JP2004339611A - Water-based anticorrosive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based anticorrosive with which the corrosion of a steel material for piping etc., with low or middle concentrated water having ≤200mg/L calcium hardness is effectively prevented without eutrophicating lakes and marshes, particularly, in a cooling water system device, such excellent effect as not to develop the obstruction of heat-conduction at a high temperature part, is displayed and to provide a corrosion prevention method. <P>SOLUTION: The water-based anticorrosive contains ≥1wt% of a compound shown with the chemical formula: R<SP>1</SP>-S-R<SP>2</SP>(each of R<SP>1</SP>,R<SP>2</SP>is a 1-20C allyl group being an unsaturated aliphatic group or alkyl group being a saturated aliphatic group and at least one of R<SP>1</SP>and R<SP>2</SP>has one or more groups selected from the groups of -CO- group, -COOH group and -CONH- group) and further contains a polymer electrolyte. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a water-based anticorrosive, particularly to a water-based anticorrosive for preventing corrosion of a metal member.

  In the steel industry, chemical plants, etc., cooling water is widely used for cooling equipment. In such a cooling water system, the piping is often formed of mild steel, and the heat exchanger is formed of copper or the like. How to prevent corrosion of metal pipes and heat exchangers is one of the problems with cooling water systems. Hardness components such as calcium are usually present in the cooling water used in the cooling water system, but some of the water evaporates for cooling. It is not unusual for calcium to be concentrated to 250 mg / liter or more. Water containing a large amount of a hardness component generally does not easily corrode metals, so that corrosion prevention can be achieved by concentrating cooling water and increasing the concentration of the hardness component. In such a system, the failure of the cooling water system can be prevented by adding only the polymer for scale prevention.

  However, if the cooling water for industrial cooling towers or cooling water that has a high heat load contains many substances that cause corrosion or scale adhesion, such as chloride ions, sulfate ions, silica, and organic substances, the cooling water is concentrated too much. I can't let it. In such a cooling water system, the hardness component is generally 250 mg / liter or less, and is highly corrosive to metals, especially mild steel. Therefore, conventionally, anticorrosion has been attempted by always adding an anticorrosive containing a specific phosphorus compound to cooling water to form a precipitation film, which is mainly composed of calcium phosphate or zinc phosphate, on the surface of mild steel.

  The cooling water system circulates water while partially evaporating the water. As the evaporation proceeds and the calcium ion concentration is concentrated to a considerably higher concentration, such water is discharged by blowing. Blowing water containing a high concentration of calcium will also release high concentrations of phosphate and zinc compounds that have been entrained and will flow into lakes and marshes in large quantities. There are strict regulations on the emission of zinc compounds, which are not allowed. If a high concentration of phosphorus compounds flows into the lake, it will cause eutrophication in lakes and marshes. Conventionally, the cooling water type anticorrosive has such a problem.

  Further, phosphate compounds such as polyphosphoric acid and phosphonic acid tend to adhere as scales to a high-temperature portion of a cooling device. There is a problem that if the phosphate compound adheres to the high temperature part, it may cause heat transfer inhibition. This is a problem common to zinc compounds. The zinc compound also has a problem that it becomes a scale and adheres to the inside of the device to lower the heat transfer efficiency.

  Therefore, the present invention is a water-based anticorrosive agent which can effectively prevent corrosion of piping steel materials and the like by low / medium concentrated water having a calcium hardness of 200 mg / liter or less without enriching lakes and marshes. It is an object of the present invention to provide a water-based anticorrosive agent and an anticorrosion method that also exhibit an excellent effect of preventing heat transfer from being inhibited in a high-temperature portion in a cooling water system or the like.

That is, the object of the present invention is achieved by the following configurations.
(1) Chemical formula (I)
R ¹ -SR ²
(R ¹ and R ² are an allyl group having 1 to 20 carbon atoms which is an unsaturated aliphatic group or an alkyl group which is a saturated aliphatic group, and at least one of R ¹ and R ² is a —CO— group; Having one or more groups selected from one or more types of groups selected from the group consisting of -COOH groups and -CONH- groups, both of which may be the same or different.) A water-based anticorrosive comprising a compound in an amount of 1% by weight or more and further comprising a polymer electrolyte.

(2) The water-based anticorrosive according to (1), which contains a phosphorus-containing substance in an amount of 1 wt% or less in terms of PO ₄ .
(3) The aqueous anticorrosive according to (2), wherein the phosphorus-containing substance is a polyphosphate or a phosphonate.
(4) The aqueous anticorrosive according to (1), further comprising an azole compound.
(5) The aqueous anticorrosive according to (4), wherein the azole compound is benzotriazole or tolyltriazole.

(6) A water-based anticorrosion method comprising using the water-based anticorrosive according to (1) at a retention concentration of 20 to 200 mg / liter.
(7) Chemical formula (I)
R ¹ -SR ²
(R ¹ and R ² are allyl groups or alkyl groups having 1 to 20 carbon atoms, and at least one of R ¹ and R ² is a group of the group consisting of a —CO— group, a —COOH— group, and a —CONH— group. Having at least one group selected from at least one group selected from the group consisting of two or more groups, which may be the same or different from each other.) A water-based anticorrosion method comprising circulating water containing a molecular electrolyte.

The present invention contains a compound represented by the chemical formula (I) in an amount of 1% by weight or more and further contains a polymer electrolyte, so that it does not enrich lakes and marshes and has a low or medium calcium hardness of 200 mg / liter or less. A water-based anticorrosion agent that can effectively prevent corrosion of piping steel materials by concentrated water, and also exhibits an excellent effect of preventing heat transfer in high-temperature parts, especially in cooling water systems. Water-based anticorrosive agent and anticorrosion method can be provided.
Therefore, it contributes to the reduction of environmental load. Since metal salts and high-concentration phosphorus compounds can not be used, there is no need to apply wastewater regulations, and there is no possibility that zinc or phosphate scale will adhere.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.
In the aqueous anticorrosive and the anticorrosion method of the present invention, the sulfide compound (thioether) represented by the above chemical formula (I) is used. Examples of such a sulfide compound include the following examples. That is,
Carboxyethylthiosuccinic acid

Acetylthio-2-methylpropionic acid _{CH 3 CO-S-C 3} H 6 -COOH
3-acetylthio-2-methyl-propionyl = chloride _{CH 3 CO-S-CH 2} -CH (CH 3) -CCl
3- (octadecylthio) propionamide _{C 18 H 37 -S-C 2} H 4 CONH 2,
And the like.

A polymer electrolyte is further contained together with the sulfide compound as described above. Examples of such polymer electrolytes include polyacrylic acid, polymaleic acid and copolymers thereof, polyethylene glycol and ester compounds thereof. The function of the polymer electrolyte is to prevent the precipitation of phosphorus compounds and zinc when they coexist, thereby enhancing the anticorrosion effect, and at the same time, prevent the adhesion of scale and corrosion products to keep the metal surface clean. , Helps to form anticorrosion film and prevents secondary corrosion. Keeps the metal surface clear and helps to form anticorrosion films with sulfide compounds.
More preferably, a trace amount of a phosphorus-containing substance, that is, a phosphorus compound, is included together with the above-described polymer electrolyte. Examples of such a phosphorus-containing substance include a polyphosphate or a phosphonate.
Further, an anticorrosive for copper metal, for example, an azole compound may be blended together with or without the phosphorus-containing substance. Examples of such azole compounds include benzotriazole and tolyltriazole.

In addition, it does not prevent the inclusion of various components contained in ordinary anticorrosive agents within a range that does not impair the object of the present invention. For example, an organic acid such as sulfamic acid or citric acid may be blended. However, zinc compounds often have many problems and are not recommended to be added in large amounts.
In the above-mentioned water-based anticorrosive or anticorrosion method, the above components may be used in the following proportions. That is, it is desirable that the sulfide compound represented by the chemical formula (I) be contained in an amount of 1% by weight or more, preferably 30% by weight or less based on the total weight of the anticorrosive. If the mixing ratio is less than 1 wt%, a sufficient anticorrosion effect cannot be expected, which is not preferable. If it exceeds 30% by weight, the stability of the drug is impaired, and the cost is increased. Most preferred is 2 to 20% by weight. When it is in this range, both the anticorrosion effect and the stability are increased, which is preferable. When a phosphorus-containing substance is contained, the upper limit is preferably set to a level that does not cause eutrophication of lakes and marshes, that is, 1 wt% based on the total weight of the anticorrosive in terms of PO ₄ .

The mixing ratio of the polymer electrolyte is preferably 1 to 50% by weight based on the total weight. If it exceeds 50% by weight, gelation may occur and the effect may be impaired. Other azoles are desirably 10% by weight or less.
Such an anticorrosive may be prepared, for example, by the following method. That is, carboxyethylthiosuccinic acid is dissolved in alcohol or amines, preferably morpholine, cyclohexylamine, diethylethanolamine, monoethanolamine, and the like, and after adding pure water thereto, a polymer electrolyte and azoles are added. .
The above anticorrosive may be used after being diluted, for example, to a retention concentration of 20 to 200 mg / liter in an aqueous system.

More specifically, for example, it may be used in the following cooling water system cooling device. FIG. 1 is an example of a cooling device for managing cooling water.
This cooling device has a heat exchanger 1 for absorbing waste heat such as a chemical reaction tank (not shown) for performing an exothermic reaction and the like. In this heat exchanger 1, a cooling pipe extends from a bottom water tank 2 for temporarily storing cooling water, and communicates with a refrigerant inlet through a pump 3. The refrigerant outlet of the heat exchanger 1 communicates with a cooling tower 5 having a blower 4 through a high-temperature pipe. From the cooling tower 5, cooled water is supplied to the bottom water tank 2 immediately below. An injection pipe provided with a pump extends to the bottom water tank 2 from the chemical injection tank 6 again.

  The above-mentioned anticorrosive is previously charged in the state of an aqueous solution into the chemical injection tank 6. The above anticorrosives may be used by diluting them in an aqueous system usually within a concentration range of 20 to 200 mg / liter. When the concentration of the above-mentioned anticorrosive in the bottom water tank 2 does not satisfy a concentration sufficient for the anticorrosion of the cooling device, that is, 20 mg / liter, the anticorrosive is supplied from the chemical injection tank 6 as needed.

  Cooling water is circulated between the bottom water tank 2, the heat exchanger 1, and the bottom water tank 2. The blower 4 is driven, and waste heat sent from a chemical reaction tank (not shown) is absorbed by the cooling water by the heat exchanger 1. If the concentration of the anticorrosive component in the bottom water tank 2 rises while circulating the cooling water, make-up water is supplied from the water supply pipe 8 to make the anticorrosive component a preferable concentration.

  When the quality of the cooling water is deteriorated or the amount of the cooling water is increased, a part of the water is discharged through the blow pipe 7 branching from the high-temperature pipe to supply new water to the bottom water tank 2 from the water supply device. Then, if necessary, the anticorrosive is replenished by the chemical injection tank 6 so that the concentration of the anticorrosive is adjusted to a preferable concentration.

Hereinafter, examples will be described, but the present invention is not limited to these contents.
[Examples 1 to 14] [Comparative Examples 1 to 11] [Reference Examples 1 and 2]
Water-based anticorrosives were prepared at the ratios shown in Tables 1 and 2, and the corrosion rate of mild steel was measured by the mass subtraction method shown in the industrial water corrosion test (JIS-K0100). That is, a disk on which the test piece was fixed was put into the test water and stirred at a constant speed for 5 days. After 5 days, the test piece was taken out, rust-removed, and the weight was measured. The corrosion rate was determined from the difference from the test piece weight measured before the start of the test.

Test conditions Sample water: pH 7.5, calcium hardness 150 mg / liter CaCO ₃ conversion)
Water temperature: 40 ° C
Stirring: 60 rpm
Test piece: Mild steel 30 mm x 50 mm x 1 mm
Copper 30mm × 50mm × 1mm
Test period: 5 days Drug concentration: All diluted to 100 mg / L concentration Use 2 L beaker

The results are shown in Tables 1 and 2. In the table, m of mdd represents mg, d represents dm ² , and the next d represents day.

  From Tables 1 and 2, it was found that when the compound represented by the chemical formula I and the polymer electrolyte coexist, the mild steel corrosion rate can be effectively suppressed due to the synergistic effect of both. Test 21 also showed that the anticorrosive agent according to the present invention (for example, Tests 17 to 19) and the conventional phosphorus-based anticorrosive agent (Test 21) exhibited the same anticorrosive effect. Therefore, the anticorrosive agent of the present invention not only has the same anticorrosive effect as the conventional phosphorus-based ones, but also has the advantage of not generating scale since it does not contain a large amount of phosphorus.

It is an example figure of a cooling device which manages cooling water.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Heat exchanger 2 Bottom water tank 3 Pump 4 Blower 5 Cooling tower 6 Chemical injection tank 7 Blow pipe 8 Water supply pipe

Claims (5)

Chemical formula (I)
R ¹ -SR ²
(R ¹ and R ² are an allyl group or an alkyl group having 1 to 20 carbon atoms, and at least one of R ¹ and R ² is a group consisting of a —CO— group, a —COOH group, and a —CONH— group Has at least one group selected from one or more types of groups selected from the group consisting of two or more, and may be the same or different from each other.) A water-based anticorrosive characterized by containing. The phosphorus-containing substance PO ₄ terms, aqueous anticorrosive according to claim 1, characterized in that it comprises less 1 wt%.   The aqueous anticorrosive according to claim 1, further comprising an azole compound.   A water-based anticorrosion method comprising using the water-based anticorrosion agent according to claim 1 at a retention concentration of 20 to 200 mg / liter. Chemical formula (1)
R ¹ -SR ²
(R ¹ and R ² are an allyl group or an alkyl group having 1 to 20 carbon atoms, and at least one of R ¹ and R ² is a group consisting of a —CO— group, a —COOH group, and a —CONH— group Having at least one group selected from one or more types of groups selected from the group consisting of the same or different from each other.) A water-based anticorrosion method comprising circulating water containing an electrolyte.

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