| The hot-dip zinc-aluminum-magnesium alloy coating is a new type of coatingswhich has excellent corrosion resistance, coating performance, ductility and highsurface strength, has been numerous applied in industry in recent years. In this paper,a new type of hot-dip zinc-aluminum-magnesium alloy flux was made. Themicrostructures and composition of the Zn-6Al-3Mg alloy at differet cooling rate andZn-6Al-3Mg alloy coating were investigated. Corrosion resistance of Zn-6Al-3Mgalloy coatings was evaluated by means of immersing corrosion test and neutralsalt-spray test.The parameter of zinc aluminum magnesium alloy flux was determined throughmany tests. Test showed that there was less smoke when immersed hot-dip platingsolution at room tempreture, the coating thickness wss uniform, bright, withoutplating, and the surface quality was qualified.The results showed that the phases of Zn-6Al-3Mg alloy coating were same asthose of Zn-6Al-3Mg alloy at air cooling rate, but the microstructure of Zn-6Al-3Mgalloy coating was different from those at three kinds of cooling rate. Themicrostructure of Zn-6Al-3Mg alloy coating consisted of Al phase, Zn/MgZn2binaryeutectic, approximate hexagonal MgZn2organization. The corrosion results of NaClsalt spray test were consistent with Na2SO4solution full immersion corrosion test, thecorrosion resistance of Zn-6Al-3Mg alloy coating was superior to Zn-5Al and purezinc coating. There are two reasons for explaining this, on the one hand, it promotedZn(OH)2to Zn4SO4(OH)6·H2O, Zn5(OH)8Cl2and Zn6Al(OH)16CO3·H2O three kindsof corrosion products which had more compact structure, better adhesive and lowerconductivity due to the addition of Mg; on the other hand, the corrosion productscould firmly adhere to the surface of coating to form a compact protective film. Itcould cut off the transmission between coating and external environment effectively,and reduce the rate of corrosion to the inside coating. |
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