JP2001049471A - Water base corrosion inhibiting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow excellent effect to be exhibited even in the initial stage of the start of treatment by adding the water as the object for corrosion inhibition with primary to tertiary amine compds. and an organic sulfur compd. in such a manner that either compd. is added, and, at fixed intervals, the other compd. is added. SOLUTION: Primary to tertiary amine compds. are respectively expressed by the formulae I, II and III, and the organic sulfur compd. is expressed by the formula IV. In the formulae, at least one among R1, R2 and R3 includes (CH2CH2O)x, also the number of C atoms in each comp. lies in the range of 10 to 30, (x) is 3 to 6, R4 and R5 are each a 1 to 20C aryl or alkyl, and at least one of R4 or R5 contains carbonyl or carboxyl. Preferably, the amt. of the primary to tertiary amine compds. to be added is controlled to 0.1 to 10 mg/l, and the amt. of the organic sulfur compd. to be added to 1 to 100 mg/l, and the addition of polymaleic acid, polyacrylic acid or a copolymer therebetween is also preferable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based anticorrosion method for preventing corrosion occurring in pipes (particularly, mild steel pipes) in various cooling water systems such as a circulation type.

[0002]

2. Description of the Related Art In the steel industry and chemical plants, cooling water is usually used as a refrigerant in a wide range for cooling high-temperature gases and liquids produced in various processes such as reaction processes. In many cases, these cooling treatments are carried out by transporting cooling water using a pipe made of mild steel, and disposing a heat exchange device for lowering the temperature of high-temperature gas or liquid on the cooling water transport path. .. Exhaust cooling water whose temperature has been raised by heat exchange with high-temperature gas or liquid is recooled by a cooling device such as a cooling tower, and is recycled and used again for cooling high-temperature gas or liquid.

In the above cooling treatment, water used as cooling water usually has hardness components such as calcium dissolved therein.
When the high temperature gas or liquid is cooled, a part of the water evaporates, so these hardness components are concentrated and the calcium hardness becomes 25
It may be 0 mg/liter (250 mg/liter in terms of CaCO ₃ ) or more. In general, water containing a large amount of hardness components is unlikely to corrode metals, and therefore cooling water is concentrated to increase the concentration of hardness components to prevent corrosion. In such a system, it is possible to prevent damage to the cooling water system only by adding a certain polymer for preventing the generation of scale.

However, when a large amount of substances, such as chloride ions, sulfate ions, silica, and organic substances, which cause corrosion or scale adhesion, are contained in the industrial cooling tower having a high heat load and the replenishing water of the cooling water, However, the cooling water cannot be concentrated so much. In such a cooling water system, the hardness component is generally 200 mg/liter or less, and the corrosiveness to metals, especially mild steel becomes high. Therefore, an anticorrosive agent containing a metal salt such as zinc or a specific phosphorus compound is added to the cooling water, and a film containing calcium phosphate or zinc phosphate as a main component on the inner and outer surfaces of a mild steel plate or pipe (called a precipitation film) ) Is formed to prevent corrosion.

Further, addition of a drug consisting only of an organic compound containing no phosphorus or metal salt has been attempted.
Calcium hardness in water is about 200 mg/liter (Ca
When the amount is 200 mg/liter or more in terms of CO ₃ , the application is difficult. Furthermore, a water-based anticorrosion agent has been developed that contains organic sulfur compounds as an active ingredient that effectively inhibits corrosion of pipes and the like without eutrophication of lakes, but it is corrosive to chloride ions and sulfate ions. When the anion concentration is high, pitting corrosion tends to occur, and it is extremely difficult to suppress the corrosion that occurs particularly in the initial stage of the start of anticorrosion treatment.

[0006]

The cooling water system normally circulates while partially evaporating water by heat exchange between the cooling water and a high temperature gas or liquid. Due to the repeated circulation, the concentration of calcium ion becomes considerably high as the partial evaporation of water is repeated. A part of such water will be discharged by blow, and new cooling water will be supplied. At the time of this blowing, the high-concentration phosphoric acid compound and zinc compound that were mixed together are also discharged, and a large amount of these metal compounds flow into the lake. There are strict regulations on the release of zinc compounds into the environment, and easy release is not permitted. Moreover, if a compound containing phosphorus at a high concentration flows into a lake or the like, it may cause eutrophication.

As described above, the conventional cooling water type anticorrosives still have many problems to be solved. In addition, a phosphoric acid compound such as polyphosphoric acid or phosphonic acid or a zinc compound tends to adhere to the high temperature portion of the cooling device as a scale. There is also a problem that if the phosphoric acid compound or the like adheres to the high temperature portion of the pipe, it also causes heat transfer inhibition. Although water-based anticorrosives that do not contain these phosphoric acid compounds and zinc compounds have also been developed, there is a problem that pitting corrosion tends to occur, and in particular, corrosion that occurs at the initial stage of the start of anticorrosion treatment cannot be sufficiently prevented.

In view of the above-mentioned circumstances, the present invention does not enrich lakes and marshes, and particularly soft steel pipes made of low/medium concentrated water having a calcium hardness of 200 mg/liter (200 mg/liter in terms of CaCO ₃ ) or less. A water-based anticorrosion method that can effectively prevent corrosion of steel pipes, etc., especially in cooling water system equipment, etc. without causing heat transfer inhibition at high temperatures and without causing corrosion of chloride ions, sulfate ions, etc. It is an object of the present invention to provide a water-based anticorrosion method that does not cause pitting corrosion even when the concentration of the anionic anion is high and exhibits an excellent effect even in the initial stage of treatment initiation.

[0009]

[At least one of R _{1 to} R ₃ contains (CH ₂ CH ₂ O) _x , and the number of carbon atoms in each compound is in the range of 10 to 30, and x is 3 to 6. ]

Formula (IV) R ₄ —S—R ₅ [R ₄ and R ₅ are aryl groups or alkyl groups having 1 to 20 carbon atoms, and at least one of R ₄ and R ₅ is carbonyl. It has a group or a carboxyl group. ]

2. The above general formula (I), (II) or (II
The addition amount of the primary to tertiary amine compound represented by I) is 0.1 to 10 mg/liter, and the above general formula (IV)
The addition amount of the organic sulfur compound represented by 1 to 100 mg/
The water-based anticorrosion method according to the above 1, wherein the water-based anticorrosion method is 1 liter.

3. Polymaleic acid, polyacrylic acid,
Alternatively, the water-based anticorrosion method according to the above 1 or 2, wherein the copolymers thereof are added together. 4. 3. The water-based anticorrosion method as described in 1 or 2 above, wherein a phosphorus-containing compound is added together. 5. 3. The water-based anticorrosion method as described in 1 or 2 above, wherein an azole compound is added together. 6. For the water to be protected against corrosion, the general formula (I), (II) or (I
The method for preserving water-based corrosion according to item 1, wherein the primary to tertiary amine compound represented by II) is added, and the organic sulfur compound represented by the general formula (IV) is added at regular intervals.

[0012]

[At least one of R _{1 to} R ₃ contains (CH ₂ CH ₂ O) _x , and the number of carbon atoms in each compound is in the range of 10 to 30, and x is 3 to 6. ]

Formula (IV) R ₄ —S—R ₅ [R ₄ and R ₅ are aryl groups or alkyl groups having 1 to 20 carbon atoms, and at least one of R ₄ and R ₅ is carbonyl. It has a group or a carboxyl group. ]

In the water-based anticorrosion method of the present invention, preferably, a primary to tertiary amine compound represented by the general formula (I), (II) or (III) is added and after a certain interval (preferably). , After a lapse of 6 to 48 hours), an organic sulfur compound represented by the general formula (IV) is added. The preferable addition amount of both is in the range of 0.1 to 10 mg/liter for the primary to tertiary amine compound and in the range of 1 to 100 mg/liter for the organic sulfur compound.

In the primary to tertiary amine compounds represented by the above general formula (I), (II) or (III), the substituent R ₁
The form of R ₃ to R ₃ is in the range of 10 to 30 carbon atoms, and preferably at least one of R _{1 to} R ₃ is (CH ₂
CH ₂ O) _X , and additionally (CH ₂ CH ₂ O) _X
More preferably, x is in the range of 3 to 6. Preferred examples of the amine compound include higher alkylamines and higher alkenylamines, and the following compounds correspond to them.

Examples of higher alkylamines include tetradecylamine ethylene oxide adducts (“ethylene oxide” is abbreviated as “EO” hereinafter), hexadecylamine EO adducts, octadecylamine EO adducts,
Examples of higher alkenylamines include oleylamine EO adducts and linoleylamine EO adducts.

Further, these higher alkylamines EO
Fatty acid amine EO adducts containing adducts or higher alkenylamine EO adducts alone or as a mixture may be used, and examples thereof include coconut oil amine EO adducts, hardened beef tallow amine EO adducts, and Examples include soybean oil amine EO adducts. Besides, these coconut oil amine EO
The adduct, soybean oil amine EO adduct, and hardened tallow amine EO adduct each have 3 to 6 (CH ₂ CH ₂ O) groups.
Since it has one, it corresponds to the primary to tertiary amine compound which is one of the components constituting the aqueous anticorrosion method of the present invention, and can be effectively used.

Next, the other component of the general formula (IV)
In the organic sulfur compound represented by, the substituents R ₄ and R ₅ are aryl groups or alkyl groups having 1 to 20 carbon atoms, and at least one of R ₄ and R ₅ is a carbonyl group or a carboxyl group. A compound having a structure having a group is preferably used. As the organic sulfur compound having such a structure, for example,

[0018] carboxyethylthio _{acid: HOOC-CH 2 -CH 2 -S} -CH (COOH) -CH
₂ -COOH, 3- acetylthio-2-methylpropionic _{acid: CH 3 CO-S-CH} 2 -CH (CH 3) -COOH, 3- acetylthio-2-methyl-propionyl _{chloride: CH 3 CO-S-CH} 2 - CH (CH ₃₎ -COCl, 3- octadecylthio - _{propionamide: C 18 H 37 -S-C} 2 H 4 CONH 2, may include compounds such as.

In the water-based anticorrosion method of the present invention, it is preferable to add a polymer together with the above-mentioned primary to tertiary amine compound or organic sulfur compound. Examples of such polymers include polymaleic acid, polyacrylic acid, and copolymers thereof. Further, this polymer can be added at the same time as the primary to tertiary amine compound or the organic sulfur compound, but it is preferable to add at the same time as the organic sulfur compound. When the polymer is added, the amount added is such that a sufficient dispersing effect is obtained, that is, the range of 1 to 100 mg/liter is preferable.

Further, in the water-based anticorrosion method of the present invention, it is more preferable to add a trace amount of a phosphorus-containing substance (that is, a phosphorus compound) together with the above-mentioned primary to tertiary amine compounds or organic sulfur compounds. As such a phosphorus compound or phosphorus-containing substance, for example, polyphosphate or phosphonate can be preferably mentioned. This phosphorus compound can be added at the same time as the primary to tertiary amine compound or the organic sulfur compound, but is preferably added at the same time as the organic sulfur compound. When the phosphorus-containing substance is added, it is preferable that the upper limit be 10 mg/liter in terms of PO ₄ , which is an addition amount that does not cause eutrophication of lakes and the like. It is preferably 0.1 to 10 mg/liter.

Furthermore, in the water-based anticorrosion method of the present invention,
It is preferable to add, for example, an azole compound as a corrosion inhibitor for copper metal together with the above-mentioned primary to tertiary amine compounds or organic sulfur compounds. Examples of such an azole compound include benzotriazole and tolyltriazole. This azole compound can be added at the same time as the primary to tertiary amine compound or the organic sulfur compound, but is preferably added at the same time as the organic sulfur compound. When adding an azole compound, the amount is preferably 10 mg/liter or less,
More preferred is mg/liter.

In the water-based anticorrosion method of the present invention, addition of various components including a commonly used anticorrosive agent, for example, a zinc compound or a molybdenum compound, within the range not impairing the object of the present invention is not hindered. Further, an organic acid such as sulfamic acid or citric acid may be added. However, zinc compounds have many problems and it is not recommended to add them in large amounts.

In the water-based anticorrosion method of the present invention, the above components may be added by the following method. That is,
After adding 0.1 to 10 mg/liter of a primary to tertiary amine compound represented by the general formula (I), (II) or (III) and keeping a certain interval (preferably, 6 to 48 hours elapse) Later), organic sulfur compounds 1 to 10 represented by the general formula (IV)
It is preferred to add 0 mg/liter. If the amount of the primary to tertiary amine compound added is less than 0.1 mg/liter, a sufficient anticorrosion effect cannot be obtained, and if it exceeds 10 mg/liter, polyacrylic acid used as a scale inhibitor or the general formula (IV ) It is not preferable because it reacts with the organic sulfur compound represented by) and the effect is reduced. Further, if the amount of the organic sulfur compound added is less than 1 mg/liter, a sufficient anticorrosion effect cannot be obtained, and if it exceeds 100 mg/liter, corrosion is accelerated depending on the water quality, which is not preferable. It is not preferable to add the primary to tertiary amine compound and the organic sulfur compound at the same time because the formation of the anticorrosion coating of the amine compound or the organic sulfur compound is hindered and the effect is reduced.

Such a water-based anticorrosion method can be used in a water system. More specifically, it may be used, for example, in the following cooling water system cooling device. FIG. 1 is a schematic diagram showing an example of a cooling device that manages cooling water. This cooling device has a heat exchanger 1 that absorbs exhaust heat generated in a chemical reaction tank (not shown) that causes an exothermic reaction or the like. In this heat exchanger 1, a cooling pipe extends from a tower bottom water tank 2 that temporarily stores cooling water, and communicates with a refrigerant inlet port with a pump 3 interposed therebetween.

The refrigerant outlet of the heat exchanger 1 communicates with a cooling tower 5 having a blower 4 via an exhaust cooling water pipe. From this cooling tower 5, the recooled water flows down to the tower bottom water tank 2 arranged immediately below and is temporarily stored. In the tower bottom water tank 2, an injection pipe equipped with a pump is extended from the chemical injection tank 6 separately.

In the above-mentioned anticorrosion method, the primary to tertiary amine compounds represented by the general formula (I), (II) or (III) are previously charged in the chemical injection tank 6 in the form of an aqueous solution. This amine compound is usually 0.1 to 1 in an aqueous system.
It is recommended to use it in the concentration range of 0 mg/liter. Tower bottom water tank 2
If the concentration of the above-mentioned amine compound in 3 is not sufficient to prevent corrosion of the cooling device, that is, 0.1 mg/liter, the amine compound is supplied from the chemical injection tank 6 at any time.

As described above, a cooling water circulation system is substantially formed between the tower bottom water tank 2→the heat exchanger 1→the cooling tower 5→the tower bottom water tank 2. The blower 4 is driven so that the heat exchanger 1 absorbs the exhaust heat sent from a chemical reaction tank (not shown) into the cooling water. When the concentration of the anticorrosive agent in the circulating water increases due to partial evaporation of water, which occurs when the heat exchanger 1 absorbs heat, while the cooling water is substantially circulated, the cold water is supplied from the attached water supply pipe 8. The amine compound in the cooling water supplied and supplied to the heat exchanger 1 is returned to a preferable concentration.

When the quality of the cooling water deteriorates or when the amount of cooling water increases, a part of the water is discharged through the blow pipe 7 branched from the exhaust cooling water pipe leading to the cooling tower 5, and the water supply pipe is supplied. Fresh water is replenished to the tower bottom water tank 2 from 8, and an amine compound is replenished from the chemical injection tank 6 as needed, and the amine compound in the cooling water supplied to the heat exchanger 1 is maintained at a preferable concentration.

After the amine compound has been sufficiently acted in this manner, the addition of the amine compound is stopped. afterwards,
The amine compound in the chemical injection tank 6 is replaced with the organic sulfur compound represented by the general formula (IV) with or without cooling water, and the organic sulfur compound is charged in the same manner as the amine compound. , Fully actuate the organic sulfur compounds.

[0030]

The present invention is described in detail below with reference to examples, but the present invention is not limited to these examples. Example 1 A corrosion test was conducted using a test piece (30 mm x 50 mm x 1 mm) of a mild steel plate. The test is based on the industrial water corrosion test method (J
It was carried out by the mass reduction method according to IS-K0100). That is, sample water [tap water contains NaHCO ₃ , NaCl, Na ₂ S
PH of 7.5 by adding O ₄ and total hardness (calculated as CaCO ₃ ) 12
0 mg/liter, chloride ion 100 mg/liter, sulfate ion 100 mg/liter] in the general formulas (I) and (II)
Alternatively, after adding 1 mg/liter of soybean oil amine EO adduct as the primary to tertiary amine compound represented by (III), the test piece is dipped, and after a certain time elapses, the compound represented by the general formula (IV)
10 mg/liter of carboxyethylthiosuccinic acid was added as an organic sulfur compound represented by, and it was immersed for 10 days under stirring (Jar tester). After the completion of the immersion, the test piece was taken out, rust was removed and the weight was measured, and the corrosion rate was determined from the weight difference before and after the immersion. The results are shown in Figure 2.

When the organic sulfur compound is added 6 to 48 hours after the addition of the amine compound, the corrosion rate is 10 mdd or less (mdd=mg/dm ² ·day), which is a practically sufficient anticorrosion effect. It was On the other hand, when the organic sulfur compound is added less than 6 hours or more than 48 hours after the addition of the amine compound, the corrosion rate is high,
It does not reach a practical level.

Example 2 Soybean oil amine EO adduct as the primary to tertiary amine compound represented by the general formula (I), (II) or (III), and carboxy as the organic sulfur compound represented by the general formula (IV). Using ethylthiosuccinic acid, changing the amount of each addition,
A corrosion test was performed using a test piece of soft steel plate (30 mm x 50 mm x 1 mm). The test is based on the industrial water corrosion test method (J
It was performed by the mass reduction method according to IS-K0100). The test solution is a test water [tap water containing NaHCO ₃ , NaCl, Na ₂ S
PH of 7.5 by adding O ₄ and total hardness (calculated as CaCO ₃ ) 12
0 mg/liter, chloride ion 100 mg/liter, sulfate ion 100 mg/liter], and soybean oil amine EO adduct (hereinafter referred to as “amine compound”) 0 to 15 mg/liter
It was adjusted by adding stepwise up to 1 liter. In the above test solution,
Hanging down the test piece fixed to the non-corrosive disc,
Stirring was started at a constant speed, and after 12 hours, carboxyethylthiosuccinic acid (hereinafter referred to as “organic sulfur compound”) was added stepwise to 0 to 150 mg/liter, and 10
It was immersed under stirring for one day (jar tester). After the completion of the immersion, the test piece was taken out, rust was removed, and the weight was measured, the corrosion rate was determined from the weight difference before and after the immersion, and the number of pitting corrosion was also measured. The results are shown in Tables 1 and 2.

[0033]

[Table 1]

[0034]

[Table 2]

As shown in Table 1, when the amount of the amine compound added was in the range of 0.1 to 10 mg/liter, the corrosion rate was 10 mdd or less, which was a practically sufficient anticorrosion effect.
Further, as shown in Table 2, in the addition amount of the organic sulfur compound, the corrosion rate was 10 in the range of 1 to 100 mg/liter.
A practically sufficient anticorrosion effect of mdd or less was obtained. Further, under any of the conditions, when the corrosion rate was 10 mdd or less, the occurrence of pitting corrosion was 1/cm ² or less, and a sufficient suppressing effect was obtained.

Example 3 Soybean oil amine EO adduct as the primary to tertiary amine compound represented by the general formula (I), (II) or (III), and carboxy as the organic sulfur compound represented by the general formula (IV). Using ethylthiosuccinic acid, a polymer, a phosphoric acid compound, and an azole were further added to change the addition amount of each, and a corrosion test was performed using a test piece (30 mm×50 mm×1 mm) of a mild steel plate. The test is based on the industrial water corrosion test method (JIS-K
0100). The test solution was a test water [pH: 7.5 by adding NaHCO ₃ , NaCl, Na ₂ SO ₄ to tap water, total hardness (calculated as CaCO ₃ ) 120 mg/
Liter, chlorine ion 100 mg/liter, sulfate ion 100
[Adjustment to mg/L]], and soybean oil amine EO adduct (hereinafter referred to as “amine compound”) was added stepwise from 0 to 10 mg/L for adjustment. The test piece fixed to a non-corrosive disk was dripped into the test solution, stirring was started at a constant speed, and 12 hours later, carboxyethylthiosuccinic acid (hereinafter, referred to as “organic sulfur compound”) was reduced to 0.
To 100 mg/liter in stages, and at the same time, one of sodium polyacrylate (hereinafter referred to as “polymer”), tripolyphosphoric acid and benzotriazole was added and immersed for 10 days under stirring (jar tester). ). After completion of the immersion, the test piece was taken out, rust was removed, and the weight was measured, the corrosion rate was determined from the weight difference before and after the immersion, and the number of pitting corrosions was measured. The results are shown in Tables 3, 4 and 5.

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

[Table 5]

As shown in Tables 3 to 5, in all the tests, the amine compound concentration was 0.1 to 10 mg/liter and the organic sulfur compound concentration was 1 to 100 mg/liter.
Polymer 1-100 mg/liter, tripolyphosphoric acid 0.1
-10 mg/liter, benzotriazole 0.1-10 m
By adding g/l at the same time as the organic sulfur compound, the corrosion rate becomes lower than the result of the same conditions shown in Example 2,
The result with enhanced anticorrosion effect was obtained.

[0041]

INDUSTRIAL APPLICABILITY According to the water-based anticorrosion method of the present invention, the primary to tertiary amine compound represented by the general formula (I), (II) or (III) and the general formula (IV) are contained in cooling water. When one compound is added to the organic sulfur compound and the other compound is added at regular intervals, the chlorine ion concentration and the sulfate ion concentration are 10 due to the synergistic effect of both compounds.
It is possible to effectively prevent corrosion and pitting of a pipe made of a steel material such as a mild steel material in an environment such as a cooling water system which is constantly in contact with cooling water at a high level of 0 to 500 mg/liter. Further, in the water-based anticorrosion method of the present invention, since it does not contain a metal such as zinc that is difficult to discharge to the environment, due to the surplus of circulating water in the cooling water system, even if partial discharge,
Since it does not destroy the environment, it is easy to handle, and a stable cooling water system can be formed at all times, which is extremely useful.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example of a cooling device that manages cooling water.

FIG. 2 is a result showing a change in corrosion rate in Example 1 when a charging interval time of an amine compound and an organic sulfur compound is changed.

[Explanation of symbols]

1 heat exchanger 2 tower bottom water tank 3 pump 4 blower 5 cooling tower 6 chemical injection tank 7 blow pipe 8 water supply pipe

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C02F 5/10 620 C02F 5/10 620F 5/12 5/12 5/14 5/14 A

Claims (6)

[Claims] 1. The water represented by the following general formulas (I) and (I
A primary to tertiary amine compound represented by I) or (III) and an organic sulfur compound represented by the following general formula (IV):
A water-based anticorrosion method, which comprises adding one compound and adding the other compound at regular intervals. General formula (I) R ₁ -NH ₂ , General formula (II) R ₁ R ₂ -NH, General formula (III) R ₁ R ₂ R ₃ -N [R _{1 to} R _{3 At} least one is ( CH ₂ CH ₂ O) _x
And the number of carbon atoms in each compound is in the range of 10 to 30, and x is 3 to 6. General formula (IV) R ₄ —S—R ₅ [R ₄ and R ₅ are aryl groups or alkyl groups having 1 to 20 carbon atoms, and at least one of R ₄ and R ₅ is It has a carbonyl group or a carboxyl group. ] 2. The addition amount of the primary to tertiary amine compound represented by the general formula (I), (II) or (III) is 0.1 to 10.
The water-based anticorrosion method according to claim 1, wherein the amount is 10 mg/liter, and the addition amount of the organic sulfur compound represented by the general formula (IV) is 1 to 100 mg/liter. 3. The water-based anticorrosion method according to claim 1, wherein polymaleic acid, polyacrylic acid, or a copolymer thereof is added together. 4. The water-based anticorrosion method according to claim 1, wherein a phosphorus-containing compound is also added. 5. The water-based anticorrosion method according to claim 1, wherein an azole compound is added together. 6. The water represented by the general formula (I) or (I
The primary to tertiary amine compound represented by I) or (III) is added, and the organic sulfur compound represented by the general formula (IV) is added at regular intervals.
The water-based anticorrosion method described.