The intention of the surface treatment of die cast is to select appropriate skills according to specific requirements to obtain high-quality films that meet the requirements. Since the various existing skills for surface treatment still have their own problems, we should have an understanding of the key issues in different treatment skills to solve these problems.
Since the chemical film formation is completely dependent on the chemical reaction between the treatment liquid and the workpiece, it does not have the effect of an external voltage like anodized film formation. Therefore, in order to form a high-quality film, in addition to strictly complying with the operation instruction of each link, sufficient attention should be paid to the uniformity of the die cast. Only the surface with uniform composition can form a uniform treatment film, so it is necessary to ensure that the composition of the magnesium alloy liquid is uniform, the composition of the die cast is uniform, and the surface of the die cast is sufficiently clean. Especially when a chromium-free treatment liquid with low film forming performance is selected to process the thin-wall (less than 2mm) die cast, the alloy liquid composition design, injection speed, mold conditions, etc. that affect the uniformity of the surface composition of the die cast must be strictly controlled to ensure the uniform and stable surface composition of the die cast.
Since the anodic oxidation film formation is carried out under the action of an applied voltage, this technology does not require the surface quality of die cast as stringent as the chemical film formation. Regarding the die cast of a certain surface sometimes even without pretreatment, a suitable treatment voltage and time can be found to obtain a high-quality film. In terms of the anodic oxidation film formation, the most critical issue is the effectiveness of the treatment liquid. The decrease in the surface quality requirements of die cast gives the release agent a chance to enter the treatment liquid. If the selection of the release agent and the treatment liquid does not match, it will cause the rapid failure of the treatment liquid. Otherwise, in the process of the film being formed by plasma micro-arc oxidation, the temperature of the treatment liquid will rise rapidly, and this temperature rise will cause the failure of some treatment liquids and affect the effectiveness of the surface treatment. Therefore, rational selection of release agent and treatment liquid, and keeping the temperature of the treatment liquid constant are key technical issues for anodic oxidation film formation.