JP6750705B2 - Initial treatment agent for circulating cooling water and method for preventing corrosion of circulating cooling water system - Google Patents

Description

The present invention relates to an initial treating agent for circulating cooling water, which is added to the circulating cooling water system when the circulating cooling water system is started to form an anticorrosive film on the surface of the metallic member of the circulating system, and a method for preventing corrosion of the circulating cooling water system.

Since the cooling water used in the circulating cooling water system contains impurities (for example, dissolved oxygen, chloride ions, sulfate ions, etc.) that become corrosion factors not a little, the surface of the metal member in contact with the cooling water can be changed over time. The problem is that failures such as corrosion can occur.

Therefore, as an initial treatment step at the time of starting the circulating cooling water system, an inorganic phosphate and a zinc compound are added to the cooling water, and the cooling water is circulated for a certain period of time to form an anticorrosion film on the surface of the metal member. Therefore, an initial treatment method for a circulating cooling water system is proposed, which provides a corrosion prevention effect.

For example, in Patent Document 1, a phosphate is added to a cooling water system so that the total phosphoric acid concentration is 70 to 120 mg PO ₄ /L, and a zinc compound is added so that the zinc concentration is 10 to 30 mg Zn/L. A cooling water-based treatment method is disclosed in which a basic treatment step of adding and forming an initial anticorrosive film on the surface of a cooling water-based metal member is performed.

JP, 2011-202243, A

In the cooling water-based treatment method disclosed in Patent Document 1, a phosphate and a zinc compound are used as an initial treatment agent used to form an anticorrosion film on the surface of a metal member, and a corrosion prevention effect is obtained. .. However, in recent years, with increasing interest in the water quality environment, it is also desired to reduce the amounts of phosphorus and zinc contained in wastewater and waste liquid discharged from factories and business establishments.

Therefore, the present invention has been made in order to solve the above problems, it is possible to satisfactorily form an anticorrosion coating on the surface of a metal member without using a phosphate and a zinc compound as an initial treatment agent. It is an object of the present invention to provide an initial treatment agent for circulating cooling water and an anticorrosion method for a circulating cooling water system, which can provide an excellent corrosion prevention effect.

The present inventor has conducted extensive studies in order to solve the above problems, and as a result, added a specific initial treatment agent to a water system in a specific amount (20 to 150 mg/L, preferably 30 to 100 mg/L in terms of tartaric acid), It has been found that the above problems can be solved by setting the pH of the aqueous system after addition of the initial treatment agent to a specific range (pH 6.0 to 8.0), and the present invention has been completed.
That is, the present invention is as follows.

[1] An initial treatment agent for circulating cooling water, which is added to the circulating cooling water system at startup to form an anticorrosion coating on the surface of the metallic member of the cooling system, and is at least 1 selected from tartaric acid and tartarate. An initial treatment agent for circulating cooling water containing a seed.
[2] For the circulating cooling water according to [1], wherein the content of at least one selected from the tartaric acid and the tartaric acid salt is 90 to 100% by mass in 100% by mass of the initial treating agent for the circulating cooling water. Initial treatment agent.
[3] A method for preventing corrosion of a circulating cooling water system including an initial treatment step of forming an anticorrosive film on the surface of a water-based metal member at the time of starting the circulating cooling water system. 1] or [2], the initial treatment agent for circulating cooling water containing at least one selected from tartaric acid and tartrate salt is added so as to be 20 to 150 mg/L in terms of tartaric acid. A method for preventing corrosion of a circulating cooling water system, wherein the pH of the water system after adding the initial treatment agent is 6.0 to 8.0.
[4] The method for preventing corrosion of a circulating cooling water system according to the above [3], wherein the initial treatment agent for circulating cooling water comprises at least one selected from tartaric acid and a tartrate salt.
[5] The method for preventing corrosion of a circulating cooling water system according to [3] or [4], wherein in the initial treatment step, the water system is circulated for 20 to 48 hours without applying a heat load to the water system.
[6] In the initial treatment step, an initial treatment agent for circulating cooling water containing at least one selected from tartaric acid and a tartrate salt is added to the aqueous system so as to be 30 to 100 mg/L in terms of tartaric acid. The method for preventing corrosion of a circulating cooling water system according to any one of [3] to [5] above, wherein the pH of the aqueous system after adding the initial treatment agent for circulating cooling water is 6.0 to 8.0. ..
[7] Corrosion of the circulating cooling water system according to any one of [3] to [6], wherein in the initial treatment step, the temperature of the water system is 10 to 40° C., and the water system is circulated for 20 to 48 hours. Prevention method.
[8] The circulating cooling water system according to any one of [3] to [7], which includes a normal operation step for holding the anticorrosion coating formed in the initial treatment step after the initial treatment step. Corrosion prevention method.
[9] The method for preventing corrosion of a circulating cooling water system according to [8], wherein a retention treatment agent is added to the water system after the initial treatment process in the normal operation process.
[10] In the normal operation step, the circulating cooling water system according to the above [8] or [9], wherein the retention treatment agent is added to the water system after the initial treatment step so as to be 20 to 100 mg/L. Corrosion prevention method.

According to the present invention, it is possible to satisfactorily form an anticorrosion coating on the surface of a metal member without using a phosphate and a zinc compound as an initial treatment agent, and an excellent corrosion prevention effect can be obtained. It is possible to provide a treatment agent and a method for preventing corrosion of a cooling water system.

It is a figure which shows the change of the corrosion rate measured over time in the initial treatment process and corrosion treatment process of Examples A1-A3 and Comparative Examples A1-A9. In Example B1 and Comparative Examples B1 and B2, the initial treatment step and the blank treatment step are set as one set, and this one set is repeated three times, and it is a diagram showing changes in corrosion weight loss measured with time. It is a schematic diagram which shows the structure of a heat transfer surface evaluation test apparatus.

[Initial treatment agent for circulating cooling water]
The initial treatment agent for circulating cooling water of the present invention (hereinafter referred to as “initial treatment agent”) is added to the water system at the time of starting the circulation cooling water system to form a circulation for forming an anticorrosion film on the surface of the metal member of the water system. An initial treatment agent for cooling water, containing at least one selected from tartaric acid and tartrate.
Thereby, even if the phosphate and the zinc compound are not used as the initial treatment agent, the anticorrosion film can be satisfactorily formed on the surface of the metal member, and an excellent corrosion prevention effect can be obtained.

(Tartaric acid and tartrate)
The initial treatment agent of the present invention contains at least one selected from tartaric acid and tartrate.
The content of at least one selected from tartaric acid and tartaric acid salt is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, still more preferably 90 to 100% by mass in 100% by mass of the initial treatment agent. It is more preferably 95 to 100% by mass, and even more preferably 100% by mass.
Here, "the content of at least one selected from tartaric acid and tartrate" means the total content of tartaric acid and tartrate in the initial treatment agent.
When the content of at least one selected from the above tartaric acid and tartaric acid salt is within the above range, a good anticorrosive film is formed on the surface of the metal member without using the phosphate and zinc compound as the initial treatment agent. And the excellent corrosion prevention effect can be easily obtained.

Tartaric acid used in the present invention is also called 2,3-dihydroxybutanedioic acid, is represented by (CH(OH)COOH) ₂ in the rational formula, and refers to a hydroxy acid having two asymmetric carbons in the molecule. ..
Tartaric acid includes L-form, D-form, meso-form and racemic form, but is not particularly limited.

In the tartaric acid salt used in the present invention, at least one hydrogen atom selected from two hydrogen atoms of two OH groups in the tartaric acid molecule and two hydrogen atoms of two COOH groups in the tartaric acid molecule is tartaric acid. Tartaric acid, which has been ionized from and became anion, reacts with a cation to form a compound. As the tartrate salt, one or two hydrogen atoms of the COOH group out of the two OH groups and two COOH groups in the tartaric acid molecule are ionized from tartaric acid, and the tartaric acid which has become an anion reacts with the cation. The compound produced is preferred.
Here, examples of the cation include an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a zinc ion, an aluminum ion, and an iron ion (II).

Specific examples of the tartrate salt formed by ionizing one hydrogen atom from tartaric acid include lithium tartrate, potassium tartrate, sodium tartrate and the like.
Specific examples of the tartrate salt formed by ionizing two or more hydrogen atoms from tartaric acid include dilithium tartrate, potassium sodium tartrate, diammonium tartrate, calcium tartrate, iron (II) tartrate, and zinc tartrate. Can be mentioned.
These tartrate salts may be used alone or in combination of two or more kinds.
Among these tartaric acid salts, sodium tartarate is preferred as the tartaric acid salt formed by ionizing one hydrogen atom from tartaric acid, and from tartaric acid, from the viewpoint of forming a good anticorrosive film on the surface of the metal member. As the tartrate salt formed by ionizing the above hydrogen atoms, calcium tartrate and iron (II) tartrate are preferable.

(Other ingredients)
The initial treatment agent in the present invention contains at least one selected from tartaric acid and tartaric acid salt as an essential component, but may contain other components as long as the effects of the present invention are not impaired.
Examples of the other components include zinc salt and calcium salt.

The content of the other components is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, and further preferably 0% by mass in 100% by mass of the initial treatment agent.
The content of the above-mentioned other components is in the above-mentioned range, and even if the phosphate and zinc compound are not used as the initial treatment agent, the anticorrosion film is easily formed well on the surface of the metal member, and excellent corrosion prevention is achieved. The effect is easily obtained.

[Corrosion prevention method for circulating cooling water system]
The method for preventing corrosion of a circulating cooling water system of the present invention (hereinafter referred to as "corrosion preventing method") is a method for preventing the corrosion of a circulating cooling water system, including an initial treatment step of forming an anticorrosion coating on the surface of a metallic member of the circulating water system at the time of startup. A method for preventing corrosion, wherein, in the initial treatment step, the initial treatment agent containing at least one selected from tartaric acid and tartaric acid salt in the aqueous system is 20 to 150 mg/L, preferably 30 to 100 mg/L in terms of tartaric acid. And the pH of the aqueous system after adding the initial treatment agent is adjusted to 6.0 to 8.0.
Thereby, even if the phosphate and the zinc compound are not used as the initial treatment agent, the anticorrosion film can be satisfactorily formed on the surface of the metal member, and an excellent corrosion prevention effect can be obtained.

The details of the mechanism by which the corrosion prevention method of the present invention achieves an excellent corrosion prevention effect are not clear, but are considered as follows.
The initial treatment agent containing at least one selected from tartaric acid and tartaric acid salt binds to calcium ions present in water to form an anticorrosion coating mainly composed of a sparingly water-soluble calcium salt on the surface of a metal member. It is thought to be done.
It is considered that the initial treatment agent containing at least one selected from tartaric acid and tartrate salt reacts with the iron component of the metal member to form iron(II) tartrate.
The formation of such an anticorrosion film prevents direct contact of an aqueous system containing impurities serving as a corrosion factor (for example, dissolved oxygen, chloride ions, sulfate ions, etc.) with the surface of the metal member, resulting in corrosion on the surface of the metal member. It is considered that the rate of progress (corrosion rate) can be reduced.

(Initial treatment process)
The corrosion prevention method of the present invention includes an initial treatment step of forming an anticorrosion coating on the surface of a water-based metal member when the circulating cooling water system is started.
In the initial treatment step of the present invention, an initial treatment agent containing at least one selected from tartaric acid and a tartaric acid salt in a water system is converted into tartaric acid in an amount of 20 to 150 mg/L, preferably 30 to 100 mg/L, and more preferably 40. To 90 mg/L, and more preferably 50 to 70 mg/L.
When the amount of the above-mentioned initial treatment agent is less than the above range (less than 20 mg/L), the amount of the initial treatment agent is too small, so that the anticorrosion film is not sufficiently formed on the surface of the metal member and the corrosion is prevented. May not be effective.
On the other hand, when the amount of the above-mentioned initial treatment agent exceeds the above range (exceeds 150 mg/L), it is easy to cause inconvenience such as chelate corrosion due to the excessive amount of the initial treatment agent. The rate at which corrosion progresses (corrosion rate) may be accelerated.

As described above, the content of at least one selected from tartaric acid and tartrate is 100% by mass of the initial treatment agent, more preferably 100% by mass.
That is, the initial treatment agent preferably comprises at least one selected from tartaric acid and tartaric acid salts.
In this case, in the water system, at least one selected from tartaric acid and a tartaric acid salt is preferably 20 to 150 mg/L, more preferably 30 to 100 mg/L, further preferably 40 to 90 mg/L, still more preferably, in terms of tartaric acid. Is added at 50 to 70 mg/L.
The addition amount of at least one selected from the above tartaric acid and tartaric acid salt is within the above range, so that an anticorrosive film is satisfactorily formed on the surface of the metal member without using the phosphate and zinc compound as the initial treatment agent. And the excellent corrosion prevention effect can be easily obtained.

In the present invention, after the addition of the initial treatment agent containing at least one selected from tartaric acid and tartrate, the pH of the aqueous system is 6.0 to 8.0, preferably 6.0 to 7.5, More preferably, it is 6.5 to 7.5.
When the pH of the aqueous system after the addition of the above-mentioned initial treatment agent is less than the above range (less than 6.0), inconvenience such as acid corrosion is likely to occur, and the rate at which corrosion progresses on the surface of the metal member (corrosion rate ) May accelerate.
On the other hand, when the pH of the aqueous system after adding the above-mentioned initial treatment agent exceeds the above range (exceeds 8.0), tartaric acid that has become an anion binds to calcium ions present in water and Therefore, an anticorrosion coating mainly composed of a sparingly soluble calcium salt may not be easily formed on the surface of the metal member.

The pH in the present specification refers to a value determined based on the operation of the glass electrode method according to the method described in JIS Z8802:2011.
In addition, pH standard solutions of phthalates, neutral phosphates, and carbonates can be used for pH calibration.

In the present invention, the pH of the aqueous system after the addition of the initial treatment agent specified in the present invention can be within a specific range (pH 6.0 to 8.0).
However, even if the pH of the aqueous system after addition of the initial treatment agent specified in the present invention is outside the specific range (pH 6.0 to 8.0), sulfuric acid, sodium hydroxide, potassium hydroxide, etc. It suffices that the pH of the aqueous system can be adjusted to a specific range (pH 6.0 to 8.0) by using the pH adjusting agent of.

The water quality of the water system applied to the initial treatment step of the corrosion prevention method of the present invention, that is, the water quality of the water system before the addition of the initial treatment agent affects the pH of the water system after the addition of the initial treatment agent to prevent corrosion. The effect may not be exhibited properly.
In the present invention, from the viewpoint of facilitating adjustment of the pH of the aqueous system after addition of the initial treatment agent specified in the present invention to a specific range (pH 6.0 to 8.0), the initial stage of the corrosion prevention method of the present invention The water quality of the water system applied to the treatment step preferably has the following parameters.

The pH of the water quality is preferably 6.0 to 8.0, more preferably 6.0 to 7.5, still more preferably 6.5 to 7.5.
The calcium hardness of the water quality is preferably 30 to 150 mgCaCO ₃ /L, more preferably 30 to 120 mgCaCO ₃ /L, and further preferably 30 to 100 mgCaCO ₃ /L.
The water-based ionic silica is preferably 5 to 35 mg SiO ₂ /L, more preferably 10 to 30 mg SiO ₂ /L, further preferably 15 to 25 mg SiO ₂ /L.

In the present invention, the initial treatment step for forming the anticorrosive film on the surface of the metal member is preferably carried out in an aqueous system for 20 to 48 hours, more preferably 24 to 36 hours, in a state where no heat load is applied to the aqueous system.
As a result, the corrosion weight loss after the initial treatment process and the normal operation process can be reduced. Then, the anticorrosion coating is easily formed on the surface of the metal member, and the excellent corrosion prevention effect is easily obtained.

As described above, it is preferable that the initial treatment step in the present invention does not apply a heat load to the water system. Specifically, the temperature of the aqueous system in the initial treatment step without applying a heat load is preferably 10 to 40°C, more preferably 15 to 35°C, and further preferably 20 to 30°C.
Here, the "state not to apply thermal load in an aqueous" is that the object to be cooled in a state before entering the normal operation process points to states that are introduced into the circulating cooling water system.
When the temperature of the water system in the initial treatment step is within the above range, evaporation of the water system can be minimized, and it becomes easy to keep the concentration of the initial treatment agent in the water system constant.

Further, as described above, it is preferable that the initial treatment step in the present invention is circulated in the water system for 20 to 48 hours. In the process of the initial treatment step, it is preferable that the concentration of the initial treatment agent in the water system is kept constant from the viewpoint of forming the anticorrosion coating evenly on the surface of the metal member.

In the process of the initial treatment step, if the concentration of the initial treatment agent in the water system is lower than the initial concentration, the concentration of the initial treatment agent in the water system is 20 to 150 mg/L in terms of tartaric acid, preferably 30 to It is preferable to add an initial treatment agent so that the amount becomes 100 mg/L.
Here, the reason why the concentration of the initial treatment agent in the water system becomes lower than the initial concentration is considered to be exhaustion in the system and adsorption to the corrosion product.

On the other hand, in the process of the initial treatment step, if the concentration of the initial treatment agent in the water system is higher than the initial concentration, the concentration of the initial treatment agent in the water system is 20 to 150 mg/L in terms of tartaric acid, preferably It is preferable to add an aqueous system so as to be 30 to 100 mg/L.

(Normal operation process)
The corrosion prevention method of the present invention may include a normal operation step for holding the anticorrosion coating formed in the initial treatment step after the above-mentioned initial treatment step.
Here, the "normal operation step" refers to a step performed for the purpose of holding the anticorrosion coating formed on the surface of the metal member in the initial treatment step so as not to come off.

In order to retain the anticorrosion coating formed in the initial treatment step, it is preferable to add a retention treatment agent to the water system after the initial treatment step.
As a result, the retention treatment agent is adsorbed on the surface of the anticorrosion coating formed on the surface of the metal member, which makes it difficult for the anticorrosion coating to peel off and the corrosion prevention effect can be easily maintained. Further, it becomes easy to obtain the scale adhesion preventing effect of preventing the insoluble component from adhering to the surface of the anticorrosion coating.

In the normal operation step of the present invention, the retention treatment agent is preferably added to the aqueous system after the initial treatment step in an amount of 20 to 100 mg/L, more preferably 30 to 80 mg/L, and further preferably 50 to 80 mg/L. Added.
The addition amount of the holding treatment agent is in the above range, the holding treatment agent is adsorbed on the surface of the anticorrosion coating formed on the surface of the metal member, making the anticorrosion coating difficult to peel off, and the corrosion prevention effect is easily maintained. .. Further, it becomes easy to obtain the scale adhesion preventing effect of preventing the insoluble component from adhering to the surface of the anticorrosion coating.

The amount of the initial treatment agent containing at least one selected from tartaric acid and tartrate contained in the aqueous system in the normal operation step is selected from tartaric acid and tartrate contained in the aqueous system in the above-mentioned initial treatment step. There is no particular limitation as long as it is less than the amount of the initial treatment agent containing at least one kind.
Even if a part of the anticorrosion coating is peeled off from the surface of the metal member due to the presence of the initial treatment agent in the water system of the normal operation process, the anticorrosion coating is formed again on the surface of the peeled metal member. Can also

The holding treatment agent is not particularly limited as long as it is adsorbed on the surface of the anticorrosion coating, makes the anticorrosion coating hard to peel off, and easily maintains the corrosion prevention effect.
As the retention treatment agent, for example, a polymer compound such as a copolymer of acrylic acid and maleic acid, a copolymer of isobutylene and maleic acid, a maleic acid polymer, a copolymer of acrylic acid/AMPS; zinc sulfate, chloride Zinc compounds such as zinc; phosphates such as inorganic phosphate and organic phosphate; and the like. These retention treatment agents may be used alone or in combination of two or more kinds. AMPS is 2-acrylamido-2-methylpropanesulfonic acid.

In the normal operation process, the water quality of the water system applied when no phosphate is used preferably has the following parameters.
The pH of water quality is preferably 8.0 to 9.2, more preferably 8.5 to 9.0, and still more preferably 8.6 to 9.0.
The calcium hardness of the water quality is preferably 350 to 650 mgCaCO ₃ /L, more preferably 400 to 600 mgCaCO ₃ /L, and further preferably 450 to 550 mgCaCO ₃ /L. When the content is within the range, the anticorrosion coating is hardly peeled off, and the corrosion prevention effect is easily maintained.
In addition, in order to adjust the calcium hardness of the water quality to the above range, a calcium source may be added to the water system. Examples of the calcium source include calcium chloride.
Acid consumption of water is preferably 130~170mgCaCO ₃ / L, more preferably 140~160mgCaCO ₃ / L, more preferably 145~155mgCaCO ₃ / L.

In addition, in the process of the normal operation process, the concentration of the retention treatment agent in the water system is kept constant from the viewpoint of facilitating suitably exhibiting the effect of retaining the anticorrosion coating formed on the surface of the metal member so as not to peel off. It is preferable.

In the process of the above-mentioned normal operation process, if the concentration of the retention treatment agent in the water system is lower than the initial concentration, the retention treatment agent is adjusted so that the concentration of the retention treatment agent in the water system becomes 20 to 100 mg/L. It is preferable to add.
Here, the reason why the concentration of the retention treatment agent in the water system becomes lower than the initial concentration is considered to be exhaustion in the system and adsorption to the corrosion product.

On the other hand, in the process of the above-mentioned normal operation process, if the concentration of the retention treatment agent in the water system is higher than the initial concentration, the concentration of the retention treatment agent in the water system is adjusted to 20 to 100 mg/L. It is preferable to add.

The present invention will be described more specifically by performing the following evaluation tests A to C, but the present invention is not limited to these examples.

(1) Evaluation test A for corrosion prevention effect
A test for evaluating the corrosion prevention effect on the surface of the metal member was conducted by the method described below, using the solutions for the initial treatment process prepared in Examples A1 to A3 and Comparative Examples A1 to A9 as targets.

(Example A1)
<Preparation of test pieces>
An iron sensor (material: SS400, 10φ×30 mm iron bar, surface area: 10.3 cm ² ) was degreased with toluene and dried to obtain a test piece.

<Preparation of solution for initial treatment step>
As raw water, water in Nogi-cho, Shimotsuga-gun, Tochigi (hereinafter referred to as "Nogi-cho water") was used.
At this time, the water quality of Nogi-machi water was pH: 7.0, calcium hardness: 40 mg CaCO ₃ /L, and ionic silica: 20 mg SiO ₂ /L.
Nogi-cho water was placed in a 1 L beaker, and sodium tartrate was added to Nogi-cho water as an initial treatment agent so as to be 30 mg/L. This beaker was moved to a constant temperature bath set at 30° C. and heated to prepare a solution for the initial treatment step of Example A1.

<Measurement of pH of solution for initial treatment step>
Here, an appropriate amount of the prepared solution for the initial treatment step was sampled, and the pH of the solution for the initial treatment step of Example A1 (Examples) was measured based on the operation of the glass electrode method according to the method described in JIS Z8802:2011. The pH of the aqueous system after addition of the initial treatment agent A1) was measured and found to be pH 7.3.
Note that pH standard solutions of phthalate, neutral phosphate, and carbonate were used for pH calibration.

<Preparation of corrosion accelerator>
As the corrosion treatment agent, a 10 mass% chloride ion solution (sodium chloride solution) and a 10 mass% sulfate ion solution (sodium sulfate solution) were used.
Put Nogimachi water in a 1L beaker, and add 10% by mass chloride ion solution (sodium chloride solution) and 10% by mass sulfuric acid ion solution (sodium sulfate solution) to Nogimachi water at 80 mg/L. Then, a corrosion acceleration solution was prepared.

<Initial processing step>
The test piece was immersed in the solution for the initial treatment step of Example A1 prepared above. Then, the stirring of the solution for the initial treatment step was started by rotating the stirrer at 300 rpm, the stirring was continued at room temperature for 24 hours, and then the stirring was terminated.
From the start to the end of the stirring of the solution for the initial treatment step, the rate at which the corrosion of the test piece progresses (corrosion rate) with the use of a corrosion meter ("K-600" manufactured by Toho Giken Co., Ltd.) Measured. The measurement result is shown in FIG.
The term "corrosion rate" as used herein refers to the unit area of the test piece and the weight reduction amount (mdd: mg/dm ² ·day) of the test piece due to corrosion per unit time.

<Corrosion process>
After completion of stirring in the initial treatment step, the solution for the initial treatment step was switched to the corrosion acceleration solution, and the test piece was immersed in the corrosion acceleration solution in the same manner as in the initial treatment step. Then, the stirring of the corrosion accelerating liquid was started by rotating the stirrer at 300 rpm, the stirring was continued for 48 hours, and then the stirring was ended.
From the start to the end of the stirring of the corrosion accelerating liquid, the rate at which the corrosion of the test piece progresses using a corrosion meter ("K-600" manufactured by Toho Giken Co., Ltd.) in the same manner as the initial treatment step ( The corrosion rate) was measured over time. The measurement result is shown in FIG.

(Example A2)
Corrosion prevention of Example A2 in the same manner as in Example A1 except that sodium tartarate was added to Nogi-cho water at 50 mg/L in the preparation of the solution for the initial treatment step of Example A1. A test was conducted to evaluate the effect.
When the pH of the solution for the initial treatment step of Example A2 (the pH of the aqueous system after the addition of the initial treatment agent of Example A2) was measured, it was pH 6.9.

(Example A3)
Corrosion prevention of Example A3 in the same manner as in Example A1 except that sodium tartarate was added to Nogi-cho water at 100 mg/L in the preparation of the solution for the initial treatment step of Example A1. A test was conducted to evaluate the effect.
When the pH of the solution for the initial treatment step of Example A3 (the pH of the aqueous system after the addition of the initial treatment agent of Example A3) was measured, it was pH 7.0.

(Comparative Example A1)
Corrosion inhibition of Comparative Example A1 in the same manner as in Example A1 except that in the preparation of the solution for the initial treatment step of Example A1, sodium tartrate was added to Nogi-cho water as an initial treatment agent at 300 mg/L. A test was conducted to evaluate the effect.
When the pH of the solution for the initial treatment step of Comparative Example A1 (pH of the aqueous system after addition of the initial treatment agent of Comparative Example A1) was measured, it was pH 7.1.

(Comparative Example A2)
In the preparation of the solution for the initial treatment step of Example A1, except that tartaric acid was added to Nogi-cho water so as to be 100 mg/L as the initial treatment agent, the corrosion prevention effect of Comparative Example A2 was performed in the same manner as in Example A1. The test which evaluated is carried out.
The pH of the solution for the initial treatment step of Comparative Example A2 (pH of the aqueous system after adding the initial treatment agent of Comparative Example A2) was pH 5.0.

(Comparative Example A3)
Corrosion prevention of Comparative Example A3 in the same manner as in Example 1 except that gluconic acid was added to Nogi-cho water so as to be 50 mg/L in the preparation of the solution for the initial treatment step of Example A1. A test was conducted to evaluate the effect.
When the pH of the solution for the initial treatment step of Comparative Example A3 (pH of the aqueous system after addition of the initial treatment agent of Comparative Example A3) was measured, it was pH 7.3.

(Comparative Example A4)
Corrosion inhibition of Comparative Example A4 in the same manner as in Example A1 except that citric acid was added to Nogi-cho water at 50 mg/L in the preparation of the solution for the initial treatment step of Example A1. A test was conducted to evaluate the effect.
The pH of the solution for the initial treatment step of Comparative Example A4 (pH of the aqueous system after the addition of the initial treatment agent of Comparative Example A4) was measured and found to be pH 6.1.

(Comparative Example A5)
In the preparation of the solution for the initial treatment step of Example A1, the corrosion inhibiting effect of Comparative Example A5 was performed in the same manner as in Example A1 except that acetic acid was added to Nogi-cho water so as to be 50 mg/L. The test which evaluated is carried out.
When the pH of the solution for the initial treatment step of Comparative Example A5 (pH of the aqueous system after addition of the initial treatment agent of Comparative Example A5) was measured, it was pH 6.1.

(Comparative Example A6)
In the preparation of the solution for the initial treatment step of Example A1, the corrosion of Comparative Example A6 was performed in the same manner as in Example A1 except that ethylenediaminetetraacetic acid was added to Nogi-cho water so as to be 50 mg/L. A test was conducted to evaluate the preventive effect.
When the pH of the solution for the initial treatment step of Comparative Example A6 (pH of the aqueous system after addition of the initial treatment agent of Comparative Example A6) was measured, it was pH 6.7.

(Comparative Example A7)
Corrosion prevention of Comparative Example A7 in the same manner as in Example A1 except that maleic acid was added to Nogi-cho water at 50 mg/L in the preparation of the solution for the initial treatment step of Example A1. A test was conducted to evaluate the effect.
When the pH of the solution for the initial treatment step of Comparative Example A7 (the pH of the aqueous system after the addition of the initial treatment agent of Comparative Example A7) was measured, it was pH 6.2.

(Comparative Example A8)
Corrosion prevention of Comparative Example A8 in the same manner as in Example A1 except that succinic acid was added to Nogi-cho water at 50 mg/L in the preparation of the solution for the initial treatment step of Example A1. A test was conducted to evaluate the effect.
The pH of the solution for the initial treatment step of Comparative Example A8 (pH of the aqueous system after the addition of the initial treatment agent of Comparative Example A8) was measured and found to be pH 6.1.

(Comparative Example A9)
In the preparation of the solution for the initial treatment step of Example A1, 100 mg PO ₄ /L of phosphate hexametaphosphoric acid and zinc chloride of zinc compound were added to Nogi-cho water as initial treatment agents so as to be 20 mg Zn/L. A test for evaluating the corrosion prevention effect of Comparative Example A9 was performed in the same manner as in Example A1 except for the above.
When the pH of the solution for the initial treatment step of Comparative Example A9 (pH of the aqueous system after the addition of the initial treatment agent of Comparative Example A9) was measured, it was pH 6.5.

The type of the initial treatment agent used in the preparation of the solutions for the initial treatment step of Examples A1 to A3 and Comparative Examples A1 to A9, the addition amount (mg/L), and the pH of the solution for the initial treatment step (initial Table 1 shows the measurement results of the pH of the aqueous system after the treatment agent was added.

In addition, in the initial treatment process and the corrosion treatment process of Examples A1 to A3 and Comparative Examples A1 to A9 described above, changes in corrosion rate (mdd: mg/dm ² ·day) measured with time are shown in FIG. 1. ..

(Summary of the results of evaluation test A)
From the results of the evaluation test A relating to the corrosion prevention effect shown in FIG. 1, the following can be understood.
The corrosion rate in Comparative Example A1 was attributed to the fact that the initial treatment agent specified in the present invention was added to the water system in an amount exceeding a specific amount (20 to 150 mg/L, especially 30 to 100 mg/L in terms of tartaric acid). It was higher than the corrosion rate of A3.
From this, it was found that Comparative Example A1 could not satisfactorily form the anticorrosion coating on the surface of the metal member, and the corrosion preventing effect could not be sufficiently obtained.

The corrosion rate in Comparative Example A2 is due to the fact that the pH of the aqueous system after addition of the initial treatment agent specified in the present invention was set to be less than the specific range (pH 6.0 to 8.0), and the corrosion rate in Examples A1 to A3 It was higher than the corrosion rate.
From this, it was found that Comparative Example A2 could not satisfactorily form the anticorrosion coating on the surface of the metal member, and the corrosion preventing effect could not be sufficiently obtained.

Moreover, the corrosion rates in Comparative Examples A3 to A8 were higher than those in Examples A1 to A3 because the initial treatment agent specified in the present invention was not used.
From this, it was found that Comparative Examples A3 to A8 were not able to satisfactorily form the anticorrosion coating on the surface of the metal member, and the corrosion preventing effect was not sufficiently obtained.

On the other hand, the corrosion rate in Examples A1 to A3 was determined by adding a specific amount (20 to 150 mg/L, especially 30 to 100 mg/L in terms of tartaric acid) of the initial treatment agent specified in the present invention to the initial treatment. Due to the fact that the pH of the aqueous system after addition of the agent was within the specified range (pH 6.0 to 8.0), it was as low as Comparative Example A9 using phosphate and zinc compound as the initial treatment agent. Met.
From this, it was found that in Examples A1 to A3, the anticorrosion film could be satisfactorily formed on the surface of the metal member, and an excellent corrosion prevention effect could be obtained.

(2) Evaluation test B for corrosion prevention effect
Using the solution for the initial treatment step prepared in Example A2 and Comparative Example A9 and the blank solution used in the above-described evaluation test A on the corrosion prevention effect, the corrosion prevention effect on the surface of the metal member was evaluated by the following method. The test was done.

(Example B1)
<Preparation of test pieces>
An SPCC test piece (size: 30 mm×50 mm×1 mm) was subjected to etching treatment with a 20 mass% nitric acid solution and a 10 mass% sulfuric acid solution and dried to obtain a test piece.
The weight W ₁ of the test piece before the corrosion test B was measured in advance.

<Initial processing step>
While the test piece was immersed in the solution for the initial treatment step of Example A2 and heated to 30° C., the rotation of the test piece was started at 150 rpm using a rotary corrosion tester (manufactured by Shinwa Kako Co., Ltd.). After continuing the rotation for 24 hours, the rotation was stopped and the first initial treatment step was completed.

<Blank process>
After the completion of the first initial treatment step, the solution for the initial treatment step of Example A2 was switched to a blank solution, and the test piece was immersed in the blank solution and heated to 30° C., and then rotational corrosion was performed as in the initial treatment step. Using the test device, the rotation of the test piece was started at 150 rpm, this rotation was continued for 24 hours, then the rotation was stopped, and the first blank treatment step was completed.
Here, the "blank solution" refers to the same as Nogimachi water used as raw water in the preparation of the initial treatment step solution of Example A1.

<Calculation of corrosion weight loss _{W A>}
After the first blanking step is completed, pulling the test piece was dried weight W ₂ of the test piece was measured to calculate the corrosion weight loss W _A of the first test piece by the following equation 1.
The weight W ₁ of the test piece before the evaluation test B was measured in advance.
(Equation 1): corrosion weight loss _{W A (mg) = | W} 2 -W 1 |

Subsequently, the second initial treatment step was performed for 24 hours in the same manner as the first time, and then the second blank treatment step was performed for 24 hours. After completion of the second blanking step, the corrosion weight loss W _A of the second test piece was calculated by the equation 1 in the same manner as the first.
Further, similarly to the first time, the third initial treatment step was performed for 24 hours, and then the third blank treatment step was performed for 24 hours. After completion of the third blanking step, the corrosion weight loss W _A of the third test piece was calculated by the equation 1 in the same manner as the first.

(Comparative Example B1)
In the initial treatment step of Example B1, the corrosion prevention effect of Comparative Example B1 was obtained in the same manner as in Example B1 except that the solution for the initial treatment step of Example A2 was changed to the solution for the initial treatment step of Comparative Example A9. An evaluation test was conducted.

(Comparative Example B2)
In the initial treatment step of Example B1, a test for evaluating the corrosion prevention effect of Comparative Example B2 was performed in the same manner as in Example B1 except that the solution for the initial treatment step of Example A2 was changed to a blank solution.

In Example B1 and Comparative Examples B1 and B2 described above, the initial treatment step and the blank treatment step were set as one set, and this one set was repeated three times, and changes in corrosion weight loss measured over time are shown in FIG.

(Summary of evaluation test B results)
From the results of the evaluation test B relating to the corrosion prevention effect shown in FIG. 2, the following can be understood.
The corrosion weight loss in Comparative Example B2 was large due to the fact that no initial treatment agent was used.
From this, it was found that Comparative Example B2 could not form an anticorrosion film on the surface of the metal member, and could not obtain the corrosion prevention effect.

On the other hand, in the corrosion weight loss in Example B1, a specific amount (20 to 150 mg/L, especially 30 to 100 mg/L in terms of tartaric acid) of the initial treatment agent specified in the present invention was added to the aqueous system, and the initial treatment agent was added. Due to the fact that the pH of the aqueous system after addition was in the specified range (pH 6.0 to 8.0), it was as low as in Comparative Example B1 using the phosphate and zinc compound as the initial treatment agent. It was
From this, it was found that Example B1 was able to satisfactorily form the anticorrosion coating on the surface of the metal member, and that an excellent corrosion prevention effect was obtained.

(3) Evaluation test C for corrosion prevention effect
Using the heat transfer surface evaluation test apparatus shown in FIG. 3, a test for evaluating the corrosion prevention effect on the surface of the metal member (specifically, the iron evaluation tube 2) was performed by the method described below.

<Heat transfer surface evaluation test equipment>
The heat transfer surface evaluation test device shown in FIG. 3 adjusts the flow rate of the test water in the test water tank (100 L capacity) 1 with the circulating water pump P ₁ and supplies the test water to the test tube 3 through the circulation line L _1. The test water is circulated in the test water tank 1 through the circulation return line L ₂ .
The evaluation tube 2 made of iron is inserted into the test tube 3, and the evaluation tube 2 made of iron can be immersed in the test water when the apparatus is started.
A heater (thermocouple) 4 is inserted in the iron evaluation tube 2, and the iron evaluation tube 2 can be heated by the heater (thermocouple) 4 when the apparatus is activated.
A flow rate adjusting valve V is provided in the circulation return line L ₂ .
The test water in the make-up water tank (300 L capacity) 5 can be replenished to the test water tank 1 through the make-up water line L ₃ as needed.
When the test water in the make-up water tank 5 is replenished to the test water tank 1, the flow speed of the replenished test water is adjusted by the circulating water pump P ₂ .
The test water tank 1 is provided with an overflow line L ₄ capable of discharging the test water to the outside when the test water exceeds a predetermined amount.

(Test 1)
<Initial processing step>
Put Nogi-cho water in a test water tank (100 L capacity), add tartaric acid as an initial treatment agent to the Nogi-cho water at 50 mg/L, and heat the water system to 30° C. 1 was prepared.
In addition, "Nogimachi water" here refers to the same water as Nogimachi water used as raw water in the preparation of the initial treatment step solution of Example A1.
At this time, the water quality of the test water 1 was pH: 7.0, calcium hardness: 40 mgCaCO ₃ /L, ionic silica: 20 mgSiO ₂ /L, acid consumption: 40 mgCaCO ₃ /L.
The heater (thermocouple) 4 is driven to set the electric power to 2 kW and the tube temperature to 80°C to apply a heat load to the water system, and the flow rate of the test water 1 in the test water tank (100 L capacity) 1 is circulated. P ₁ is adjusted to 0.5 m/s, the test water 1 is supplied to the test tube 3 through the circulation line L ₁ , and the test water 1 is returned to the test water tank 1 through the circulation return line L _2. It went for 24 hours.
Note that the actual temperature of the water system was controlled to be 30° C. even when a heat load was applied to the water system in the initial treatment step.

<Normal operation process>
After the completion of the aqueous circulation in the initial treatment step, 50 mg/L of a copolymer of acrylic acid and maleic acid as a retention treatment agent was added to test water 1 in a test water tank (100 L volume) 1, and zinc chloride as a zinc compound. Is added so as to be 2 mg/L, and further, 10 mass% calcium chloride solution is added so that the calcium hardness is 500 mgCaCO ₃ /L, and 5 mass% weight is added so that the acid consumption is 150 mgCaCO ₃ /L. A sodium carbonate solution was added and the aqueous system was heated to 30° C. to prepare test water 2 for the normal operation process.
At this time, the water quality of the test water 2 was pH: 8.6, calcium hardness: 500 mgCaCO ₃ /L, and acid consumption: 150 mgCaCO ₃ /L.
The heater (thermocouple) 4 is driven to set the electric power to 2 kW and the tube meat temperature to 80° C. to apply a heat load to the water system, and the flow rate of the test water 2 in the test water tank (100 L capacity) 1 is circulated. P ₁ is adjusted to 0.5 m/s, the test water 2 is supplied to the test tube 3 through the circulation line L ₁ , and the test water 2 is returned to the test water tank 1 through the circulation return line L _2. It went for 48 hours.
Note that the actual temperature of the water system was controlled to be 30° C. even when a heat load was applied to the water system in the normal operation process.

<Calculation of corrosion weight loss _{W B>}
After the usual aqueous circulation completion of operation step, raising the iron evaluation tube 2, dried and weighed W ₄ Evaluation tube 2, and the corrosion weight loss W _B rating tube 2 Test 1 was calculated by the following equation 2.
The weight W ₃ of the evaluation tube 2 before the evaluation test C was measured in advance.
(Formula 2): Corrosion weight loss W _B (mg)=|W ₄ −W ₃ |

(Test 2)
In the initial treatment step of the test 1, the heater (thermocouple) 4 was not driven, that is, the heat load was not applied to the water system, and the series of water system circulation was performed for 24 hours. A test was conducted to evaluate the corrosion prevention effect.
Note that the actual temperature of the water system was controlled to be 30° C. even when no heat load was applied to the water system in the initial treatment step.

Table 2 shows the measurement results of the corrosion weight loss after the initial treatment process and the normal operation process of Test 1 and Test 2 described above.

(Summary of evaluation test C results)
The following can be seen from the results of the evaluation test C on the corrosion prevention effect shown in Table 2.
The corrosion weight loss in Test 1 was large due to the fact that a heat load was applied to the water system and a series of water system circulation was performed in the initial treatment step.
On the other hand, the corrosion weight loss in Test 2 was small due to the fact that a series of water system circulation was performed without applying a heat load to the water system in the initial treatment step.
From this, it was found that the test 2 can form the anticorrosion film on the surface of the metal member better than the test 1, and the excellent corrosion prevention effect can be obtained.

1: Test water tank 2: Evaluation tube 3: Test tube 4: Heater 5: Make-up water tank L1: Circulation line L2: Circulation return line L3: Make-up water line L4: Overflow line P1: Circulation water pump P2: Circulation water pump V : Flow control valve

Claims (8)

A method for preventing corrosion of a circulating cooling water system, which comprises an initial treatment step of forming an anticorrosion coating on a surface of a metallic member of the circulating water system when the circulating cooling water system is started,
In the initial step, the aqueous, the circulating cooling water for the initial treatment agent containing at least one selected from tartaric acid and tartrate was added at a 20~150mg / L tartaric acid terms, the circulating A method for preventing corrosion of a circulating cooling water system, wherein the temperature of the water system is set to 40° C. or lower and the pH of the water system is set to 6.0 to 8.0 in a state where a heat load is not applied after the initial treatment agent for cooling water is added. The method for preventing corrosion of a circulating cooling water system according to claim 1 , wherein the initial treatment agent for circulating cooling water comprises at least one selected from tartaric acid and a tartrate salt. The method for preventing corrosion of a circulating cooling water system according to claim 1 or 2 , wherein in the initial treatment step, the water system is circulated for 20 to 48 hours without applying a heat load to the water system. In the initial treatment step, an initial treatment agent for circulating cooling water containing at least one selected from tartaric acid and a tartrate salt is added to the aqueous system so as to be 30 to 100 mg/L in terms of tartaric acid, and the circulation cooling is performed. The method for preventing corrosion of a circulating cooling water system according to any one of claims 1 to 4 , wherein the pH of the water system after the initial treatment agent for water is added is 6.0 to 8.0. In the initial step, the a temperature of 10 to 40 ° C. aqueous, is 20-48 hours water circulation, corrosion prevention method of the circulating cooling water system as claimed in any one of claims 1-4. Wherein after the initial treatment step, the initial processing step includes a normal operation process for holding the anticorrosive film formed of corrosion prevention method of the circulating cooling water system as claimed in any one of claims 1 to 5. In the normal operation step, in the aqueous system after the initial treatment step, a copolymer of acrylic acid and maleic acid, a copolymer of isobutylene and maleic acid, a maleic acid polymer, acrylic acid/2-acrylamido-2-methyl The circulation cooling according to claim 6 , wherein a retention treatment agent for retaining the anticorrosion coating formed in the initial treatment step is added, which contains at least one selected from copolymerization of propanesulfonic acid, zinc compound and phosphate. Water-based corrosion prevention method. The method for preventing corrosion of a circulating cooling water system according to claim 6 or 7 , wherein the retention treatment agent is added to the water system after the initial treatment process so as to be 20 to 100 mg/L in the normal operation process.