JP6932409B1 - Anticorrosive agents and anticorrosive methods in water systems - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anticorrosive agent and an anticorrosive method having low addition cost and water treatment cost of wastewater. The present invention is an anticorrosive agent for a metal member in an aqueous system, and an anticorrosive agent containing one or more selected from (A) aluminum lactate and (B) an inorganic acid salt and an organic acid salt. Provided is a method for preventing corrosion of metal members in an aqueous system using the above. [Selection diagram] None

Description

The present invention relates to an anticorrosive agent and an anticorrosive method for metal members in an aqueous system.

Metal pipes such as carbon steel are widely used for boilers, cooling / temperature control pipes, and the like. Since metal tubes used for such applications corrode when they come into contact with an aqueous solution, they are generally subjected to anticorrosion treatment. Although the anticorrosive treatment is carried out by various methods, the method of adding an anticorrosive agent to the water system is generally performed.

As an anticorrosive agent that suppresses the corrosion of carbon steel in the existing neutral freshwater environment, sodium molybdenum (Mo) acid (Na) and sodium tungsten (W) acid are added alone, zinc diphosphate and Na Moate are added. Examples include those to be mixed and added. When Na Moate is added alone, a very high concentration of Moate ion exceeding 1,000 ppm is required and the usage cost is high. When zinc diphosphate and Na Moate are mixed and added, even at a concentration of about 100 ppm. Although it has been reported to be effective, both diphosphate ion and zinc ion have a large environmental load, and the emission regulation is several ppm, which requires a high cost for water treatment of wastewater (Non-Patent Document 1). Therefore, there is a demand for anticorrosive agents and anticorrosive methods with low addition costs and wastewater treatment costs.

Kaneko et al., Evaluation of the effect of Na W acid and Na zinc / Na Moate phosphate on the corrosion of PCV materials in diluted artificial seawater, 62nd floor Material and Environmental Discussion Meeting (2015) 9-12

The present invention has been made in view of the above problems, and an object of the present invention is to provide an anticorrosive agent and an anticorrosive method having low addition cost and water treatment cost of wastewater.

As a result of studies to solve the above problems, the present inventors have found that by using aluminum lactate (Al), which has not been used as an anticorrosive agent, Al ions, inorganic acid ions and / or By mixing organic acid ions, it has the effect of suppressing corrosion at a lower concentration than Mo acid ion or W acid ion alone, and by using lactic acid Al, which has a small environmental load, the water treatment cost of wastewater is reduced, and the existing water treatment cost is reduced. The present invention has been completed by finding that it is possible to obtain an anticorrosive agent having a lower addition cost and a lower water treatment cost for wastewater than the anticorrosive agent.
That is, the gist of the present invention relates to the following.

[1] A method for preventing corrosion of a metal member in a water system, which comprises a step of adding an anticorrosive agent to the water system to form an initial anticorrosive film on the surface of the metal member in the water system.
The anticorrosive agent
One or more selected from (A) aluminum lactate and (B) inorganic and organic acid salts,
Anticorrosion method containing.
[2] The inorganic acid salt and organic acid salt of the component (B) are molybdenate, tungstate, borate, chromate, dichromate, nitrite, phosphate, silicate, and the like. The anticorrosion method according to [1], which is one or more selected from benzoate and siliceous salt.
[3] The salt in the inorganic acid salt and the organic acid salt of the component (B) is one or more selected from sodium salt, potassium salt, and ammonium salt, according to [1] or [2]. Anticorrosion method.
[4] The inorganic and organic acid salts of the component (B) are sodium molybate _{(Na 2 MoO 4} ), potassium molybdenate (K ₂ MoO ₄ ), and ammonium molybdate ((NH ₃ ) ₂ MoO ₄ ). , Sodium tungstate (Na ₂ WO ₄ ), potassium tungstate (K ₂ WO ₄ ), sodium borate (Na ₂ O · xB ₂ O ₅ ) (x is _{the number corresponding to Na 2} O), chromium acid Sodium (Na ₂ CrO ₄ ), Sodium dichromate (Na ₂ Cr ₂ O ₇ ), Sodium nitrite (Na ₂ NO ₂ ), Sodium phosphate (Na ₃ PO ₄ ), Sodium silicate (Na ₂ O · xSiO) ₂ ) (x is _{the number corresponding to Na 2} O), sodium benzoate (NaC ₆ H ₅ CO ₂ ), and sodium silicate (NaC ₆ H ₅ CH = CHCO ₂ ). The anticorrosion method according to any one of [1] to [3], which is more than one type.
[5] The concentration ratio of aluminum ions to inorganic acid ions and / or organic acid ions in the aqueous system is aluminum ion: inorganic acid ion and / or organic acid ion = 4: 1 to 1: 4 (molar concentration ratio). The anticorrosion method according to any one of [1] to [4], wherein the anticorrosive agent is added so as to have the ratio of.
[6] The anticorrosive agent is added so that the total ion concentration of aluminum ions and inorganic acid ions and / or organic acid ions in the aqueous system is in the range of 0.1 to 10.0 mM, according to [1] to [5]. The anticorrosion method described in either.

[7] The inorganic acid ion is a molybdate ion.
The anticorrosive method according to any one of [1] to [6], wherein the anticorrosive agent is added so that the aluminum ion concentration in the aqueous system is in the range of 0.15 to 1.5 mM and the molybdate ion concentration is in the range of 0.15 to 1.5 mM. ..
[8] The inorganic acid ion is a tungstate ion, and the inorganic acid ion is a tungstate ion.
The anticorrosive method according to any one of [1] to [6], wherein the anticorrosive agent is added so that the aluminum ion concentration in the aqueous system is in the range of 0.05 to 5.0 mM and the tungstate ion concentration is in the range of 0.05 to 5.0 mM. ..
[9] The inorganic acid ions are molybdate ions and tungstate ions.
The anticorrosive agent is added so that the aluminum ion concentration in the aqueous system is in the range of 0.033 to 0.33 mM, the molybdate ion concentration is in the range of 0.033 to 0.33 mM, and the tungstate ion concentration is in the range of 0.033 to 0.33 mM, [1] to [ 6] The anticorrosive method according to any one of.
[10] The anticorrosion method according to any one of [1] to [9], wherein the metal member is carbon steel.
[11] The anticorrosive method according to any one of [1] to [10], wherein the pH of the aqueous system when an anticorrosive agent is added to the aqueous system is 4 or more and less than 6.
[12] A step of adding a corrosion inhibitor to the water system in order to maintain the initial anticorrosive film after the step of forming the initial anticorrosive film.
The anticorrosion method according to any one of [1] to [11], which comprises.

[13] One or more selected from (A) aluminum lactate and (B) inorganic and organic acid salts,
An anticorrosive agent for metal parts in water systems containing.
[14] The inorganic acid salt and organic acid salt of the component (B) are molybdenate, tungstate, borate, chromate, dichromate, nitrite, phosphate, silicate, and the like. The anticorrosive agent according to [13], which is one or more selected from benzoate and siliceous salt.
[15] The salt in the inorganic acid salt and the organic acid salt of the component (B) is one or more selected from sodium salt, potassium salt, and ammonium salt, according to [13] or [14]. Anticorrosive agent.
[16] The inorganic acid salt and organic acid salt of the component (B) are sodium molybdate (Na ₂ Mo).
O ₄ ), potassium molybate _{(K 2 MoO 4} ), ammonium molybdate ((NH ₃ ) ₂ MoO ₄ ), sodium tungstate (Na ₂ WO ₄ ), potassium tungstate (K ₂ WO ₄ ), sodium borate (Na ₂ O · xB ₂ O ₅ ) (x is _{the number corresponding to Na 2} O), sodium chromate (Na ₂ CrO ₄ ), sodium dichromate (Na ₂ Cr ₂ O ₇ ), sodium nitrite (Na ₂ NO ₂ ), sodium phosphate (Na ₃ PO ₄ ), sodium silicate (Na ₂ O · xSiO ₂ ) (x is _{the number corresponding to Na 2} O), sodium benzoate (NaC ₆ H ₅₎ The anticorrosive agent according to any one of [13] to [15], which is one or more selected from CO ₂ ) and sodium silicate (NaC ₆ H ₅ CH = CHCO _2).
[17] The anticorrosive agent according to any one of [13] to [16], wherein the metal member is carbon steel.

According to the present invention, it is possible to provide an anticorrosive agent and an anticorrosive method which have an effect of suppressing corrosion at a low concentration and have a small environmental load. That is, according to the present invention, it is possible to provide an anticorrosive agent and an anticorrosive method having low addition cost and water treatment cost of wastewater.

FIG. 1 is a diagram (photograph) showing the appearance of carbon steel after a 100-hour corrosion test. FIG. 2 is a diagram showing the corrosion weight loss of carbon steel in the solution to which each anticorrosive agent is added. FIG. 3 is a diagram showing the concentration of the anticorrosive agent of the present invention and the amount of corrosion loss of carbon steel. FIG. 4 is a diagram showing the effect of the anticorrosive agent on the corrosion weight loss of rusted steel. FIG. 5 is a diagram showing the effect of the anticorrosive agent on the corrosion weight loss of steel in a gas-liquid alternating environment. FIG. 6 is a diagram showing the corrosion weight loss of carbon steel in a solution to which each anticorrosive agent is added under gamma ray irradiation.

Hereinafter, the present invention will be described.
<Anti-corrosion method>
One aspect of the present invention is
A method for preventing corrosion of metal members in a water system, which comprises a step of adding an anticorrosive agent to the water system to form an initial anticorrosive film on the surface of the metal member in the water system.
The anticorrosive agent
One or more selected from (A) aluminum lactate and (B) inorganic and organic acid salts,
The present invention relates to an anticorrosion method (hereinafter, may be referred to as "the anticorrosion method of the present invention") containing.

Further, another aspect of the present invention is
A method for preventing corrosion of metal parts in a water system, which includes a step of adding an anticorrosive agent to the water system.
The anticorrosive agent
One or more selected from (A) aluminum lactate and (B) inorganic and organic acid salts,
Containing, anticorrosion method.

The present inventors have conducted various studies in search of anticorrosive agents and anticorrosive methods having low addition costs and wastewater treatment costs.
Among them, the present inventors have provided an anticorrosive agent that suppresses corrosion of metal members such as carbon steel in an aqueous environment containing a type of chemical substance (aluminum lactate) that has not been used as a metal anticorrosive agent. Invented. The anticorrosive agent of the present invention is a mixture of aluminum lactate (Al lactate) with an inorganic acid salt (for example, sodium molybate (Na Moate) or sodium tungstate (Na W acid)) and / or an organic acid salt. It can be used by simply adding it to the water system as it is.
The present inventors consider that the Al ion contained in Al lactate and the inorganic acid ion contained in the inorganic acid salt (for example, Mo acid ion or W acid ion contained in Na Moate or Na W acid) or the organic acid ion are steel. It was found that metal corrosion was suppressed by forming a protective film (initial anticorrosion film) mainly composed of Al ₂ O _{3 on the surface, and the present invention was completed based on such findings.}

≪Water system≫
The anticorrosion method of the present invention suppresses corrosion of metal members in an aqueous system. Specific examples of the water are fresh water, and examples thereof include, but are not limited to, tap water, pure water, ultrapure water, back-penetration filtered water, deionized water, and mineral water. The pH is not limited, but from the viewpoint of the usage environment and the like, it is usually neutral at 25 ° C., and a pH of about 4 to 9 is preferable.

≪Metal parts≫
The anticorrosion method of the present invention can be applied to a metal member in which corrosion occurs in an aqueous system and suppression of the corrosion is desired. The metal member may be either a member containing metal or a member made of metal. Examples of the metal member include, but are not limited to, carbon steel, stainless steel, aluminum steel, and the like, and carbon steel is preferable from the viewpoint of versatility and the like. The carbon steel is not limited, but for example, the metal members exemplified by SGV410, SGV480, SS400, S45C, S50C, FC2000 and the like may be used alone or in combination of two or more. As the metal member, a commercially available metal member may be used. The metal member is not limited, but may be used, for example, for piping in a circulation system or the like.

≪Aluminum lactate≫
The aluminum lactate is not limited, and a commercially available product can be used.

≪Inorganic acid salt and organic acid salt≫
The inorganic acid salt and the organic acid salt are not limited as long as they can form an initial anticorrosion film together with Al ions. Specifically, for example, molybdates, tungstates, borates, chromates, dichromates, nitrites, phosphates, silicates, benzoates, silicates and the like These are preferably molybdates and tungstates. Examples of the molybdate include ortho-molybdate, para-molybdate, and meta-molybdate, and the ortho-molybdate is preferable. Examples of the tungstate include orthotungstate, paratungstate, metatungstate and the like, and orthotungstate is preferable. The salt-inorganic acid salt and the organic acid salt may be used alone or in combination of two or more. Commercially available products can be used as the inorganic acid salt and the organic acid salt.

The salt in the inorganic acid salt and the organic acid salt is not limited, and examples thereof include a sodium salt, a potassium salt, and an ammonium salt, and a sodium salt is preferable. The salt may be used alone or in combination of two or more.

Specific examples of the inorganic acid salt and the organic acid salt include sodium molybdate (general name is sodium molybdate and official name is disodium molybdate. In the present specification, the general name is used, but officially. It is the same as the compound indicated by the name. The same applies to other inorganic acid salts.) (Na ₂ MoO ₄ ), potassium molybdate (K ₂ MoO ₄ ), ammonium molybdate ((NH ₃ ) ₂ MoO ₄₎ ), Sodium molybdate (Na ₂ WO ₄ ), potassium tungstate (K ₂ WO ₄ ), sodium borate (Na ₂ O · xB ₂ O ₅ ) (x is the number corresponding to _{Na 2 O), chromium} Sodium acid (Na ₂ CrO ₄ ), sodium dichromate (Na ₂ Cr ₂ O ₇ ), sodium nitrite (Na ₂ NO ₂ ), sodium phosphate (Na ₃ PO ₄ ), sodium silicate (Na ₂ O · xSiO ₂ ) (x is _{the number corresponding to Na 2} O), sodium benzoate (NaC ₆ H ₅ CO ₂ ), sodium molybdate (NaC ₆ H ₅ CH = CHCO ₂ ), etc. are preferable. Is sodium molybdate, potassium molybdate, ammonium molybdate, sodium tungstate, potassium tungstate, and sodium borate, more preferably sodium molybdate and sodium tungstate.

In the anticorrosion method of the present invention, the step of forming an initial anticorrosion film on the surface of a metal member in an aqueous system (hereinafter, may be referred to as "initial anticorrosion film forming step") includes aluminum lactate, an inorganic acid salt and / or an organic acid salt. Can be carried out by adding an anticorrosive agent containing lactic acid to an aqueous system. The surface of the metal member may be a surface that is in continuous contact with the water system or a surface that is intermittently in contact with the water system.

The initial anticorrosion film forming step can usually be carried out at room temperature. As long as the effect of the present invention is not impaired, it can be applied even when a low temperature part / a high temperature part is generated depending on the condition of the treatment target.

The initial anticorrosion film forming step is preferably carried out in 1 to 5 days, more preferably in the range of 3 to 5 days. One day or more is preferable to form a sufficient initial anticorrosive film, and the properties of the initial anticorrosive film do not change significantly even if the treatment period is longer than necessary, and the amount of the drug used to maintain the concentration of the anticorrosive agent increases. It is preferably within 5 days from the viewpoint of cost such as

When an anticorrosive agent is added to a neutral water system, the pH of the water system is usually more acidic, for example, 4 or more and less than 6. After the initial anticorrosion film forming step is completed, the pH at, for example, 25 ° C. may be adjusted to, for example, about 4 to 9 or 6 or more, if necessary, such as the usage environment.

In the anticorrosion method of the present invention, the concentration ratio of aluminum ions due to the addition of an anticorrosive agent to inorganic acid ions and / or organic acid ions (that is, when only inorganic acid ions are contained as the anticorrosive agent, aluminum ions: inorganic acid ions Total ions, when containing only organic acid ions as an anticorrosive agent, aluminum ions: total ions of organic acid ions, and when containing inorganic acid ions and organic acid ions as anticorrosive agents, aluminum ions: inorganic acid ions and organic acid ions The total ion) may vary depending on the environment in which it is used, the metal member, the type / combination of the anticorrosive agent, etc., and is not limited, but for example, aluminum ion: inorganic acid ion and / or organic acid ion = 4: 1 to 1: It may be 4 (molar concentration ratio), 2: 1 to 1: 2, or 1: 1.

When the anticorrosive agent is a combination of aluminum lactate and sodium molybdate, or a combination of aluminum lactate and one kind of inorganic acid ion or organic acid ion such as a combination of aluminum lactate and sodium tungstate, in the aqueous system after the addition of the anticorrosive agent. As the concentration ratio of aluminum ion to inorganic acid ion or organic acid ion, for example, 2: 1 to 1: 1 is preferable, and 2: 1 is more preferably exemplified.

When the anticorrosive agent is a combination of aluminum lactate, aluminum lactate such as a combination of sodium molybdate and sodium tungstate, and two kinds of inorganic acid ions and / or organic acid ions, the aluminum ions in the aqueous system after the addition of the anticorrosive agent As the concentration ratio with the inorganic acid ion and / or the organic acid ion, for example, 1: 1: 1 to 2: 1: 1 is preferable, and 1: 1: 1 can be more preferably exemplified.

In the anticorrosion method of the present invention, the total ion concentration of aluminum ions in the water system due to the addition of the anticorrosion agent and inorganic acid ions and / or organic acid ions (that is, when only inorganic acid ions are contained as the anticorrosive agent, aluminum ions and inorganic acids Total ions of ions, total ions of aluminum ions and organic acid ions when containing only organic acid ions as an anticorrosive agent, aluminum ions, inorganic acid ions and organic acids when containing inorganic acid ions and organic acid ions as anticorrosive agents The total ion of the ion) can vary and is not limited depending on the environment in which it is used, the metal member, the type / combination of the anticorrosive agent, etc., but is not limited, for example, 0.01 mM or more, 0.05 mM or more, 0.1 mM or more, 0.3 mM or more, 0.5. Above mM, above 1.0 mM, and below 100.0 mM, below 50.0 mM, 1
It may be 0.0 mM or less, 5.0 mM or less, 3.0 mM or less, 1.0 mM or less, and may be a consistent combination thereof.

When the anticorrosive agent is a combination of aluminum lactate and sodium molybdate, the concentration of aluminum ions and molybdate ions in the water system after the addition of the anticorrosive agent is preferably 0.3 mM to 3.0 mM, for example.

In one aspect, the anticorrosive agent of the present invention can be added so that the aluminum ion concentration in the aqueous system after the addition of the anticorrosive agent is in the range of 0.15 to 1.5 mM and the molybdate ion concentration is in the range of 0.15 to 1.5 mM.

When the anticorrosive agent is a combination of aluminum lactate and sodium tungstate, the concentration of aluminum ions and tungstate ion in the water system after the addition of the anticorrosive agent is preferably 0.1 mM to 10.0 mM, for example.

In one aspect, the anticorrosive agent of the present invention can be added so that the aluminum ion concentration in the aqueous system after the addition of the anticorrosive agent is in the range of 0.05 to 5.0 mM and the tungstate ion concentration is in the range of 0.05 to 5.0 mM.

When the anticorrosive agent is a combination of aluminum lactate, sodium molybdate and sodium tungstate, the concentration of aluminum ion, molybdate ion and tungstate ion in the aqueous system after the addition of the anticorrosive agent is, for example, 0.1 mM to 1.0 mM. It can be preferably exemplified.

In one aspect, the present invention has an aluminum ion concentration in the range of 0.033 to 0.33 mM, a molybdate ion concentration of 0.033 to 0.33 mM, and a tungstate ion concentration in the range of 0.033 to 0.33 mM in the aqueous system after the addition of the anticorrosive agent. Anticorrosive agents can be added.

Another aspect of the present invention is a step of adding a corrosion inhibitor to the water system in order to maintain the initial anticorrosive film after the step of forming the initial anticorrosive film in the anticorrosive method of the present invention (hereinafter, "film"). It relates to anticorrosion methods including (sometimes referred to as "maintenance process").
That is, after the completion of the initial anticorrosion film forming step, a step for maintaining the initial anticorrosion film may be performed. This film maintenance step can be carried out by adding an appropriate amount of various existing corrosion inhibitors to the water system.

At the time of transition from the initial anticorrosion film forming step to the film maintenance step, the entire amount of water in the system may be replaced, but it is also possible to shift to the film maintenance step while leaving a part or all of the water. The corrosion inhibitor added in the film maintenance step is not particularly limited, but an inorganic acid salt-based anticorrosive agent, an organic acid salt-based anticorrosive agent, etc., which are exemplified by Na Moate and Na W acid anticorrosive agents, can be used. .. The amount of the corrosion inhibitor added in the film maintenance step varies depending on the type of the anticorrosive agent used, but is the amount at which the anticorrosive film produced in the previous step is maintained.

In the present invention, in the initial anticorrosive film forming step and the film maintaining step, a slime inhibitor, a scale inhibitor, an azole-based anticorrosive agent for copper, another anticorrosive agent and the like may be further used in combination, if necessary.

<Corrosion inhibitor>
Another aspect of the present invention is
One or more selected from (A) aluminum lactate and (B) inorganic and organic acid salts,
The present invention relates to an anticorrosive agent for a metal member in an aqueous system (hereinafter, may be referred to as “the anticorrosive agent of the present invention”). The matters described in the anticorrosive method of the present invention are all applied to the description of the anticorrosive agent of the present invention.

The anticorrosive agent of the present invention may contain the components (A) and (B) in the same packaging material, or the components may be put in separate packaging materials and mixed at the time of use. good. The anticorrosive agent of the present invention may contain an additive component usually used in the art as long as the effect of the present invention is not impaired. Examples of such an additive component include a pH adjuster, a stabilizer and the like.

Hereinafter, the present invention will be specifically described with reference to Examples, but these are examples of the present invention, and the scope of the present invention is not limited thereto.

<Example 1> Evaluation of anticorrosion performance 1
In order to compare the performance of the anticorrosive agent of the present invention with the existing anticorrosive agent, corrosion of carbon steel (SGV480 equivalent material) was performed using a solution in which various test chemicals were added to a 3 mM NaCl solution so as to be 1 mM each. The test was carried out at 25 ° C. for 100 hours. When two types of chemicals were mixed, 0.5 mM was added, and when three types were mixed, 0.33 mM was added to unify the total ion concentration of the anticorrosive agent. In addition, for reference, a test was also conducted on a solution without an anticorrosive agent and a solution in which only Al lactate, which has not been used as an anticorrosive agent, was added alone.
FIG. 1 shows a photograph of the appearance of carbon steel after a 100-hour corrosion test. From the photograph, in the case of control sample 1 without anticorrosive agent, the surface of carbon steel turned black due to corrosion and black rust (Fe ₃ O ₄ ) was formed, and red rust (γ-Fe OOH) was deposited on the bottom of the test container. You can see that. In the case of Al lactic acid in Sample 2, Na Moate in Sample 3, Na W acid in Sample 4, and Zinc diphosphate + Na Moate in Sample 5, the amount of red rust is smaller than that without the anticorrosive agent, but carbon. The steel surface is discolored black. On the other hand, in the examples of Sample 6 of the present invention, Al lactic acid + Na lactic acid, Sample 7 of Al lactic acid + Na lactic acid, and Sample 8 of Al lactic acid + Na lactic acid + Na W acid, the surface retains metallic luster, and existing anticorrosive agents and lactic acid It is considered to have higher anticorrosion performance than Al.

Figure 2 shows the corrosion weight loss of each solution after removing the corrosion products formed on the surface of the test piece after the 100-hour corrosion test. The smaller the value of corrosion weight loss, the more the corrosion is suppressed.
It can be confirmed that the existing anticorrosive agents (Samples 3, 4 and 5) and Al lactate (Sample 2) have a larger corrosion weight loss than those without the anticorrosive agent. The reason why the corrosion weight loss increases despite the addition of the anticorrosive agent is that the corrosion promoting effect due to the increase in electrical conductivity becomes dominant if the ion concentration required for anticorrosion is not present. On the other hand, in the anticorrosive agent of the present invention, Al lactic acid Al + Na Moate in Sample 6, Al + Na Lactate + Na W in Sample 7, and Al + Na Lactate + Na W in Sample 8 have the same anticorrosive agent concentration in the solution as other solutions. It was confirmed that the amount of lactic acid was reduced. In this test, this experiment was carried out with four test pieces under each condition, and the same reproducible results were confirmed in all cases. As described above, it was possible to develop an anticorrosive agent that suppresses the corrosion of carbon steel in a neutral freshwater environment at a concentration lower than that of the existing anticorrosive agent and has a lower environmental load than the existing anticorrosive agent.

<Example 2> Examination of Corrosion Inhibitor Concentration Fig. 3 shows the relationship between the total corrosion inhibitor concentration in solution and the corrosion weight loss of carbon steel (SGV480 equivalent material) when the anticorrosive agent concentration of the present invention is changed and added. .. The corrosion weight loss is the value after the immersion test for 100 hours, and the smaller the corrosion weight loss value, the more the corrosion is suppressed. The straight line in the figure shows the standard corrosion weight loss value when the test was performed with a 3 mM NaCl solution containing no anticorrosive agent.
When the total anticorrosive agent concentration is 0.1 mM, 0.05 mM for each of the two types and 0.033 mM for each of the three types so that the mixing ratio of Al lactate and Na Moate is equal to 3 mM NaCl when preparing the solution. Was added so that the mixing ratio was equal at each concentration. From the graph, in this test, the corrosion weight loss of Al + Na lactate was lower than that of NaCl alone when the total anticorrosive concentration was in the range of 0.3-3 mM. With Al lactate + sodium W acid, the total corrosion inhibitor concentration was lower at all concentrations from 0.1 mM to 10 mM than with NaCl alone. In the case of Al lactate + Na Moate + Na W acid, the total corrosion inhibitor concentration was 0.1 mM and 1 mM, and the corrosion weight loss was lower than that in the case of NaCl alone.
That is, in this test, the total anticorrosive agent concentration at which the anticorrosive agent exerts its corrosion-suppressing ability is 0.3 mM to 3 mM for Al lactate + Na Moate, 0.1 mM to 10 mM for Al + Na lactate + 0.1 mM for Al + Na lactate + Na W acid. It is considered to be from mM to 1 mM.

Table 1 shows the corrosion reduction of carbon steel (SGV480 equivalent material) when the addition ratio of the two types of chemicals added in the anticorrosive agent of the present invention is changed.
The solution used in the test was prepared by adding a drug to 3 mM NaCl at various ratios so that the total anticorrosive agent concentration was 1 mM. The corrosion weight loss is the value after the immersion test for 100 hours, and the corrosion weight loss in 3 mM NaCl without the corrosion inhibitor was 0.916 mgcm ^-2 . Therefore, if the corrosion weight loss is less than this value, the corrosion inhibitor Means to be effective. From Table 1, in either case of Al lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate + Na lactate. In addition, the higher the ratio of Al lactate, the smaller the value of corrosion loss in both cases, and the value of loss of corrosion was the smallest in this test when Al lactate: Na Moate = 2: 1. Therefore, it is considered that the corrosion suppressing effect is the highest. In addition, in the case of a mixture of 3 types of Al lactic acid + Na Moate + Na W acid, the corrosion weight loss is 0.771 mgcm ^-2 and 1: 1: 1 at a ratio such that Al lactic acid: Na Moate: Na W acid = 2: 1: 1. Although the amount of ^{corrosion loss is larger than 0.734 mgcm -2 in} the case of, it can be seen that it has an effect as an anticorrosive agent for carbon steel.

<Example 3> Evaluation of anticorrosion performance 2
FIG. 4 shows the corrosion weight loss when the already rusted carbon steel (material equivalent to SGV480) is immersed in the solution to which the anticorrosive agent of the present invention is added.
In the test, carbon steel was immersed in a 3 mM NaCl solution for 100 hours to sufficiently rust the surface, and then immersed in each solution shown in FIG. 4 for 400 hours. The solution containing the anticorrosive agent was prepared by adding various agents in the same ratio so that the total anticorrosive agent concentration was 1 mM. For reference, the test was also conducted with a solution containing zinc diphosphate + sodium moate, which has been reported as an existing anticorrosive agent. The broken line in the figure shows the corrosion weight loss without the anticorrosive agent, and when the corrosion weight loss is smaller than this value, it means that the corrosive agent has an effect. From Fig. 4, the existing anticorrosive agent zinc diphosphate + Na Moate has a higher corrosion weight loss value than the case without the anticorrosive agent, and the concentration added this time has the effect of suppressing the corrosion of rusted steel. It turns out that there is no. On the other hand, the three types of anticorrosive agents of the present invention (Al lactic acid + Na lactate, Al + Na lactate + Na lactate + Na lactate + Na W acid) have lower corrosion weight loss when the total anticorrosive agent concentration is 1 mM than when no anticorrosive agent is used. It can be seen that not only non-rusted steel but also once rusted steel has a corrosion suppressing effect.

<Example 4> Evaluation of anticorrosion performance 3
Figure 5 shows the results of investigating the effect of suppressing the corrosion of carbon steel (SGV480 equivalent material) in a gas-liquid alternating environment using the solution to which the anticorrosive agent of the present invention was added. The gas-liquid alternating environment is an environment that simulates the corrosion of steel placed in the gas-liquid interface environment or steel in the liquid film environment by alternately exposing the steel to the air and the liquid while rotating it.
The test was conducted in a gas-liquid alternating environment (in air) in a solution prepared by adding Al lactate and Na Moate at a ratio of 1: 1 to 3 mM NaCl with carbon steel so that the anticorrosive agent concentration was 1 mM. After exposure to the solution every 30 seconds), the corrosion weight loss was measured. For reference, tests were also conducted on solutions without the addition of anticorrosive agents. From FIG. 5, the corrosion loss of carbon steel in the gas-liquid alternating environment is significantly reduced as compared with the case where no anticorrosive agent is added. In the gas-liquid alternating environment, the anticorrosive agent of the present invention is compared with the normal immersion state. It can be seen that the effect of suppressing corrosion is particularly high.

<Example 5> Evaluation of anticorrosion performance 4
Table 2 shows the results of investigating the effect of suppressing corrosion of carbon steel, which is different from the material equivalent to SGV480, using the solution to which the anticorrosive agent of the present invention was added. In this test, three types of materials, SS400, S45C, and FC200, were selected as commonly used carbon steels.
In the test, carbon steel was added to 3 mM NaCl to a corrosive inhibitor concentration of 1 mM so that the ratio of each drug was 1: 1 or 1: 1: 1 and exposed to a solution prepared for 100 hours. After that, the corrosion weight loss was measured. In Table 2, when the amount of corrosion is reduced by adding an anticorrosive agent as compared with the case of NaCl alone, the amount of mass reduction is shown underlined. From Table 2, it can be seen that in the case of SS400, the corrosion is reduced when Al lactic acid + Na lactate + Na lactate + Na Moate + Na W acid is added as compared with the case of NaCl alone. On the other hand, it can be seen that the amount of corrosion of S45C and FC200 was reduced when all the anticorrosive agents were added, as compared with the case of NaCl alone. From the above, it can be said that the anticorrosive agent of the present invention exerts a corrosion suppressing effect on a wide range of carbon steels.

<Example 6> Evaluation of anticorrosion performance 5
Fig. 6 shows the corrosion weight loss when a carbon steel corrosion test was carried out for 100 hours under gamma-ray irradiation using a solution in which various anticorrosive agents developed in this study were added to a 3 mM NaCl solution so as to be 1 mM each. show.
From FIG. 6, it can be seen that when the anticorrosive agent of the present invention is added, the amount of corrosion loss is reduced as compared with the case without the anticorrosive agent, and the corrosion is reduced. Comparing the amount of corrosion loss without gamma-ray irradiation in Fig. 2, corrosion is promoted by the effect of gamma-ray irradiation without anticorrosive agent, whereas with the addition of Al lactate + Na Moate, there is no irradiation in Fig. 2. It can be seen that the corrosion weight loss is reduced when gamma-ray irradiation is performed as compared with the case of. From this, it can be said that the anticorrosive agent of the present invention has an effect of suppressing the corrosion of carbon steel even under gamma ray irradiation, and in particular, the anticorrosive agent composed of Al lactate + Na Moate is an anticorrosive agent suitable for the gamma ray irradiation environment. ..

As described above, it has been shown that the anticorrosive agent of the present invention has an effect of suppressing corrosion at a low concentration and is an anticorrosive agent having a small environmental load.
Further, the anticorrosive agent of the present invention has an anticorrosive effect on already rusted metal members, has an excellent anticorrosive effect even in a gas-liquid alternating environment, has an anticorrosive effect on a wide range of members, and has an anticorrosive effect even in a gamma ray irradiation environment. It was shown that it has excellent characteristics such as excellent rust.

In this study, it was clarified that the effect as an anticorrosive agent is recognized by the combined addition of Moate and W acid salt to Al lactate, which has not been used as an anticorrosive agent so far. Mo and W acid salts are classified as oxidized rust inhibitors by Aramaki (Aramaki, Anticorrosion Control, 48 (2004) 151), and oxidized rust inhibitors are originally present on the surface of steel γ-Fe ₂ O. It has been reported that a fairly dense passivation film of oxide or hydroxide is formed on the protective film of No. _{3 to suppress corrosion.} Oxidized inhibitors have the same mechanism of action in that they act as oxidants and are reduced to form a passivation film. It is thought that this will be effective as an anticorrosive agent. Oxidized rust preventives include chromate (Na ₂ CrO ₄ ), dichromate (Na ₂ Cr ₂ O ₇ ), nitrite (Na ₂ NO ₂ ), phosphate (Na ₃ PO ₄ ), and Kay. Acid salt (Na _{2 O.xSiO 2} ), borate salt (Na ₂ O.xB ₂ O ₅ ), benzoate salt (NaC ₆ H ₅ CO ₂ ), chamolate (NaC ₆ H ₅ CH = CHCO ₂₎ ), Reported by Aramaki mentioned above. That is, it is considered that the effect of suppressing corrosion is enhanced by combining these oxidized rust preventives with Al lactic acid.

It is considered that the present invention can be used as an anticorrosive agent and an anticorrosive method for metal members such as carbon steel constituting boilers, cooling / temperature control piping, etc. in an aqueous environment.

Claims (17)

A method for preventing corrosion of a metal member in a water system, which comprises a step of adding an anticorrosive agent to the water system to form an initial anticorrosive film on the surface of the metal member in the water system.
The anticorrosive agent
One or more selected from (A) aluminum lactate and (B) inorganic and organic acid salts,
Anticorrosion method containing. The inorganic acid salt and organic acid salt of the component (B) are molybdenate, tungstate, borate, chromate, dichromate, nitrite, phosphate, silicate, and benzoate. The anticorrosion method according to claim 1, wherein the anticorrosion method is one or more selected from silicate. The salts of the inorganic acid salt and the organic acid salt of the component (B) are sodium salt, potassium salt, and the like.
The anticorrosion method according to claim 1 or 2, wherein one or more of them are selected from ammonium salts. The inorganic and organic acid salts of the component (B) are sodium molybate _{(Na 2 MoO 4} ), potassium molybdenate (K ₂ MoO ₄ ), ammonium molybdate ((NH ₃ ) ₂ MoO ₄ ), and tungsten acid. Sodium (Na ₂ WO ₄ ), potassium tungstate (K ₂ WO ₄ ), sodium borate (Na ₂ O · xB ₂ O ₅ ) (x is _{the number corresponding to Na 2} O), sodium chromate (Na) ₂ CrO ₄ ), sodium dichromate (Na ₂ Cr ₂ O ₇ ), sodium nitrite (Na ₂ NO ₂ ), sodium phosphate (Na ₃ PO ₄ ), sodium silicate (Na ₂ O · xSiO ₂ ) ( x is _{the number corresponding to Na 2} O), sodium benzoate (NaC ₆ H ₅ CO ₂ ), and sodium silicate (NaC ₆ H ₅ CH = CHCO ₂ ). The anticorrosion method according to any one of claims 1 to 3. The concentration ratio of aluminum ions to inorganic acid ions and / or organic acid ions in the aqueous system is the ratio of aluminum ions: inorganic acid ions and / or organic acid ions = 4: 1 to 1: 4 (molar concentration ratio). Any 1 of claims 1 to 4, wherein the anticorrosive agent is added so as to become
The anticorrosion method described in the section. The anticorrosive agent is added so that the total ion concentration of aluminum ions and inorganic acid ions and / or organic acid ions in the water system is in the range of 0.1 to 10.0 mM, according to any one of claims 1 to 5. The described anticorrosion method. The inorganic acid ion contained in the inorganic acid salt is a molybdate ion.
The anticorrosive method according to any one of claims 1 to 6, wherein the anticorrosive agent is added so that the aluminum ion concentration in the aqueous system is in the range of 0.15 to 1.5 mM and the molybdate ion concentration is in the range of 0.15 to 1.5 mM. .. The inorganic acid ion contained in the inorganic acid salt is a tungstate ion, and is
The anticorrosion method according to any one of claims 1 to 6, wherein the anticorrosion agent is added so that the aluminum ion concentration in the water system is in the range of 0.05 to 5.0 mM and the tungstate ion concentration is in the range of 0.05 to 5.0 mM. .. The inorganic acid ions contained in the inorganic acid salt are molybdate ion and tungstate ion, and are
Claims 1 to 6 add the anticorrosive agent so that the aluminum ion concentration in the aqueous system is in the range of 0.033 to 0.33 mM, the molybdate ion concentration is in the range of 0.033 to 0.33 mM, and the tungstate ion concentration is in the range of 0.033 to 0.33 mM. The anticorrosive method according to any one of the above. The anticorrosion method according to any one of claims 1 to 9, wherein the metal member is carbon steel. The anticorrosive method according to any one of claims 1 to 10, wherein the pH of the aqueous system when the anticorrosive agent is added to the aqueous system is 4 or more and less than 6. After the step of forming the initial anticorrosive film, a step of adding a corrosion inhibitor to the water system in order to maintain the initial anticorrosive film.
The anticorrosion method according to any one of claims 1 to 11, which comprises. One or more selected from (A) aluminum lactate and (B) inorganic and organic acid salts,
An anticorrosive agent for metal parts in water systems containing. The inorganic acid salt and organic acid salt of the component (B) are molybdenate, tungstate, borate, chromate, dichromate, nitrite, phosphate, silicate, and benzoate. The anticorrosive agent according to claim 13, which is one or more selected from, and chamochrome. The salts of the inorganic acid salt and the organic acid salt of the component (B) are sodium salt, potassium salt, and the like.
The anticorrosive agent according to claim 13 or 14, which is one or more selected from ammonium salts. The inorganic and organic acid salts of the component (B) are sodium molybate _{(Na 2 MoO 4} ), potassium molybdenate (K ₂ MoO ₄ ), ammonium molybdate ((NH ₃ ) ₂ MoO ₄ ), and tungsten acid. Sodium (Na ₂ WO ₄ ), potassium tungstate (K ₂ WO ₄ ), sodium borate (Na ₂ O · xB ₂ O ₅ ) (x is _{the number corresponding to Na 2} O), sodium chromate (Na) ₂ CrO ₄ ), sodium dichromate (Na ₂ Cr ₂ O ₇ ), sodium nitrite (Na ₂ NO ₂ ), sodium phosphate (Na ₃ PO ₄ ), sodium silicate (Na ₂ O · xSiO ₂ ) ( x is _{the number corresponding to Na 2} O), sodium benzoate (NaC ₆ H ₅ CO ₂ ), and sodium silicate (NaC ₆ H ₅ CH = CHCO ₂ ). The anticorrosive agent according to any one of claims 13 to 15. The anticorrosive agent according to any one of claims 13 to 16, wherein the metal member is carbon steel.

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