Effect of Chemical Conversion time on Corrosion Resistance of a New Aluminum-Lithium Alloy 2198

A new aluminium-lithium alloy 2198 was treated by chemical conversion using Alodine1500 chromate for different periods of time. The effect of chemical conversion time on corrosion resistance of the aluminium-lithium alloy was studied through polarization curves, electrochemical impedance spectroscopy and corrosion morphology in 3.5% (mass fraction) NaCl solution. The results show that after chemical conversion the corrosion resistance of the aluminum-lithium alloy was improved. The aluminum-lithium alloy had the best corrosion resistance,when the chemical conversion time was 5 min. With the prolongation of chemical conversion time, the chemical conversion coating increased in thickness, making the pitting degree of aluminum-lithium alloy decline. However, if the chemical conversion time was over long, the chemical conversion coating became loose and porous, and the corrosion resistance decreased instead.