Study On The Hot Dipped Process And Of Corrosion Resistance Of Novel Zinc-based Alloy Cating

Hot-dip is an effective and economical method of steel protection. But with the increasing environmental pollution, the traditional hot dip galvanized products can not meet the actual needs, and more and more attention has been paid to alloy coatings that have a higher corrosion resistance special properties.The 55%Al-Zn, Zn-Mg, Zn-Al-Mg coating have been further studied. Hot dip technology and corrosion resistance of a new alloy coating based on the previous studies was discussed in this article, which containing trace amounts of rare earth and titanium. Al, Mg, Re, and Ti were added in master alloys way. And in order to reduce the loss of alloying elements, the surface of molten alloy was protected with a new type of covering agent.The weight loss rate of alloy coatings with different content of Re and Ti were measured by immersion testing and salt spray testing to determine the corrosion resistance. The results showed that:the corrosion rate of Zn-1% Al-2%Mg-0.15% Re alloy coating is smallest, and have the best corrosion resistance, and when rare earth content continues increasing, corrosion rate decreases; in the containing Ti alloy coatings, small amount of Ti based of Zn-1% Al can also improve corrosion resistance of coatings. And with the Ti content increases, the corrosion rate decreases and then increases, and the one which contains 0.05% Ti is the lowest.Electrochemical test shows that the addition of rare earth and titanium all can inhibit electrochemical corrosion. The higher corrosion potential is, the smaller corrosion current density is. And the larger capacitive loop radius is, the greater the resistance of corrosion reactions has. The low frequency part of electrochemical impedance spectroscopy (EIS) of alloy coatings containing Re and Ti appear certain degree of migration. And it may be related to the formation of passive film which is conducive to the improvement of corrosion resistance. Electrochemical test results are consistent with the immersion test.The Re elements can reduce surface tension, remove O, S elements, play a role in grain refinement, and reduce intergranular corrosion rate. Organizational boundaries of coating containing Re integrated into the shallow groove. And the corrosion products after hydrochloric acid corrosion are denser comprised with pure zinc. The effect of grain refinement is the best when the content of Re reaches to 0.1%. The surface of coating containing Ti is uniform cellular organization, and the surface morphology qualities improve. Spectrum from the cross-section of the line scan detected cerium, but do not detect titanium.X-ray diffraction analysis shows that the corrosion products of coatings added Mg and Re are mainly in the form of alkaline zinc sulfate which can attach to the substrate surface to prevent corrosion to the interior of samples and improve corrosion resistance. In addition, zinc aluminum complex oxides are detected, which can increase the corrosion resistance. And in the coatings added Ti, there is a small amount of zinc titanium oxides, which indicates that the titanium element can play a role in enhancing by formation oxide film.The hot dip time and temperature of the new alloy is similar with the pure zinc, due to the low Al, Mg, Ti, and Re content in the coatings. On the basis of the original galvanizing line it can produce these new alloy coatings, so the coatings have wide application prospect.