JP2012215410A - Corrosion resistance testing method for copper-based member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corrosion resistance testing method for a copper-based member with which the corrosion resistance of a copper-based member can be tested promptly.SOLUTION: The corrosion resistance of anti-corrosion coating is tested by bringing a copper-based member into contact with a corrosive liquid containing a corrosive component and an anti-corrosion agent for copper, and generating corrosion in the anti-corrosion coating of the copper-based member. Preferably, an azole-based anti-corrosion agent is at least one of tolyltriazole, benzotriazol, and mercapto benzothiazole, corrosion anion is chloride ion and/or sulfate ion, and an oxidant is hydrogen peroxide.

Description

  The present invention relates to a method for testing corrosion resistance of a copper-based member, and more specifically, the surface of a copper-based member such as a copper tube in contact with a water system such as a cooling water system or a corrosion-resistant film formed on the surface using a chemical agent. The present invention relates to a method of generating food and testing anticorrosion properties.

  Copper has excellent thermal conductivity and is widely used in heat transfer tubes such as air conditioners and heat exchangers. However, copper-based materials used in such applications have pitting corrosion due to corrosion. Is a problem. In particular, the efficiency of recent equipment is increasing, and the thickness of copper pipes used in heat exchangers is extremely thin, so the occurrence of pitting corrosion can lead to through leakage of copper pipes. high. For this reason, it is indispensable for stable operation of the equipment not to cause pitting corrosion in the copper-based member.

  Conventionally, water treatment in which an azole copper anticorrosive agent such as tolyltriazole, benzotriazole, or mercaptobenzothiazole is added to the water system in order to suppress pitting corrosion of a copper-based member such as a copper pipe that contacts the water system such as a cooling water system. Has been done. Azole-based copper anticorrosives have been widely applied because they exhibit excellent corrosion-inhibiting effects on copper-based members in contact with aqueous systems (for example, Patent Documents 1 and 2). The example of Patent Document 2 describes performing a corrosion test in which the formed anticorrosion film is brought into contact with a NaOBr solution. In an example of Patent Document 3, it is described that the anticorrosion performance is determined using a sodium sulfide aqueous solution having a concentration of 100 ppm or an ammonia aqueous solution having a concentration of 500 ppm.

  However, in the above conventional corrosion test, the anticorrosion film is totally corroded and not pitting corrosion (local corrosion).

  The uneven state of the copper surface is considered to affect the corrosion resistance reduction, and as a countermeasure against corrosion, it is recommended to use as clean a material as possible that is free from foreign matters such as scratches, dirt and deposits. In order to reduce the corrosion risk, it is considered important to eliminate the uneven surface state and to form a corrosion-resistant film in the initial stage.

  However, the relationship between the surface state of the copper tube and the corrosion resistance has not been sufficiently clarified, and it cannot be said that the method of forming a corrosion-resistant film on the copper tube and the effect thereof are necessarily clear.

JP-A-5-222555 Japanese Patent Laid-Open No. 6-212459 Japanese Patent Laid-Open No. 10-265979

  An object of this invention is to provide the corrosion resistance test method of the copper-type member which can test rapidly the pitting corrosion resistance of a copper-type member. Moreover, this invention aims at providing the corrosion-resistance test method of the copper-type member which can evaluate corrosion resistance about the various surface states (a damage | wound, wet-dry, etc.) of the copper-type member in the one aspect | mode.

  The method for testing corrosion resistance of a copper-based member according to claim 1 is a method for testing corrosion resistance by bringing a copper-based member into contact with a corrosive liquid, wherein the corrosive liquid contains a corrosive component and a copper anticorrosive, The sexual component is a corrosive anion and an oxidizing agent.

  The corrosion resistance test method for a copper-based member according to claim 2 is characterized in that, in claim 1, the anticorrosive is an azole anticorrosive.

  The corrosion resistance test method for a copper-based member according to claim 3 is characterized in that, in claim 2, the azole anticorrosive is at least one of tolyltriazole, benzotriazole, and mercaptobenzothiazole.

  The method for testing corrosion resistance of a copper-based member according to claim 4 is the method according to any one of claims 1 to 3, wherein the corrosive anion is chloride ion and / or sulfate ion, and the oxidizing agent is hydrogen peroxide. It is a feature.

  The corrosion resistance test method for a copper-based member according to claim 5 is the method according to any one of claims 1 to 4, wherein a corrosion-resistant film is formed on the surface of the copper-based member, and the corrosion resistance of the corrosion-resistant film is tested. It is a feature.

  According to the corrosion resistance test method for copper-based members of the present invention, the corrosive liquid contains an anticorrosive agent for copper in addition to the corrosive components (corrosive anion and oxidizer). Therefore, the pitting corrosion resistance of the copper-based member can be evaluated.

  The reason why such pitting corrosion occurs is considered as follows. That is, anticorrosives for copper such as azole anticorrosives are anticorrosives that mainly suppress the anodic reaction, and are prone to local corrosion. While there is a small amount of this anticorrosive agent for copper, and there is a corrosion resistant weak part in a strong corrosion environment where an oxidizing agent and a corrosive anion exist, the weak part becomes the starting point of corrosion and a hole with a patina mound. It becomes food.

  Hereinafter, the present invention will be described in detail.

  In the present invention, when a copper-based member made of copper or a copper alloy is brought into contact with a corrosive liquid to cause corrosion, a liquid containing a corrosive component and an anticorrosive agent is used as the corrosive liquid. This corrosive liquid contains both corrosive anions and oxidizing agents as corrosive components. The copper-based member may have an anticorrosion film or may not have an anticorrosion film. The copper-based member that does not have the anticorrosive film may have a non-uniform state such as scratches, wet and dry surfaces.

  As the corrosive anion, ions of mineral acids such as chloride ions, sulfate ions and nitrate ions are preferable, and at least one of chloride ions and sulfate ions is particularly preferable. The concentration of the corrosive anion in the corrosive solution is preferably about 50 to 50,000 mg / L (0.05 to 50 g / L), particularly about 100 to 500 mg / L.

  As the oxidizing agent, hydrogen peroxide, hypochlorous acid, sodium hypochlorite and the like are preferable, and hydrogen peroxide is particularly preferable. The concentration of hydrogen peroxide in the corrosive solution is preferably about 1 to 50 mg / L, particularly about 5 to 20 mg / L.

  As the anticorrosive, an azole anticorrosive for copper is suitable, and specifically, one or more of tolyltriazole, benzotriazole, mercaptobenzothiazole and the like are suitable. The concentration of the azole anticorrosive in the corrosive solution is preferably about 0.1 to 200 mg / L, particularly about 1 to 20 mg / L.

As the anticorrosive agent, an inorganic salt such as calcium chloride, magnesium chloride, sodium hydrogen carbonate or sodium carbonate, or a silica anticorrosive film forming agent such as sodium silicate may be used in combination. When the inorganic salt is contained in the corrosive liquid, the concentration is preferably about 5 to 300 mg / L, particularly about 30 to 150 mg / L. When the silica anticorrosive film forming agent is contained, the concentration is preferably about 5 to 150 mg / L, particularly about 10 to 100 mg / L as silica (SiO ₂ ).

  In order to bring the copper-based member into contact with the corrosive liquid, it is convenient and preferable to immerse the copper-based member in the corrosive liquid. It may be liquid. Although the temperature at the time of a contact may be normal temperature, it is good also as heating conditions. The contact time may be about 1 to 48 hours, particularly about 3 to 24 hours, but may be longer.

  In the present invention, the corrosion resistance of the material itself can be evaluated and the effect of the anticorrosive agent can be confirmed without selecting a place in the actual water system or in a laboratory such as a laboratory.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

[Examples 1 and 2]
A tube made of phosphorous-deoxidized copper (C1220) was cut into a length of 2 cm, and further divided by half, was used as a test piece. This test piece was immersed in 1 L of an anticorrosive film forming agent-containing water shown in Table 1, and an anticorrosive film was formed with various anticorrosive film forming agents. The water temperature was 30 ° C., and the treatment was performed for 24 hours under stirring with a stirrer.

  As described above, the test piece on which the anticorrosion film was formed was immersed in a water quality corrosion test solution (30 ° C., stirrer stirring) shown in Table 2 to which hydrogen peroxide was added as an oxidizing agent, and the surface of the test piece after 24 hours. When the occurrence of pitting corrosion was observed, all the corrosion forms were pitting corrosion with patina.

[Comparative Examples 1 and 2]
In Examples 1 and 2 above, the test was performed in the same manner except that the corrosion test solution was a solution containing only a corrosive component in Table 2 and not containing benzotriazole. As a result, all corrosion forms were general corrosion.

[Comparative Examples 3 and 4]
In Examples 1 and 2, when the same test was performed except that the corrosion test solution was a solution containing only 10 mg / L of hydrogen peroxide and 10 mg / L of benzotriazole, no clear pitting corrosion was observed. Corrosion was minor.

[Examples 3, 4, and 5]
A tube made of phosphorous-deoxidized copper (C1220) was cut into a length of 2 cm, and further divided by half, was used as a test piece.
In Example 3, a scratch test piece in which the test part of the test piece was scratched with a cutter knife and the new surface was exposed before the test was started was used as the test test piece.
In Example 4, tap water was dropped onto the test part of the test piece, and the wet and dry test piece which was naturally dried was used as the test test piece.
In Example 5, a carbon adhesion test piece in which graphite was adhered to a test part of the test piece with a commercially available pencil (hardness 5B) was used as the test test piece.
Otherwise, the corrosion test was performed in the same manner as in Example 1, and the occurrence of pitting corrosion on the surface of the test piece after 24 hours was observed. As a result, all of the corrosion forms were pitting corrosion with a greenish blue mound.

  As a result, in Example 3, it was confirmed that patina was selectively generated in the scratched portion, and the corrosion resistance of the scratched portion was reduced as compared with the periphery. Furthermore, as a result of observation by SEM about the starting point of corrosion, it was confirmed that patina was generated starting from the edge of the scratch. It is presumed that the edge portion, which is the boundary between the copper surface and the new surface exposed by the scratch, is active and becomes the starting point of corrosion.

  In Example 4, it was confirmed that patina was selectively generated at the boundary between the discolored portion and the non-discolored portion of the copper surface caused by wetting and drying, and the corrosion resistance of the wetting and drying portion was lower than that of the surrounding area. As a result of observing the starting point of corrosion by SEM, it was generated on the side of the color changing portion near the boundary between the color changing portion and the non-color changing portion. It has been confirmed that chloride ions and the like are concentrated around the center of the water droplets by wetting and drying, and the point where the oxide film breaks due to the concentration of corrosive anions such as chloride ions during the wetting and drying process is the starting point. Therefore, it is presumed that the potential difference from the surrounding area where the oxide film is formed becomes the driving force for the progress of local corrosion, and the patina has grown.

  In Example 5, it was confirmed that patina was selectively generated at the location where the carbon was adhered, and the corrosion resistance of the location where the carbon was adhered was lower than the surroundings. As a result of SEM observation of the starting point of corrosion, carbon is not attached to the copper surface in a uniform band shape, but is attached to spots, and corrosion occurs starting from the vicinity of the carbon adhering part. I confirmed. The occurrence of corrosion is presumed to be due to the location where carbon adhered as an effective cathode.

[Comparative Examples 5 to 7]
In Examples 3 to 5, the corrosion test solutions were tested in the same manner except that a solution containing only corrosive components and not containing benzotriazole in Table 2 was used. As a result, all corrosion forms were general corrosion.

[Comparative Examples 8 to 10]
In Examples 3 to 5, when the same test was conducted except that the corrosion test solution was a solution containing only 10 mg / L of hydrogen peroxide and 10 mg / L of benzotriazole, no clear pitting corrosion was observed. Corrosion was minor.

  From the above examples and comparative examples, it was confirmed that according to the present invention, a pitting corrosion promotion test of a copper-based member is possible.

Claims (5)

In a method for testing corrosion resistance by contacting a copper-based member with a corrosive liquid,
A method for testing a corrosion resistance of a copper-based member, wherein the corrosive liquid contains a corrosive component and an anticorrosive agent for copper, and the corrosive component is a corrosive anion and an oxidizing agent.   The method for testing corrosion resistance of a copper-based member according to claim 1, wherein the anticorrosive is an azole-based anticorrosive.   3. The method for testing corrosion resistance of a copper-based member according to claim 2, wherein the azole anticorrosive is at least one of tolyltriazole, benzotriazole, and mercaptobenzothiazole.   The corrosion resistance test method for a copper-based member according to any one of claims 1 to 3, wherein the corrosive anion is chloride ion and / or sulfate ion and the oxidizing agent is hydrogen peroxide.   5. The method for testing corrosion resistance of a copper-based member according to claim 1, wherein a corrosion-resistant film is formed on a surface of the copper-based member, and the corrosion resistance of the corrosion-resistant film is tested.