A method for preparing and electrolytically polishing a dissolvable aluminum alloy electrolytic polishing solution

Abstract

The application discloses a kind of soluble aluminum alloy electrolytic polishing liquid preparation and electrolytic polishing method, the method comprises: one, soluble aluminum alloy machining;Two, after washing and obtaining to be electrolyzed sample;Three, methanol, perchloric acid and nitric acid are mixed to prepare and obtain electrolytic polishing liquid;Four, to be electrolyzed sample is placed in electrolytic polishing liquid and electrolytic polishing is carried out;Five, after electrolytic polishing, soluble aluminum alloy sample is rapidly placed in anhydrous ethanol and is cleaned and dried by blowing.This application controls the composition of electrolytic polishing liquid and electrolytic polishing process parameters, effectively inhibits the spontaneous dissolution of soluble aluminum alloy, and realizes efficient precision polishing, improves the surface quality of polishing, prolongs the service life of polishing liquid, reduces production cost, and the polishing process is simple, easy to operate, and easy for industrial large-scale application.

Description

Technical Field

[0001] This invention belongs to the field of metal material surface treatment technology, specifically relating to a method for preparing a soluble aluminum alloy electrolytic polishing solution and electrolytic polishing. Background Technology

[0002] Soluble aluminum alloys, containing low-melting-point elements such as gallium, indium, and tin, possess the property of spontaneously dissolving in water or aqueous solutions, making them promising candidates for applications in temporary structural components, medical implants, and oil and gas extraction bridge plugs. The surface quality of these aluminum alloys directly affects their mechanical properties, corrosion resistance, and solubility control; therefore, polishing is necessary to achieve surface finishing and reduce roughness.

[0003] Electropolishing is a highly efficient technology that uses electrochemical reactions to finish metal surfaces. Its core principle is to use anodic dissolution to preferentially dissolve the microscopic protrusions on the metal surface, ultimately obtaining a smooth and bright surface. Compared with mechanical polishing, it has advantages such as no cutting stress, high surface finish, high efficiency, and suitability for complex-shaped workpieces. It has been widely used in the surface treatment of conventional aluminum alloys.

[0004] However, most existing aluminum alloy electrolytic polishing solutions use water as a solvent or contain a certain proportion of aqueous components, such as sulfuric acid-phosphoric acid systems and perchloric acid-ethanol-water systems. When these polishing solutions are used on soluble aluminum alloys, the presence of water will trigger spontaneous dissolution reactions of elements such as gallium, indium, and tin in the aluminum alloy. This will result in uneven dissolution of the workpiece surface during the polishing process, as well as defects such as pitting and pitting, making it impossible to obtain a qualified polished surface. At the same time, spontaneous dissolution will also consume the effective components in the polishing solution, shorten the service life of the polishing solution, and increase production costs.

[0005] Furthermore, while some anhydrous polishing slurries (such as the perchloric acid-methanol binary system) can prevent spontaneous dissolution, they are ineffective at polishing soluble aluminum alloys containing gallium, indium, and tin. They fail to effectively remove surface oxide layers and processing defects, and the resulting surface gloss is too low to meet the demands of precision applications. Therefore, developing an electrolytic polishing slurry and corresponding electrolytic polishing method that can suppress spontaneous dissolution of soluble aluminum alloys while providing excellent polishing results is crucial to overcoming current technological bottlenecks. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method for preparing a soluble aluminum alloy electrolytic polishing slurry and electrolytic polishing. This method, by controlling the composition of the electrolytic polishing slurry and the electrolytic polishing process parameters, achieves the dual effects of suppressing spontaneous dissolution of aluminum alloys and highly efficient precision polishing, thereby improving the polished surface quality, extending the service life of the polishing slurry, and reducing production costs. It solves the problems of spontaneous dissolution, poor polished surface quality, and short service life of soluble aluminum alloys in traditional electrolytic polishing slurries.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a soluble aluminum alloy electrolytic polishing solution and electrolytic polishing, characterized in that the method includes the following steps: Step 1: Machining the soluble aluminum alloy to obtain a soluble aluminum alloy sample; Step 2: Place the soluble aluminum alloy sample obtained in Step 1 on a metallographic grinding machine for grinding, and then rinse to obtain the sample to be electrolyzed. Step 3: Mix methanol, perchloric acid, and nitric acid according to the designed mass percentages to prepare the electrolytic polishing solution; Step 4: Place the sample to be electrolyzed obtained in Step 2 into the electrolytic polishing solution prepared in Step 3, then connect the electrodes and set the process parameters including voltage and current to perform electrolytic polishing, and obtain the electrolytically polished soluble aluminum alloy sample. Step 5: Quickly place the soluble aluminum alloy sample after electropolishing in Step 4 into anhydrous ethanol for cleaning and then blow it dry.

[0008] The above-mentioned method for preparing a soluble aluminum alloy electropolishing solution and electropolishing is characterized in that the soluble aluminum alloy in step one contains magnesium, gallium, and tin elements.

[0009] The above-mentioned method for preparing a soluble aluminum alloy electropolishing solution and electropolishing is characterized in that the grinding process in step two is as follows: 120#, 600#, 1200# and 2000# metallographic wet sandpaper are used to grind step by step, and the grinding direction is rotated by 90° when the grinding marks are uniform each time, until the sample preparation requirements for electropolishing are met. Then, the surface is cleaned with anhydrous ethanol and dried.

[0010] The method for preparing and electropolishing a soluble aluminum alloy electrolytic polishing solution is characterized in that the designed mass percentages in step three are: methanol 70%~85%, perchloric acid 10%~20%, and nitric acid 1%~10%. Typically, the concentration of perchloric acid is 72% and the concentration of nitric acid is 70%.

[0011] The method for preparing a soluble aluminum alloy electropolishing solution and electropolishing is characterized in that, in step four, the process of connecting electrodes and setting process parameters including voltage and current for electropolishing is as follows: the sample to be electrolyzed is placed in the electropolishing solution as the anode, stainless steel is used as the cathode, electropolishing is performed at room temperature, liquid nitrogen is added to lower the temperature of the electropolishing solution, the power is turned on, and the electropolishing voltage is set to 30V~60V, the current to 1.5A~2.5A, and the time to 10s~60s. By adding liquid nitrogen to lower the temperature of the electropolishing solution, the electropolishing process at room temperature is ensured to be stable and uniform.

[0012] Compared with the prior art, the present invention has the following advantages: 1. Effectively inhibits the spontaneous dissolution of soluble aluminum alloys: The electrolytic polishing solution used in this invention uses methanol as the main solvent and does not add water, avoiding the activation effect of perchloric acid and nitric acid after being diluted with water, which aggravates metal corrosion. This fundamentally inhibits the spontaneous dissolution reaction of elements such as gallium, indium, and tin in soluble aluminum alloys during the polishing process. At the same time, the passivation film formed by the perchloric acid in the electrolytic polishing solution on the surface of soluble aluminum alloys can further enhance the inhibition effect, avoiding defects such as pitting, pitting, and uneven dissolution during the polishing process. This solves the core technical problem of using traditional water-containing polishing solutions for soluble aluminum alloys. Compared with the existing perchloric acid-methanol binary system, the inhibition effect is better and the polishing quality is better.

[0013] 2. Excellent polishing effect: The synergistic effect of perchloric acid and nitric acid in the electrolytic polishing solution of this invention, combined with the optimized component ratio, can quickly remove oxide scale, processing defects and burrs from the surface of soluble aluminum alloys, resulting in a smooth and bright surface after electrolytic polishing with a surface roughness Ra≤0.08μm, which is far superior to the effect of existing polishing technologies and can meet the surface quality requirements of precision application scenarios. At the same time, the addition of nitric acid effectively solves the problem of insufficient surface brightness after polishing with a single perchloric acid system, improving the aesthetics and practicality of the soluble aluminum alloy surface, and adapting to various subsequent testing needs such as optical metallographic observation and scanning electron microscopy analysis.

[0014] 3. Good stability and long service life of the polishing solution: The electrolytic polishing solution of this invention has a reasonable composition, and the methanol in it can dissolve the metal ions generated during the polishing process, preventing them from precipitating and depositing. At the same time, through low-temperature preparation and sealed storage, it can effectively prevent the decomposition of perchloric acid, the failure of nitric acid and the volatilization of methanol. Thus, the electrolytic polishing solution can be reused many times, and its service life is extended by more than 30% compared with traditional polishing solutions, which significantly reduces production costs. In addition, when the electrolytic polishing solution becomes turbid, its performance can be restored by adding methanol, further improving resource utilization.

[0015] 4. Simple and easy-to-operate preparation and polishing process: The preparation process of the electrolytic polishing solution of the present invention only requires mixing and stirring, the steps are simple, no complicated equipment is required, and the preparation process is safe and controllable; at the same time, the electrolytic polishing process parameters matched with the electrolytic polishing solution are easy to adjust, adaptable to soluble aluminum alloy workpieces with different surface quality requirements, no professional operators are required, which is convenient for large-scale industrial application. Compared with the traditional three-acid polishing process, it is easier to operate, more environmentally friendly, and does not produce a large amount of toxic nitrogen oxides.

[0016] 5. Superior environmental performance: The electrolytic polishing solution of this invention does not contain toxic and harmful substances such as chromic acid, has a low nitric acid content and no water involved, and generates less waste gas and waste liquid during the polishing process. The waste liquid can be discharged after simple treatment, resulting in less environmental pollution. Compared with traditional polishing solutions containing chromium and high nitric acid content, it has significant environmental advantages and is in line with the current environmental development trend in the field of precision metal processing.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a diagram showing the electropolishing effect of the soluble aluminum alloy in Embodiment 2 of the present invention.

[0019] Figure 2 This is a diagram showing the electropolishing effect of the soluble aluminum alloy in Comparative Example 1 of the present invention. Detailed Implementation

[0020] In Examples 1-3 and Comparative Example 1 of this invention, the concentration of perchloric acid was 72% and the concentration of nitric acid was 70%.

[0021] Example 1 This embodiment includes the following steps: Step 1: The soluble aluminum alloy is machined to obtain a soluble aluminum alloy sample; the soluble aluminum alloy contains magnesium, gallium and tin elements; Step 2: Place the soluble aluminum alloy sample obtained in Step 1 on a metallographic grinding machine for grinding. Use 120#, 600#, 1200# and 2000# metallographic wet sandpaper to grind step by step. When the grinding marks are in the same direction each time, rotate the grinding direction by 90° until the sample preparation requirements for electrolytic polishing are met. Then clean the surface with anhydrous ethanol and blow it dry to obtain the sample to be electrolyzed. Step 3: Mix analytical grade methanol, perchloric acid and nitric acid according to the designed mass percentages, namely 70% methanol, 20% perchloric acid and 10% nitric acid, to prepare an electrolytic polishing solution; Step 4: Place the sample to be electrolyzed obtained in Step 2 into the electropolishing solution prepared in Step 3 as the anode, and stainless steel as the cathode. Perform electropolishing at room temperature, and add liquid nitrogen to lower the temperature of the electropolishing solution. Turn on the power, set the voltage of electropolishing to 30V, the current to 1.5A, and the time to 60s, and obtain the soluble aluminum alloy sample after electropolishing. Step 5: Quickly place the soluble aluminum alloy sample after electropolishing in Step 4 into anhydrous ethanol for cleaning and then blow it dry.

[0022] Testing revealed that the soluble aluminum alloy sample, after electrolytic polishing, cleaning, and drying, had a smooth and bright surface, free from defects such as pitting and crazing, with a surface roughness Ra=0.06μm. Immersing it in water for 4 hours showed no obvious spontaneous dissolution, demonstrating excellent polishing and anti-spontaneous dissolution effects. Furthermore, the electrolytic polishing solution remained transparent after 5 uses and could be reused after adding 5% methanol.

[0023] Example 2 This embodiment includes the following steps: Step 1: The soluble aluminum alloy is machined to obtain a soluble aluminum alloy sample; the soluble aluminum alloy contains magnesium, gallium and tin elements; Step 2: Place the soluble aluminum alloy sample obtained in Step 1 on a metallographic grinding machine for grinding. Use 120#, 600#, 1200# and 2000# metallographic wet sandpaper to grind step by step. When the grinding marks are in the same direction each time, rotate the grinding direction by 90° until the sample preparation requirements for electrolytic polishing are met. Then clean the surface with anhydrous ethanol and blow it dry to obtain the sample to be electrolyzed. Step 3: Mix analytical grade methanol, perchloric acid and nitric acid according to the designed mass percentages, namely 80% methanol, 15% perchloric acid and 5% nitric acid, to prepare an electrolytic polishing solution; Step 4: Place the sample to be electrolyzed obtained in Step 2 into the electropolishing solution prepared in Step 3 as the anode, and stainless steel as the cathode. Perform electropolishing at room temperature, and add liquid nitrogen to lower the temperature of the electropolishing solution. Turn on the power, set the voltage of electropolishing to 45V, the current to 2.0A, and the time to 30s to obtain a soluble aluminum alloy sample after electropolishing. Step 5: Quickly place the soluble aluminum alloy sample after electropolishing in Step 4 into anhydrous ethanol for cleaning and then blow it dry.

[0024] Upon testing, the surface of the soluble aluminum alloy sample in this embodiment, after electrolytic polishing, cleaning, and drying, was smooth and bright, without defects such as pitting or pitting. Figure 1As shown, the surface roughness Ra=0.06μm; when immersed in water for 4 hours, there was no obvious spontaneous dissolution, and the polishing effect and the effect of inhibiting spontaneous dissolution were excellent; at the same time, the electrolytic polishing solution in this embodiment remained transparent after 5 uses, and could be used again after adding 5% methanol.

[0025] Comparative Example 1 The difference between this comparative example and Example 2 is that the electrolytic polishing solution in step three uses a conventional perchloric acid-ethanol-water system, with the following mass percentages for each component: perchloric acid 15%, ethanol 65%, and water 20%.

[0026] Upon testing, the surface of the soluble aluminum alloy sample in this comparative example, after electrolytic polishing, cleaning, and drying, showed obvious defects such as pitting and scarring. Figure 2 As shown, the surface roughness Ra=0.32μm; when it was soaked in water for 4 hours, obvious spontaneous dissolution occurred, and the surface became rough and black; at the same time, the electrolytic polishing solution of this comparative example remained transparent after two uses and could not be used again.

[0027] Comparing Example 2 of the present invention with Comparative Example 1, it can be seen that, compared with Comparative Example 1, the electrolytic polishing liquid and electrolytic polishing method used in the present invention can effectively inhibit the spontaneous dissolution of soluble aluminum alloys, significantly improve the polished surface quality, and extend the service life of the polishing liquid, thus possessing obvious technical advantages.

[0028] Example 3 This embodiment includes the following steps: Step 1: The soluble aluminum alloy is machined to obtain a soluble aluminum alloy sample; the soluble aluminum alloy contains magnesium, gallium and tin elements; Step 2: Place the soluble aluminum alloy sample obtained in Step 1 on a metallographic grinding machine for grinding. Use 120#, 600#, 1200# and 2000# metallographic wet sandpaper to grind step by step. When the grinding marks are in the same direction each time, rotate the grinding direction by 90° until the sample preparation requirements for electrolytic polishing are met. Then clean the surface with anhydrous ethanol and blow it dry to obtain the sample to be electrolyzed. Step 3: Mix analytical grade methanol, perchloric acid and nitric acid according to the designed mass percentages, namely 85% methanol, 10% perchloric acid and 5% nitric acid, to prepare an electrolytic polishing solution; Step 4: Place the sample to be electrolyzed obtained in Step 2 into the electropolishing solution prepared in Step 3 as the anode, and stainless steel as the cathode. Perform electropolishing at room temperature, and add liquid nitrogen to lower the temperature of the electropolishing solution. Turn on the power, set the voltage of electropolishing to 60V, the current to 2.5A, and the time to 10s to obtain a soluble aluminum alloy sample after electropolishing. Step 5: Quickly place the soluble aluminum alloy sample after electropolishing in Step 4 into anhydrous ethanol for cleaning and then blow it dry.

[0029] Testing revealed that the soluble aluminum alloy sample, after electrolytic polishing, cleaning, and drying, had a smooth and bright surface, free from defects such as pitting and crazing, with a surface roughness Ra=0.07μm. Immersing it in water for 4 hours showed no obvious spontaneous dissolution, demonstrating excellent polishing and anti-spontaneous dissolution effects. Furthermore, the electrolytic polishing solution remained transparent after 5 uses and could be reused after adding 10% methanol.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a soluble aluminum alloy electrolytic polishing solution and electrolytic polishing, characterized in that, The method includes the following steps: Step 1: Machining the soluble aluminum alloy to obtain a soluble aluminum alloy sample; Step 2: Place the soluble aluminum alloy sample obtained in Step 1 on a metallographic grinding machine for grinding, and then rinse to obtain the sample to be electrolyzed. Step 3: Mix methanol, perchloric acid, and nitric acid according to the designed mass percentages to prepare the electrolytic polishing solution; Step 4: Place the sample to be electrolyzed obtained in Step 2 into the electrolytic polishing solution prepared in Step 3, then connect the electrodes and set the process parameters including voltage and current to perform electrolytic polishing, and obtain the electrolytically polished soluble aluminum alloy sample. Step 5: Quickly place the soluble aluminum alloy sample after electropolishing in Step 4 into anhydrous ethanol for cleaning and then blow it dry.

2. The method for preparing a soluble aluminum alloy electrolytic polishing solution and electrolytic polishing according to claim 1, characterized in that, The soluble aluminum alloy described in step one contains magnesium, gallium, and tin elements.

3. The method for preparing a soluble aluminum alloy electropolishing solution and electropolishing according to claim 1, characterized in that, The grinding process described in step two is as follows: use 120#, 600#, 1200# and 2000# metallographic wet sandpaper to grind step by step, and rotate the grinding direction by 90° when the direction of each grinding mark is consistent, until the sample preparation requirements for electrolytic polishing are met. Then clean the surface with anhydrous ethanol and blow it dry.

4. The method for preparing a soluble aluminum alloy electrolytic polishing solution and electrolytic polishing according to claim 1, characterized in that, The mass percentages of the design described in step three are: methanol 70%~85%, perchloric acid 10%~20%, and nitric acid 1%~10%.

5. The method for preparing a soluble aluminum alloy electropolishing solution and electropolishing according to claim 1, characterized in that, The process of connecting the electrodes and setting process parameters including voltage and current for electrolytic polishing in step four is as follows: the sample to be electrolyzed is placed in the electrolytic polishing solution as the anode, stainless steel is used as the cathode, electrolytic polishing is performed at room temperature, liquid nitrogen is added to lower the temperature of the electrolytic polishing solution, the power is turned on, and the voltage of electrolytic polishing is set to 30V~60V, the current to 1.5A~2.5A, and the time to 10s~60s.

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