JP2022143394A - Anticorrosive agent and anticorrosive method in water system - Google Patents

Abstract

To provide an anticorrosive agent and an anticorrosive method with reduced cost of addition and reduced cost of wastewater treatment.SOLUTION: An anticorrosive agent for a metal member in a water system contains (A) aluminium lactate, and (B) one or more selected from inorganic acid salts and organic acid salts. There is also provided an anticorrosive method for a metal member in a water system using the anticorrosive agent.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to an anticorrosion agent and anticorrosion method for metal members in a water system.

Metal pipes such as carbon steel pipes are widely used for boilers, cooling/temperature control pipes, and the like. Metal pipes used for such applications are generally subjected to anti-corrosion treatment because they corrode when in contact with an aqueous solution. Anticorrosive treatment is carried out by various methods, but a method of adding an anticorrosive agent to a water system is generally performed.

Sodium molybdate (Mo) and Na tungstate (W) alone, zinc diphosphate and Na Mo are added as corrosion inhibitors to suppress the corrosion of carbon steel in existing neutral freshwater environments. Mixed addition is mentioned. When adding sodium molybdenum, etc. alone, a very high concentration of molybdenum ions exceeding 1,000 ppm is required, resulting in high usage costs. Although it has been reported that they are effective, both diphosphate ions and zinc ions have a large environmental load, and the discharge regulation is several ppm, which requires high costs for wastewater treatment (Non-Patent Document 1). Therefore, anticorrosion agents and anticorrosion methods with low addition costs and low waste water treatment costs are desired.

Kaneko et al., Effect evaluation of W acid Na and zinc/Mo acid Na mixed phosphate on corrosion of PCV materials in diluted artificial seawater, 62nd Conference on Materials and Environment (2015) 9-12

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an anticorrosive agent and a method of anticorrosion that are low in cost for addition and water treatment of waste water.

The present inventors conducted studies to solve the above problems, and found that by using aluminum lactate (Al), which has not been used as an anticorrosive agent, Al ions and inorganic acid ions and / or By mixing organic acid ions, it has the effect of suppressing corrosion at a lower concentration than Mo acid ions or W acid ions alone. The present inventors have completed the present invention by finding that the anticorrosive agent can be made with a lower addition cost and a lower waste water treatment cost than the anticorrosive agent of .
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, comprising adding an anticorrosive agent to the water system to form an initial anticorrosion film on the surface of the metal member in the water system,
The anticorrosive agent is
(A) aluminum lactate, and (B) one or more selected from inorganic acid salts and organic acid salts,
A corrosion prevention method comprising:
[2] The inorganic and organic acid salts of component (B) are molybdates, tungstates, borates, chromates, dichromates, nitrites, phosphates, silicates, The anticorrosion method according to [1], which is one or more selected from benzoates and cinnamates.
[3] According to [1] or [2], wherein the salt in the inorganic acid salt and organic acid salt of component (B) is one or more selected from sodium salts, potassium salts, and ammonium salts. anti-corrosion method.
[ ₄ ] The inorganic and organic acid salts of component (B) are sodium molybdate ( _Na2MoO4 ), potassium molybdate _{( K2MoO4} ), and ammonium molybdate ( _{( NH3} ) _2MoO4 ). , sodium tungstate ( _Na2WO4 ), potassium tungstate ( _K2WO4 ), sodium borate _{( Na2O.xB2O5} ) ₍ x is the _number corresponding to _Na2O ), chromic _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 x SiO ₂ ) one or _two selected from (x is a number corresponding to _Na2O ), sodium benzoate _{( NaC6H5CO2} ), and sodium cinnamate _{( NaC6H5CH} = _CHCO2 ) The corrosion prevention method according to any one of [1] to [3], which is more than one type.
[5] The concentration ratio of aluminum ions and inorganic acid ions and/or organic acid ions in the aqueous system is aluminum ions: inorganic acid ions and/or organic acid ions = 4:1 to 1:4 (molar concentration ratio) The corrosion prevention method according to any one of [1] to [4], wherein the anticorrosion agent is added so that the ratio is
[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 water system is in the range of 0.1 to 10.0 mM, [1] to [5]. The anti-corrosion method according to any one of the above.

[7] the inorganic acid ion is a molybdate ion,
The corrosion prevention method according to any one of [1] to [6], wherein the anticorrosion agent is added so that the aqueous system has an aluminum ion concentration of 0.15 to 1.5 mM and a molybdate ion concentration of 0.15 to 1.5 mM. .
[8] the inorganic acid ion is a tungstate ion,
The anticorrosion method according to any one of [1] to [6], wherein the anticorrosive agent is added so that the aqueous system has an aluminum ion concentration of 0.05 to 5.0 mM and a tungstate ion concentration 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 aqueous system has an aluminum ion concentration of 0.033 to 0.33 mM, a molybdate ion concentration of 0.033 to 0.33 mM, and a tungstate ion concentration of 0.033 to 0.33 mM. 6] The anticorrosion method according to any one of the items.
[10] The corrosion prevention method according to any one of [1] to [9], wherein the metal member is carbon steel.
[11] The anticorrosion method according to any one of [1] to [10], wherein the pH of the water system when the anticorrosion agent is added to the water system is 4 or more and less than 6.
[12] After the step of forming the initial anticorrosion coating, further adding a corrosion inhibitor to the aqueous system to maintain the initial anticorrosion coating;
Corrosion prevention method according to any one of [1] to [11], comprising

[13] (A) aluminum lactate, and (B) one or more selected from inorganic acid salts and organic acid salts,
A corrosion inhibitor for metal members in an aqueous system containing
[14] The inorganic and organic acid salts of component (B) are molybdates, tungstates, borates, chromates, dichromates, nitrites, phosphates, silicates, The anticorrosive agent according to [13], which is one or more selected from benzoates and cinnamates.
[15] According to [13] or [14], wherein the salt in the inorganic acid salt and organic acid salt of component (B) is one or more selected from sodium salts, potassium salts, and ammonium salts. anticorrosion agent.
[16] The inorganic acid salt and organic acid salt of component (B) are sodium molybdate (Na ₂ Mo
_O4 ), potassium molybdate _{( K2MoO4} ), ammonium molybdate ( _{( NH3} ) _2MoO4 ), sodium tungstate _{( Na2WO4} ), potassium tungstate _{( K2WO4} ), sodium borate ( _Na2O.xB2O5 ) ( _x is a _number corresponding to _Na2O ), sodium _{chromate ( Na2CrO4} ), sodium dichromate _{( Na2Cr2O7} ), sodium nitrite ( _Na2NO2 ), sodium phosphate ( _Na3PO4 ), sodium silicate ( _Na2O.xSiO2 ) ( _x is the _number corresponding to _Na2O ), sodium _{benzoate ( NaC6H5} CO ₂ ), and sodium cinnamate (NaC ₆ H ₅ CH=CHCO ₂ ), or two or more of them, the anticorrosive agent according to any one of [13] to [15].
[17] The anticorrosive agent according to any one of [13] to [16], wherein the metal member is carbon steel.

ADVANTAGE OF THE INVENTION According to this invention, it has the effect which suppresses corrosion at a low concentration, and also can provide the anticorrosion agent and anticorrosion method with a small environmental burden. That is, according to the present invention, it is possible to provide an anticorrosive agent and anticorrosion method with low cost for addition and low cost for water treatment of waste water.

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

The present invention will be described below.
<Corrosion prevention method>
One aspect of the present invention is
A method for preventing corrosion of a metal member in a water system, comprising the step of adding an anticorrosive agent to the water system to form an initial anticorrosion film on the surface of the metal member in the water system,
The anticorrosive agent is
(A) aluminum lactate, and (B) one or more selected from inorganic acid salts and organic acid salts,
Containing, it relates to a corrosion prevention method (hereinafter sometimes referred to as "corrosion prevention method of the present invention").

In addition, another aspect of the present invention is
A method for preventing corrosion of a metal member in a water system, comprising adding an anticorrosive agent to the water system,
The anticorrosive agent is
(A) aluminum lactate, and (B) one or more selected from inorganic acid salts and organic acid salts,
Containing, it relates to a corrosion prevention method.

The present inventors have conducted various studies in search of anticorrosion agents and anticorrosion methods that are low in cost for addition and water treatment of waste water.
Among them, the present inventors have found a corrosion inhibitor that suppresses corrosion of metal members such as carbon steel in an aqueous environment containing a chemical substance (aluminum lactate) that has not been used as a metal corrosion inhibitor so far. devised. The anticorrosive agent of the present invention is a mixture of aluminum lactate (Al lactate) with an inorganic acid salt (for example, sodium molybdate (Mo acid Na) or sodium tungstate (W acid Na)) and/or an organic acid salt. It can be used by simply adding it to an aqueous system as it is.
The present inventors have found that Al ions contained in Al lactate and inorganic acid ions contained in inorganic acid salts (for example, Mo acid ions or W acid ions contained in Mo acid Na or W acid Na) or organic acid ions The present inventors have found that metal corrosion is suppressed by forming a protective film (initial anticorrosion film) mainly composed of Al ₂ O ₃ on the surface, and have completed the present invention based on this finding.

≪Water system≫
The corrosion prevention method of the present invention suppresses corrosion of metal members in water systems. Specific examples of water include, but are not limited to, fresh water, tap water, pure water, ultrapure water, reverse osmosis filtered water, deionized water, and mineral water. Although the pH is not limited, it is usually neutral at 25° C., preferably about pH 4 to 9, from the viewpoint of the usage environment and the like.

≪Metal member≫
The anti-corrosion method of the present invention can be applied to metal members that are subject to corrosion in aqueous systems and for which suppression of 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, and aluminum steel. Carbon steel is preferred from the viewpoint of versatility. Examples of carbon steel include, but are not limited to, SGV410, SGV480, SS400, S45C, S50C, and FC2000. Metal members may be used singly or in combination of two or more. A commercially available metal member can be used for the metal member. The metal member can be used for, but not limited to, piping in a circulatory system or the like.

≪Aluminum lactate≫
Aluminum lactate is not limited, and commercially available products can be used.

≪Inorganic acid salts and organic acid salts≫
Inorganic acid salts and organic acid salts are not limited as long as they can form an initial anticorrosive film together with Al ions. Specifically, for example, molybdate, tungstate, borate, chromate, dichromate, nitrite, phosphate, silicate, benzoate, and cinnamate. and preferably molybdate and tungstate. The molybdate includes ortho-molybdate, para-molybdate, meta-molybdate and the like, preferably ortho-molybdate. The tungstate includes orthotungstate, paratungstate, metatungstate, and the like, preferably orthotungstate. Salt inorganic acid salts and organic acid salts may be used alone or in combination of two or more. Commercially available products can be used as inorganic acid salts and organic acid salts.

Examples of inorganic acid salts and organic acid salts include, but are not limited to, sodium salts, potassium salts, and ammonium salts, with sodium salts being preferred. Salts may be used singly or in combination of two or more.

Specific examples of inorganic acid salts and organic acid salts include, for example, sodium molybdate (generic name is sodium molybdate, formal name is disodium molybdate. In this specification, the general name is described, but the formal name is The same is true for other inorganic acid salts.) (Na ₂ MoO ₄ ), potassium molybdate (K ₂ MoO ₄ ), ammonium molybdate ((NH ₃ ) ₂ MoO ₄ ), sodium tungstate ( _Na2WO4 ), potassium tungstate ( _K2WO4 ), sodium borate _{( Na2O.xB2O5} ) _{( x} is the _number corresponding to _Na2O ), chromium sodium phosphate ( _Na2CrO4 ), sodium dichromate _{( Na2Cr2O7} ), sodium nitrite _{( Na2NO2} ), sodium phosphate _{( Na3PO4} ) _, sodium silicate _{( Na2O}・_xSiO2 ) (x is a number corresponding to _Na2O ), sodium benzoate ( _NaC6H5CO2 ), sodium _{cinnamate ( NaC6H5CH = CHCO2} ) and the like, preferably is sodium molybdate, potassium molybdate, ammonium molybdate, sodium tungstate, potassium tungstate and sodium borate, more preferably sodium molybdate and sodium tungstate.

In the anti-corrosion method of the present invention, the step of forming an initial anti-corrosion film on the surface of a metal member in an aqueous system (hereinafter sometimes referred to as "initial anti-corrosion film forming step") comprises aluminum lactate and an inorganic acid salt and/or an organic acid salt. can be added to the aqueous system. The metal member surface may be a surface in continuous contact with the water system or a surface in intermittent contact with the water system.

The initial anti-corrosion film forming step can be usually carried out at room temperature. In addition, as long as the effect of the present invention is not hindered, the present invention can be applied to cases where a low temperature portion and a high temperature portion are generated depending on the condition of the object to be processed.

The initial anticorrosive film forming step is preferably carried out for 1 to 5 days, more preferably 3 to 5 days. One day or more is preferable in order to form a sufficient initial anticorrosive film. Within 5 days is preferable from the viewpoint of cost, etc.

When an anticorrosive agent is added to a neutral water system, the pH of the water system usually becomes more acidic, for example, 4 or more and less than 6. After the initial anticorrosive film formation step is completed, the pH at 25° C. may be adjusted to, for example, about 4 to 9, or 6 or more, for example, according to the needs of the usage environment and the like.

In the corrosion prevention method of the present invention, the concentration ratio of aluminum ions to inorganic acid ions and/or organic acid ions due to the addition of the anticorrosive agent (that is, when only inorganic acid ions are included as the anticorrosive agent, the ratio of aluminum ions to inorganic acid ions is Total ions, when only organic acid ions are included as anticorrosives, aluminum ions: total ions of organic acid ions, when inorganic acid ions and organic acid ions are included as anticorrosives, aluminum ions: inorganic acid ions and organic acid ions Total ions) may vary depending on the environment to be used, metal members, types and combinations of anticorrosive agents, etc., and is not limited, but for example, aluminum ions: inorganic acid ions and / or organic acid ions = 4: 1 to 1: It can be 4 (molar ratio), 2:1 to 1:2, or 1:1.

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

When the anticorrosive is aluminum lactate and a combination of aluminum lactate and two inorganic acid ions and/or organic acid ions, such as a combination of sodium molybdate and sodium tungstate, the aluminum ions and , inorganic acid ions and/or organic acid ions is, for example, preferably 1:1:1 to 2:1:1, more preferably 1:1:1.

In the anticorrosion method of the present invention, the total ion concentration of aluminum ions and inorganic acid ions and/or organic acid ions in the water system by adding the anticorrosive agent (that is, when only inorganic acid ions are included as the anticorrosive agent, aluminum ions and inorganic acid Total ions of ions, total ions of aluminum ions and organic acid ions when only organic acid ions are included as anticorrosive agents, aluminum ions, inorganic acid ions and organic acid when inorganic acid ions and organic acid ions are included as anticorrosives The total ion of ions) may vary depending on the environment used, the metal member, the type and combination of anticorrosive agents, etc., and is not limited, but is, for example, 0.01 mM or more, 0.05 mM or more, 0.1 mM or more, 0.3 mM or more, 0.5 ≥ 1.0 mM, ≤ 100.0 mM, ≤ 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, or any compatible combination thereof.

When the anticorrosive is a combination of aluminum lactate and sodium molybdate, the concentration of aluminum ions and molybdate ions in the aqueous system after addition of the anticorrosive 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 aqueous system after addition of the anticorrosive agent has an aluminum ion concentration of 0.15 to 1.5 mM and a molybdate ion concentration of 0.15 to 1.5 mM.

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

In one aspect, the anticorrosive agent of the present invention can be added such that the aqueous system after addition of the anticorrosive agent has an aluminum ion concentration of 0.05 to 5.0 mM and a tungstate ion concentration of 0.05 to 5.0 mM.

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

In one aspect, the anticorrosive agent of the present invention is added so that the water system has an aluminum ion concentration of 0.033 to 0.33 mM, a molybdate ion concentration of 0.033 to 0.33 mM, and a tungstate ion concentration of 0.033 to 0.33 mM. of corrosion inhibitors can be added.

Another aspect of the present invention is a step of adding a corrosion inhibitor to the aqueous system to maintain the initial anticorrosion film (hereinafter referred to as "film (sometimes referred to as "maintenance step").
That is, a process for maintaining the initial anticorrosive coating may be performed after the initial anticorrosive coating forming process is finished. This film maintenance step can be carried out by adding appropriate amounts of various existing corrosion inhibitors to the water system.

Although the entire amount of water in the system may be replaced when shifting from the initial anticorrosive film formation step to the film maintenance step, it is also possible to shift to the film maintenance step while leaving some or all of the water in the system. The corrosion inhibitor added in the film maintenance process is not particularly limited, but inorganic acid salt-based corrosion inhibitors and organic acid salt-based corrosion inhibitors exemplified by Mo acid Na and W acid Na corrosion inhibitors can be used. . The amount of the corrosion inhibitor to be added in the film maintenance step varies depending on the type of anticorrosive agent used, but should be the amount that maintains the anticorrosion film formed in the previous step.

In the present invention, slime inhibitors, scale inhibitors, azole anticorrosive agents for copper, other anticorrosive agents, and the like may be used in combination in the initial anticorrosive film formation step and the film maintenance step, if necessary.

<Anticorrosive agent>
Another aspect of the present invention is
(A) aluminum lactate, and (B) one or more selected from inorganic acid salts and organic acid salts,
Containing, it relates to an anticorrosive agent for metal members in a water system (hereinafter sometimes referred to as "anticorrosive agent of the present invention"). In addition, all the matters explained in the anticorrosion method of the present invention are applied to the explanation of the anticorrosion 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 each component may be placed in separate packaging materials and mixed at the time of use. good. The anticorrosive agent of the present invention may contain additive components commonly used in the technical field within a range that does not impair the effects of the present invention. Such additive components include, for example, pH adjusters, stabilizers, and the like.

EXAMPLES The present invention will be specifically described below with reference to examples, but these are examples of the present invention and the scope of the present invention is not limited to these.

<Example 1> Evaluation 1 of anticorrosion performance
In order to compare the performance of the anticorrosive agent of the present invention and the existing anticorrosive agent, corrosion of carbon steel (SGV480 equivalent material) was performed using a solution in which various test chemicals were added to 3 mM NaCl solution so that each concentration was 1 mM. The test was held at 25°C for 100 hours. When two kinds of chemicals were mixed, 0.5 mM each was added, and when three kinds of chemicals were mixed, 0.33 mM each was added to unify the total ion concentration of the anticorrosive agent. For reference, a solution without anticorrosive agent and a solution containing only Al lactate, which has never been used as an anticorrosive agent, were also tested.
Figure 1 shows a photograph of the appearance of carbon steel after a 100-hour corrosion test. From the photograph, in the control sample 1 without anticorrosive agent, the surface of the carbon steel turned black and black rust (Fe ₃ O ₄ ) was formed due to corrosion, and red rust (γ-FeOOH) was deposited on the bottom of the test container. It can be seen that In the case of Comparative Example of Al lactate (Sample 2), Mo acid Na (Sample 3), W acid Na (Sample 4), and Zinc diphosphate + Mo acid Na (Sample 5), the amount of red rust is less than without the anticorrosive agent, but carbon The steel surface is black and discolored. On the other hand, the surfaces of Al lactate + Na Mo acid + Sodium Mo acid, Sample 7, Al lactate + Na Mo acid + Na W acid, and Sample 8 of the present invention retain a metallic luster. It is considered that the anticorrosion performance is higher than that of Al.

Fig. 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. A smaller corrosion weight loss value means that corrosion is more suppressed.
It can be confirmed that the existing anticorrosive agents (Samples 3, 4, 5) and Al lactate (Sample 2) have a larger corrosion weight loss than no anticorrosive agent. The reason why the corrosion weight loss increases despite the addition of the anticorrosive agent is that if the ion concentration necessary for corrosion prevention is not present, the corrosion acceleration effect due to the increase in electrical conductivity becomes dominant. On the other hand, in the anticorrosive agents of the present invention, Sample 6 (Al lactate + Na Mo acid), Sample 7 (Al lactate + Na W acid), and Sample 8 (Al lactate + Na Mo acid + Na W acid), the concentration of the anticorrosive agent in the solution is the same as in the other solutions. A reduction in corrosion weight loss was confirmed. In this test, this experiment was performed with four specimens for each condition, and all of them confirmed the same reproducible results. As described above, we have developed an anticorrosive agent that suppresses corrosion of carbon steel in a neutral freshwater environment at a concentration lower than that of existing anticorrosive agents and that has a lower environmental impact than existing anticorrosive agents.

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

Table 1 shows the corrosion weight loss of carbon steel (SGV480 equivalent material) when the addition ratio of the two agents added in the anticorrosive agent of the present invention is changed.
The solutions used in the tests were prepared by adding drugs in varying ratios to 3 mM NaCl to give a total anticorrosive concentration of 1 mM. The corrosion weight loss is the value after a 100-hour immersion test, and the corrosion weight loss in 3 mM NaCl containing no corrosion inhibitor was 0.916 ^mgcm means to be effective. From Table 1, both Al lactate + Na Moate and Al lactate + Na Wate have a lower corrosion weight loss value than the case without anticorrosive agent at any concentration ratio. In addition, the higher the ratio of Al lactate, the smaller the value of corrosion weight loss in both cases, and the value of corrosion weight loss is the smallest in this test when Al lactate:Na Moate is 2:1. Therefore, it is considered that the corrosion inhibition effect is the highest. In addition, in the case of mixing three types of Al lactate + Na Mo acid + Na W acid, the ratio of Al lactate: Na Mo acid: Na W acid = 2:1:1, and the corrosion weight loss is 0.771 mgcm ^-2 and 1:1:1. Although the corrosion weight loss is larger than 0.734 mgcm ^-2 in the case of , it is found to be effective as an anticorrosive agent for carbon steel.

<Example 3> Evaluation 2 of anticorrosion performance
FIG. 4 shows the corrosion weight loss when already rusted carbon steel (SGV480 equivalent material) is immersed in the solution containing the anticorrosive agent of the present invention.
In the test, the 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. A solution containing anticorrosive agents 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 and Na Moate, which have been reported as existing anticorrosive agents. The dashed line in the figure indicates the corrosion weight loss in the absence of the anticorrosive agent, and if the corrosion weight loss is smaller than this value, it means that the anticorrosive agent has an effect. As shown in Fig. 4, the existing anticorrosive agents, zinc diphosphate + sodium Moate, have 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. I know not. On the other hand, with the three types of anticorrosive agents of the present invention (Al lactate + Na Mo acid, Al lactate + Na W acid, Al lactate + Na Mo acid + Na W acid), at a total anticorrosive concentration of 1 mM, the corrosion weight loss was lower than in the case of no anticorrosive agent. It can be seen that it has a corrosion inhibitory effect not only on steel that has not rusted but also on steel that has already rusted.

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

<Example 5> Evaluation 4 of anticorrosion performance
Table 2 shows the results of investigating the effect of suppressing corrosion of carbon steel, which is different from SGV480-equivalent materials, using the solution containing the anticorrosive agent of the present invention. In this test, three types of materials, SS400, S45C, and FC200, were selected as commonly used carbon steels.
In the test, carbon steel was exposed to a solution prepared by adding 3 mM NaCl to 1 mM anticorrosive agent at a ratio of 1:1 or 1:1:1 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 compared to the case of using only NaCl, the amount of decrease in mass is underlined. From Table 2, it can be seen that in the case of SS400, corrosion is reduced when Al lactate + Na Mo acid and Al lactate + Na Mo acid + Na W acid are added compared to when NaCl alone is added. On the other hand, it can be seen that S45C and FC200 show less corrosion when all corrosion inhibitors are added than when only NaCl is added. From the above, it can be said that the anticorrosive agent of the present invention exerts a corrosion inhibitory effect on a wide range of carbon steels.

<Example 6> Evaluation 5 of anticorrosion performance
Fig. 6 shows the corrosion weight loss when a carbon steel corrosion test was conducted under gamma ray irradiation for 100 hours using a 3 mM NaCl solution containing 1 mM each of the various anticorrosive agents developed in this research. show.
It can be seen from FIG. 6 that when the anticorrosive agent of the present invention is added, the weight loss due to corrosion is reduced as compared with the case where the anticorrosive agent is not added, and corrosion is reduced. In addition, when comparing the corrosion weight loss with no gamma ray irradiation in Fig. 2, corrosion is accelerated due to the effect of gamma ray irradiation without anticorrosive agents, whereas when Al lactate + Na Moate is added, there is no irradiation in Fig. 2. It can be seen that the corrosion weight loss is reduced in the case of gamma ray irradiation compared to the case of . From this, it can be said that the anticorrosive agent of the present invention has the 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 suitable for the gamma ray irradiation environment. .

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

In this study, it was clarified that Al lactate, which has not been used as an anticorrosive agent, is effective as an anticorrosive agent by adding Mo acid salt and W acid salt in combination. Mo acid salts and w acid salts are classified as oxidative rust inhibitors by Aramaki (Aramaki, Rust Control Management, 48 (2004) 151), and oxidative rust inhibitors are γ-Fe ₂ O originally present on the surface of steel. It is reported that corrosion is suppressed by forming a fairly dense passivation film of oxide or hydroxide on the protective film of ₃ . Since the mechanism of action is the same in that the oxidative inhibitor acts as an oxidizing agent while itself is reduced to form a passive film, in addition to the Mo and W salts used this time, Al lactate and Al lactate are added in combination. It is considered that the anticorrosive effect is exhibited by doing so. Oxidative rust inhibitors include chromates (Na ₂ CrO ₄ ), dichromates (Na ₂ Cr ₂ O ₇ ), nitrites (Na ₂ NO ₂ ), phosphates (Na ₃ PO ₄ ), silica _acid ( _Na2O.xSiO2 ), borate _{( Na2O.xB2O5} ), benzoate _{( NaC6H5CO2} ), _{cinnamate ( NaC6H5CH = CHCO2} ) ) reported by Aramaki mentioned above. In other words, it is considered that the effect of suppressing corrosion is enhanced by combining these oxidative rust inhibitors with Al lactate.

INDUSTRIAL APPLICABILITY The present invention can be used as an anticorrosion agent and anticorrosion method for metal members such as carbon steel that constitute boilers, cooling and temperature control piping, etc. in an aqueous environment.

Claims (17)

A method for preventing corrosion of a metal member in a water system, comprising the step of adding an anticorrosive agent to the water system to form an initial anticorrosion film on the surface of the metal member in the water system,
The anticorrosive agent is
(A) aluminum lactate, and (B) one or more selected from inorganic acid salts and organic acid salts,
A corrosion prevention method comprising: The inorganic and organic acid salts of component (B) are molybdates, tungstates, borates, chromates, dichromates, nitrites, phosphates, silicates, and benzoates. , and cinnamate. 3. The corrosion prevention method according to claim 1 or 2, wherein the salt in the inorganic acid salt and organic acid salt of component (B) is one or more selected from sodium salts, potassium salts and ammonium salts. The inorganic and organic acid salts of component (B) are sodium molybdate (Na ₂ MoO ₄ ), potassium molybdate (K ₂ MoO ₄ ), ammonium molybdate ((NH ₃ ) ₂ MoO ₄ ), tungstic acid sodium ( _Na2WO4 ), potassium tungstate _{( K2WO4} ), sodium borate _{( Na2O.xB2O5} ) ₍ x is the _number corresponding to _Na2O ), 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 x SiO ₂ ) ( x is a number corresponding to Na ₂ O), sodium benzoate (NaC ₆ H ₅ CO ₂ ), and sodium cinnamate (NaC ₆ H ₅ CH=CHCO ₂ ), or two or more A corrosion prevention method according to any one of claims 1 to 3. The concentration ratio of aluminum ions and inorganic acid ions and/or organic acid ions in the water system is aluminum ions: inorganic acid ions and/or organic acid ions = 4:1 to 1:4 (molar concentration ratio). The corrosion prevention method according to any one of claims 1 to 4, wherein the anticorrosion agent is added so that The anticorrosive agent according to any one of claims 1 to 5, wherein 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. Corrosion protection method as described. The inorganic acid ion is molybdate ion,
The corrosion prevention method according to any one of claims 1 to 6, wherein the anticorrosive agent is added so that the aqueous system has an aluminum ion concentration of 0.15 to 1.5 mM and a molybdate ion concentration of 0.15 to 1.5 mM. . The inorganic acid ion is a tungstate ion,
The corrosion prevention method according to any one of claims 1 to 6, wherein the anticorrosive agent is added so that the aqueous system has an aluminum ion concentration of 0.05 to 5.0 mM and a tungstate ion concentration of 0.05 to 5.0 mM. . The inorganic acid ions are molybdate ions and tungstate ions,
Claims 1 to 6, wherein the anticorrosive agent is added so that the aqueous system has an aluminum ion concentration of 0.033 to 0.33 mM, a molybdate ion concentration of 0.033 to 0.33 mM, and a tungstate ion concentration of 0.033 to 0.33 mM. Corrosion prevention method according to any one of. The corrosion prevention method according to any one of claims 1 to 9, wherein the metal member is carbon steel. The anticorrosion method according to any one of claims 1 to 10, wherein the pH of the water system when the anticorrosion agent is added to the water system is 4 or more and less than 6. After the step of forming the initial anticorrosion coating, further adding a corrosion inhibitor to the aqueous system to maintain the initial anticorrosion coating;
Corrosion prevention method according to any one of claims 1 to 11, comprising (A) aluminum lactate, and (B) one or more selected from inorganic acid salts and organic acid salts,
A corrosion inhibitor for metal members in an aqueous system containing The inorganic and organic acid salts of component (B) are molybdates, tungstates, borates, chromates, dichromates, nitrites, phosphates, silicates, and benzoates. 14. The anticorrosive agent according to claim 13, which is one or more selected from , and cinnamate. 15. The anticorrosive agent according to claim 13 or 14, wherein the salt in the inorganic acid salt and organic acid salt of component (B) is one or more selected from sodium salts, potassium salts and ammonium salts. The inorganic and organic acid salts of component (B) are sodium molybdate (Na ₂ MoO ₄ ), potassium molybdate (K ₂ MoO ₄ ), ammonium molybdate ((NH ₃ ) ₂ MoO ₄ ), tungstic acid sodium ( _Na2WO4 ), potassium tungstate _{( K2WO4} ), sodium borate _{( Na2O.xB2O5} ) ₍ x is the _number corresponding to _Na2O ), 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 x SiO ₂ ) ( x is a number corresponding to Na ₂ O), sodium benzoate (NaC ₆ H ₅ CO ₂ ), and sodium cinnamate (NaC ₆ H ₅ CH=CHCO ₂ ), or two or more There, 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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