KR102524270B1 - Anti-corrosion method for metal members of the cooling water system - Google Patents

Abstract

In the present invention, step (1) of adding at least one compound (A) selected from tartaric acid and tartarate to a cooling water system and bringing it into contact with a metal member; It relates to a method for preventing corrosion of a metal member of a cooling water system comprising a step (2) of adding one or more types of compounds (B) selected from zinc salts and bringing them into contact with the metal member.

Description

Anti-corrosion method for metal members of the cooling water system

The present invention relates to a method for preventing corrosion of a metal member of a cooling water system by forming an anticorrosive film on the surface of a metal member constituting a portion in contact with cooling water in the cooling water system.

BACKGROUND ART Water-cooled heat exchangers are used to indirectly cool various fluids in air-conditioning facilities such as buildings and local facilities and plants. Metals such as carbon steel and stainless steel are generally used for various members such as heat exchangers in cooling water systems and piping around them.

These metal members are easily corroded by dissolved oxygen in the water when continuously or intermittently contacted with the cooling water. If wall-thinning or pitting corrosion occurs in metal members such as piping due to corrosion, it may cause damage to equipment or contamination of products in plants. may cause a serious accident.

As a method of preventing such a metal member from being corroded, for example, in Patent Literature 1, a phosphoric acid-based and zinc-based anticorrosive agent is used in the basic treatment at the start of the cooling water system, thereby forming a strong anticorrosive film on the surface of the metal member. It is proposed to form

Patent Document 1: Japanese Unexamined Patent Publication No. 2011-202243

However, in recent years, there has been a demand for reduction of phosphorus or the like content in wastewater due to heightened interest in environmental preservation and strengthened regulations on wastewater. In a plant or the like without a wastewater treatment facility, it was difficult to respond to such a demand, and in some cases, the use of phosphoric acid-based and zinc-based anticorrosives had to be stopped.

In addition, since the phosphoric acid-based anticorrosive agent forms an anticorrosive film by precipitation, a long time of about 4 days was required for the basic treatment. For this reason, shortening of the basic treatment period has also been desired.

Therefore, there has been a demand for an anticorrosive method capable of obtaining excellent anticorrosive effect in a shorter time without using a phosphoric acid anticorrosive agent.

The present invention has been made to solve the above problems, and is a metal member of a cooling water system that can impart an excellent anticorrosive effect to the surface of the metal member of the cooling water system with a shorter treatment time without using a phosphoric acid-based anticorrosive agent. Its purpose is to provide a method of

The present invention has been made based on the use of a tartaric acid-based compound and further application of a zinc-based compound to bring about a good anticorrosive effect to a metal member of a cooling water system.

That is, the present invention provides the following [1] to [8].

[1] Step (1) of adding at least one compound (A) selected from tartaric acid and tartrate to a cooling water system and bringing it into contact with a metal member, and after the step (1), zinc into the cooling water system and a step (2) of adding at least one compound (B) selected from zinc salts and bringing them into contact with the metal member.

[2] In the step (1), the metal member of the cooling water system described in [1] above, in which the compound (A) is added at a concentration of 30 to 100 mg/L in terms of tartaric acid into the cooling water system. method method.

[3] The method for corrosion protection of metal members in a cooling water system according to [1] or [2] above, wherein the pH of the cooling water system in step (1) is 6.0 to 8.0.

[4] In the step (1), the metal member of the cooling water system according to any one of [1] to [3], wherein the contact time between the metal member and the compound (A) is 20 to 30 hours. method method.

[5] In the step (2), it is described in any one of [1] to [4] above that the compound (B) is added at a concentration of 1 to 50 mg/L in terms of zinc into the cooling water system. Anticorrosive method of metal members of cooling water system in

[6] In the step (2), the metal member of the cooling water system according to any one of [1] to [5], wherein the contact time between the metal member and the compound (B) is 20 to 30 hours. method method.

[7] The method for corrosion protection of metal members of a cooling water system according to any one of [1] to [6] above, wherein the cooling water system is a circulating cooling water system.

[8] The method of corrosion protection of a metal member of a cooling water system according to any one of [1] to [7], wherein the steps (1) and (2) are the basic treatment of the cooling water system.

According to the present invention, an excellent anticorrosive effect can be imparted to the surface of the metal member of the cooling water system in a shorter treatment time without using a phosphoric acid-based anticorrosive agent. Therefore, the anticorrosive method of the present invention can contribute to maintaining the cooling capacity of the cooling water system while responding to environmental preservation.

1 is a schematic diagram showing an outline of a cooling water system heat exchanger testing apparatus in an embodiment.

Below, this invention is demonstrated in detail.

An anticorrosive method for a metal member of a cooling water system of the present invention is step (1) of adding at least one compound (A) selected from tartaric acid and tartaric acid into the cooling water system and bringing it into contact with the metal member and a step (2) of adding one or more compounds (B) selected from zinc and zinc salts into the cooling water system to contact the metal member after the step (1).

Thus, in the anticorrosive method of the present invention, the zinc-based compound (B) is used after using the tartaric acid-based compound (A) as an anticorrosive agent. The tartaric acid-based compound has an effect of suppressing the anode reaction on the surface of the metal member. Further, the zinc-based compound has an effect of suppressing a cathode reaction on the surface of the metal member. According to the anticorrosive method of the present invention, excellent anticorrosive effect can be imparted to the metal member by synergistic effect of both.

(cooling water system)

The cooling water system in the present invention refers to a system through which cooling water used for operation of a heat exchanger or the like is passed through in an air conditioning facility such as a building or a regional facility, a plant, or the like.

The cooling water system may be of a one-time type, an open circulation type, or a closed circulation type. The present invention can exhibit excellent anticorrosive effects in a circulating cooling water system, particularly in an open circulation cooling water system.

The present invention can be applied to any state of the cooling water system, such as during startup or normal operation, but is particularly preferably applied to basic processing during startup such as initial startup or operation resumption.

When starting the cooling water system, since there are many corrosion products in the system and the anticorrosive agent is easily consumed, the anticorrosive agent is usually added at a concentration of 3 to 10 times that of normal operation to obtain sufficient anticorrosive effect is done Such anticorrosion treatment at the time of activation of the cooling water system is referred to as a basic treatment, and is sometimes referred to as an initial treatment.

The anticorrosive method of the present invention can exhibit excellent anticorrosive effect in such basic treatment.

If the cooling water system is of the water quality of a general cooling water system, the anticorrosion effect by the anticorrosive method of the present invention is sufficiently exhibited. Preferred pH is 6.0 to 8.0, more preferably 6.0 to 7.5, still more preferably 6.5 to 7.5.

The calcium hardness is preferably 30 to 150 mgCaCO ₃ /L, more preferably 30 to 120 mgCaCO ₃ /L, and still more preferably 30 to 100 mgCaCO ₃ /L.

A preferred ionic silica concentration is 5 to 35 mgSiO ₂ /L, more preferably 10 to 30 mgSiO ₂ /L, and even more preferably 15 to 25 mgSiO ₂ /L.

(Metal member)

The metal member is a metal member constituting a portion in contact with the cooling water of the cooling water system. Examples of the metal member include metal parts in heat exchangers, refrigerators, various pipes and valves, and the like.

As the metal to which the present invention is applied, iron-based is preferable, and excellent anticorrosion effect is obtained in, for example, carbon steel pipes for boilers and heat exchangers (STB steel pipes).

(Process (1))

In the anticorrosion method of the present invention, first, at least one compound (A) selected from tartaric acid and tartaric acid is added to the cooling water system and brought into contact with the metal member.

Compound (A) is a tartaric acid-based compound, that is, a compound selected from tartaric acid and tartaric acid salts.

It is thought that the tartaric acid-based compound imparts an anticorrosive effect to the metal member by adsorbing the hydroxy group in the molecule to the surface of the metal member to form an adsorption film. Such an adsorption film has a faster film formation rate than a precipitation film, which is an anticorrosive film using a phosphoric acid-based anticorrosive agent, and can shorten the anticorrosive treatment time.

Although the details of the mechanism by which the anticorrosive effect is obtained by the compound (A) are not clear, it is estimated as follows.

Tartaric acid ions generated from compound (A) and calcium ions present in the cooling water combine to form an adsorption film mainly composed of calcium salt, which is sparingly soluble in water, on the surface of the metal member. Compound (A) can also form an adsorbed film by iron (II) stannate by reacting with the iron component of the metal member.

By this adsorption film (corrosive film), the direct contact of corrosion factors contained in the cooling water system, such as dissolved oxygen, chloride ions, and sulfate ions, with the metal member is inhibited, and on the surface of the metal member It is thought to slow down the rate of corrosion.

Tartaric acid is L-form, D-form, meso-form, or racemic form, regardless of whether it is.

The tartrate is a tartrate ion (anion) in which one or more hydrogen atoms selected from hydrogen atoms of two hydroxyl groups and hydrogen atoms of two carboxy groups in the tartaric acid molecule are ionized from tartaric acid, and a cation derived from a base These are ionic compounds. As said cation, an alkali metal ion, alkaline-earth metal ion, magnesium ion, zinc ion, aluminum ion, iron ion (II), ammonium ion etc. are mentioned, for example.

Specific examples of the stannate include sodium hydrogen stannate, potassium hydrogen stannate, lithium tartrate, sodium tartrate, potassium tartrate, potassium sodium tartrate, calcium tartrate, iron (II) tartrate, zinc tartrate and ammonium tartrate. Among them, sodium tartrate, potassium tartrate, and potassium sodium tartrate are preferred from the viewpoints of good anticorrosive effect and availability.

A compound (A) may be used individually by 1 type, or 2 or more types may be used together.

Compound (A) is preferably added at a concentration of 30 to 100 mg/L in terms of tartaric acid in the cooling water system, more preferably 40 to 90 mg/L, still more preferably 50 to 70 mg/L.

By making the said concentration into 30 mg/L or more, a favorable anticorrosive effect is obtained. In addition, if it is 100 mg/L or less, it is possible to suppress the occurrence of corrosion due to the chelating action of tartrate ions on the metal member.

The pH of the cooling water system in step (1) is preferably 6.0 to 8.0, more preferably 6.0 to 7.5, still more preferably 6.5 to 7.5.

By setting the pH to 6.0 or higher, occurrence of acid corrosion in the metal member can be suppressed. In addition, by setting the pH to 8.0 or less, tartrate ions react with metal ions (for example, iron ions) eluted from the surface of the metal member, so that an anticorrosive film is easily formed.

In addition, pH in this invention is a value measured by the glass electrode method based on JIS Z 8802:2011.

Depending on the water quality of the cooling water system, it is possible to select which of tartaric acid and tartaric acid salts to use as the compound (A) so that the pH is within the above range. In addition, you may adjust the said pH using general pH adjusters, such as sulfuric acid, sodium hydroxide, and potassium hydroxide, for example.

The contact time between the metal member and the compound (A) is preferably 20 to 30 hours, more preferably 20 to 28 hours, still more preferably 20 to 24 hours.

When the contact time is 20 hours or more, a good anticorrosion effect is obtained. In addition, since the improvement of the anticorrosive effect over time cannot be expected when it exceeds 30 hours, it is preferable to be 30 hours or less from the viewpoint of the anticorrosive effect.

The contact time corresponds to the passage time of the cooling water in the cooling water system. In addition, in the case of a circulating cooling water system, the circulation time of the cooling water may be regarded as the contact time. In order to disperse the compound (A) at a uniform concentration on the surface of the metal member, the cooling water system is preferably in a water-passing state, and also preferably circulated from the viewpoint of efficiency.

When the anticorrosive method of the present invention is applied to the basic treatment, it is preferable that step (1) is performed in a state in which no heat load is applied to the cooling water system.

The "state in which no heat load is applied" as used herein is a state before normal operation, in which the high-temperature fluid cooled by the cooling water is not introduced into the contact surface with the cooling water system, and the cooling water is not heated by the high-temperature fluid. It means that it is in a non-heating state, that is, in a non-heating state.

The specific temperature in a state where no heat load is applied is preferably 10 to 40°C, more preferably 15 to 35°C, still more preferably 20 to 30°C.

By setting the temperature within the above range, evaporation in the cooling water system is suppressed, making it easier to keep the concentration of the compound (A) constant.

The concentration of the compound (A) in the cooling water system is preferably maintained constant from the viewpoint of obtaining a uniform anticorrosive effect on the surface of the metal member.

In the course of the process, when the concentration of Compound (A) is reduced due to significant depletion due to adhesion of corrosion products present in the cooling water system, etc., Compound (A) is added to increase the above concentration range. It is desirable to do so. In addition, when the concentration of the compound (A) increases during the process due to evaporation or the like in the cooling water system, water may be replenished and diluted.

(Process (2))

After step (1), one or more compounds (B) selected from zinc and zinc salts are added into the cooling water system and brought into contact with the metal member.

Compound (B) is a compound selected from zinc-based compounds, that is, zinc and zinc salts. As said zinc salt, zinc chloride, zinc sulfate, etc. are mentioned, for example. A compound (B) may be used individually by 1 type, or 2 or more types may be used together.

As described above, after treating the metal member with the compound (A) having an effect of inhibiting the anode reaction on the surface, by further treating the metal member with the compound (B) having the effect of inhibiting the cathodic reaction, a short-time method By the synergistic effect of both compounds in the treatment, it is possible to impart an excellent anticorrosive effect to the metal member.

In addition, when compounds (A) and (B) are added simultaneously, tartrate ions act as a dispersant for zinc ions, and good anticorrosion effect is not obtained.

Compound (B) is preferably added at a concentration of 1 to 50 mg/L in terms of zinc in the cooling water system, more preferably 2 to 30 mg/L, still more preferably 3 to 20 mg/L, particularly preferably It is preferably 3 to 10 mg/L.

When the concentration is within the above range, a good anticorrosive effect is obtained. However, since scale easily adheres to the metal member as the concentration increases, the upper limit is preferably 50 mg/L or less, more preferably 30 mg/L or less, still more preferably 20 mg/L or less, particularly preferably It is 10 mg/L or less.

The contact time between the metal member and the compound (B) is preferably 20 to 30 hours, more preferably 20 to 28 hours, still more preferably 20 to 24 hours.

When the contact time is 20 hours or more, a good anticorrosion effect is obtained. In addition, since it is not expected to improve the anticorrosive effect over time when it exceeds 30 hours, it is preferable to be 30 hours or less in terms of the anticorrosive effect.

In addition, the contact time is the same as the meaning of the contact time for the compound (A). In order to disperse the compound (B) at a uniform concentration on the surface of the metal member, the cooling water system is preferably in a water-passing state, and also preferably circulated from the viewpoint of efficiency.

When the anticorrosive method of the present invention is applied to the basic treatment, it is preferable that step (2) is also performed in a state in which no heat load is applied to the cooling water system, similarly to step (1). The specific temperature is also the same as in step (1) from the viewpoint of making it easy to keep the concentration of compound (B) constant.

The concentration of the compound (B) in the cooling water system is preferably maintained constant from the viewpoint of obtaining a uniform anticorrosive effect on the surface of the metal member.

In the course of the process, when the concentration of Compound (B) is reduced due to significant consumption of Compound (B), it is preferable to add Compound (B) so as to reach the above concentration range. In addition, when the concentration of compound (B) increases during the process due to evaporation or the like in the cooling water system, water may be replenished and diluted.

When the cooling water system is in a water passing state, the water flow rate, i.e., the flow rate, of the cooling water system is not particularly limited. A good anticorrosion effect is obtained according to the anticorrosive method of the present invention even if the speed is equal to or lower than that of 0.3 to 1.0m/s in general, specifically 0.2 to 0.5m/s.

When the anticorrosive method of the present invention is applied to the basic treatment, normal operation starts after the steps (1) and (2) as the basic treatment are finished. During the normal operation, Compound (A) and/or Compound (B) may be contained in the cooling water system.

Normal operation can be carried out by adding known water treatment agents such as slime inhibitors, scale inhibitors, and other anticorrosive agents to the cooling water system.

(Example)

The present invention will be described in more detail below, but the present invention is not limited by the following examples.

The water used in each of the following tests was tap water from Nogi-machi, Shimotsuga-gun, Tochigi Prefecture, Japan (pH 7.0, calcium hardness: 40 mgCaCO ₃ /L, ionic silica concentration: 20 mgSiO ₂ /L).

[Test 1] Corrosion loss evaluation

(Example 1)

After immersing a SPCC (cold-rolled steel sheet) test piece of 30 mm x 50 mm and 1 mm in thickness in 20% by mass nitric acid for 30 seconds, further immersing in 10% by mass sulfuric acid for 60 seconds, followed by etching. processing was done. After washing this test piece with water, it was made to dry, and the weight (W1) before a test was measured.

Water was put into a 1-L beaker, sodium tartrate was added at a concentration of 50 mg/L (in terms of tartaric acid), and a test solution adjusted to pH 7.5 was obtained. The test piece was immersed in the test solution for 24 hours in a rotational corrosion tester (manufactured by SHINWA CHEMICAL INDUSTRIES, LTD.; test solution temperature 30 ° C., test piece rotation speed 150 rpm), and then the test solution was chlorinated Zinc was added at a concentration of 5 mg/L (in terms of zinc), and immersion was continued for a further 24 hours. After exchanging this test liquid with water and immersing for 24 hours, the test piece was taken out and dried, and the weight (W2) after the test was measured.

A value obtained by subtracting the weight after the test (W2) from the weight before the test (W1) (W1-W2) was determined as the corrosion loss.

(Comparative Example 1)

In Example 1, the corrosion loss was determined in the same manner as in Example 1, except that after immersing in a test solution of sodium tartrate solution for 48 hours without adding zinc chloride, the test solution was replaced with water.

(Comparative Example 2)

In Example 1, the corrosion loss was determined in the same manner as in Example 1, except that after immersing in a test solution of an aqueous solution to which sodium tartrate and zinc chloride were added simultaneously from the beginning for 48 hours, the test solution was replaced with water.

The results of Test 1 are shown in Table 1 below.

As can be seen from the results shown in Table 1, it can be said that when zinc chloride was added to sodium tartrate later (Example 1), the corrosion loss was small and a good anticorrosive film was formed.

In addition, in the case of simultaneous addition of zinc chloride and sodium tartrate (Comparative Example 2), tartrate ions act as a dispersant for zinc ions, and the anticorrosive film is more resistant than when only sodium tartrate is added (no zinc chloride is added) (Comparative Example 1). It is thought that it is more difficult to form and the corrosion loss is increased.

[Test 2] Simulation test

In the cooling water system heat exchanger testing apparatus as shown in Fig. 1, a tube 2 (STB340 (carbon steel tube for heat exchanger) in a shell and tube heat exchanger 1, an outer diameter of 19 mm, a thickness of 2.3 mm, a length of 1350 mm, 2 dog), normal operation was performed after the basic treatment of the following Examples and Comparative Examples, and the maximum pitting corrosion depth and scale adhesion speed were evaluated.

The heat exchanger 1 is connected to the cooling tower 3, and from the 500 L water storage tank 4 under the cooling tower 3, cold water to which a prescribed chemical is added is supplied by a water pump P1. The cold water flows through the tube 2 in the heat exchanger 1. To the outside of the tube 2 in the heat exchanger 1, steam (heat source) 10 is supplied via a temperature control valve V1. The steam is cooled by the cold water flowing through the tube 2 and discharged to the drain 11. By heat exchange with the steam (10), the cold water is heated to become hot water, and is sent to the cooling tower (3) to be sprayed on the filler (5). Air is withdrawn into the cooling tower 3 from the periphery of the cooling tower 3 and is exhausted by the fan 6 at the top.

A water treatment chemical is added from the chemical tank 7 to the cold water in the water storage tank 4 by means of the chemical injection pump P2. The concentration of the water treatment chemical in the cold water in the water storage tank 4, the water quality, etc., was determined by the automatic conductivity management device 8 (“Kuriauto (registered trademark) C-505”, Kurita Kogyo Co., Ltd.) Ltd.), and appropriately blown by interlocking the drug injection pump (P2) and the blow pump (P3). In addition, make-up water 20 is added as needed.

[Test 2-1] Confirmation of the effect of the amount of zinc chloride added

(Example 2)

The ground treatment of the tube 2 was carried out as follows. In the storage tank 4, synthetic water (calcium hardness 100 mgCaCO ₃ /L, total hardness 150 mgCaCO ₃ /L, acid consumption 30 mgCaCO ₃ /L) was stored, and sodium tartrate was added at a concentration of 50 mg/L (tartaric acid equivalent amount). ) and adjusted to pH 7.5. The circulation valve V2 was opened and this water was passed through one test tube A in the tube 2 at a flow rate of 5.3 L/min (flow rate 0.5 m/s). The flow rate was measured with a flow meter 9 near the inlet of the heat exchanger 1 (the same applies below).

After 24 hours, zinc chloride was added to the water at a concentration of 2 mg/L (in terms of zinc), and then water was passed through the test tube (A) at the same flow rate (flow rate) for 24 hours.

(Examples 3 to 5 and Comparative Example 3)

In Example 2, the concentration of zinc chloride added later was changed to 5 mg/L (zinc equivalent), 10 mg/L (zinc equivalent), 30 mg/L (zinc equivalent), and 0 mg/L (not added). Except for this, the base treatment of the tube 2 was performed in the same manner as in Example 2.

(Reference Example 1)

The ground treatment of the tube 2 was carried out as follows. In the storage tank 4, the same synthetic water as in Example 2 was stored, and sodium hexametaphosphate at a concentration of 100 mg/L (in terms of phosphoric acid) and zinc chloride at a concentration of 20 mg/L (in terms of zinc) were simultaneously added, and the pH was 7. adjusted to 5. The circulation valve V2 was opened, and this water was passed through the test tube A at the same flow rate (flow rate) as in Example 2 for 4 days.

[Water passing test (1)]

After the basic treatment according to each of the above examples, comparative examples and reference examples, synthetic water (pH 8.5 to 8.7, calcium hardness 450 to 500 mgCaCO ₃ /L, acid consumption 130 to 170 mgCaCO ₃ in the storage tank 4) /L, 10 to 15 mg solid/L of maleic acid polymer, and 1.8 to 2.2 mg/L of zinc chloride (in terms of zinc)) were prepared. In the synthetic water, maleic acid polymer and zinc were injected so as to maintain the above concentration range, and sodium hypochlorite as a slime control agent was injected so that the total residual chlorine concentration was 0.1 to 0.2 mg/L.

The operation of the device was started, and the operation was performed by passing water through the test tube (A) at a flow rate of 0.5 m/s. The inlet water temperature (cold water) of the water supplied to the heat exchanger 1 was controlled to be 30°C and the outlet water temperature (hot water) to be 40°C. The water passage test was completed on the 14th day of operation.

After completion of the water permeation test, the test tube (A) was removed. The test tube (A) was cut in units of 200 mm in length and split in half in the longitudinal direction to prepare a tube for evaluation. By obtaining the maximum pitting depth and scale attachment speed as follows, the basic treatment methods of each of the above Examples, Comparative Examples and Reference Examples were evaluated.

· Maximum depth of pitting

The inner surface of each tube for evaluation was observed with the naked eye, and the pitting depth was measured with a dial gauge. The maximum value of pitting depths measured for all evaluation tubes was taken as the maximum pitting depth.

The maximum pitting depth is an index of anticorrosive effect, and the smaller the value, the better the anticorrosive effect.

· Scale attachment speed

For each tube for evaluation, the deposits on the inner surface of the tube were collected, dried, and the mass was measured. The deposit was regarded as a scale, and the surface area of the inner surface of each tube for evaluation was calculated as 1 cm2 and the amount of scale adhered per month [mg/(cm2·month)]. The maximum value of the amount of scale adhesion calculated for all evaluation tubes was used as the scale adhesion rate.

It can be said that the smaller the value of the scale adhesion rate, the better the scale adhesion inhibition effect.

Table 2 below shows these evaluation results.

As can be seen from the results shown in Table 2, by adding zinc chloride after adding sodium tartrate in the base treatment of the tube 2 (Examples 2 to 5), the conventional phosphoric acid-based anticorrosive agent was replaced with zinc chloride. Compared to the case of combined use (Reference Example 1), it was confirmed that a high anticorrosive effect can be obtained with a shorter treatment time even if the amount of sodium tartrate and zinc chloride added, that is, the amount of anticorrosive agent added is small.

In addition, when the concentration of zinc chloride added is suppressed to a predetermined amount (Examples 2 and 3), the effect of inhibiting scale adhesion is superior to that of the conventional method of using it in combination with sodium phosphate (Reference Example 1) by using it in combination with sodium tartrate. I was able to confirm that

In addition, when the concentration of zinc chloride is increased (Examples 4 and 5), it is thought that the scale adhesion speed increases because zinc ions become a scale-causing substance.

[Test 2-2] Confirmation of the effect of flow velocity

(Examples 6 and 7, Comparative Example 4 and Reference Example 2)

In Examples 3 and 5, Comparative Example 3 and Reference Example 1, instead of passing water through the test tube (A), the flow rate to the test tube (B), which is another one of the tubes (2), was 3.2 L/min (flow rate 0.3 m/s) The base of the tube 2, respectively, in Examples 6, 7, Comparative Example 4 and Reference Example 2, in the same manner as in Examples 3 and 5, Comparative Example 3 and Reference Example 1, respectively. processing was done.

[Water passing test (2)]

After the basic treatment according to each of the above Examples, Comparative Examples and Reference Examples, the same water passage test as the water passage test (1) of Test 2-1 was conducted. In the water passage test (2) in this test 2-2, instead of passing water through the test tube (A) in the above water passage test (1), water was passed through the test tube (B) at a flow rate of 0.3 m/s. It was carried out in the same way as the above water passing test (1).

After the completion of the water permeation test, the test tube (B) is removed, and the maximum pitting depth and scale adhesion speed are obtained in the same way as in the evaluation method in the above test 2-1, and each of the above examples, comparative examples and reference examples The basic treatment method was evaluated.

Table 3 below shows these evaluation results.

As can be seen from the results shown in Table 3, even in the case of a low flow rate (0.3 m/s) (Examples 6 and 7), the flow rate is 0.5 m/s (Examples 3 and 5). It was confirmed that a high anticorrosive effect could be obtained.

1: shell and tube heat exchanger
2 : tube
3 : cooling tower
4: water tank
5: filling material
6 : fan
7: chemical tank
8: Conductivity automatic management device
9: flow meter
10 : Steam
11 : Drain
20: replenishment water

Claims (8)

A step (1) of adding at least one compound (A) selected from tartaric acid and tartaric acid at a concentration of 30 to 100 mg/L in terms of tartaric acid into a cooling water system and bringing it into contact with a metal member;
After the step (1), a step of adding one or more compounds (B) selected from zinc and zinc salts at a concentration of 1 to 50 mg/L in terms of zinc into the cooling water system and bringing them into contact with the metal member. (2)
Anticorrosive method of metal members of a cooling water system provided.
According to claim 1,
An anticorrosion method for metal members of a cooling water system in which the pH of the cooling water system in the step (1) is 6.0 to 8.0.
According to claim 1 or 2,
In the step (1), the contact time between the metal member and the compound (A) is 20 to 30 hours.
According to claim 1 or 2,
In the step (2), the contact time between the metal member and the compound (B) is 20 to 30 hours.
According to claim 1 or 2,
A method of corrosion protection of a metal member of a cooling water system in which the cooling water system is a circulating cooling water system.
According to claim 1 or 2,
A method of corrosion protection of a metal member of a cooling water system in which the steps (1) and (2) are performed in the basic treatment of the cooling water system.
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