Mechanical Plating Of Zn-al Alloy Principle And Non-crystalline Layer Research

The purpose of this paper is to study the craft principle and formation mechanism of the mechanical plating Zn-Al alloy.Through the experiment of observing, finding that the surface of Al powders is covered by Al₂O₃ oxide film, because the chemical property of Al is lively, that is more difficult to remove. So, the state of Al powders surface must be adjusted in the course of the mechanical plating. This causes the Zn and Al powders common to absorb and deposit law is different from single Zn powder in the surface of the parts during the course of plating and covering. The reinforced way and the shape of the Al powders have been confirmed through the observing experiment. With the perpendic- ularity experiment, the craft of the mechanical plating Zn-Al alloy has been confirmed. The mechanical plating Zn-Al alloy is plating and covering with this craft and taking some samples. Through testing the appearance, the hole rate of layer, the combine intensity, the composition detection of structure and the corrosion-resistant performance of the samples, finding that the Zn-Al alloy plate layer with Zn plate layer of appearance is closed, has no hole, metal is combined intensity to be kind with the matrices, and the corrosion-resistant performance is superior to Zn plating layer. The Al content is on the low side in the Zn-Al alloy layer, this has something to do with the Al powders shape and directly: Flaky Al powders are very difficult to pile up closely with the small globular Zn powders because the granularity of the flaky Al powders is big and the wetting dispersiving among the plating liquid is bad. Only the granularity of the Al powders is near to the particle size of the Zn powders and small than the thickness of the plating layer can be pile up closely into the layer. Some small grains of Al powders of might react and consume among the plating liquid. The large particles Al powders are apt to be struck from the layer by the impact of medium and coming off from it. So, only the granularity of the Al powders equal to the big particle of the Zn powders can appear in the plating layer. It causes the Al content of the plate layer on the low side.Through analyzing the plate layer of broken shape by SEM, finding that: Al powders are combined closely with Zn powders in the plate layer. The structure of the plate layer is formed by metal little powder particle to inlay closely each other. The big particle among them has in various degree deformation and the area of deformation contact has cold welding phenomenon. This plate structure of layer is similar to the Zn plate layer. Through analyzing the compositionto metal little powder particle of the plate layer by SE and finding that: The surface of particle has a small amount of Sn, M to exist. The theory is true about driving metal in mechanical plating. It is proved that the subject of the plate layer is piled up by metal little powder particle, and between the particles there is to exist the crystalline driving metal.The form mode of the layer is different from electrolytic crystallization and metallurgical crystallization, because the course of the mechanical plating is go on at the room temperature entirely. The metal powder as the main body of plate layer is formed by the impact force and effect of the plating liquid system. It has none-crystallization. Metal little powder surface of particle store in the crystallization the driving metal which is reacting from the plating liquid. But there is little content with driving metal .Thus, proceed from the whole angle and defined it as having none-crystallization shape layer.The none-crystallization mechanism about the mechanical plating Zn-Al alloy can be described as: with the cooperative effect about the additives, the surface of the metal little powder has been activated and getting together as conglobations in the plating liquid system. Then they are absorbed and deposited and reached the part surface continuously. And then form urgent real plating layer dense under the force of the medium. There is a few crystallization, but as the main body of the plate layer of, the metal little powder particle has not taken place crystallization.