CN112955583B - Method for preventing corrosion of metal member of cooling water system - Google Patents
Method for preventing corrosion of metal member of cooling water system Download PDFInfo
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- CN112955583B CN112955583B CN201980072390.4A CN201980072390A CN112955583B CN 112955583 B CN112955583 B CN 112955583B CN 201980072390 A CN201980072390 A CN 201980072390A CN 112955583 B CN112955583 B CN 112955583B
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
- C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
- C23F11/18—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using inorganic inhibitors
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
- C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
- C23F11/10—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using organic inhibitors
- C23F11/12—Oxygen-containing compounds
Abstract
A method for preventing corrosion of a metal member of a cooling water system, comprising: a step (1) in which at least one compound (A) selected from tartaric acid and tartrate is added to a cooling water system so as to bring the compound (A) into contact with a metal member; and a step (2) of adding one or more compounds (B) selected from zinc and zinc salts to the cooling water system after the step (1) to bring the compound (B) into contact with the metal member.
Description
Technical Field
The present invention relates to a method for preventing corrosion of a metal member of a cooling water system, which prevents a corrosion-preventing film from being formed on a surface of the metal member constituting a portion which comes into contact with cooling water in the cooling water system.
Background
In air conditioning equipment, machinery (plant), and the like of buildings, regional facilities, and the like, a water-cooled heat exchanger is used to indirectly cool various fluids. In such a cooling water system, metals such as carbon steel and stainless steel are generally used for various members such as a heat exchanger and pipes around the heat exchanger.
These metal members are likely to be corroded by dissolved oxygen in water if they are constantly or intermittently brought into contact with cooling water. If corrosion causes a decrease in thickness or pitting of metal members such as pipes, damage to equipment or contamination of products in mechanical equipment may occur, which may lead to serious accidents.
As an anticorrosion method for such a metal member, for example, patent document 1 proposes that a strong anticorrosion film be formed on the surface of the metal member by using a phosphoric acid-based or zinc-based anticorrosion agent in a base treatment at the time of starting up a cooling water system.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2011-202243
Disclosure of Invention
Problems to be solved by the invention
However, in recent years, due to an increase in concern about environmental protection or an increase in drainage restriction, it is required to reduce the content of phosphorus and the like in water. Mechanical equipment or the like not provided with wastewater treatment equipment is difficult to meet such a demand, and the use of phosphoric acid-based and zinc-based anticorrosive agents has to be stopped in some cases.
Further, since the phosphoric acid-based anticorrosive agent forms an anticorrosive film by precipitating the film, a long time of about 4 days is required in the above-mentioned basic treatment. Therefore, it is also desirable to shorten the basic processing period.
Therefore, an etching preventing method is required which can obtain an excellent etching preventing effect in a shorter time without using a phosphoric acid-based etching preventing agent.
The present invention has been made to solve the above-described problems, and an object thereof is to provide a method for preventing corrosion of a metal member of a cooling water system, which can provide an excellent corrosion preventing effect to the surface of the metal member of the cooling water system in a shorter treatment time without using a phosphoric acid-based corrosion inhibitor.
Means for solving the problems
The present invention is based on the following findings: by using a tartaric acid compound and further using a zinc compound, a good corrosion-preventing effect is imparted to a metal member of a cooling water system.
Namely, the present invention provides the following [1] to [8 ].
[1] A method for preventing corrosion of a metal member of a cooling water system, comprising:
a step (1) in which at least one compound (A) selected from tartaric acid and tartrate is added to a cooling water system so as to bring the compound (A) into contact with a metal member; and
and (2) adding one or more compounds (B) selected from zinc and zinc salts to the cooling water system after the step (1) to bring the compound (B) into contact with the metal member.
[2] The method for preventing corrosion of a metal member in a cooling water system according to the above [1], wherein the compound (A) is added to the cooling water system in a concentration of 30mg/L to 100mg/L in terms of tartaric acid in the step (1).
[3] The method for preventing corrosion of a metal member in a cooling water system according to the above item [1] or [2], wherein the pH of the cooling water system in the step (1) is 6.0 to 8.0.
[4] The method for preventing corrosion of a metal member for a cooling water system according to any one of the above items [1] to [3], wherein in the step (1), the contact time of the metal member with the compound (A) is 20 to 30 hours.
[5] The method for preventing corrosion of a metal member in a cooling water system according to any one of the above items [1] to [4], wherein the compound (B) is added to the cooling water system in a concentration of 1mg/L to 50mg/L in terms of zinc in the step (2).
[6] The method for preventing corrosion of a metal member for a cooling water system according to any one of the above items [1] to [5], wherein in the step (2), the contact time of the metal member with the compound (B) is 20 to 30 hours.
[7] The method for preventing corrosion of a metal member of a cooling water system according to any one of the above items [1] to [6], wherein the cooling water system is a circulating cooling water system.
[8] The method for preventing corrosion of a metal member of a cooling water system according to any one of the above items [1] to [7], wherein the steps (1) and (2) are performed in a basic treatment of the cooling water system.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, it is possible to provide a metal member surface of a cooling water system with an excellent anticorrosive effect in a shorter treatment time without using a phosphoric acid-based anticorrosive agent. Therefore, the corrosion prevention method of the present invention can contribute to the maintenance of the cooling capacity of the cooling water system while coping with environmental protection.
Drawings
Fig. 1 is a schematic diagram showing an outline of a heat exchanger test apparatus of a cooling water system in an example.
Detailed Description
The present invention will be described in detail below.
The method for preventing corrosion of a metal member of a cooling water system of the present invention comprises: a step (1) in which at least one compound (A) selected from tartaric acid and tartrate is added to a cooling water system so as to bring the compound (A) into contact with a metal member; and a step (2) of adding one or more compounds (B) selected from zinc and zinc salts to the cooling water system after the step (1) to bring the compound (B) into contact with the metal member.
As described above, in the etching preventing method of the present invention, the tartaric acid-based compound (a) is used as the etching inhibitor, and then the zinc-based compound (B) is used. The tartaric acid compound has an effect of inhibiting an anodic reaction on the surface of the metal member. Further, the zinc-based compound has an effect of suppressing a cathode reaction in the surface of the metal member. According to the corrosion prevention method of the present invention, an excellent corrosion prevention effect can be imparted to the metal member by the synergistic effect of both.
(Cooling Water System)
The cooling water system in the present invention refers to a system in which cooling water for operation of a heat exchanger is passed through air conditioning equipment such as buildings and local facilities, and machinery.
The cooling water system may be any one of a through-flow type, an open circulation type, or a closed circulation type. The present invention can exhibit an excellent anticorrosive effect in a circulating cooling water system, particularly an open circulating cooling water system.
The present invention can be applied to the above-described cooling water system in any state such as at the time of start-up or during steady operation, and is particularly preferably applied to basic processing at the time of start-up such as initial start-up or re-operation.
Since corrosion products are likely to be present in large amounts in the system and the corrosion inhibitor is likely to be consumed at the time of starting the cooling water system, the corrosion inhibitor is usually added at a use concentration of 3 to 10 times that at the time of steady operation to perform corrosion prevention treatment for obtaining a sufficient corrosion prevention effect. The corrosion prevention treatment at the start-up of the cooling water system is referred to as a base treatment and may be referred to as an initial treatment.
The etching resist method of the present invention can exhibit an excellent etching resist effect in such a basic treatment.
The cooling water system can sufficiently exhibit the corrosion prevention effect by the corrosion prevention method of the present invention as long as the cooling water system has a water quality of a general cooling water system. The preferable pH is 6.0 to 8.0, more preferably 6.0 to 7.5, and still more preferably 6.5 to 7.5.
Furthermore, the preferred calcium hardness is 30mgCaCO3/L～150mgCaCO3Per liter, more preferably 30mgCaCO3/L～120mgCaCO3Per liter, more preferably 30mgCaCO3/L～100mgCaCO3/L。
Further, the preferable concentration of ionic silica is 5mgSiO2/L～35mgSiO2/L, more preferably 10mgSiO2/L～30mgSiO2PerL, more preferably 15mgSiO2/L～25mgSiO2/L。
(Metal Member)
The metal member is a metal member constituting a portion of the cooling water system that is in contact with the cooling water. The metal member is, for example, a metal part in a heat exchanger, a refrigerator, various pipes, a valve, or the like.
The metal to which the present invention is applied is preferably an iron-based metal, and can obtain an excellent corrosion prevention effect in, for example, a carbon steel pipe for a boiler/heat exchanger (STB steel pipe).
(step (1))
In the corrosion prevention method of the present invention, first, one or more compounds (a) selected from tartaric acid and tartrate are added to the cooling water system so as to contact the metal member.
The compound (a) is a tartaric acid-based compound, i.e., a compound selected from tartaric acid and a tartrate salt.
The tartaric acid compound is considered to impart an anticorrosive effect to a metal member by forming an adsorption film by adsorbing hydroxyl groups in the molecule on the surface of the metal member. The rate of formation of such an adsorption film is higher than that of a deposited film as an etching resist formed by a phosphoric acid-based etching resist, and the etching resist treatment time can be shortened.
Although the details of the mechanism by which the compound (a) can obtain the etching-preventing effect are not clear, the following is presumed.
Tartaric acid ions generated from the compound (A) are bonded to calcium ions present in the cooling water, and an adsorption film mainly containing a calcium salt which is hardly soluble in water is formed on the surface of the metal member. Further, the compound (a) may react with the iron component of the metal member to form an adsorption film by iron (II) tartrate.
Consider that: such an adsorption film (corrosion-preventing film) inhibits the metal member from coming into direct contact with corrosion factors contained in the cooling water system such as dissolved oxygen, chloride ions, and sulfate ions, and thus can reduce the corrosion rate at the surface of the metal member.
Tartaric acid may be any of L-, D-, meso-or racemic (raceme).
The tartrate is a compound in which one or more hydrogen atoms selected from hydrogen atoms of two hydroxyl groups and hydrogen atoms of two carboxyl groups in a tartaric acid molecule are ionized from tartaric acid to form a tartrate ion (anion), and a cation derived from a base is ionically bonded to the tartrate ion. Examples of the cation include: alkali metal ions, alkaline earth metal ions, magnesium ions, zinc ions, aluminum ions, Iron Ions (II), ammonium ions, and the like.
Specific examples of the tartrate include: sodium hydrogen tartrate, potassium hydrogen tartrate, lithium tartrate, sodium tartrate, potassium tartrate, sodium potassium tartrate, calcium tartrate, iron (II) tartrate, zinc tartrate, ammonium tartrate, etc. Among these, sodium tartrate, potassium tartrate, sodium potassium tartrate are preferable from the viewpoint of a good anticorrosive effect, easy availability, and the like.
The compound (A) may be used alone or in combination of two or more.
The compound (A) is preferably added to the cooling water system at a concentration of 30mg/L to 100mg/L, more preferably 40mg/L to 90mg/L, and still more preferably 50mg/L to 70mg/L, in terms of tartaric acid.
By setting the concentration to 30mg/L or more, a good anticorrosive effect can be obtained. Further, if the content is 100mg/L or less, the metal member is inhibited from being corroded by chelation of tartaric acid ions.
The pH of the cooling water system in the step (1) is preferably 6.0 to 8.0, more preferably 6.0 to 7.5, and still more preferably 6.5 to 7.5.
By setting the pH to 6.0 or more, the metal member can be inhibited from acid corrosion. When the pH is 8.0 or less, tartaric acid ions react with metal ions (for example, iron ions) eluted from the surface of the metal member, and thereby an anticorrosive film is easily formed.
The pH in the present invention is a value measured by a glass electrode method according to Japanese Industrial Standards (JIS) Z8802: 2011.
Depending on the water quality of the cooling water system, either tartaric acid or a tartrate salt can be selected and used as the compound (a) so that the pH falls within the above range. The pH can be adjusted using a general pH adjuster such as sulfuric acid, sodium hydroxide, and potassium hydroxide.
The contact time between the metal member and the compound (a) is preferably 20 to 30 hours, more preferably 20 to 28 hours, and still more preferably 20 to 24 hours.
If the contact time is 20 hours or more, a good anticorrosive effect can be obtained. In addition, when it exceeds 30 hours, improvement of the anticorrosive effect with time cannot be expected, and therefore, from the viewpoint of the anticorrosive effect, 30 hours or less is preferable.
In the case where cooling water is supplied to the cooling water system, the contact time corresponds to the water supply time. In the case of a circulating cooling water system, the circulation time of the cooling water can be considered. The cooling water system is preferably in a water-permeable state in order to distribute the compound (a) to the surface of the metal member at a uniform concentration, and is preferably circulated from the viewpoint of efficiency.
When the corrosion prevention method of the present invention is applied to the basic treatment, the step (1) is preferably performed in a state where no heat load is applied to the cooling water system.
The "state where no heat load is applied" referred to in the present specification means a state before steady operation, that is, a state where a high-temperature fluid to be cooled by the cooling water is not introduced into a contact surface with a cooling water system and the cooling water is not heated by the high-temperature fluid, that is, a non-heat-transfer state.
The specific temperature in the state where no heat load is applied is preferably 10 to 40 ℃, more preferably 15 to 35 ℃, and further preferably 20 to 30 ℃.
By setting the temperature within the range, evaporation in the cooling water system is suppressed, and the concentration of the compound (a) is easily maintained to be constant.
The concentration of the compound (a) in the cooling water system is preferably maintained constant from the viewpoint that a uniform corrosion preventing effect can be obtained on the surface of the metal member.
When the concentration of the compound (a) is lowered due to significant consumption of the compound (a) in the middle of the process, for example, due to adhesion to corrosion products present in the cooling water system, it is preferable to add the compound (a) so as to achieve the above concentration range. Further, in the case where the concentration of the compound (a) increases due to evaporation or the like in the cooling water system during the process, water may be supplemented for dilution.
(step (2))
After the step (1), one or more compounds (B) selected from zinc and zinc salts are added to the cooling water system so as to be in contact with the metal member.
The compound (B) is a zinc-based compound, i.e., a compound selected from zinc and zinc salts. Examples of the zinc salt include zinc chloride and zinc sulfate. The compound (B) may be used alone or in combination of two or more.
As described above, by treating the metal member with the compound (a) having an effect of suppressing the anodic reaction on the surface thereof and then further with the compound (B) having an effect of suppressing the cathodic reaction, it is possible to impart an excellent anticorrosive effect to the metal member by the synergistic effect of both compounds in a short anticorrosive treatment.
When the compound (a) and the compound (B) are added simultaneously, tartaric acid ions act as a dispersant for zinc ions, and thus a good corrosion-preventing effect cannot be obtained.
The compound (B) is preferably added to the cooling water system at a concentration of 1mg/L to 50mg/L in terms of zinc, more preferably 2mg/L to 30mg/L, still more preferably 3mg/L to 20mg/L, and particularly preferably 3mg/L to 10 mg/L.
When the concentration is within the above range, a good etching preventing effect can be obtained. However, since the metal member is likely to have dirt (scale) adhered thereto when the concentration is high, the upper limit is preferably 50mg/L or less, more preferably 30mg/L or less, still more preferably 20mg/L or less, and particularly preferably 10mg/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, and still more preferably 20 to 24 hours.
If the contact time is 20 hours or more, a good anticorrosive effect can be obtained. In addition, when it exceeds 30 hours, improvement of the anticorrosive effect with time cannot be expected, and therefore, from the viewpoint of the anticorrosive effect, 30 hours or less is preferable.
The contact time is the same as that for the compound (a). In order to distribute the compound (B) to the surface of the metal member at a uniform concentration, the cooling water system is preferably in a water-passing state, and is preferably circulated from the viewpoint of efficiency.
When the corrosion prevention method of the present invention is applied to the basic treatment, the step (2) is preferably performed in a state where no thermal load is applied to the cooling water system, as in the step (1). The specific temperature is also the same as in the step (1) from the viewpoint of easily maintaining the concentration of the compound (B) constant.
The concentration of the compound (B) in the cooling water system is preferably maintained constant from the viewpoint that a uniform anticorrosive effect can be obtained on the surface of the aforementioned metal member.
When the concentration of the compound (B) is lowered due to significant consumption of the compound (B) during the process, it is preferable to add the compound (B) so as to achieve the above concentration range. Further, in the case where the concentration of the compound (B) increases due to evaporation or the like in the cooling water system during the process, water may be supplemented for dilution.
When the cooling water system is in a water-passing state, the flow rate, which is the water-passing speed of the cooling water system, is not particularly limited, but when the corrosion prevention method of the present invention is applied to the base treatment, the flow rate at the time of steady operation of the cooling water system is usually 0.3m/s to 1.0m/s, whereas even at the same or a low speed, specifically, even at 0.2m/s to 0.5m/s, a good corrosion prevention effect can be obtained by the corrosion prevention method of the present invention.
When the corrosion prevention method of the present invention is applied to the base treatment, the stable operation is started after the steps (1) and (2) as the base treatment are finished. In this case, the cooling water system may contain the compound (A) and/or the compound (B) during the steady operation.
In the cooling water system, a known water treatment agent such as a slime inhibitor, a scale inhibitor, or another corrosion inhibitor may be added to perform stable operation.
Examples
The present invention will be described in more detail below, but the present invention is not limited to the following examples.
The water used in the following tests was tap water (pH 7.0, calcium hardness 40 mgCaCO) of Hayamunting (Kyowa Kogyo, Japan, Kogyo)3Concentration of ionic silica 20mgSiO2/L)。
[ test 1] evaluation of Corrosion reduction amount
(example 1)
A test piece of SPCC (cold rolled steel sheet) having a thickness of 1mm and a thickness of 30mm X50 mm was immersed in nitric acid having a concentration of 20 mass% for 30 seconds, and then immersed in sulfuric acid having a concentration of 10 mass% for 60 seconds, thereby carrying out etching treatment. The test piece was washed with water, dried, and the weight before the test (W1) was measured.
Water was put into a 1L beaker, and sodium tartrate was added at a concentration of 50mg/L (in terms of tartaric acid) to obtain a test solution adjusted to pH 7.5. The test piece was immersed in the test solution for 24 hours by a rotary corrosion test apparatus (manufactured by Xinhe chemical Co., Ltd.; test solution temperature 30 ℃ C., test piece rotation speed 150rpm), and then zinc chloride was added to the test solution at a concentration of 5mg/L (zinc equivalent) and the immersion was continued for 24 hours. The test solution was replaced with water and immersed for 24 hours, and then the test piece was lifted and dried to measure the weight after the test (W2).
The amount of corrosion reduction was determined as the value (W1-W2) obtained by subtracting the post-test weight (W2) from the pre-test weight (W1).
Comparative example 1
The amount of corrosion reduction was determined in the same manner as in example 1, except that in example 1, no zinc chloride was added, and the test solution of the aqueous sodium tartrate solution was immersed for 48 hours, and then the test solution was replaced with water.
Comparative example 2
The amount of corrosion reduction was determined in the same manner as in example 1, except that the test solution of example 1, to which the aqueous solution of sodium tartrate and zinc chloride was added at the same time from the start, was immersed for 48 hours and then replaced with water.
The results of test 1 are shown in table 1 below.
TABLE 1
From the results shown in table 1, it is understood that when zinc chloride was added to sodium tartrate later (example 1), the amount of corrosion reduction was small, and it can be said that a good anticorrosive coating film was formed.
It should be noted that: in the case where zinc chloride and sodium tartrate were added simultaneously (comparative example 2), the tartaric acid ions acted as a dispersant for zinc ions, and the formation of an anticorrosive coating was more difficult than in the case where only sodium tartrate was added (no zinc chloride was added) (comparative example 1), and therefore the amount of corrosion reduction increased.
[ test 2] simulation of an actual machine test
In a heat exchanger test apparatus for a cooling water system as shown in fig. 1, after performing base treatment of the following examples and comparative examples on tubes (tubes) 2(STB340 (carbon steel tube for heat exchanger), outer diameter 19mm, thickness 2.3mm, length 1350mm, 2 tubes) in a multi-tube heat exchanger 1, stable operation was performed, and the maximum pitting corrosion depth and the fouling adhesion rate were evaluated.
The heat exchanger 1 is connected to the cooling tower 3, and cold water to which a predetermined chemical is added is supplied from a 500L water storage tank 4 at the lower part of the cooling tower 3 by a water feed pump P1. The cold water flows through the pipe 2 in the heat exchanger 1. The vapor (heat source) 10 is supplied to the outside of the tube 2 in the heat exchanger 1 via the temperature adjustment valve V1. The vapor is cooled by cold water flowing through the pipe 2 and discharged as drain 11. The cold water is heated by the heat exchange with the steam 10 to become warm water, and the warm water is sent to the cooling tower 3 and is dispersed to the filler 5. Air is sucked into the cooling tower 3 from the side periphery of the cooling tower 3 and is exhausted by an upper exhaust fan (fan) 6.
The cold water in the water storage tank 4 is treated by adding water from the chemical tank 7 by 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, and the like are controlled by an automatic conductivity control device 8 ("kuraiuo" (registered trademark) C-505 ", manufactured by shiitake industries co., ltd.), and the chemical injection pump P2 and the discharge pump (blow pump) P3 may be interlocked to appropriately discharge the chemical. Further, make-up water 20 may be added as necessary.
[ test 2-1] confirmation of the Effect of the amount of Zinc chloride added
(example 2)
The base treatment of the tube 2 is performed as follows. Synthetic water (calcium hardness 100 mgCaCO) is stored in the water storage tank 43Per liter, total hardness 150mgCaCO3L, acid consumption 30mgCaCO3/L), sodium tartrate was added at a concentration of 50mg/L (in terms of tartaric acid) to adjust the pH to 7.5. The circulation valve V2 was opened, and the water was fed to one of the test tubes A in the tube 2 at a flow rate of 5.3L/min (flow rate of 0.5 m/s). The flow rate is measured by a flow meter 9 near the inlet of the heat exchanger 1 (hereinafter, the same applies).
After 24 hours, zinc chloride was added to the water at a concentration of 2mg/L (zinc equivalent), and the water was allowed to flow into the test tube A for 24 hours while maintaining the flow rate (flow velocity).
(examples 3 to 5 and comparative example 3)
In example 2, the base treatment of the tube 2 was performed in the same manner as in example 2 except that the concentration of zinc chloride to be added later was changed to 5mg/L (zinc equivalent), 10mg/L (zinc equivalent), 30mg/L (zinc equivalent), and 0mg/L (not added).
(reference example 1)
The base treatment of the tube 2 is performed as follows. The same synthetic water as in example 2 was stored in the water storage tank 4, and sodium hexametaphosphate (phosphate equivalent) was added at a concentration of 100mg/L and zinc chloride (zinc equivalent) was added at the same time, and the pH was adjusted to 7.5. The circulation valve V2 was opened, and the water was introduced into the test tube a at the same flow rate (flow rate) as in example 2 for 4 days.
[ Water flow test (1) ]
After the base treatments of the examples, comparative examples and reference examples described above, synthetic water (pH 8.5 to 8.7, calcium hardness 450 mgCaCO) was prepared in the water reservoir 43/L～500mgCaCO3Acid consumption 130 mgCaCO/L3/L～170mgCaCO3(ii)/L, maleic acid polymer 10-15 mgsolid/L, zinc chloride 1.8-2.2 mg/L (zinc equivalent)). Then, the maleic acid polymer and zinc are injected with chemicals so as to maintain the concentration range, and sodium hypochlorite is injected with chemicals so that the total residual chlorine concentration becomes 0.1mg/L to 0.2mg/L as a slime control agent into the synthetic water.
The operation of the apparatus was started, and water was passed 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 30 ℃ and the outlet water temperature (hot water) was controlled to 40 ℃. On the 14 th day of operation, the water passage test was terminated.
After the water passage test was completed, the test tube A was removed. The test tubes A were cut at intervals of 200mm in length and divided into halves to prepare evaluation tubes. The method of the basic treatment of each of the above examples, comparative examples and reference examples was evaluated by obtaining the maximum pitting depth and the dirt adhesion rate as follows.
Maximum pitting depth
For each evaluation tube, the inner surface of the tube was visually observed, and the pitting depth was measured by a dial gauge (dial gauge). The maximum value among the pitting depths measured for all the evaluation tubes was set as the maximum pitting depth.
The maximum cavitation depth is an index of the corrosion prevention effect, and it can be said that the smaller the value, the more excellent the corrosion prevention effect.
Speed of adhesion of dirt
The deposits on the inner surface of the tube were collected and dried for each tube for evaluation, and the mass was measured. The deposit was regarded as fouling, and the surface area of the inner surface of the tube was calculated for each evaluation tube to be 1cm2In the average 1 month period, the amount of the soil adhered [ mg/(cm) ]2·month)]. The maximum value among the amounts of adhesion of dirt calculated for all the evaluation tubes was defined as the adhesion rate of dirt.
The smaller the value of the dirt adhesion rate, the more excellent the dirt adhesion suppression effect.
The evaluation results of these are shown in table 2 below.
TABLE 2
As can be seen from the results shown in table 2, it was confirmed that: by adding zinc chloride after adding sodium tartrate in the basic treatment of the pipe 2 (examples 2 to 5), even when the amount of sodium tartrate and zinc chloride added, that is, the amount of the anticorrosive added is small, a high anticorrosive effect can be obtained in a shorter treatment time, as compared with the case where zinc chloride is used in combination with a conventional phosphoric acid-based anticorrosive (reference example 1).
Further, it was confirmed that: when the zinc chloride was added in a predetermined amount (examples 2 and 3), the effect of inhibiting the adhesion of scale was more excellent than that of the conventional method in which sodium phosphate was used in combination (reference example 1).
It should be noted that: when the addition concentration of zinc chloride is increased (examples 4 and 5), zinc ions become a cause of fouling, and thus the fouling adhesion rate increases.
[ test 2-2] confirmation of the influence of flow Rate
(example 6, example 7, comparative example 4 and reference example 2)
In examples 3, 5, comparative examples 3 and reference example 1, the base treatment of the pipe 2 was performed as examples 6, 7, 4 and 2, respectively, in the same manner as in examples 3, 5, 3 and reference example 1, respectively, except that water was passed through the test pipe a, and water was passed through the other test pipe B of the pipe 2 at a flow rate of 3.2L/min (flow rate of 0.3 m/s).
[ Water passage test (2) ]
After the basic treatments of the above examples, comparative examples and reference examples, the same water flow test as the water flow test (1) of the above test 2-1 was carried out. The water flow test (2) in this test 2-2 was carried out in the same manner as in the water flow test (1) except that in the water flow test (1), water was passed through the test tube B at a flow rate of 0.3m/s instead of the test tube A.
After the water passage test was completed, the test tube B was removed, the maximum pitting depth and the dirt adhesion rate were determined in the same manner as in the evaluation method in the test 2-1, and the evaluation was performed with respect to the methods of the basic treatment in the examples, comparative examples and reference examples described above.
These evaluation results are shown in table 3 below.
TABLE 3
As can be seen from the results shown in table 3, it was confirmed that: even in the case of a low flow rate (0.3m/s) (examples 6 and 7), a high anticorrosive effect similar to that in the case of a flow rate of 0.5m/s (examples 3 and 5) was obtained.
Description of the reference numerals
1: multi-tube heat exchanger (Heat exchanger)
2: pipe
3: cooling tower
4: water storage tank
5: filling material
6: exhaust fan
7: medicament groove
8: automatic conductivity management device
9: flow meter
10: steam generation
11: discharging water
20: make-up water
Claims (8)
1. A method for preventing corrosion of a metal member of a cooling water system, comprising:
a step (1) in which at least one compound (A) selected from tartaric acid and tartrate is added to a cooling water system so as to bring the compound (A) into contact with a metal member; and
and (2) adding one or more compounds (B) selected from zinc and zinc salts to the cooling water system after the step (1) to bring the compound (B) into contact with the metal member.
2. The method for preventing corrosion of a metal member of a cooling water system according to claim 1, wherein the compound (A) is added to the cooling water system in a concentration of 30 to 100mg/L in terms of tartaric acid in the step (1).
3. The method for preventing corrosion of a metal member of a cooling water system according to claim 1 or 2, wherein the pH of the cooling water system in the step (1) is 6.0 to 8.0.
4. The method for preventing corrosion of a metal member for a cooling water system according to claim 1 or 2, wherein in the step (1), the contact time of the metal member with the compound (a) is 20 to 30 hours.
5. The method for preventing corrosion of a metal member of a cooling water system according to claim 1 or 2, wherein the compound (B) is added to the cooling water system in the step (2) at a concentration of 1mg/L to 50mg/L in terms of zinc.
6. The method for preventing corrosion of a metal member for a cooling water system according to claim 1 or 2, wherein in the step (2), the contact time of the metal member with the compound (B) is 20 to 30 hours.
7. The method for preventing corrosion of a metal member of a cooling water system according to claim 1 or 2, wherein the cooling water system is a circulating cooling water system.
8. The method for preventing corrosion of a metal member of a cooling water system according to claim 1 or 2, wherein the step (1) and the step (2) are performed in a basic process of the cooling water system.
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| Application Number | Priority Date | Filing Date | Title |
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| JP2018-206770 | 2018-11-01 | ||
| JP2018206770A JP6635173B1 (en) | 2018-11-01 | 2018-11-01 | Corrosion protection method for metal members of cooling water system |
| PCT/JP2019/041153 WO2020090526A1 (en) | 2018-11-01 | 2019-10-18 | Method for inhibiting corrosion of metal member of cooling water system |
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| CN112955583A CN112955583A (en) | 2021-06-11 |
| CN112955583B true CN112955583B (en) | 2022-05-27 |
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| JP (1) | JP6635173B1 (en) |
| KR (1) | KR102524270B1 (en) |
| CN (1) | CN112955583B (en) |
| PH (1) | PH12021550984A1 (en) |
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| WO (1) | WO2020090526A1 (en) |
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| JP5499823B2 (en) | 2010-03-26 | 2014-05-21 | 栗田工業株式会社 | Cooling water treatment method |
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- 2018-11-01 JP JP2018206770A patent/JP6635173B1/en active Active
-
2019
- 2019-10-18 CN CN201980072390.4A patent/CN112955583B/en active Active
- 2019-10-18 KR KR1020217013062A patent/KR102524270B1/en active IP Right Grant
- 2019-10-18 WO PCT/JP2019/041153 patent/WO2020090526A1/en active Application Filing
- 2019-10-23 TW TW108138305A patent/TWI786339B/en active
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2021
- 2021-04-30 PH PH12021550984A patent/PH12021550984A1/en unknown
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| DE2513735A1 (en) * | 1974-04-01 | 1975-10-02 | Calgon Corp | CORROSION PROTECTION AGENT |
| CN102400149A (en) * | 2010-09-13 | 2012-04-04 | 朱海霞 | Cooling water corrosion inhibitor |
| CN102730849A (en) * | 2011-03-30 | 2012-10-17 | 栗田工业株式会社 | Method for preventing scale from forming in cooling water system |
| CN105026513A (en) * | 2013-02-26 | 2015-11-04 | 贝克休斯公司 | Corrosion inhibitors for cooling water applications |
| CN104562031A (en) * | 2013-10-14 | 2015-04-29 | 中国石油化工股份有限公司 | Pre-filming composition and pre-filming method |
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| Publication number | Publication date |
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| KR20210082178A (en) | 2021-07-02 |
| PH12021550984A1 (en) | 2021-11-08 |
| WO2020090526A1 (en) | 2020-05-07 |
| KR102524270B1 (en) | 2023-04-20 |
| JP2020070478A (en) | 2020-05-07 |
| TWI786339B (en) | 2022-12-11 |
| CN112955583A (en) | 2021-06-11 |
| JP6635173B1 (en) | 2020-01-22 |
| TW202028535A (en) | 2020-08-01 |
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