Electrolyte for realizing blackening of magnesium alloy surface and blackening process method

Abstract

The invention provides an electrolyte for realizing blackening of a magnesium alloy surface and a blackening process method. A coloring solution of a silicic acid system is adopted, and the coloring solution comprises additives such as ferric ammonium citrate and the like. In the coloring process, a magnesium alloy is subjected to down-current two-step constant-current micro-arc oxidation treatment in a prepared micro-arc oxidation solution to prepare a black ceramic membrane. In order to further improve the corrosion resistance and the stability of a membrane layer, hole sealing treatment iscarried out in hole sealing liquid. The coloring micro-arc oxidation solution is safe, environmentally friendly and high in stability, by optimizing a micro-arc oxidation manner, positive and negativecurrent density parameters are adjusted, self-repairing hole sealing is carried out on the interior of the membrane layer, the problems that the surface is loose and porous, and the thickness of a compact inner layer is small are solved, membrane layer compactness control is achieved, the membrane layer is thicker and more compact, finally the hole sealing liquid is good in stability, the influence on the color of the membrane layer does not exist, and the corrosion resistance is improved. By means of the technology, blackening treatment of the magnesium alloy is achieved, and the applicationfield of the magnesium alloy is broadened.

Description

technical field [0001] The invention belongs to the technical field of magnesium alloy surface coloring, and in particular relates to an electrolyte for realizing the blackening of the surface of the magnesium alloy and a process method for realizing the blackening of the surface of the magnesium alloy by micro-arc oxidation. Background technique [0002] Due to its low density, high specific strength, good electromagnetic shielding performance and easy recycling, magnesium alloys are widely used in lightweight automobiles and electronic products, but the poor corrosion resistance and single surface decoration of magnesium alloys restrict their development. The biggest obstacle is that the surface coloring technology is the simplest and most effective method to improve the corrosion resistance of magnesium alloys while satisfying its decorative properties. The advantage of the micro-arc oxidation coloring technology is that it can complete the coloring of the coating on the ...

AI Technical Summary

Problems solved by technology

However, the surface of the magnesium alloy obtained by this technology is mostly off-white, which greatly limits its application range. Using this technology to achieve a variety of colors on the surface of the magnesium alloy, especially black, has unique optical properties and adaptability in electronic products. Wide range of application prospects

[0003] There are following deficiencies in the present existing magnesium alloy micro-arc oxidation preparation black technical method: (1) electrolytic solution contains harmful elements such as P, as: by adding ferric citrate in the phosphoric acid electrolyte system to carry out two times on the magnesium alloy surface Micro-arc oxidation is black, the film layer is loose and porous, and the corrosion resistance and wear resistance are not good

(2) Most of the micro-arc oxidation process adopts a one-stage constant current or constant pressure process, resulting in a relatively rough surface of the film layer, porous and accompanied by cracks, such as: application publication number CN201710335350.7 discloses a magnesium alloy black micro Arc oxidation film preparation method, cracks and burning appear on the surface of the black film layer prepared by a one-stage constant pressure process method

(3) The pulse frequency is large and the oxidation time is long, which increases the energy consumption required for production. For example, the application publication number CN201810635295.8 discloses a magnesium alloy micro-arc oxidation smooth black ceramic film and its preparation method, using bipolar The first stage and the second stage of the two-stage micro-arc oxidation treatment are carried out on the magnesium alloy in the constant current mode in which the current density is changed by the pulse pulse, but the pulse frequency required for the second stage of the method is as high as 1200-1600Hz, and the oxidation time is as long as 25min , high energy consumption, resulting in increased production costs, which is not conducive to large-scale industrial production applications

[0004] In order to further improve the stability of the micro-arc oxidation film, it is often necessary to carry out sealing treatment, and there are the following deficiencies in the current sealing technology of the black micro-arc oxidation film of magnesium alloy: (1) the color and luster brightness decreases after sealing, such as : Application Publication No. CN201810033434.X discloses a surface treatment method for magnesium alloys. The sealing agent used in the sealing treatment in the third step includes the following components: silicate and benzotriazole. After sealing, it is easy to White gray and discoloration occur, and the film color is not good

(2) The sealing effect is not good, such as: AZ31B magnesium alloy surface silane treatment research (2008, Chinese Journal of Corrosion and Protection), soaking in the silane solution of bistriethoxysilylphenyl tetrasulfide for about one minute, After soaking in salt water for 2 hours, corrosion spots have appeared on the surface of the sample, and the anti-corrosion effect is not significant

(3) The sealing process takes a long time, which is not conducive to the improvement of production efficiency. For example, the application publication number CN201911352063.2 discloses a method for preparing a non-ferrous alloy anti-corrosion layer. The porous micro-arc oxidation is placed in sol-gel by dipping method Sealing is carried out in the glue solution, but the sol-gel solution requires a large amount of organic solvent preparation and 3-7 hours of stirring and 12-34 hours of drying at different temperatures to prepare a stable seal. On the surface, not only the process is cumbersome, but also can only meet the effect of further stabilizing anti-corrosion, but for the colored film layer, this technical method will change the original color of the film layer, and the color and brightness will decrease after sealing, which is difficult to meet the requirements of improving anti-corrosion effect. Satisfy the decorative function of the colored film layer

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