Acid tungstate conversion liquid and method for forming conversion coating on magnesium-lithium alloy
An acid tungstate, magnesium-lithium alloy technology, applied in the surface treatment solution of the alloy, the surface treatment solution forms a conversion film on the surface of the alloy, which can solve the problems of toxicity and withdrawal, and achieve the improvement of corrosion resistance and other properties. Effect
Inactive Publication Date: 2010-08-18
HARBIN ENG UNIV
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Problems solved by technology
At present, among the many anti-corrosion treatment methods for magnesium-lithium alloys, the most mature one is chromate conversion coating. Its treatment process is mature and its performance is stable. However, due to toxicity problems, the chromate conversion coating process has been subject to more and more restrictions and Will eventually withdraw from the stage of history
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[0041] The following examples describe the present invention in more detail:
[0042] A) The sample is polished, and then soaked in acetone for 10 minutes;
[0043] B) Clean the sample after A) degreasing with hot water, then clean it with running water, and dry it with hot air;
[0044] C) The sample after B) is subjected to alkaline degreasing. The alkaline degreasing process adopted is sodium hydroxide 20g / L, trisodium phosphate 10g / L, temperature 50°C, time 10min, and then washed with water and blown with hot air. Dry;
[0045] D) Put the sample after C) into the acidic tungstate conversion solution for conversion treatment.
[0046] The preparation method and process specifications of the acidic tungstate conversion solution are as follows (the reagents and distilled water used in the experiment are all analytically pure):
[0047] 1) Accurately weigh 10g / L sodium tungstate with an electronic balance, the solubility of sodium tungstate in water is relatively small, ful...
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The invention provides acid tungstate conversion liquid and a method for forming a conversion coating on a magnesium-lithium alloy. The acid tungstate conversion liquid is prepared from sodium tungstate serving as main salt, sodium fluoride serving as an accelerator, sodium acetate serving as a buffer, sodium pyrophosphate serving as a coordinating agent and glacial acetic acid serving as a pH modifier. An acid tungstate conversion coating prepared by the method is grey white, relatively uniform, continuous, flat and dense without remarkable pocking mark or peeling, and has an excellent binding force with a magnesium-lithium alloy substrate. But the coating is relatively thin; the conversion coating has a laminated structure in the aspect of microcosmic shape; and a plurality of particle points are distributed on the surface of the conversion coating. The conversion coating has the advantages of low preparation cost, few preparation steps, simple operation, temperate reaction condition, environment friendliness and energy conservation, few conditions needing controlling and easy realization, higher corrosion resistance than a chromate conversion coating and the like, and is very applicable to mass production.
Description
technical field [0001] The invention relates to an alloy surface treatment solution. The invention also relates to a method for forming a conversion film on the alloy surface with a surface treatment solution. Specifically, it is a solution and method for forming a chromium-free conversion film on a magnesium-lithium alloy. It belongs to the field of inorganic metal materials. Background technique [0002] Magnesium-lithium alloy is the lightest metal structure material with a very low density of only 1.30g / cm 3 ~1.65g / cm 3 , is the only magnesium alloy system with a density lower than that of the magnesium matrix, even lower than the density of water, and is 10% to 30% lighter than standard magnesium alloys. The alloy has a high unit modulus of elasticity, a compressive yield limit 2 / 3 to 1 times higher than that of ordinary magnesium alloys, insensitive to notches, good impact toughness, high bending strength, no obvious anisotropy of mechanical properties, good plasti...
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IPC IPC(8): C23C22/36C23C22/78
Inventor 黄晓梅周海霞
Owner HARBIN ENG UNIV