| A356 alloy is very widely used casting aluminum alloy. It have good casting properties and therefore is widely used in automotive, aerospace and other fields, especially occupies very important position in car wheel production. But because of the uniformity of alloying elements affect the organization, the poor corrosion resistance, so the need for alloy surface treatment.Anodic oxidation technology is the most successful and widely surface treatment technology. The craft is simple, economic and environmental protection. The oxide film has good corrosion resistance and wear resistance. It is also a major way of surface treatment of aluminum alloy. But because A356 alloy containing higher content of silicon, easy to cause silicon segregation, hinder the current flow, is difficult to obtain good performance of the oxide film using conventional anodic oxidation technology. With the application popularization of A356 alloy, which has become a problem needed to resolve.This study is based on two mainly problems existed in the anodic oxidation of cast Al-Si alloy: The first one is due to the presence of silicon makes the anodic oxidation film slower; The second one is casting aluminum alloy generally adopt hard anodic oxidation to generate oxidation film now, but it need at low temperature(under5℃) reaction. It increase the energy consumption of the anodic oxidation. My Experiment using SEM, EDS and polarization curve analysis test method, to detection A356 alloy anode oxidation membrane surface morphology, chemical composition and corrosion resistance. Analysis the mechanism of film forming and influence factors.Experimental study on the influence of additives on A356 alloy anodic oxidation, simply discuss the influencing mechanism; Studied the influence of electrolyte concentration change and electrical parameters on A356 anodic oxidation film speed and coating corrosion resistance. Through the analysis found that the morphology and composition as well as the introduction of the pulse power of additives have no way to completely eliminate the effects of silicon, just increase the membrane layer formation rate and reaction temperature range; Silicon in the alloy will not occur oxidation reaction, cause the uniformity of the oxide film is reduced, phenomenon of oxide film. Through the optimization of electrolyte and electrical parameters of A356 alloy anodic oxidation process for research, finally found a kind of high efficiency and energy saving of anodic oxidation process, improve the film forming rate and reaction temperature range of the oxide film. |
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