The Study On The Galvanic Corrosion And Protection Of Magnesium Alloy Coupled With Other Alloys

The galvanic corrosion that blocked the adhibition of magnesium alloy was an important issue. In allusion to the galvanic corrosion of magnesium alloy, this paper made the research on the galvanic corrosion of AZ31 magnesium alloy with A6N01S-T5 aluminum alloy, 201stainless steel and Q235 low carbon steel by immersion test in 3.5% NaCl sodium chloride solution at ambient temperature and pressure, and by analysis methods such as scan electron microscope(SEM) and X-ray diffraction(XRD). Based on the result, concrete protective measures on how to lessen or prevent galvanic corrosion were proposed, such as using the rubber gasket between magnesiumalloy and dissimilar alloys and spraying the organic coating.First, there was the research on the galvanic corrosion of AZ31 magnesium alloy with A6N01S-T5 aluminum alloy, 201stainless steel and Q235 low carbon steel. AZ31 magnesium alloy was accelerated as anode coupled with dissimilar alloys. The rimous corrosion products sticked to the surface of magnesium alloy. The weight loss increased, and the average corrosion rate reduced gradually with the time. There was a relationship about the sensitivity of magnesium alloy for dissimilar alloys,γ(Al)>γ(Q235)>γ(201).As cathode, 201 stainless steel and Q235 low carbon steel were protected. And there were more and more thick Mg(OH)₂ films covering surfaces of tow steels with the time. They aluminum alloy was protected, which contacted with magnesium alloy, but the other part occurred the serious cathodic corrosion that exposed in 3.5% NaCl sodium chloride solution. So the corrosion products was mixture, containing Al(OH),Mg₆Al₂(OH)₁₈·4.5H₂O mainly.Then, there was the research on the protective measures about AZ31 magnesium alloy, using the rubber gasket and the organic coating. There were rubber gaskets between magnesium alloy and dissimilar alloys. This approach could decrease the galvanic corrosion and prevent the crevice corrosion. The weight loss and average corrosion of magnesium alloy was obviously decreased in this way.The surfaces of metal materials sprayed zinc chromate epoxy primer for 2 times + fluorocarbon topcoat for 2 times. This organic coating prevented the galvanic corrosion completely in 45d. By immersion test after 45d, the organic coating without wrinkles, blisters, peeling and other phenomenon, was a heavy-duty coating.