KR102025866B1

KR102025866B1 - Composition of electrolytic polishing liquid for stainless steel

Info

Publication number: KR102025866B1
Application number: KR1020130008858A
Authority: KR
Inventors: 손인준; 이지웅
Original assignee: 경북대학교 산학협력단
Priority date: 2013-01-25
Filing date: 2013-01-25
Publication date: 2019-11-04
Also published as: KR20140095896A

Abstract

The present invention relates to a stainless steel electrolytic polishing liquid composition, more specifically, 400 ml / l to 800 ml / l ethylene glycol, 50 ml / l to 300 ml / l perchloric acid and 50 g / l to 200 g / l citric acid It relates to a more environmentally friendly stainless steel electropolishing liquid composition comprising. Accordingly, the electropolishing liquid composition is more environmentally friendly by using ethylene glycol, perchloric acid and citric acid instead of high concentration acids such as sulfuric acid, phosphoric acid and chromic acid, and can be subjected to an electropolishing process in a mild temperature range of 0 ° C to 30 ° C. have.
Further, electrolytic polishing of stainless steel using the electrolytic polishing liquid composition of the present invention has an effect of having excellent surface roughness (arithmetic mean surface roughness, Ra).

Description

Composition of electrolytic polishing liquid for stainless steel}

The present invention relates to a stainless steel electrolytic polishing liquid composition, more specifically, 400 ml / l to 800 ml / l ethylene glycol, 50 ml / l to 300 ml / l perchloric acid and 50 g / l to 200 g / l citric acid It relates to a more environmentally friendly stainless steel electropolishing liquid composition comprising.

Electro-polishing is the reverse process of plating, and the recent development of industries that require cleanliness, such as the semiconductor industry, requires the precision and cleanliness of materials at the same time. Electropolishing, a new non-contact polishing method, is needed. Existing mechanical machining methods have left traces of micro-processing on the workpiece surface, resulting in inherently clean surfaces.

In general, electropolishing is performed by applying a voltage between the anode and the cathode by using a metal product dissolved in an electrolyte as an anode, and using an insoluble metal as a cathode. A method of polishing the surface of metal products by electrolysis. In order to polish a metal product by electrolytic polishing, an electrolytic solution is filled in an electrolytic cell, a metal product to be polished is installed as an anode, a cathode which is not dissolved in an electrolyte solution is installed, and a direct current or pulse wave is formed between the anode and the cathode. Apply power. In electropolishing, if a current is applied even under conditions where the metal product is not easily dissolved in the electrolyte, the metal product is forcibly dissolved little by little. When electropolishing proceeds, a high viscosity liquid layer (viscosity layer) containing a large amount of metal ions dissolved from the anode surrounds the anode, and in the viscous layer saturated with metal ions, the metal is no longer dissolved and forms a high anode potential. And actively bond with oxygen to form an oxide film. At this time, the dissolved metal ions are mainly accumulated in the concave portion of the metal surface, the movement and diffusion of the metal ions in the concave portion is small, the electricity does not pass well, the metal is not dissolved. On the other hand, since the metal ion layer is formed thin in the convex portion of the metal surface, the current is concentrated to easily dissolve the metal surface, thereby smoothing the product surface as a whole.

Looking at the effects of the electropolishing as described above, the first is the planarization of the surface. By selectively dissolving the micro parts of the product surface, the surface roughness can be improved by about 50% to 90% compared to the general machined parts. In addition, this planarized surface prevents contamination by inhibiting the inflow of impurity particles.

The second is the corrosion resistance of the surface of the product. The surface treated with electropolishing has a surface containing a large amount of chromium oxide, which makes it very strong from oxidation by external influences. Therefore, electropolishing has a superior corrosion resistance in the process of producing a strong protective film. That is, since the corrosion-inducing substance contained in the strained layer is removed through electropolishing, the corrosion resistance is improved.

Third, it is possible to obtain the effect of removing hydrogen from the metal surface that leads to fatigue destruction and bacterial growth on the stainless steel surface.

On the other hand, in order to increase the effect (for example, planarization ability) of said electrolytic polishing, the electrolytic polishing liquid which ensured the electroconductivity required for flowing an electrolytic current is used. In general, the electrolytic polishing solution uses a high concentration of 70% phosphoric acid, 25% sulfuric acid, and 5% chromic acid, and performs electrolytic polishing at a solution temperature of 90 ° C. and an electrolytic voltage of 10V. However, the process as described above has a disadvantage in that the high viscosity of the liquid, the loss of the liquid buried in the treated article, waste water treatment costs are considerably high because the pollutants such as chromic acid, sulfuric acid and phosphoric acid are introduced into the waste water treatment plant in a large amount.

In addition, the electrolytic polishing using a mixture of the existing high concentration of phosphoric acid, sulfuric acid, and chromic acid has a homogeneous dissolving action by the formation of anodic coating at high temperature by phosphoric acid, dissolving the sulfuric acid anodizing film, and reduction of chromic acid. The reaction is achieved by anti-fit behavior by the production of trivalent chromium on the surface of the treated article. Among the above reactions, dissolution of phosphoric acid and anodization reaction are the main reactions. At this time, if free phosphoric acid is not produced, the dissolved metal ions are oxidized and adsorbed on the surface to form locally insoluble substances, resulting in glossiness of the surface appearance. This tends to decrease considerably, requiring additional work, which leads to complex processes and high production costs.

Under the above background, the inventors of the present invention are studying an electropolishing liquid composition which is more environmentally friendly than conventional electrolytic polishing liquids consisting of phosphoric acid, sulfuric acid, and chromic acid, and which can be used under relatively mild process conditions. The present invention was completed by confirming that stainless steel was electropolished using the mixed composition, which had a similar arithmetic mean surface roughness (Ra) value as compared to the positive control group (a conventional electrolytic polishing solution containing sulfuric acid and phosphoric acid). .

It is an object of the present invention to provide a more environmentally friendly stainless steel electrolytic polishing liquid composition comprising ethylene glycol, perchloric acid and citric acid.

In order to solve the above problems, the present invention is a stainless steel electrolysis comprising ethylene glycol 400 ml / l to 800 ml / l, perchloric acid 50 ml / l to 300 ml / l and citric acid 50 g / l to 200 g / l A polishing liquid composition is provided.

The term "ethylene glycol" used in the present invention is one of the simplest dihydric alcohols as a compound widely used as an automotive antifreeze, and is also referred to as monoethylene glycol or ethane-1,2-diol. Ethylene glycol is used in cold-resistant coolants, pharmaceuticals, and cosmetics. The electrolytic polishing liquid composition of the present invention can adjust the viscosity of the composition by including the ethylene glycol.

The term "perchloric acid" used in the present invention is a colorless liquid that is volatile and highly hygroscopic, and the electropolishing liquid composition of the present invention contains the perchloric acid as an oxidizing agent.

As used herein, the term "citric acid" is one of polybasic carboxylic acids having a hydroxyl group (-OH), which is contained as a free acid in the seed or juice of a plant. Citric acid is used as an additive in fruit juices and soft drinks, or as medicines, diuretic beverages, anticoagulants, and the like. The electrolytic polishing liquid composition of the present invention contains the citric acid as a precipitation inhibitor.

In addition, the electrolytic polishing liquid composition of the present invention may further include benzotriazole as a corrosion inhibitor, and when benzotriazole is included, it is preferable to include benzotriazole at 0.1 g / L to 10 g / L. .

In addition, the electrolytic polishing liquid composition of the present invention can be carried out electrolytic polishing at room temperature, preferably in the temperature range of 0 ℃ to 30 ℃.

The electropolishing liquid composition according to the present invention is more environmentally friendly by using ethylene glycol, perchloric acid and citric acid instead of high concentration acids such as sulfuric acid, phosphoric acid and chromic acid, and the electropolishing process may be performed at a mild temperature range of 0 ° C to 30 ° C. Can be.

Further, electrolytic polishing of stainless steel using the electrolytic polishing liquid composition of the present invention has an effect of having excellent surface roughness (arithmetic mean surface roughness, Ra).

Hereinafter, the present invention will be described in more detail with reference to the following examples and experimental examples. However, the following Examples and Experimental Examples are for illustrating the present invention and the scope of the present invention is not limited to the following Examples and Experimental Examples.

Example 1 to 4: Stainless steel Electrolytic Polishing Liquid Composition

Ethylene glycol, perchloric acid and citric acid were mixed in different contents to prepare a stainless steel electrolytic polishing liquid composition, and the content of each component is shown in Table 1 below.

division Example 1 Example 2 Example Example 4 Ethylene Glycol (ml / l) 500 500 500 500 Perchloric acid (ml / l 200 200 300 100 Citric Acid (g / ℓ) 120 120 120 120 Benzotriazole (g / L) - One - - Distilled Water (ml / l 300 300 200 400

Comparative example 1: Preparation of sodium chloride containing electrolytic polishing liquid composition

300 ml of ethylene glycol, 60 g of sodium chloride, 40 g of citric acid, and 300 ml of distilled water were mixed to prepare an electrolytic polishing liquid composition.

Comparative example 2: Preparation of an electropolishing liquid composition containing sulfuric acid and phosphoric acid

An electropolishing solution consisting of 30% sulfuric acid and 70% phosphoric acid was prepared.

Experimental Example : Surface Roughness Analysis

1) Surface roughness according to the stirring speed

In order to check the surface roughness change according to the stirring during the electropolishing process, using the stainless steel electrolytic polishing liquid prepared in Examples 1 and 3, the electropolishing process was performed at different stirring speeds, and the surface roughness analysis was performed. Was carried out. Electropolishing was carried out using a DC power source using electrolytic degreased 2 × 2 cm sized STS304 specimens as anodes and 4 × 10 cm sized Ti sheets as cathodes. The surface roughness Ra value was confirmed by moving the probe to a measuring length of 4 mm using a surface roughness measuring instrument (model name; Taylsurf PGI 120). Table 2 shows the electropolishing process conditions and analysis results.

division Voltage time Temperature Stirring speed Ra Example 1 6 V 10 minutes 20 ℃ 0 rpm 0.0761 250 rpm 0.0925 500 rpm 0.1506 750 rpm 0.1135 Example 3 10 V 5 minutes 13.5 ℃ 0 rpm 0.0881 300 rpm 0.1238

2) Surface Roughness by Addition of Benzotriazole

In order to confirm the surface roughness effect according to the addition of benzotriazole, the stainless steel electrolytic polishing liquid without the bezotriazole of Example 1 and the stainless steel electrolytic polishing liquid with the benzotriazole of Example 2 were used. Comparative analysis was performed by electrolytic polishing process. Electropolishing was carried out using a DC power source using electrolytic degreased 2 × 2 cm sized STS304 specimens as anodes and 4 × 10 cm sized Ti sheets as cathodes. The surface roughness Ra value was confirmed by moving the probe to a measuring length of 4 mm using a surface roughness measuring instrument (model name; Taylsurf PGI 120). Table 3 shows the process conditions and results.

division Voltage time Temperature Ra Pit occurrence Example 1 8 V 10 minutes 20 ℃ 0.1094 (Locally occurring) Example 2 0.0860 radish

As shown in Table 3, it was confirmed that the addition of benzotriazole has the effect of suppressing the occurrence of fit.

3) Surface roughness according to temperature

In order to confirm the surface roughness change according to the temperature change, the electrolytic polishing process was performed by changing the temperature conditions without stirring using the electrolyte solution compositions prepared in Examples 1, 3, and 4 and the surface roughness was analyzed. Electropolishing was carried out using a DC power source using electrolytic degreased 2 × 2 cm sized STS304 specimens as anodes and 4 × 10 cm sized Ti sheets as cathodes. The surface roughness Ra value was confirmed by moving the probe to a measuring length of 4 mm using a surface roughness measuring instrument (model name; Taylsurf PGI 120). Table 4 shows the process conditions and results.

division Voltage time Temperature Ra Example 1 6 V 10 minutes 10 ℃ 0.1292 20 ℃ 0.0761 30 ℃ 0.0994 15 mins 10 ℃ 0.1313 20 ℃ 0.0596 30 ℃ 0.0723 20 minutes 10 ℃ 0.0829 20 ℃ 0.0550 30 ℃ 0.1161 Example 3 8 V 5 minutes 10 ℃ 0.2267 20 ℃ 0.1746 10 minutes 10 ℃ 0.1498 20 ℃ 0.1033 10 V 5 minutes 10 ℃ 0.1238 20 ℃ 0.1030 10 minutes 10 ℃ 0.0881 20 ℃ 0.1043 Example 4 8 V 10 minutes 20 ℃ 0.0886 40 ℃ 0.3652

4) Surface roughness according to voltage

In order to confirm the surface roughness change according to the voltage change, the electrolytic polishing process was performed while changing the voltage using the electrolyte solution compositions prepared in Examples 1, 3 and Comparative Example 1 and the surface roughness was analyzed. Electropolishing was carried out using a DC power source using electrolytic degreased 2 × 2 cm sized STS304 specimens as anodes and 4 × 10 cm sized Ti sheets as cathodes. The surface roughness Ra value was confirmed by moving the probe to a measuring length of 4 mm using a surface roughness measuring instrument (model name; Taylsurf PGI 120). Table 5 shows the process conditions and the results.

division Voltage time Temperature Ra Example 1 6 V 5 minutes 20 ℃ 0.1499 8 V 0.1561 10 V 0.1330 6 V 10 minutes 0.0761 8 V 0.1094 10 V 0.1027 6 V 15 mins 0.0596 8 V 0.0676 10 V 0.0955 6 V 20 minutes 0.0550 8 V 0.0492 10 V 0.1341 Example 3 8 V 15 mins 20 ℃ 0.0744 10 V 0.0720 8 V 20 minutes 0.0798 10 V 0.1623 Comparative Example 1 5 V 10 minutes 20 ℃ 0.6663 8 V 0.6174 10 V 0.3853 Comparative Example 2 5 V 10 minutes 80 ℃ 0.1063 8 V 0.0671 10 V 0.0590

Claims

Stainless steel electrolytic polishing liquid composition comprising ethylene glycol 400 ml / l to 800 ml / l, perchloric acid 50 ml / l to 300 ml / l and citric acid 50 g / l to 200 g / l.

The electrolytic polishing liquid composition of claim 1, wherein the composition further comprises 0.1 g / l to 10 g / l of benzotriazole.

The electrolytic polishing liquid composition of claim 1, wherein the composition is capable of electropolishing in a temperature range of 0 ° C to 30 ° C.