Study Of Connection Corrosion Behaviors Of Magnesum Alloy Coupled With Aluminum Alloy

The connection corrosion behaviors of bare, chromated and micro-arc oxidized magnesium alloy and the protection effects of this two kinds of surface treatments were studied using the contrast experiments by applying GB/T 10125—1997 test criteria named " man-made atmosphere corrosion test — salt-fog test" The determinations of corrosion properties of different coatings were researched with calculating the corrosion weightlessness rates and observing surface corrosion appearances, then the connection corrosion behaviors of magnesium alloy were studied under different corrosion solution concentrations, environment temperatures and PH values.The results indicate that the connection corrosion of magnesium alloy was greatly accelerated by galvanic corrosion and slit corrosion effect. Because the electrode potential of magnesium alloy is lower than aluminum alloy, when sets to the corrosion atmosphere, which contains NaCl after connecting with aluminum, alloy. After it carried on the suitable surface treatment, the corrodes obviously reduced, also the connection corrosion effects greatly had reduced. Along with the corrosion solution concentration and environment temperature increasing, the connection corrosion rate of bare speeds up, and the corrosion depth is more serious than the situation of lower concentration and temperature. Because magnesium alloy is alkali metal, when corrosion solution was acidity, the corrosion rate is 6 times in contrast with it in the alkali corrosion environment. In contrast of the two kinds of surface treatments crafts, the effect of micro-arc oxidation is better. Because the chromate processing film is easy to be dissolved, the effect of connection corrosion protective of magnesium alloy coupled with aluminum alloy is limited in 24 hours. But the ceramic coating of micro-arc oxidation is not sensitive to connection corrosion due to its high impedance value and excellent binding force. The ceramic coating has little damage phenomenon and displays the good protection effect for 72 hours. But the ceramic coating has its limitation that is worse in the acidic environment.