrosion Resistance Of 2A12 Aluminum Alloy Sheet

2A12 aluminum alloy is a kind of high-quality structural material,with the advantages of low density,high specific strength and good processing performance,so it has been widely used in aerospace field.However,during the process of heat treatment,the precipitation phase at the grain boundary will seriously affect the corrosion resistance of the materials.At present,it is the most direct and effective method to improve the corrosion resistance of 2A12 aluminum alloy by anodizing technology.In this paper,the electrochemical corrosion behavior of 2A12aluminum alloy plate and the influence of anodizing process on the corrosion resistance of 2A12 aluminum alloy plate are systematically studied.The research contents include the following aspects:(1)A research has been conducted on the electrochemical behavior of2A12 aluminum alloy in Na Cl solutions with different concentration,pH value and temperature by adopting electrochemical impedance spectroscopy(EIS)and polarization curves.The results show that the influence of solution concentration,pH value and temperature on corrosion resistance of 2A12 aluminum alloy in Na Cl solutions follows the following order:pH value>temperature>concentration.The corrosion resistance of 2A12 aluminum alloy deteriorates with the increase of Na Cl concentration.The higher the Na Cl solution temperature is,the higher the corrosion current density I_corr will be,with the corrosion resistance of 2A12 aluminum alloy decreasing as well.The corrosion resistance of the alloy is the strongest under the neutral solution condition,while the worst under the alkaline condition.The corrosion current density I_corr increases with the decrease of pH value under the acid condition,with the corrosion resistance of the alloy decreasing simultaneously.(2)The influences of anodizing process on the corrosion resistance of 2A12 aluminum alloy was studied by scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and electrochemical workstation.The results show that:in a certain range,with the increase of anodizing time or electrolyte concentration,the thickness of anodic oxide film increases and the thickness of anodic oxide film also becomes more uniform,which are beneficial to the improvement of corrosion performance.When the anodizing voltage is too low or high,the anodic oxide film is too thin to achieve the protection effect.By comprehensive consideration,the anodic oxide film prepared under the conditions of 65min anodizing time,20 V anodizing voltage and 70 g/L electrolyte concentration has the best protection performance.(3)The effect of anodizing process on the corrosion resistance of2A12 aluminum alloy after temperature shock was studied by SEM,thickness meter and electrochemical workstation.The results show that with the increasing oxidation time or electrolyte concentration,the crack density of anodic oxide film increases after temperature shock,which lead to the corrosion resistance of the anodic oxide film get worse.When the anodizing voltage is too low,although there is no crack on the surface of the anodic oxide film after temperature shock,the anodic oxide film is too thin to achieve the protection effect.Considering the cracking behavior and corrosion resistance of anodic oxide film after temperature shock,the anodic oxide film prepared under the conditions of 35 min anodizing time,15 V anodizing voltage and 45 g/L electrolyte concentration has the best protection performance after temperature shock.