JP2006328516A - Surface treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove depositions such as a chemical liquid and metal deposited on the surface of a member composing a vacuum treatment apparatus such as a vacuum vessel without using nitric acid or the like having high dangerousness. <P>SOLUTION: In the surface treatment method where a metallic member composing a vacuum treatment device is used as a work, the surface of the work is subjected to electrolytic polishing, partial electrolytic polishing, chemical polishing, pickling or electrolytic pickling, and thereafter, the surface of the work is cleaned with an alkali based chelating liquid obtained by adding carboxylic acid or carbonate to a dilute alkali liquid of 0.5 to <3 wt.% in such a manner that its concentration reaches 0.5 to <10 wt.%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface treatment method for cleaning the surface of a metal part constituting a vacuum processing apparatus.

Stainless steel members that make up vacuum processing equipment such as vacuum vessels are welded, machined, etc. to form the shape of the vacuum vessel, and then remove the lubricant and hand grease etc. that have adhered during the processing process Surface treatment is done.
In recent years, the size of the vacuum apparatus has increased, and it has become difficult to process all the members constituting the large-sized vacuum processing apparatus at one time. Therefore, the present applicant has proposed partial electrolytic treatment in Japanese Patent Application No. 2004-21901.
Even in this partial electrolytic treatment, cleaning with pure water or the like is necessary to remove the chemical solution used for the treatment. A metal deposit called smut on the surface in the process of partial electrolysis treatment (in the case of stainless steel, oxides and salts of Cr, Ni, Fe, etc. are non-uniformly deposited) used a high-pressure jet. It is difficult to remove even by washing with pure water. In a vacuum atmosphere, the metallic deposits are released into the space, or are hit by charged particles during the subsequent film formation and released into the space. There was a problem that could contaminate the device. In order to remove these metallic deposits, there has been a problem that after partial electrolytic treatment, it is necessary to use nitric acid, which is highly dangerous when handled.
As the surface treatment method of the apparatus, there are the conventional electrolytic polishing and chemical polishing other than the above-mentioned partial electrolytic treatment. However, in any of these methods, the above-mentioned smut adheres to the metal surface after the treatment. . If the smut is adhered as it is, there is a problem that the vacuum device may be contaminated by being discharged into the space as in the case of the partial electrolytic treatment. Further, in order to remove these metallic deposits, there has been a problem that after partial electrolysis treatment, it is necessary to use nitric acid, which is highly dangerous when handled.

  Accordingly, the present invention solves the above-mentioned conventional problems, and uses highly dangerous nitric acid or the like for the deposits such as chemicals and metals adhering to the surface of the members constituting the vacuum processing apparatus such as a vacuum vessel. Furthermore, it aims at removing without carrying out immersion treatment.

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies, and based on the knowledge that the above-mentioned problems can be solved by using an alkaline chelating solution instead of nitric acid, the following means for solving the problems I found.
That is, the surface treatment method of the present invention is a surface treatment method in which a metal part constituting a vacuum processing apparatus is an object to be processed as claimed in claim 1, wherein the surface of the object to be processed is electropolished. After partial electrolytic treatment, chemical polishing, pickling or electrolytic pickling, the carboxylic acid is adjusted to a concentration of 0.5 wt% or more and less than 10 wt% in a dilute alkali solution of 0.5 wt% or more and less than 3 wt%. Alternatively, the surface of the object to be treated is washed with an alkaline chelating solution obtained by adding a carboxylate.
Moreover, the surface treatment method according to claim 2 is characterized in that, in the surface treatment method according to claim 1, the temperature of the alkaline chelating solution is set to 10 to 80 ° C.

  According to the surface treatment method of the present invention, the surface of the workpiece can be cleaned with a relatively simple configuration. Moreover, since deposits such as metals on the surface of the object to be processed can be removed without using nitric acid, there is little danger. Furthermore, if the vacuum processing apparatus is constituted by the surface-treated member according to the present invention, the gas released can be reduced in a vacuum atmosphere.

The present invention is a surface treatment method using a metal part constituting a vacuum processing apparatus as an object to be processed, and the surface of the object to be processed is subjected to electrolytic polishing, partial electrolytic treatment, chemical polishing, pickling or electrolytic pickling. Later, an alkaline chelate obtained by adding a carboxylic acid or a carboxylate salt to a dilute alkali solution of 0.5 wt% or more and less than 3 wt% so that the concentration becomes 0.5 wt% or more and less than 10 wt% The surface of the object to be processed is washed with a liquid.
The metal parts constituting the vacuum processing apparatus are not particularly limited as long as they are parts placed in a vacuum processing environment. An example is a metal container. Examples of the metal include stainless steel, aluminum alloy, titanium alloy, and the like.
As the treatment medium, the material and the shape are not limited as long as a current can flow between the electrodes. For example, a nonwoven fabric can be used.

The electrolytic polishing, chemical polishing, pickling or electrolytic acidity are known, and the partial electrolytic treatment is to connect the workpiece to the anode side of the power source and to the cathode side on the surface of the workpiece. A treatment medium for contacting an electrolytic solution is connected, and a direct current is passed between the electrodes through the electrolytic solution to electrolytically polish the surface of the object to be treated. More preferably, the surface roughness (R _max ) of the product is 0.1 μm. A specific example is described in Japanese Patent Application No. 2004-21901.
The electrolytic solution used for the electrolytic polishing or partial electrolytic treatment includes at least one of an inorganic acid, an organic acid, an inorganic acid salt, and an organic acid salt. Specifically, phosphoric acid, sulfuric acid, Ammonium citrate, ammonium chloride, ammonium dihydrogen phosphate, ammonium sulfate, sodium nitrate, citric acid and the like can be mentioned.
Moreover, as a processing medium which can be used for a partial electrolysis process, if a direct current can be sent between the said electrodes, a material and a shape will not be limited, For example, a nonwoven fabric can be used.
The electrolytic current density in the electrolytic polishing or the partial electrolytic treatment varies depending on the object to be treated, but is 0.1 to 0.5 A / cm ² for stainless steel, for example.

  Examples of the alkaline chelating solution include a solution obtained by adding citric acid, sodium citrate, ammonium oxalate, sodium phthalate, potassium tartrate, sodium gluconate, malic acid, etc. to a dilute alkaline aqueous solution such as sodium hydroxide. Can do.

  The alkaline chelating solution is preferably set to 10 ° C to 80 ° C. If the temperature is less than 10 ° C., the reaction rate is remarkably reduced, and if it exceeds 80 ° C., the handleability is poor and there is a risk of alkaline corrosion.

  The treatment with the alkaline chelating solution is preferably carried out by soaking it in a treatment medium such as cloth. This is because the surface treatment can be locally performed even if the workpiece is enlarged.

SUS304 (300 mm x 150 mm x 1 mm) to be treated was subjected to partial electrolytic treatment with sodium dihydrogen phosphate and sodium nitrate neutral salt, and red and blue smuts generated on the surface were treated with the following two chelating solutions. The following processing was performed.
a) A solution in which sodium citrate is added to a 1% by weight sodium hydroxide solution to a concentration of 3% by weight. b) An apple having a concentration of 3% by weight in a 1% by weight sodium hydroxide solution. Solution to which acid was added Each chelate solution was heated to 40 to 50 ° C. and included in a cleaning cloth to wipe the entire surface of the object to be treated. After completion of wiping, high-pressure jet cleaning was performed with pure water heated to 50 ° C., and the chemical solution and the alkaline chelate solution used for the electropolishing were removed. And it dried with the liquid nitrogen vaporized as finishing.
In order to confirm the effect of removing smut, ion chromatography analysis was performed. Specifically, for the object to be treated before and after cleaning, after wiping the entire surface with a cleaning cloth soaked with pure water, 100 ml of pure water soaked in the cleaning cloth is extracted, and the amount of each ion per unit area is extracted. Calculated.
The results are shown in Table 1 for a and in Table 2 for b.

From Table 1 and Table 2, after removal of the smut, the number of cations of Na ⁺ was reduced as well as the anion that became the adhering salt of the alloy component compared to before removal.

SUS304 (300mm x 150mm x 1mm) to be treated is subjected to partial electrolytic treatment with sodium dihydrogen phosphate and sodium nitrate neutral salt, and the following two types of chelating solutions for red and blue smut generated on the surface The following processing was performed.
a) A solution in which sodium citrate is added to a 1% by weight sodium hydroxide solution heated to 40 ° C. to a concentration of 3% by weight b) A 1% by weight sodium hydroxide solution heated to 40 ° C. In addition, the chelate solution of solutions a and b to which malic acid was added so as to have a concentration of 3% by weight was included in a cleaning cloth, and the entire surface of the object to be treated was wiped. After the wiping was completed, in order to confirm the effect of removing smut, each used cleaning cloth was immersed in 100 ml of pure water, and the elution amount of the metal component in each chelate solution was extracted into pure water. And the metal used as an analysis object was measured by atomic absorption analysis as Fe, Cr, Ni which is a component of a stainless alloy.
In addition, in order to show that the detected stainless steel component is from the smut portion and not from the stainless steel itself, the smut is removed with a 30% by weight nitric acid solution, washed with water, and then treated with a. A sample extracted from the used cleaning cloth was prepared, and this was designated as c.
The results are shown in Table 3.

From the above results, Fe and Cr were detected from the cleaning cloth using a and b. On the other hand, in c, an element constituting Fe, Cr, Ni stainless steel was not detected.
From this result, it was found that the smut was removed in a and b without damaging the workpiece itself.

  A SUS304 (300 mm × 150 mm × 1 mm) workpiece is subjected to partial electrolytic treatment with a neutral salt of ammonium dihydrogen phosphate and sodium nitrate so that the concentration in a 1 wt% sodium hydroxide solution is 3 wt%. The gas release characteristics of a solution obtained by adding a sodium citrate solution to a cleaning cloth and wiping with a cleaning cloth were evaluated.

The gas release characteristics were evaluated by the change in the gas release rate per unit area released while the temperature was raised from room temperature to 500 ° C. using the temperature programmed desorption method.
FIG. 1 is a diagram showing a change in gas release rate per unit area, where 1 is a gas release rate of a sample treated with a chelate solution, and 2 in the figure is a sample not treated. The gas release rate.
From FIG. 1, the sample subjected to the treatment with the chelate solution had a lower gas release rate particularly at a temperature of 250 ° C. or higher than the sample not treated. The source of gas released in this temperature region was removed by treatment with a chelating solution.

An SUS304 (300 mm × 150 mm × 1 mm) object to be processed was subjected to electrolytic polishing treatment with a 70% phosphoric acid and 30% sulfuric acid solution, and the smut generated on the surface was subjected to the following treatment with the following one type of chelating solution.
a) A solution in which sodium citrate is added to a 1% sodium hydroxide solution to a concentration of 3%. The chelate solution is heated to 40 ° C. to 50 ° C. and contained in a clean cloth. The entire surface was wiped. After completion of the wiping, high-pressure jet cleaning using pure water heated to 50 ° C. was performed to remove the chemical solution used for the electropolishing and the alkaline chelate solution. As a finish, it was dried with vaporized liquid nitrogen.
In order to confirm the effect of removing smut, ion chromatography analysis was performed. Specifically, for the object to be treated before and after cleaning, after wiping the entire surface with a clean cloth soaked with pure water, 100 ml of pure water soaked in the clean cloth is extracted, and the amount of each ion per unit area Was calculated. The results are shown in the table.

From the above table, it can be seen that after smut removal, both the cations of Na ⁺ were reduced together with the anion that became the adhering salt of the alloy component compared to before removal.

The graph which shows the change of the gas release rate per unit area of Example 3

Explanation of symbols

1 Gas release rate per unit area of sample treated with chelate solution 2 Gas release rate per unit area of sample not treated with chelate solution

Claims (2)

  A surface treatment method using a metal part constituting a vacuum processing apparatus as an object to be processed, wherein the surface of the object to be processed is subjected to electrolytic polishing, partial electrolytic treatment, chemical polishing, pickling or electrolytic pickling. With an alkaline chelate solution obtained by adding a carboxylic acid or a carboxylate salt to a dilute alkali solution of 5 wt% or more and less than 3 wt% so that the concentration is 0.5 wt% or more and less than 10 wt%, A surface treatment method comprising washing a surface of an object to be treated.   The surface treatment method according to claim 1, wherein the temperature of the alkaline chelating solution is 10 to 80 ° C.

Images