A magnesium alloy electrolyte plasma polishing liquid and polishing method

Abstract

The present application proposes an electrolyte plasma polishing liquid for magnesium alloy and a polishing method thereof. The polishing liquid comprises: 20-30 g / L potassium sulfate; 5-10 g / L hydrogen fluoride ammonia; 10-20 g / L dodecylbenzene sulfonic acid; 5-10 g / L Tween 20; 15-30 g / L potassium sodium tartrate, 5-15 g / L aminoacetic acid, and the solvent is water. After sodium tartrate and aminoacetic acid are compounded, potassium sodium tartrate can form a stable complex with magnesium metal, and aminoacetic acid can effectively control the complexation speed. The surfactants Tween 20 and dodecylbenzene sulfonic acid are compounded, both of which are acidic, which is conducive to the production of a mixed gas layer. The molecules of the two surfactants are easily electrostatically adsorbed / repelled through chemical bonds to produce a synergistic effect, which effectively improves the gloss and flatness of the magnesium alloy metal surface. The polishing process is carried out at two different voltages. The low voltage avoids oxidation from occurring too quickly to form rough spots, which is conducive to the formation of a stable gas layer.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface polishing, and in particular relates to a magnesium alloy electrolyte plasma polishing liquid and a polishing method. Background Art

[0002] Magnesium alloys have the advantages of high specific strength and specific stiffness, good thermal and electrical conductivity, damping and shock absorption, electromagnetic shielding, easy processing and forming, and easy recycling. They have extremely important application value and broad application prospects in the fields of automobiles, electronic communications, aerospace, and national defense and military, and are known as "green engineering materials in the 21st century." However, magnesium alloy surfaces will inevitably produce various burrs, cracks, sand holes, and roughness problems. Poor surface quality will make them unsuitable for use in medical, aviation, and communications.

[0003] At present, the main method for surface treatment of magnesium alloy is polishing process. The existing polishing processes mainly include chemical polishing, mechanical polishing, electrolytic polishing, electrolyte plasma polishing, etc. Mechanical polishing has low cost and simple operation, but low efficiency, uneven polishing surface, and difficult to control polishing time. It is suitable for surface treatment of small areas; electrolytic polishing can ensure consistent color inside and outside, lasting gloss, and high production efficiency, but the pre-polishing treatment is complicated; chemical polishing equipment is simple and can process parts with complex shapes, but strong acids such as nitric acid are required during the chemical polishing process, which causes serious environmental pollution; electrolyte plasma polishing is a process that uses plasma technology to treat the surface of the workpiece. Its principle is to ionize gas or water vapor to form high-energy plasma through the action of high-frequency electric field, and use the physical and chemical action of plasma to finish the surface of the workpiece. During the plasma polishing process, high-energy positive ions and electrons collide with the surface of the workpiece, transfer energy and change the physical and chemical properties of the surface. These high-energy particles can remove the oxide layer, pollutants and tiny dents on the surface, making the surface smooth. In addition, the plasma action can also activate the surface, improve its surface activity, and facilitate subsequent polishing and processing. Plasma polishing machines can control the properties and effects of plasma by adjusting parameters such as gas type, gas flow, voltage and current. By optimizing parameters, different material surfaces can be polished and processed to meet different needs. This technology can be widely used in the process of polishing and improving the surface quality of metal materials, ceramic materials, plastic materials, etc. Compared with traditional electrolytic polishing and chemical polishing, it has lower costs and is widely used in industry.

[0004] The key to electrolyte plasma polishing technology is to select the corresponding polishing liquid and polishing process parameters for different polishing metals. The composition of the polishing liquid and the parameters of the polishing process parameters directly determine the polishing effect of the specific metal. Therefore, the purpose of this application is to propose a specific polishing liquid and polishing method that can be used for magnesium alloys. Summary of the invention

[0005] The object of the present invention is to provide an electrolyte plasma polishing liquid for magnesium alloy and a polishing method thereof.

[0006] An electrolyte plasma polishing liquid for magnesium alloy, comprising:

[0007] Potassium sulfate 20-30g / L;

[0008] Hydrogen fluoride ammonia 5-10g / L;

[0009] Anionic surfactant dodecylbenzenesulfonic acid 10-20g / L;

[0010] Nonionic surfactant Tween 20 5-10g / L;

[0011] Potassium sodium tartrate: 15-30g / L,

[0012] Aminoacetic acid 5-15g / L,

[0013] The solvent is water.

[0014] Specifically, the plasma polishing liquid contains a brightener, and the brightener is benzotriazole or sodium gluconate;

[0015] The specific electrolyte plasma polishing process is as follows: add the polishing liquid into the polishing tank, set the temperature of the polishing liquid to 60-90°C, set the voltage to perform a first polishing at 100-120V for 1-5min, then perform a second polishing at a high voltage of 300-350V for 3-10min, connect the workpiece to the positive pole of the power supply, connect the polishing tank to the negative pole of the power supply, immerse the workpiece in the polishing liquid, and take it out after polishing;

[0016] Specifically, the workpiece is subjected to preliminary mechanical polishing before plasma polishing.

[0017] Technical effects:

[0018] (1) The present application uses potassium sodium tartrate and aminoacetic acid as a composite complexing agent, and controls the ratio of the two, wherein the concentration of potassium sodium tartrate is 15-30 mg / mL, and the concentration of aminoacetic acid is 5-15 mg / ml. The composite complexing agent complexes with metal ions, accelerates the dissolution of oxide scales, and increases the reaction rate. After sodium tartrate and aminoacetic acid are compounded, potassium sodium tartrate can form a stable complex with magnesium metal, while aminoacetic acid can effectively control the complexing speed. The two act synergistically to reduce the concentration of free metal ions and ensure the complexing effect.

[0019] (2) Surfactant selection: The anionic surfactant dodecylbenzene sulfonic acid and the nonionic surfactant Tween 20 are compounded. The two surfactants, dodecylbenzene sulfonic acid and Tween 20, can form an adsorption film layer on the surface of the workpiece, which can make the ions in the electrolyte more evenly distributed on the surface of the workpiece. Therefore, the reaction can be more stable, and the surface glossiness can be uniform. At the same time, Tween 20 and dodecylbenzene sulfonic acid are both acidic, which is conducive to the production of mixed gas layers. When used in electrolyte plasma polishing liquid, it helps to improve the polishing efficiency. In addition, the research results show that the concentration and ratio of the two surfactants have a crucial influence on the polishing effect. The concentration of dodecylbenzene sulfonic acid is 10-20g / L, the concentration of Tween 20 is 5-10g / L, and the mass ratio of dodecylbenzene sulfonic acid to Tween 20 is controlled at 2-3:1. After the two surfactants are compounded in a suitable ratio, the molecules are easily electrostatically adsorbed / repelled through chemical bonds, synergistically enhancing the glossiness and flatness of the metal surface.

[0020] (3) Potassium sulfate and ammonium bifluoride are used as conductive salts to improve the conductivity of the electrolyte. At the same time, ammonium bifluoride can corrode the oxide layer, thereby further reducing the roughness of the alloy surface.

[0021] (4) Through two depositions at different voltages, the low voltage prevents oxidation from occurring too quickly and forming rough spots, which is conducive to the formation of a stable gas layer. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] The plasma polishing liquid for magnesium alloy electrolyte comprises: 25 g / L potassium sulfate; 8 g / L hydrogen fluoride ammonia; 15 g / L dodecylbenzene sulfonic acid, an anionic surfactant; 8 g / L Tween 20, a nonionic surfactant; 20 g / L potassium sodium tartrate, 10 g / L aminoacetic acid, and water as a solvent.

[0025] Example 2

[0026] The plasma polishing liquid for magnesium alloy electrolyte comprises: 20 g / L potassium sulfate; 8 g / L hydrogen fluoride ammonia; 15 g / L dodecylbenzene sulfonic acid, an anionic surfactant; 5 g / L Tween 20, a nonionic surfactant; 20 g / L potassium sodium tartrate, 5 g / L aminoacetic acid, and water as a solvent.

[0027] Comparative Example 1

[0028] The plasma polishing liquid for magnesium alloy electrolyte includes: 25 g / L potassium sulfate; 8 g / L hydrogen fluoride ammonia; 15 g / L dodecylbenzene sulfonic acid, anionic surfactant; 20 g / L potassium sodium tartrate; the concentration of aminoacetic acid is 10 g / L; the solvent is water.

[0029] Comparative Example 2

[0030] The plasma polishing liquid for magnesium alloy electrolyte comprises: 25 g / L potassium sulfate; 8 g / L hydrogen fluoride ammonia; 8 g / L nonionic surfactant Tween 20; 20 g / L potassium sodium tartrate, 10 g / L aminoacetic acid, and water as solvent.

[0031] Comparative Example 3

[0032] The plasma polishing liquid for magnesium alloy electrolyte comprises: 25 g / L potassium sulfate; 8 g / L hydrogen fluoride ammonia; 15 g / L dodecylbenzene sulfonic acid, an anionic surfactant; 8 g / L Tween 20, a nonionic surfactant; the concentration of aminoacetic acid is 10 g / L, and the solvent is water.

[0033] Comparative Example 4

[0034] The plasma polishing liquid for magnesium alloy electrolyte comprises: 25 g / L potassium sulfate; 8 g / L hydrogen fluoride ammonia; 15 g / L dodecylbenzene sulfonic acid, an anionic surfactant; 8 g / L Tween 20, a nonionic surfactant; 15 g / L potassium sodium tartrate, and the solvent is water.

[0035] Comparative Example 5

[0036] The plasma polishing liquid for magnesium alloy electrolyte comprises: 25 g / L potassium sulfate; 15 g / L dodecylbenzene sulfonic acid, an anionic surfactant; 8 g / L Tween 20, a nonionic surfactant; 20 g / L potassium sodium tartrate; 10 g / L aminoacetic acid; and water as a solvent.

[0037] Comparative Example 6

[0038] The plasma polishing liquid for magnesium alloy electrolyte comprises: 25 g / L potassium sulfate; 8 g / L hydrogen fluoride ammonia; 8 g / L dodecylbenzene sulfonic acid, an anionic surfactant; 15 g / L Tween 20, a nonionic surfactant; 20 g / L potassium sodium tartrate, 10 g / L aminoacetic acid, and water as the solvent.

[0039] Comparative Example 8

[0040] The plasma polishing liquid for magnesium alloy electrolyte comprises: 25 g / L potassium sulfate; 8 g / L hydrogen fluoride ammonia; 15 g / L dodecylbenzene sulfonic acid, an anionic surfactant; 8 g / L Tween 20, a nonionic surfactant; 10 g / L potassium sodium tartrate, 20 g / L aminoacetic acid, and water as a solvent.

[0041] The polishing methods of Examples 1-2 and Comparative Examples 1-8 are as follows:

[0042] Add polishing liquid into the polishing tank, set the temperature of the polishing liquid to 80℃, set the polishing voltage to polish at 120V for 1min, then polish for the second time at a high voltage of 300V for 7min, connect the magnesium alloy workpiece to the positive pole of the power supply, connect the polishing tank to the negative pole of the power supply, immerse the workpiece in the polishing liquid, and take it out after polishing.

[0043] Comparative Example 9:

[0044] The difference from Example 1 is that low voltage polishing is not performed.

[0045] The polishing effects of Examples 1-2 and Comparative Examples 1-9 were tested, and the results are shown in the following table.

[0046] Table 1

[0047] Roughness(μm) Surface state Example 1 1.19 High gloss, bright, no sand spots Example 2 1.30 High gloss, no sand spots Comparative Example 1 8.21 Dark surface with many sand spots Comparative Example 2 7.34 Gray surface, sand spots Comparative Example 3 5.53 Poor gloss, with sand spots Comparative Example 4 6.67 Poor gloss, with sand spots Comparative Example 5 4.87 Low gloss, with sand spots Comparative Example 6 2.87 Low gloss, a few sand spots Comparative Example 7 4.15 Low gloss, with sand spots Comparative Example 8 3.25 Low gloss, with sand spots Comparative Example 9 2.4 Has a certain glossiness, no sand spots

Claims

1. An electrolyte plasma polishing liquid for magnesium alloy, comprising: Potassium sulfate 20-30g / L; Ammonium bifluoride 5-10g / L; Anionic surfactant dodecylbenzenesulfonic acid 10-20g / L; Nonionic surfactant Tween 20 5-10g / L; Potassium sodium tartrate: 15-30g / L, Aminoacetic acid 5-15g / L, The solvent is water.

2. According to claim 1, the electrolyte plasma polishing liquid for magnesium alloy contains a brightener, and the brightener is benzotriazole or sodium gluconate.

3. A method for electrolyte plasma polishing of magnesium alloy, characterized in that: The electrolyte plasma polishing liquid of any one of claims 1-2 is used, and the electrolyte plasma polishing process is: add the polishing liquid into the polishing tank, set the temperature of the polishing liquid to 60-90°C, set the voltage in a manner of first polishing at 100-120V for 1-5min, and then perform a secondary polishing at a high voltage of 300-350V for 3-10min, connect the workpiece to the positive pole of the power supply, connect the polishing tank to the negative pole of the power supply, immerse the workpiece in the polishing liquid, and take it out after polishing.

4. According to the method for magnesium alloy electrolyte plasma polishing as described in claim 3, the workpiece is first subjected to preliminary mechanical polishing before plasma polishing.