Preprocessing method of magnesium alloy electro-coating technology

Abstract

The invention discloses a preprocessing method of the magnesium alloy electro-coating technology. The preprocessing method comprises the step of carrying out phosphating processing on a magnesium alloy workpiece in a phosphating solution. The formula of the phosphating solution comprises the components of 15-20g / L of zinc oxide, 10-15ml / L of phosphoric acid, 3-5g / L of sodium fluoride, 10-12g / L of sodium nitrate, 2-3g / L of ammonium molybdate, 4-8g / L of hydroxylamine sulphate, and 4-5g / L of lauryl sodium sulfate. The PH value of the phosphating solution is 3-5, the temperature of the phosphating solution is 40-50DEG C, the phosphating time is 15-20 minutes, and 2-3g / L of nickel nitrate and 4-8g / L of manganous nitrate are further added into the phosphating solution. According to the preprocessing method, when phosphating processing is carried out on the magnesium alloy workpiece, the nickel salt and the manganese salt are added in the phosphating solution, therefore, the tissue structure of a phosphating film is effectively improved, the follow-up electro-coating technology is optimized, and the film obtained through the electro-coating technology has the excellent corrosion resistance.

Description

technical field

[0001] The invention relates to the technical field of metal material surface treatment, in particular to a pretreatment method of magnesium alloy electrophoretic coating process. Background technique

[0002] Magnesium alloy has superior properties such as high specific strength, good machining performance, good shock absorption capacity, good thermal conductivity, good electromagnetic shielding performance, excellent hydrogen storage performance, high die-casting productivity, easy cutting, easy recycling, etc. It is a kind of performance Superior light metal structural materials, magnesium alloys, as high-quality alloy structural materials, are widely used in aerospace, automotive, electronics and medical equipment industries.

[0003] However, magnesium has poor corrosion resistance and is easily corroded during application. There are many types of magnesium alloy corrosion, which can be divided into electrochemical corrosion, stress corrosion cracking, ...