Application of high-valent soluble metal salts in metal solid electrolytic polishing

Abstract

The invention discloses the application of a high-valent soluble metal salt in metal solid electrolytic polishing, wherein the high-valent soluble metal salt is used as an electrolyte in the metal solid electrolytic polishing, and the metal element valence of the high-valent soluble metal salt is ≥ +2. The invention adopts a high-valent soluble metal salt as an electrolyte and is applied to solid electrolytic polishing of high-strength and corrosion-resistant metal materials such as titanium alloys, nickel alloys, tungsten alloys, copper alloys or steel, can achieve fast and good polishing effects, has the characteristics of low carbon, environmental protection and high efficiency, and has broad application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment, and particularly relates to the application of high-valent soluble metal salts in metal solid electrolytic polishing. Background Art

[0002] With the development of society, metals with shiny surfaces are becoming more and more valued. In addition to improving aesthetics, they can also reduce friction, improve mechanical precision, improve cutting performance, and extend service life. In particular, the precision manufacturing and high-end consumer goods industries have strict requirements on the brightness of metal surfaces. Materials such as titanium alloys, nickel alloys, and tungsten alloys have excellent corrosion resistance and high strength and toughness. They can only achieve a smooth surface through multiple steps of manual polishing. General chemical polishing and electrochemical polishing processes do not work. The high strength of the material also makes manual polishing more difficult, with a long construction period, and it is difficult to obtain a unified standard and a low defect rate. It is also difficult to achieve a high leveling effect on corners, gaps, and other parts.

[0003] CN113699579A discloses a metal polishing method, which first uses mild electrolytic conditions to perform aqueous solution electrolytic polishing on the workpiece to be polished, so that the surface of the workpiece to be polished reaches a preliminary brightness, and then uses a spherical solid electrolyte to perform composite electrolytic polishing on the workpiece to achieve the initial brightness, so that the surface of the workpiece to be polished reaches the final mirror brightness. Although it can achieve a mirror brightness surface, the process is relatively complicated. At the same time, its composite electrolytic polishing is a mechanical action and an electrolytic action at the same point at the same time. Due to the huge difference in hardness between particles and metal samples, when the mechanical action is too intense, the spherical solid will inevitably be destroyed, making the spherical solid unable to be recycled, and the cost of composite electrolytic polishing increases.

[0004] CN109415839A discloses a method for smoothing and polishing metals through ion transport of free solids and a solid for executing the method, which smoothes and polishes metal parts through solid particles containing conductive liquids, and mainly realizes electrochemical polishing through the conductive effect of conductive liquids, and converts traditional liquid-phase electrochemical polishing into solid-phase polishing through the adsorption of conductive liquids by porous materials. Although a huge change has been made in form and the first step has been taken, the essence is no different from liquid-phase electrochemical polishing. CN111032929A, CN113195799A, CN112534088A, and CN115038822A series of patents introduce the application of strong acid electrolyte solutions such as sulfuric acid, hydrochloric acid, and sulfonic acid as conductive liquids in solid-phase polishing, and propose that conductive liquids can not only conduct electricity, but also corrode and oxidize metal objects, and the polishing performance has been improved to a certain extent, but strong acid electrolytes are highly dangerous to users, and transportation and post-processing are also difficult. Summary of the invention

[0005] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, based on the mechanism of ion exchange, the present invention realizes solid electrolytic polishing of metal parts under neutral conditions, and provides an electrolyte product with the characteristics of fast, low-carbon, environmentally friendly, high-quality flatness and smoothness for high-strength corrosion-resistant metal materials such as titanium alloys, nickel alloys, and tungsten alloys.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The invention provides application of a high-valent soluble metal salt in metal solid electrolytic polishing. The high-valent soluble metal salt is used as an electrolyte in metal solid electrolytic polishing. The metal element valence of the high-valent soluble metal salt is ≥+2.

[0008] Preferably, the metal element valence of the high-valent soluble metal salt is selected from +2, +3, +4, +5, +6 or +7, that is, the high-valent soluble metal salt is selected from at least one of a divalent soluble metal salt, a trivalent soluble metal salt, a tetravalent soluble metal salt, a pentavalent soluble metal salt, a hexavalent soluble metal salt, and a heptavalent soluble metal salt.

[0009] Preferably, the polishing medium of the metal solid electrolytic polishing comprises solid particles containing an electrolyte, wherein the electrolyte comprises a high-valent soluble metal salt. Furthermore, the electrolyte is located inside the solid particles and plays a role in conducting electricity and transporting ions. The electrolyte can adjust the conductivity and ion exchange rate of the solid particles.

[0010] Preferably, the mass percentage of high-valent soluble metal salts in the electrolyte is 0.1% to 15%; further preferably, the mass percentage of high-valent soluble metal salts in the electrolyte is 1% to 15%; further preferably, the mass percentage of high-valent soluble metal salts in the electrolyte is 3% to 15%; further preferably, the mass percentage of high-valent soluble metal salts in the electrolyte is 3% to 9%.

[0011] Preferably, the high-valent soluble metal salt includes at least one of metal chloride, metal fluoride, metal sulfate and metal nitrate.

[0012] Preferably, the metal element of the high-valent soluble metal salt includes at least one of Groups IIA, IIB, IIIA, IIIB, IVA, IVB, VA, VB, VIB, VIIB, and VIII; further preferably, the metal element of the high-valent soluble metal salt includes at least one of zinc and strontium.

[0013] Further preferably, the high-valent soluble metal salt includes at least one of zinc chloride, zinc fluoride, zinc sulfate, zinc nitrate, strontium chloride, strontium fluoride, strontium sulfate, and strontium nitrate.

[0014] Preferably, the electrolyte further comprises one or a combination of water and polar organic solvents; the polar organic solvent comprises at least one of small molecule alcohols, small molecule ketones, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, dioxane, and ionic liquids. Further preferably, the small molecule alcohol comprises at least one of methanol, ethanol, n-propanol, isopropanol, butanol, and butanediol; the small molecule ketone comprises at least one of acetone, butanone, and cyclohexanone.

[0015] Preferably, the electrolyte further includes a pH regulator. The pH regulator is an acid or a base, and the pH value of the electrolyte is adjusted by an acidic or alkaline substance. Among them, the acid is preferably at least one of sulfuric acid, hydrochloric acid, nitric acid, and an organic acid; the base is preferably at least one of sodium hydroxide, potassium hydroxide, and an organic amine. The acid or base can be selected according to the different solid particles. For example, an alkaline substance can be selected for an acidic solid particle, and an acidic substance can be selected for an alkaline solid particle.

[0016] Preferably, the pH value of the electrolyte is 5-8; more preferably, the pH value of the electrolyte is 5-7; even more preferably, the pH value of the electrolyte is 6-7.

[0017] Preferably, in the solid particles, the mass percentage of the electrolyte is 30% to 70%; more preferably, the mass percentage of the electrolyte is 40% to 60%.

[0018] Preferably, the solid particles are porous solid particles.

[0019] Preferably, the solid particulate matter includes one or more of ion exchange resin, silica gel, molecular sieve; further preferably, the solid particulate matter includes one or more of ion exchange resin, silica gel, molecular sieve containing at least one of carboxyl, hydroxyl, and amine groups; further preferably, the solid particulate matter includes an acrylic acid-type ion exchange resin containing at least one of carboxyl, hydroxyl, and amine groups. The acrylic acid-type ion exchange resin containing at least one of carboxyl, hydroxyl, and amine groups can be prepared by polymerizing monomers containing carboxyl, hydroxyl, or amine groups with acrylic acid (ester) monomers, which is a conventional method in the art, such as those disclosed in CN114908409A, CN114908410A, and CN115029768A, or directly purchasing commercially available products. Further preferably, the solid particulate matter includes a carboxylic acid-type acrylic acid ion exchange resin containing COOH / COO - Group.

[0020] Preferably, the metal is selected from one or more of titanium alloy, nickel alloy, tungsten alloy, copper alloy and steel.

[0021] It should be noted that electropolishing is to immerse the metal in a special chemical solution composed of various components, relying on high electrochemical potential to oxidize the metal to obtain a smooth and bright surface. The chemical solution used in conventional electropolishing is a strong acid or a highly volatile liquid, which is not convenient for transportation and storage, and is harmful to workers. Waste liquid treatment is also a big problem. Solid electropolishing uses solid particles with ion adsorption / exchange / complexation capabilities and internal conductive solutions to replace the electrolyte. The solid particles are in contact with the metal parts to be polished, thereby achieving polishing of the surface of the metal parts. Although the solid particles are in contact with the metal parts to be polished, the relative movement rate of this contact is low, and the hardness of the solid particles is lower than that of the metal parts, so the physical mechanical polishing process can be ignored.

[0022] Preferably, the method for solid metal electrolytic polishing comprises the following steps:

[0023] S1: placing solid particles containing electrolyte and a metal part to be polished in an electrochemical polishing device;

[0024] Wherein, the metal part to be polished is connected to the positive electrode of the power supply of the electrochemical polishing device, and the solid particles are connected to the negative electrode of the power supply of the electrochemical polishing device;

[0025] S2: Powering on the electrochemical polishing device to perform electrolytic polishing, during which the metal part to be polished and the solid particles undergo relative frictional motion.

[0026] Preferably, in step S2, the applied voltage is 20V to 120V; further preferably, the applied voltage is 50V to 100V.

[0027] Preferably, in step S2, the rate of relative friction movement is 20 r / min to 120 r / min; further preferably, the rate of relative friction movement is 80 r / min to 100 r / min.

[0028] Preferably, in step S2, the polishing time is 10 min to 120 min; more preferably, the polishing time is 20 min to 80 min; even more preferably, the polishing time is 30 min to 60 min.

[0029] The beneficial effects of the present invention are:

[0030] The present invention adopts high-valent soluble metal salt as electrolyte and is applied to solid electrolytic polishing of high-strength corrosion-resistant metal materials such as titanium alloy, nickel alloy, tungsten alloy, copper alloy or steel. It can achieve fast and good polishing effect, has the characteristics of low carbon, environmental protection and high efficiency, and has broad application prospects. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below by specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

[0032] The carboxylic acid type acrylic acid ion exchange resin used below is a COOH type acrylic acid ion exchange resin prepared by referring to the preparation method of polyacrylate porous resin microspheres with carboxyl groups disclosed in the specific embodiment of CN114908409A. The carboxylic acid type acrylic acid ion exchange resin used to prepare the solid particles in Examples 1 to 6 and Comparative Examples 1 to 8 all use the same resin.

[0033] Table 1 shows the zinc salt type, zinc salt content, electrolyte pH value and mass content of the electrolyte of the solid particles of Examples 1 to 6 and Comparative Examples 1 to 8.

[0034] Table 1 Solid particles of Examples 1 to 6 and Comparative Examples 1 to 8

[0035]

[0036]

[0037] Referring to Table 1, the preparation method of the solid particles of Example 1 is as follows:

[0038] Take 20 kg of water, add a certain amount of sodium hydroxide and 1200 g of zinc sulfate, stir well to obtain an electrolyte solution. Soak 10 kg of carboxylic acid type acrylic acid ion exchange resin in the electrolyte solution, filter after the pH stabilizes to 6.5, and dry at room temperature to obtain the solid particles of Example 1.

[0039] In the solid particles finally prepared in this embodiment, the content of sulfate (zinc sulfate) in the electrolyte is 6 wt %, and the content of the electrolyte solution is 50 wt %.

[0040] Among them, the test method for the mass content of the electrolyte solution in the solid particles is to place the final solid particles in a 150°C forced air drying oven, and then calculate according to the following formula: mass content of electrolyte solution = (weight loss mass ÷ solid particles before test) × 100%.

[0041] Referring to the preparation method of the solid particles in Example 1 above, by adjusting the salt type, dosage or pH value, the solid particles of Examples 2-6 and Comparative Examples 1-8 shown in Table 1 were prepared respectively.

[0042] Application example 1: Metal solid electrolytic polishing of nickel alloy

[0043] The surface roughness of the nickel alloy part used in the test before polishing is 4.81 μm. The nickel alloy part is connected to the positive electrode of the power supply of the electrochemical polishing device, and the solid particles of Examples 1 to 2, 4-5 and Comparative Examples 1 to 7 are placed in a metal mesh bag and connected to the negative electrode of the power supply of the electrochemical polishing device. The electrochemical polishing device is powered on for electrolytic polishing. During electrolytic polishing, the metal part to be polished and the solid particles undergo relative friction motion. The applied voltage is 90V, the relative motion rate is 90r / min, and the polishing time is 30min.

[0044] Among them, the polishing time of Example 2, Comparative Example 1, Comparative Example 3, and Comparative Example 5 is 60 minutes, and the polishing time of other examples or comparative examples is 30 minutes.

[0045] The polishing results of Application Example 1 are shown in Table 2. The surface roughness of the metal part is the roughness test result of the surface of the metal part after solid electrolytic polishing using an optical profilometer.

[0046] Table 2 Polishing results of application example 1

[0047]

[0048]

[0049] Combining Table 1 and Table 2, we can see that:

[0050] 1. Example 1 and Comparative Examples 1-2 are test groups for investigating changes in electrolyte pH. From the test results, the best effect is achieved when the pH value is 6.5, which can achieve a certain brightening effect. When the pH value exceeds 7, zinc salt precipitation will occur, resulting in almost no current and almost no polishing effect. When the pH value is too low, the polishing performance will also decrease due to the weak ion exchange performance.

[0051] 2. Example 1 and Comparative Examples 3-4 are test groups for investigating changes in the mass content of electrolyte in solid particles. From the test results, Example 1 with a content of 50% has the best polishing effect, while Comparative Example 3 with a content of 30% requires a longer polishing time. This is because the electrolyte content is too little, the current during the polishing process is too low, and the metal ions cannot be smoothly migrated. Comparative Example 4 with a content of 80% has a yellowing phenomenon. This is because the electrolyte content is too high, exceeding the saturated adsorption range of the solid particles, and there is some liquid on the surface of the solid particles, which prolongs the time for the metal ions to migrate into the solid particles, resulting in the inability to transfer the metal ions in time. The metal ions stay on the metal surface and will further oxidize to form precipitates.

[0052] 3. Examples 1-2, 4 and Comparative Examples 5-6 are test groups for investigating changes in zinc salt concentration. From the test results, both 6% and 15% zinc sulfate contents can achieve good polishing effects, with 6% having the best polishing effect. However, Comparative Example 5, which does not contain zinc sulfate (i.e., the zinc salt content is 0), and Comparative Example 6, which has a zinc sulfate content of 25%, have poor polishing effects, with the former having a dull metal and the latter having a yellow metal. This is because a low zinc salt concentration will result in low electrical conductivity, a small polishing current, and low polishing efficiency; a high zinc salt concentration will cause solid particles to be sticky and easily adsorbed on the surface of the metal sample, making it impossible for the metal sample to fully contact with different particles, hindering the ion migration process, and thus causing the surface of the metal sample to turn yellow.

[0053] 4. Examples 4-6 are test groups for investigating different types of zinc salts. From the test results, it can be seen that no matter zinc sulfate, zinc chloride or zinc nitrate is used, these soluble zinc salts can obtain a good metallic brightening effect.

[0054] 5. Example 1 and Comparative Example 7 are test groups for investigating the effects of different soluble salt types. From the test results, it can be seen that the use of zinc salt as an electrolyte has a better polishing effect on the solid electrolytic polishing of nickel alloy parts than sodium salt.

[0055] Application Example 2: Metal Solid Electrolytic Polishing of Chromium-Cobalt-Molybdenum-Tungsten Alloy

[0056] The surface roughness of the chromium-cobalt-molybdenum-tungsten alloy part used in the test before polishing is 5.90 μm. The chromium-cobalt-molybdenum-tungsten alloy is connected to the positive electrode of the power supply of the electrochemical polishing device, and the solid particles of Example 1 or Comparative Example 7 are placed in a metal net bag and connected to the negative electrode of the power supply of the electrochemical polishing device. The electrochemical polishing device is powered on for electrolytic polishing. During electrolytic polishing, the metal part to be polished and the solid particles undergo relative friction motion. The applied voltage is 50 V, the relative motion rate is 90 r / min, and the polishing time is 30 min.

[0057] The polishing results of Application Example 2 are shown in Table 3.

[0058] Table 3 Polishing results of application example 2

[0059] Solid particles Metal parts to be polished Polishing time Polishing results of metal parts Metal surface roughness / μm Example 1 Chromium-Cobalt-Molybdenum-Tungsten Alloy 40min Bright 0.32 Comparative Example 7 Chromium-Cobalt-Molybdenum-Tungsten Alloy 40min Bright 0.61

[0060] It can be seen from the test results in Table 3 that, for the solid electrolytic polishing of chromium-cobalt-molybdenum-tungsten alloy, Example 1 using zinc sulfate as the electrolyte has a better polishing effect than Comparative Example 1 using sodium sulfate as the electrolyte.

[0061] Application Example 3: Metal Solid Electrolytic Polishing of Stainless Steel 316

[0062] The surface roughness of the stainless steel 316 used in the test before polishing is 2.97 μm. The stainless steel 316 is connected to the positive electrode of the power supply of the electrochemical polishing device, and the solid particles of Example 1 or Comparative Example 7 are placed in a metal net bag and connected to the negative electrode of the power supply of the electrochemical polishing device. The electrochemical polishing device is powered on for electrolytic polishing. During electrolytic polishing, the metal part to be polished and the solid particles undergo relative friction movement. The applied voltage is 50 V, the relative movement rate is 90 r / min, and the polishing time is 20 min.

[0063] The polishing results of Application Example 3 are shown in Table 4.

[0064] Table 4 Polishing results of application example 3

[0065] Solid particles Metal parts to be polished Polishing time Polishing results of metal parts Metal surface roughness / μm Example 1 Stainless Steel 316 20min Bright 0.18 Comparative Example 7 Stainless Steel 316 20min Bright 0.27

[0066] It can be seen from the test results in Table 4 that, for the solid electrolytic polishing of stainless steel 316, Examples 1 and 2 using zinc sulfate have better polishing effects than Comparative Example 1 using sodium sulfate.

[0067] Application example 4: Metal solid electrolytic polishing of copper alloy

[0068] The copper alloy part used in the test is brass, and its surface roughness before polishing is 1.86 μm. The copper alloy part is connected to the positive electrode of the power supply of the electrochemical polishing device, and the solid particles of Example 2-3 or Comparative Example 8 are placed in a metal net bag and connected to the negative electrode of the power supply of the electrochemical polishing device. The electrochemical polishing device is powered on for electrolytic polishing. During electrolytic polishing, the metal part to be polished and the solid particles undergo relative friction motion. The applied voltage is 50 V, the relative motion rate is 90 r / min, and the polishing time is 20 min.

[0069] The polishing results of Application Example 4 are shown in Table 5.

[0070] Table 5 Polishing results of application example 4

[0071]

[0072]

[0073] It can be seen from the test results in Table 5 that, for the solid electrolytic polishing of copper alloy, Examples 2 and 3 using zinc sulfate also have better polishing effects than Comparative Example 8 using sodium sulfate.

[0074] From the solid electrolytic polishing experimental results of the above-mentioned different metal parts, it can be seen that the use of zinc salt, a high-priced soluble metal salt, as an electrolyte has a better polishing effect than sodium salt for the solid electrolytic polishing of metal parts containing corrosion-resistant metal components such as chromium, cobalt, molybdenum, tungsten, stainless steel 316, nickel alloy or copper alloy.

[0075] In summary, the present invention applies high-valent soluble metal salts to solid electrolytic polishing of high-strength and corrosion-resistant metal materials such as titanium alloys, nickel alloys, tungsten alloys, copper alloys or steel, which can achieve fast and good polishing effects, has the characteristics of low carbon, environmental protection and high efficiency, and has broad application prospects.

[0076] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. Application of high-valent soluble metal salts in metal solid electrolytic polishing, characterized in that: The high-valent soluble metal salt is used as an electrolyte in metal solid electrolytic polishing; the metal element of the high-valent soluble metal salt is zinc; The polishing medium of the metal solid electrolytic polishing comprises solid particles containing an electrolyte, wherein the electrolyte comprises a high-valent soluble metal salt; In the solid particles, the mass percentage of electrolyte is 30% to 70%; In the electrolyte, the mass percentage of the high-valent soluble metal salt is 0.1% to 15%; The electrolyte also includes a pH adjuster; the pH value of the electrolyte is 5-8.

2. The use according to claim 1, characterized in that: The high-valent soluble metal salt includes at least one of metal chloride, metal fluoride, metal sulfate and metal nitrate.

3. The use according to claim 1, characterized in that: The electrolyte further comprises one of water and polar organic solvent or a combination thereof; the polar organic solvent comprises at least one of small molecule alcohol, small molecule ketone, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, dioxane and ionic liquid.

4. The use according to claim 1, characterized in that: The solid particles include one or more of ion exchange resin, silica gel, and molecular sieve.

5. The use according to claim 1, characterized in that: The metal is selected from one or more of titanium alloy, nickel alloy, tungsten alloy, copper alloy and steel.

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