Magnesium-lithium alloy molybdate and phosphate conversion solution and method for forming conversion coating

Abstract

The invention provides magnesium-lithium alloy molybdate and phosphate conversion solution and a method for forming a conversion coating. The magnesium-lithium alloy molybdate and phosphate conversion solution is prepared from sodium molybdate serving as main salt, monosodium phosphate serving as secondary main salt, citric acid serving as a coordinating agent, sodium fluoride serving as an accelerator, sodium nitrate serving as an accelerating agent, and glacial acetic acid serving as a pH regulator. By using the magnesium-lithium alloy molybdate and phosphate conversion solution to treat a magnesium-lithium alloy, the formed molybdate-phosphate coating has high surface coverage degree on the magnesium-lithium alloy, is uniform and dense, and greatly improves the corrosion resistance of the matrix. The magnesium-lithium alloy molybdate and phosphate conversion solution and the method for forming the conversion coating have the advantages of simple and practicable process, short coating time, low cost, little influence on fatigue property of the magnesium-lithium alloy, low requirement on matrix materials, and no influence of the matrix materials.

Description

technical field [0001] The invention relates to an alloy surface treatment liquid, and the invention also relates to an alloy surface treatment method. Specifically, it is a conversion solution for forming a conversion film on a magnesium-lithium alloy and a method for forming the conversion film. It belongs to the field of inorganic metal materials. Background technique [0002] Magnesium-lithium alloys are favored by researchers in many fields due to their excellent properties. Research at home and abroad focuses on designing alloys and improving casting conditions, reducing impurity content, adding alloy elements, and manufacturing high-purity magnesium-lithium alloys and high-temperature corrosion-resistant magnesium-lithium alloys. Alloys, but there are very few reports on the surface modification of magnesium-lithium alloys to improve and improve their corrosion resistance. Research on magnesium-lithium alloys in China has just started, and many issues are still in t...

AI Technical Summary

Problems solved by technology

The traditional chromate conversion coating technology is mature, which greatly improves the corrosion resistance of magnesium-lithium alloys. However, due to the toxicity of hexavalent chromium, research and development of environmentally friendly chromium-free molybdate-phosphate to replace chromate conversion coatings Conversion coating is of great significance

Traditional molybdate conversion coatings are generally adjusted with phosphoric acid, which does not improve the corrosion resistance of magnesium-lithium alloys much, and can only reduce the corrosion current by an order of magnitude.

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