| As the phenomenon of galvanic corrosion when magnesium join to other metal ,the corrosion regularity of surface treatment AZ31 magnesium alloy and 45# steel joint samples in different corrosive condition was studied systematically by salt spray tests. The property of no film, micro-arc oxidation film and chromate film influenced the corrosion of joint samples which was analyzed in same corrosive conditions by calculate the corrosion effects and observe macro-photograph micro-photograph. The corrosive regularity influenced by corrosive condition factors and the corrosion resistance of different thickness of micro-arc oxidation film also be compared.The results indicate that the corrosion of joint samples on magnesium alloy is more serious than it of non-joint samples. There is much corrosion pit on surface of magnesium alloy joint samples and the corrosion degree grows weaker gradually from the boundary of two metals to the other area. The chromate film's micro-photograph shows that there is much crack on the surface of film. It is easy to being corroded and the corrosion style is mainly interstitial corrosion. The micro-arc oxidation ceramic coating is compact, which can block the galvanic corrosion reaction between magnesium and steel. However, micro-pore distributing on the surface of ceramic coating will enhance the probability of Cl- traverse into film through diffusion effect, consequently the basis will be corroded, mainly be pitting corroded. Therefore, the corrosion resistance of micro-arc oxidation coating is better than the chromate film of joint samples.The corrosion effect is greater when there is Cl- in the solution and the increase of Cl- concentration during 0～10 percent can accelerate the corrosion effect, but this acceleration is not infinite. When the concentration of Cl- reaches some value, the effect will weaken obviously. The galvanic corrosion can be delayed because of the protective film on the surface of magnesium ally and makes some self-corrosion on 45# steel. The existence of Fe2+ in chlorides can accelerate the corrosion of joint samples. The influence of temperature during 25～45 degree of joint samples is little and the increase of corrosion velocity fluctuates in a small range. |
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