Manufacturing method of magnesium alloy transmission box with ultrahigh corrosion resistance

The invention discloses a manufacturing method of a magnesium alloy transmission box with ultrahigh corrosion resistance. The manufacturing method comprises the following steps: performing foaming, forming a cluster structure, swabbing I, swabbing II, hardening, roasting, swabbing III, smelting and pouring, and micro-arc oxidation in sequence, and obtaining a casting of the magnesium alloy transmission box attached with a dense Al2O3 oxidation film on the surface layer. The manufacturing method disclosed by the invention has the following characteristics: during the formwork roasting process, the foamed plastic is burned up in advance to avoid the influence of high-temperature foam gasification to the quality of the casting during the pouring process, avoid the influence of carbon dust to the strength of the magnesium alloy, and ensure the purity of the magnesium alloy material; the nanometer powered aluminum dip-coated before pouring is molten and tightly attached to the surface of the casting at high temperature in the pouring process to form a complete aluminum protective film, and then form the dense Al2O3 oxidation film during the follow-up micro-arc oxidation process, so as to tightly coat the magnesium alloy, improve the oxidation resistance and the corrosion resistance of the magnesium alloy, and solve the problem that the oxidation resistance and the corrosion resistance of the magnesium alloy for the existing transmission box are insufficient.