JP5849417B2 - Method for stopping pitting corrosion of copper-based member and pitting corrosion stopping agent - Google Patents

Description

  The present invention relates to a method of stopping a pitting corrosion in progress using a chemical agent for a copper-based member such as a copper pipe in contact with an aqueous system such as a cooling water system, and a pitting corrosion stopper for the same.

  Copper has a characteristic of excellent thermal conductivity, and is widely used for heat transfer tubes such as air conditioners and heat exchangers. However, these copper-based members in contact with water systems have a problem of corrosion. In particular, the efficiency of recent equipment is increasing, and the thickness of copper pipes used in heat exchangers is extremely thin. Therefore, the occurrence of corrosion has a high risk of lead-through leakage of copper pipes. . Therefore, it is indispensable for stable operation and long life of the equipment that the copper-based member does not corrode and does not proceed with the generated corrosion.

  In general, the corrosion reaction proceeds by a pair of metal elution reaction (anode reaction) and oxidant reduction reaction (cathode reaction). For example, in a pH neutral to weakly alkaline environment such as cooling water, dissolved oxygen in the water becomes a catalyst for the cathode reaction as an oxidizing agent.

Conventionally, in order to suppress corrosion of a copper-based member in contact with an aqueous system, water treatment in which an azole-based anticorrosive agent for copper such as benzotriazole, tolyltriazole, or mercaptobenzothiazole is added to the aqueous system has been performed (for example, Patent Documents). 1, 2). It is known that by adding these azole copper anticorrosives to an aqueous system such as a cooling water system, it exhibits an excellent corrosion-inhibiting effect on copper-based members in contact with the aqueous system, and is widely applied. .
That is, the azole-type anticorrosive agent for copper is excellent in the effect of suppressing the metal elution reaction (anode reaction) in the corrosion reaction, and exhibits a good corrosion-inhibiting effect.

  However, even when an azole copper anticorrosive is added, the occurrence and progression of corrosion may not be sufficiently suppressed. For example, an anti-corrosion film made of an azole anti-corrosive agent is locally destroyed for some reason, such as an excessive addition of an oxidizing agent, and as a result, the azole anti-corrosive agent cannot suppress the elution of copper from the destroyed part of the film. The destruction part becomes a local anode, and corrosion may progress.

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

  The present invention solves the above-mentioned conventional problems, and stops the progress of pitting corrosion generated in a copper-based member such as a copper pipe in contact with an aqueous system such as a cooling water system by using a chemical agent, thereby effectively preventing the recurrence of corrosion. In particular, for pitting corrosion occurring on copper-based members of equipment during operation, it is possible to reliably stop the progress of pitting corrosion without stopping the operation of the equipment. It is an object to provide a method and a pitting corrosion stopper.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have generated pitting corrosion, which is a compound having a chelating action on copper with respect to an aqueous system in contact with an ongoing copper-based member, and an aqueous system. It has been found that by adding a compound that is excellent in the corrosion-inhibiting effect of the contacted copper-based member, particularly the cathode reaction-inhibiting effect, the progress of pitting corrosion can be stopped in a short period of time and recurrence can be prevented.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] (A) A compound having a chelating action on copper (hereinafter referred to as “component (A)”) and (B) a compound represented by the following formula (1) with respect to an aqueous system in contact with a copper-based member (Hereinafter referred to as “component (B)”) and / or (C) pitting corrosion of a copper-based member to which a compound represented by the following formula (2) (hereinafter referred to as “(C) component”) is added. A stopping method, wherein the component (B) is one or more selected from the group consisting of imidazole compounds, imidazoline compounds, imidazolinium salt compounds and imidazolium salt compounds. A method for stopping pitting corrosion of a copper-based member.

(In the above formula (1), ring A is a nitrogen-containing unsaturated 5-membered ring in which the ^1st and 3rd positions are nitrogen atoms and the 2nd, 4th and 5th positions are carbon atoms, and R ¹ is alkyl. to display the group or alkenyl group, the carbon atom at the 4-position and 5-position are bonded hydrogen atom. However, the nitrogen atom of 1-position and 3-position of the nitrogen-containing unsaturated 5-membered ring a represents an alkyl group, hydroxyalkyl group, carboxyalkyl group (a hydroxyalkyl group, carboxyalkyl group may form a salt.) If no rather good may have a substituent group selected from, these substituents Is bonded to a hydrogen atom or has no hydrogen atom or substituent .)

(In the formula (2), R ² represents an alkyl group or an alkenyl group, and X, Y, and Z each independently represent a hydrogen atom, an alkyl group, a benzyl group, a hydroxyalkyl group, or a carboxyalkyl group, Group and carboxyalkyl group may form a salt.)

[2] The component (A) is one or more selected from the group consisting of citric acid and salts thereof, ethylenediaminetetraacetic acid and salts thereof, and methylglycine diacetic acid and salts thereof. The method for stopping pitting corrosion of a copper-based member according to [1].

[ 3 ] The method for stopping pitting corrosion of a copper-based member according to [ 1 ] or [2] , wherein the component (B) is 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine.

[ 4 ] The component (C) is [1] to [1], wherein X in the formula (2) is a hydrogen atom, Y is a hydroxyethyl group, and Z is a carboxymethyl group or a carboxymethyl group forming a salt. 3 ] The method for stopping pitting corrosion of a copper-based member according to any one of the above.

[5] (1) the number of carbon atoms in the alkyl group or Arukenirukiru group ^{R 1} in the formula is 6 to 18, wherein (2) 6 carbon atoms in the alkyl or alkenyl group ^{R 2} in formula 18. The method for stopping pitting corrosion of a copper-based member according to any one of [1] to [ 4 ], wherein

[ 6 ] The component (A), the component (B), and / or the component (C) are added to an aqueous system in contact with a copper-based member of a device in operation. [1] to [ 5 ] A method for stopping pitting corrosion of a copper-based member according to any one of the above.

[ 7 ] A pitting corrosion stopping agent for a copper-based member that stops pitting corrosion of the copper-based member by adding to the aqueous system in contact with the copper-based member, and (A) a compound having a chelating action on copper (Hereinafter referred to as “component (A)”) and (B) a compound represented by formula (1) below (hereinafter referred to as “component (B)”) and / or (C) formula (2) below. A pitting corrosion stopper for a copper-based member containing a compound represented by the formula (hereinafter referred to as “component (C)”), wherein the component (B) is an imidazole compound, an imidazoline compound, or an imidazolinium salt. A pitting corrosion stopper for a copper-based member, which is one or more selected from the group consisting of a base compound and an imidazolium salt-based compound .

(In the above formula (1), ring A is a nitrogen-containing unsaturated 5-membered ring in which the ^1st and 3rd positions are nitrogen atoms and the 2nd, 4th and 5th positions are carbon atoms, and R ¹ is alkyl. to display the group or alkenyl group, the carbon atom at the 4-position and 5-position are bonded hydrogen atom. However, the nitrogen atom of 1-position and 3-position of the nitrogen-containing unsaturated 5-membered ring a represents an alkyl group, hydroxyalkyl group, carboxyalkyl group (a hydroxyalkyl group, carboxyalkyl group may form a salt.) If no rather good may have a substituent group selected from, these substituents Is bonded to a hydrogen atom or has no hydrogen atom or substituent .)

(In the formula (2), R ² represents an alkyl group or an alkenyl group, and X, Y, and Z each independently represent a hydrogen atom, an alkyl group, a benzyl group, a hydroxyalkyl group, or a carboxyalkyl group, Group and carboxyalkyl group may form a salt.)

[ 8 ] The component (A) is one or more selected from the group consisting of citric acid and salts thereof, ethylenediaminetetraacetic acid and salts thereof, and methylglycine diacetic acid and salts thereof. [ 7 ] The pitting corrosion stopper for copper-based members according to [ 7 ].

[ 9 ] The pitting corrosion stopper for copper-based members according to [ 7 ] or [8] , wherein the component (B) is 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine.

[ 10 ] The component (C) is [ 7 ] to [ 7 ] wherein X in the formula (2) is a hydrogen atom, Y is a hydroxyethyl group, and Z is a carboxymethyl group or a carboxymethyl group forming a salt. 9 ] The pitting corrosion stopper for copper-based members according to any one of [ 9 ].

[11] (1) the number of carbon atoms in the alkyl group or Arukenirukiru group ^{R 1} in the formula is 6 to 18, wherein (2) the number of carbon atoms in the alkyl or alkenyl group of ^{R 2} in the formula 6 18. The pitting corrosion stopper for copper-based members according to any one of [ 7 ] to [ 10 ], wherein

  In the present invention, by the action of the component (A), it is possible to dissolve and remove the corrosion product (greenish blue) generated in the ongoing pitting corrosion, while removing the corrosive substance in the pitting corrosion portion and preventing corrosion. A surface state capable of forming a film can be obtained. On the other hand, by the action of the components (B) and / or (C), it is possible to form an anticorrosive film having an excellent cathode reaction suppressing effect on the copper surface. Therefore, it becomes possible to effectively suppress the recurrence of pitting corrosion by the effect of the formed anticorrosion film.

  Therefore, according to the present invention, the pitting corrosion generated in the copper-based member such as the copper pipe in contact with the water system such as the cooling water system is effectively stopped by using the chemical, and the recurrence of the corrosion is surely suppressed. Thus, it is possible to maintain the stable operation of the device and extend the lifetime. In particular, according to the present invention, it is possible to take a measure to stop the progress of pitting corrosion without stopping the operation of the pitting caused to the copper-based member of the operating equipment, which is extremely advantageous industrially. is there.

In an Example, it is a figure which shows the evaluation electrode used for evaluation of the progress state of pitting corrosion, (a) A figure is a front view, (b) A figure is sectional drawing which follows the bb line of (a) figure. . It is a graph which shows transition of the pitting corrosion current in Examples 8 and 9 and Comparative Examples 6 and 7.

  Embodiments of a pitting corrosion stopping method and a pitting corrosion stopping agent for a copper-based member of the present invention will be described in detail below.

  In this invention, the following (A) component, (B) component, and / or (C) component are added to the aqueous system which touches a copper-type member, It is characterized by the above-mentioned.

<(A) component>
The component (A) according to the present invention is not limited as long as it has a chelating action on copper and can dissolve and remove the corrosion product (greenish blue) generated by copper pitting corrosion. For example, citric acid and The salt (for example, alkali metal salt), ethylenediaminetetraacetic acid and its salt (for example, alkali metal salt), methylglycine diacetic acid and its salt (for example, alkali metal salt) are preferable, and these may be used alone. In addition, two or more kinds may be used in combination. Of these, trisodium methylglycine diacetate is particularly preferable because of its excellent chelating action on copper.

<(B) component>
The component (B) according to the present invention is a compound represented by the following formula (1).

(In the above formula (1), ring A is a nitrogen-containing unsaturated 5-membered ring in which the ^1st and 3rd positions are nitrogen atoms and the 2nd, 4th and 5th positions are carbon atoms, and R ¹ is alkyl. Represents a group or an alkenyl group, provided that the nitrogen atom and carbon atom of the nitrogen-containing unsaturated 5-membered ring A may have any substituent other than R ^1. )

Examples of the component (B) include imidazole compounds, imidazoline compounds, imidazolinium salt compounds, and imidazolium salt compounds. In particular, R ¹ in the above formula (1) is a hydrophobic carbon number of 6 Those having an alkyl group or alkenyl group of ˜18, particularly those in which R ¹ is an alkyl group having 6 to 18 carbon atoms are preferred.

As such a compound, a compound in which various functional groups are introduced into a nitrogen-containing unsaturated 5-membered ring A can be used, for example, a carbon to which a substituent R ^{1 of the} nitrogen-containing unsaturated 5-membered ring A is bonded. An alkyl group, hydroxyalkyl group, carboxylalkyl group (a hydroxyalkyl group, a carboxyalkyl group may form a salt such as an alkali metal salt such as a sodium salt or a potassium salt) on the nitrogen atom adjacent to the atom. A compound into which one or more selected from the above are introduced can be suitably used.

  Examples of such compounds include 2-hexylimidazole, 2-heptylimidazole, 2-octylimidazole, 2-nonylimidazole, 2-decylimidazole, 2-undecylimidazole, 2-dodecylimidazole, 2-tridecylimidazole, 2 -Tetradecylimidazole, 2-pentadecylimidazole, 2-hexadecylimidazole, 2-heptadecylimidazole, 2-octadecylimidazole, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine (carbon of alkyl group) The number is 6 to 18), 2-alkyl-N-hydroxyethyl-N-carboxylatemethylimidazolinium salt (the alkyl group has 6 to 18 carbon atoms), 2-alkyl-N, N-bishydroxyethylimidazo Examples thereof include nium salts (the alkyl group has 6 to 18 carbon atoms), 1-methyl-1-hydroxyethyl-2-tallow alkyl-imidazolinium salt, and the like, and 2-alkyl-N-carboxymethyl-N-hydroxyethyl Imidazolinium betaine (the alkyl group has 6 to 18 carbon atoms) is preferred, and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine is particularly preferred.

  These (B) components may be used individually by 1 type, and may use 2 or more types together.

<(C) component>
The component (C) according to the present invention is a compound represented by the following formula (2).

(In the formula (2), R ² represents an alkyl group or an alkenyl group, and X, Y, and Z each independently represent a hydrogen atom, an alkyl group, a benzyl group, a hydroxyalkyl group, or a carboxyalkyl group, Group and carboxyalkyl group may form a salt.)

The number of carbon atoms of the alkyl group or alkenyl group of R ^{2 in} the above formula (2) is preferably 6 to 18, particularly 11.

  X, Y, and Z are each independently a hydrogen atom, a hydroxyethyl group, or a carboxymethyl group (the hydroxyethyl group or carboxymethyl group forms a salt such as an alkali metal salt such as sodium salt or potassium salt). It is preferable that

  As the component (C), one type may be used alone, or two or more types may be used in combination.

  Moreover, you may use together 1 type, or 2 or more types of (B) component, and 1 type or 2 or more types of (C) component with 1 type or 2 or more types of (A) component.

<Amount added to water system>
The amount of the component (A) used in the present invention added to the aqueous system is not particularly limited as long as it is a concentration that can dissolve and remove the copper corrosion product (greenish blue) generated in the pitting portion. It can be used by adjusting the concentration to obtain an optimum effect depending on the water quality. The concentration of component (A) added to the aqueous system is usually in the range of 50 to 5000 mg / L, preferably in the range of 100 to 4000 mg / L.

The amount of the component (B) and / or component (C) added to the aqueous system is not particularly limited as long as it can suppress the corrosion of the copper base material due to the component (A) and can form an anticorrosive film on the surface of the copper-based member. However, it can be used by adjusting the concentration to obtain an optimum effect depending on the water quality to be treated, the surface area of the copper-based member and the like. The concentration of component (B) and / or (C) added to the aqueous system is usually in the range of 0.5 to 100 mg / L, preferably 1 to 50 mg / L. In addition, when using together (B) component and (C) component, it is made for the total addition density | concentration of these to become the said range.

  Although there is no restriction | limiting in particular about the addition weight ratio of (A) component, (B) component, and / or (C) component, Usually, (B) component and / or (C) component with respect to (A) component It is preferable to add so that the ratio of the above becomes 0.5 to 50% by weight, particularly about 1 to 20% by weight.

<Conditions of target water system>
The temperature (water temperature) of the aqueous system at the time of treatment according to the present invention (that is, at the time of adding the component (A) and the component (B) and / or the component (C)) is a condition that can obtain the effect of the present invention. If it does not have a restriction | limiting in particular, The range of 5-60 degreeC is preferable. Moreover, as a pH of the aqueous system at the time of a process, a process is normally performed in the range of 4-11.

  The flow rate of the aqueous system during the treatment according to the present invention is not particularly limited as long as the effect of the present invention can be obtained, but the treatment is usually performed in the range of 0.1 to 2 m / s. Although it is possible to perform the treatment even in a stationary condition, in this case, since the diffusion of the added drug to the surface of the copper-based member becomes rate-limiting, measures such as increasing the concentration of addition are required.

  There is no restriction | limiting in particular in the addition method to the aqueous system of (A) component and (B) and / or (C) component, It is also possible to add each component separately, (A) component and (B) beforehand It is also possible to add to the aqueous system as a water treatment agent in which the component (C) and / or component (C) are mixed.

  In the present invention, water treatment agents other than the above components (A) to (C), such as anticorrosives, scale inhibitors, dispersants, slime control agents, release agents, as long as the effects of the present invention are not impaired. It is possible to use an antifoaming agent in combination.

  The method for stopping pitting corrosion of a copper-based member of the present invention may be carried out by adding the component (A), the component (B) and / or the component (C) to an aqueous system that is in contact with the copper-based member of an operating device. This is industrially extremely advantageous. However, it goes without saying that the pitting corrosion stopping method for a copper-based member of the present invention may be performed in a state where the operation is stopped.

<Pitting corrosion stopper for copper-based members>
The pitting corrosion stopper of the copper-based member of the present invention contains the aforementioned component (A), component (B), and / or component (C), and these are integrated into a single agent. Alternatively, each component may be provided separately.

  There is no restriction | limiting in particular in the content rate of each component in the pitting corrosion stopper of the copper-type member of this invention, Moreover, the pitting corrosion stopper of the copper-type member of this invention is other than (A)-(C) component. Although it may contain other chemicals such as anticorrosive, scale inhibitor, dispersant, slime control agent, release agent, antifoaming agent, (A) component and (B) component and / or (C) In order to sufficiently obtain the excellent effect of the combined use of the components, the pitting corrosion stopper of the present invention has a ratio of the component (B) and / or the component (C) of 0.5 to 50 with respect to the component (A). It is preferable to contain these in an amount of about 1% by weight, particularly about 1 to 20% by weight.

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

  In addition, each chemical | medical agent of the (A)-(C) component used below is shown with the following abbreviations.

<(A) component>
MG: trisodium methylglycine diacetate ED: disodium ethylenediaminetetraacetate CA: citric acid <component (B)>
AC: 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine <(C) component>
AA: (2) In the formula, R ² is an undecyl group, X is a hydrogen atom, Y is a hydroxyethyl group, and Z is a carboxymethyl group

[Examples 1 to 7, Comparative Examples 1 to 5: Effect of dissolution and removal of patina and corrosion]
Adjusted water (not added in Comparative Example 1) with each drug added at the concentration shown in Table 2 to the test water shown in Table 1 was placed in a 1 L beaker, and the following test piece I was placed in this adjusted water: , II were immersed, stirred with a stirrer, and an experiment was conducted to investigate the effect of removing and dissolving patina and the effect on corrosion under the condition of a water temperature of 30 ° C.

Specimen I: Copper pitting corrosion occurred, and the copper tube in which the corrosion product patina was generated was halved.
Cut to a length of 2 cm in the longitudinal direction.
Test piece II: Copper piece # 400 polished (W30 mm × L50 mm × t1 mm)

The test piece I was immersed in adjustment water, and the greenish blue state change (whether the patina was removed) on the surface of the test piece I was confirmed.
Moreover, the test piece II was immersed in adjustment water, the corrosion rate was calculated | required from the weight change of the test piece II before and behind immersion, and the corrosion inhibitory effect was evaluated.
These results are shown in Table 2 together with the comprehensive judgment results.

In Examples 1 to 7 in which the component (A) and the component (B) and / or the component (C) are added, the patina of the test piece I is dissolved and removed, and the corrosion rate of the test piece II can be suppressed to a low value. On the other hand, in Comparative Example 2 in which only component (A) was added, the corrosion rate increased, while in Comparative Examples 3 to 5 in which only component (B) or component (C) was added, the patina of test piece I As a result, it was not dissolved and removed.
As described above, according to the present invention, it was confirmed that a surface state capable of forming an anticorrosion film can be realized by dissolving and removing patina, and a state where the base material is not corroded can be realized by forming the anticorrosion film.

[Examples 8 and 9, Comparative Examples 6 and 7: Pitting corrosion stopping effect]
The progress of pitting corrosion was evaluated using the evaluation electrode 1 having the structure shown in FIG. Here, a phosphorous deoxidized copper wire of φ0.45 mm is used as the artificial anode 2 and a φ3 cm phosphorous deoxidized copper specimen having a hole of φ1 mm in the center as the artificial cathode 3 is insulated with the resin 4. Thus, an evaluation electrode 1 was obtained. Reference numeral 5 denotes a coated conductor.
The surface of the artificial anode 2 and the surface of the artificial cathode 3 of the evaluation electrode 1 were wet-polished with # 400 polishing paper.
The evaluation electrode 1 was immersed in water quality test water shown in Table 3.

  Using a potentiogalvanostat (potentiostat / galvanostat HA-151A type, manufactured by Hokuto Denko), the artificial anode 2 part was covered with a corrosion product by applying a predetermined current to the artificial anode 2 for a predetermined time. Measures were taken to condition. A carbon rod was used as a counter electrode, a saturated KCl silver-silver chloride electrode was used as a reference electrode, 2 parts of the artificial anode of the evaluation electrode 1 was used as a sample electrode, and corrosion products were generated in 2 parts of the artificial anode. Here, a current of 10 μA was applied for 2 hours, and 2 parts of the artificial anode were covered with a corrosion product.

  The anode which took measures to make the artificial anode 2 part covered with the corrosion product immediately passes through the artificial cathode 3 and a non-resistance ammeter (Toho Giken portable non-resistance ammeter MODEL AM-03). Connection was made, and the current accompanying the progress of pitting corrosion was measured.

  Sodium hypochlorite is periodically added to the test water, and the current accompanying the progress of pitting corrosion flowing between the artificial anode 2 and the artificial cathode 3 (hereinafter referred to as “pitting corrosion current”) continues to be about A state where 110 nA (corresponding to a pitting corrosion progressing speed of about 0.8 mm / y) was changed (a state where pitting corrosion progressed) was reproduced and evaluated.

  In such an evaluation, the chemicals shown in Table 4 were added to the test water at the concentrations shown in Table 4 (however, no chemicals were added in Comparative Example 6), and the transition of the pitting current was confirmed.

The transition of the pitting current is shown in FIG.
In Examples 8 and 9 according to the method of the present invention, a rapid decrease in the pitting current was observed immediately after the addition of the component (A) and the component (B) and / or the component (C). An increase was not confirmed. On the other hand, in Comparative Example 6 in which various chemicals were not added, no decrease in pitting current was observed. Further, in Comparative Example 7 in which only the component (C) was added, although a gradual decrease in pitting current was observed, no current behavior indicating a short-term stop of pitting corrosion was observed.
As described above, it was confirmed that the pitting corrosion in progress can be quickly stopped by the method of the present invention.

1 Evaluation Electrode 2 Artificial Anode 3 Artificial Cathode 4 Resin 5 Coated Conductor

Claims (11)

For the aqueous system in contact with the copper-based member, (A) a compound having a chelating action on copper (hereinafter referred to as “component (A)”), and (B) a compound represented by the following formula (1) (hereinafter, In a method for stopping pitting corrosion of a copper-based member to which “(B) component” and / or (C) a compound represented by the following formula (2) (hereinafter referred to as “(C) component”) is added. There,
The component (B) is one or more selected from the group consisting of an imidazole compound, an imidazoline compound, an imidazolinium salt compound, and an imidazolium salt compound. How to stop pitting corrosion.

(In the above formula (1), ring A is a nitrogen-containing unsaturated 5-membered ring in which the ^1st and 3rd positions are nitrogen atoms and the 2nd, 4th and 5th positions are carbon atoms, and R ¹ is alkyl. to display the group or alkenyl group, the carbon atom at the 4-position and 5-position are bonded hydrogen atom. However, the nitrogen atom of 1-position and 3-position of the nitrogen-containing unsaturated 5-membered ring a represents an alkyl group, hydroxyalkyl group, carboxyalkyl group (a hydroxyalkyl group, carboxyalkyl group may form a salt.) If no rather good may have a substituent group selected from, these substituents Is bonded to a hydrogen atom or has no hydrogen atom or substituent .)

(In the formula (2), R ² represents an alkyl group or an alkenyl group, and X, Y, and Z each independently represent a hydrogen atom, an alkyl group, a benzyl group, a hydroxyalkyl group, or a carboxyalkyl group, Group and carboxyalkyl group may form a salt.)   The component (A) is one or more selected from the group consisting of citric acid and salts thereof, ethylenediaminetetraacetic acid and salts thereof, and methylglycine diacetic acid and salts thereof. The method for stopping pitting corrosion of a copper-based member according to claim 1. The component (B), 2-alkyl -N- carboxymethyl pitting stopping method of copper-based member according to claim 1 or 2 methyl -N- hydroxyethyl imidazolinium betaine. The component (C) is any one of claims 1 to 3 , wherein X in the formula (2) is a hydrogen atom, Y is a hydroxyethyl group, and Z is a carboxymethyl group or a carboxymethyl group forming a salt. The method for stopping pitting corrosion of a copper-based member according to item 1. The carbon number of the alkyl group or alkenyl group of R ^{1 in} the formula (1) is 6-18, and the carbon number of the alkyl group or alkenyl group of R ^{2 in} the formula (2) is 6-18. The method for stopping pitting corrosion of a copper-based member according to any one of claims 1 to 4 . The said (A) component, (B) component, and / or (C) component are added to the water system which contacts the copper-type member of the apparatus in operation | movement in any one of Claim 1 thru | or 5 characterized by the above-mentioned. The method for stopping pitting corrosion of a copper-based member as described. A pitting corrosion stopper for a copper-based member that stops pitting corrosion of the copper-based member by adding to an aqueous system in contact with the copper-based member, and (A) a compound having a chelating action on copper (hereinafter, "(A) component") and (B) a compound represented by the following formula (1) (hereinafter referred to as "(B) component") and / or (C) represented by the following formula (2). A pitting corrosion stopper for a copper-based member containing a compound (hereinafter referred to as “component (C)”) ,
(B) The hole of the copper-based member, wherein the component is one or more selected from the group consisting of an imidazole compound, an imidazoline compound, an imidazolinium salt compound, and an imidazolium salt compound Stop food.

(In the above formula (1), ring A is a nitrogen-containing unsaturated 5-membered ring in which the ^1st and 3rd positions are nitrogen atoms and the 2nd, 4th and 5th positions are carbon atoms, and R ¹ is alkyl. to display the group or alkenyl group, the carbon atom at the 4-position and 5-position are bonded hydrogen atom. However, the nitrogen atom of 1-position and 3-position of the nitrogen-containing unsaturated 5-membered ring a represents an alkyl group, hydroxyalkyl group, carboxyalkyl group (a hydroxyalkyl group, carboxyalkyl group may form a salt.) If no rather good may have a substituent group selected from, these substituents Is bonded to a hydrogen atom or has no hydrogen atom or substituent .)

(In the formula (2), R ² represents an alkyl group or an alkenyl group, and X, Y, and Z each independently represent a hydrogen atom, an alkyl group, a benzyl group, a hydroxyalkyl group, or a carboxyalkyl group, Group and carboxyalkyl group may form a salt.) Wherein component (A), claim 7, wherein the citric acid and its salts, is ethylenediaminetetraacetic acid and salts thereof, and one or more selected from methylglycine diacetic acid and the group consisting of a salt thereof A pitting corrosion stopper for copper-based members as described in 1 above. The pitting corrosion stopper for a copper-based member according to claim 7 or 8 , wherein the component (B) is 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine. The component (C) is any one of claims 7 to 9 , wherein X in the formula (2) is a hydrogen atom, Y is a hydroxyethyl group, and Z is a carboxymethyl group or a carboxymethyl group forming a salt. The pitting corrosion terminator for copper-based members according to item 1. The carbon number of the alkyl group or alkenyl group of R ^{1 in} the formula (1) is 6-18, and the carbon number of the alkyl group or alkenyl group of R ^{2 in} the formula (2) is 6-18. The pitting corrosion stopper for a copper-based member according to any one of claims 7 to 10 .

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