JPH0813172A - Corrosion inhibitory composition for organic acid pickling - Google Patents

Abstract

PURPOSE:To obtain an corrosion-inhibitory composition which effectively inhibits metal corrosion from occurring at the time of performing acid washing and causes no secondary corrosion even if the composition remains on the washed metal after the acid washing by blending a specific alkynyl alcohol and a specific amine together in a specified ratio. CONSTITUTION:This composition contains an alkynyl alcohol and an amine in a ratio by weight of the former to the latter of 9:1 to 1:9 and effectively inhibits the attack against metal, in particular iron, of an organic acid pickling solution for removing scale, rust, etc., on the surface of the metal. As the alkynyl alcohol, at least one compound represented by formulas I to III (wherein: each of R1, R2 and R3 is H or an alkyl group; and each of (m), (n), (k), (i) and (l) is 0 or 1 to 10) is used. As the amine, at least one compound represented by formulas IV and V (wherein each of R6, R7 and R8 is H or an alkyl, an aryl, benzyl, a heterocyclic or hydroxyl group) is used. The adequate amount to be used of the composition is about 0.1 to 2.0wt.% to the amount of the organic acid in the washing solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the prevention of metal corrosion by an acid cleaning solution used for removing scale and rust on a metal surface, and more particularly to a corrosion inhibiting composition effective for an organic acid cleaning solution.

[0002]

2. Description of the Related Art Various heat exchange system devices such as heat exchangers and coolers generate various scales and deposits due to water circulation. An acid cleaning liquid is generally used to chemically remove these, but not only an inorganic acid but also an organic acid having a chelating property such as citric acid, glycolic acid, and EDTA (ethylenediaminetetraacetic acid) is effective. is there. However, since the acid cleaning liquid corrodes the metal surface, it is desirable to use the corrosion inhibiting composition together.

Under these circumstances, various corrosion inhibitors and compositions have been studied so far. For example, it is a thiourea derivative or a quaternary ammonium salt. For example, the title of the report “Chemical Cleaning of Boiler and Acid Corrosion Inhibitor”, Journal Name “Fuel and Combustion” Vol. 42, No. 7, pp. 577 to 599 (1975) can be referred to. .

Further, Japanese Patent Publication No. 44-13244 discloses an acid cleaning corrosion inhibitor comprising a mixture of acetylenic alcohol, amines and epoxy derivatives. A ternary mixture of acetylene alcohol, amines and non-acetylene alcohol is also disclosed as a corrosion inhibitor for acid cleaning in JP-B-44-13243. Specific imidazolines have been proposed as acid cleaning corrosion inhibitors alone (Japanese Patent Publication No. 52-42528). In addition, imidazoles are also known as volatile acid cleaning corrosion inhibitors (JP-A-62-238383). Although thiourea derivatives and quaternary ammonium salts have a strong corrosion inhibiting effect,
It changes into sulfate ions and halogen ions, and these ions induce secondary corrosion and stress corrosion cracking. In recent years, in acid cleaning, as a requirement required for a corrosion inhibitor, it has become an indispensable condition that, in addition to the ability to prevent corrosion, the inhibitor remains on an object and does not have an adverse effect. Other currently known acid-cleaning corrosion inhibitors or corrosion-inhibiting compositions do not contain elemental sulfur or halogen, but their corrosion-inhibiting effect is not very satisfactory.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and effectively suppresses metal corrosion that occurs during acid cleaning, and after cleaning with acid, the apparatus to be cleaned is It is an object of the present invention to provide a corrosion-inhibiting composition that does not induce secondary corrosion even if it remains.

[0006]

The present invention comprises (A) an alkynyl alcohol and (B) an amine, and the weight ratio of the (A) component to the (B) component is 9: 1-1. : 9 is a corrosion inhibiting composition for organic acid cleaning. (A)
The component and the component (B) act synergistically, exhibit excellent corrosion inhibiting ability, and can achieve the object of the present invention.

According to the present invention, the alkynyl alcohol (A) and the amine (B) are contained, and the weight ratio of the component (A) to the component (B) is 9: 1 to 1: 9. , The alkynyl alcohol has the general formula

[0008]

Embedded image

(In the above formula, R represents a hydrogen atom or an optionally branched alkyl group having 1 to 10 carbon atoms;
R ₁ , R ₂ and R ₃ independently represent a hydrogen atom or an optionally branched alkyl group having 1 to 10 carbon atoms, which may be the same or different; R ₄ and R ₅ independently represents a hydrogen atom or an optionally branched alkyl group having 1 to 10 carbon atoms, which may be the same or different; m is 0 or an integer of 1 to 10; Shown; l and i may be the same or different 0
Or an integer of 1 to 10; and n and k are the same or different integers of 1 to 10. ) One or more compounds represented by
The amine has the general formula

[0010]

[Chemical 4]

(In the above formula, R ₆ represents an optionally branched alkyl group having 11 to 18 carbon atoms; R ₇ is a hydrogen atom, or an optionally branched alkyl group having 1 to 20 carbon atoms. Represents an aryl group having 6 to 20 carbon atoms, a benzyl group or a heterocyclic group; and R ₈ represents a hydrogen atom, a hydroxylethyl group, a benzyl group or an optionally branched alkyl group having 1 to 20 carbon atoms. The present invention provides a corrosion inhibiting composition for organic acid cleaning, comprising one or more compounds represented by the formula (1).

[0012]

The present inventors have made various alkynyl alcohols (containing at least one carbon-carbon triple bond in the molecule).
The composition of the present invention was found as a result of testing the metal corrosion inhibitory ability of the combination of the amine with amines and finding the optimum combination.

The present invention will be described in more detail below.

Alkynyl alcohols that can be used in the present invention include (A) (1), (A) (2), (A) (3).
Represented by each of the formulas.

In formula (A) (1) as the preferred alkynyl alcohol, 2-propyn-1-ol, 3-butyn-1-ol, 1-butyn-3-ol, 1-pentyn-3-ol, 2- Pentin-1-ol, 3-pentyn-1-ol, 4-pentyn-1-ol, 4-
Pentin-2-ol, 2-heptin-1-ol, 4
-Heptin-2-ol, 5-heptin-3-ol,
1-hexyne-3-ol, 2-hexyn-1-ol, 3-hexyne-1-ol, 5-hexyne-1-ol, 5-hexyne-3-ol, 3-heptin-1-
All, 1-octyne-3-ol, 3-octyne-1
-Ol, 3-nonin-1-ol, 2-decin-1-
All, 3-decyn-1-ol, 4-ethyl-1-octin-3-ol, 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol can be mentioned.

In formula (A) (2), 2.5-dimethyl-
3-hexyne-2.5-diol and 3.6-dimethyl-4-octyne-3.6-diol are preferred.

In formula (A) (3), ethynyl-1-cyclohexanol is preferred.

In the present invention, at least one alkynyl alcohol selected from the above group is used.
Particularly preferably, 2-propyn-1-ol, 1-hexyne-3-ol or 4-ethyl-1-octyne-
Use 3-ol.

The amine that can be used in the present invention is represented by the formula (B) (1) and the formula (B) (2). Preferred amines include coconut amine in formula (B) (1).

In the formula (B) (2), 2-phenylimidazoline, 2-benzylimidazoline, 2-naphthylimidazoline and imidazoline such as 2-undecyl-1-hydroxyethylimidazoline are preferable amines.

The present invention uses at least one amine selected from the group as described above. Particularly preferably,
Coconut amine or 2-undecyl-1-hydroxyethyl imidazoline is used.

In the composition of the present invention, the composition ratio of the component (A) and the component (B) is (A) / (B) 9: 1 to 1: 9 by weight. Preferably, (A) / (B) is 1: 1. If the composition ratio is out of this range, the corrosion inhibiting ability of the composition decreases.

A particularly preferred composition of the present invention is that the component (A) is selected from the group consisting of 2-propyn-1-ol, 1-hexyn-3-ol and 4-ethyl-1-octin-3-ol. The one or more alkynyl alcohols mentioned above and the component (B) contain at least one amine selected from the group consisting of 2-undecyl-1-hydroxyethylimidazoline and coconut amine. A specific composition having extremely high corrosion prevention ability is (A)
Component 1-hexyne-3-ol and component (B) 2-undecyl-1-hydroxyethylimidazoline. Another specific composition comprises (A) component 4-ethyl-1-octyne-3-ol and (B) component 2-undecyl-1-hydroxyethylimidazoline.

Although the mechanism of the metal corrosion inhibiting action by the composition of the present invention is not clear, the combination of the component (A) and the component (B) suitable for the composition is obtained by using an iron piece as a sample and measuring the corrosion potential. The composition of the present invention can be obtained by determining the corrosion current (anode polarization, cathode polarization curve) and searching for a combination having a high degree of polarization. For example, "Modern Electrochemistry" Chapter 10 "Corrosion and Corrosion of Metals" pp. 190-19
See page 2 (Baifukan, 1984).

In this manner, the completion of the individual combination of the alkynyl alcohol as the component (A) and the amine as the component (B) constitutes one aspect of the present invention. Therefore, the alkynyl alcohol as the component (A) is not limited to the alkynyl alcohols exemplified above, but may be represented by formulas (A) (1) to (1) to
(A) It is selected from among alkynyl alcohols represented by (3), and the same applies to the amine of the component (B) of the formula (B).
It is possible for those skilled in the art to select an optimal combination from the amines represented by (1)-(B) and (2) without undue experimentation.

The composition of the present invention comprises (A) component and (B)
However, if necessary, other additional components such as a surfactant (dispersing the active ingredient in an acid washing liquid) may be included. However, the additional component added does not itself have a corrosion inhibiting action.

The composition of the present invention suppresses the attack of organic acid cleaning liquids on metals (particularly iron). Suitable organic acids for use together are formic acid, citric acid, malonic acid, glycolic acid, ascorbic acid, EDTA and the like. In the present invention, the corrosion inhibiting composition is used in an amount effective to inhibit metal corrosion, but preferably has a composition of about 0.1 to about 2.0% by weight based on the total volume of organic acid. The material is used in an organic acid wash.

The composition of the present invention comprises a nuclear power plant,
Most suitable for organic acid cleaning liquid that removes scale adhering to large once-through boilers for power generation, etc.
It can also be applied to devices made from brass).

[0029]

The present invention will be described below with reference to Examples and Comparative Examples, but these should not be construed as limiting the scope of the present invention.

Example 1 Component (A) 2-propyne-1
-Ol and (B) component 2-undecyl-1-hydroxyethylimidazoline were mixed in equal parts by weight (1: 1) to obtain a corrosion inhibiting composition of the present invention.

Example 2 Component (A) 1-hexyne-3
-Ol and (B) component 2-undecyl-1-hydroxyethylimidazoline were mixed in equal parts by weight to obtain a corrosion inhibiting composition of the present invention.

Example 3 Component (A) 4-ethyl-1-
Octyne-3-ol, (B) component 2-undecyl-1
-Hydroxyethyl imidazoline was mixed in equal parts by weight to obtain a corrosion inhibiting composition of the present invention.

(Example 4) Component (A) 1-hexyne-3
-All and (B) component coconut amine were mixed in equal parts by weight to obtain a corrosion inhibiting composition of the present invention.

Corrosion potential / current measurement test Acid cleaning solution at a temperature of 60 ° C. (3.5% malonic acid + 1.5%
1 liter of ascorbic acid) and 1-hexyn-3-ol (500 mg / liter) and 2
-Undecyl-1-hydroxyethyl imidazoline (5
00 mg / liter) mixture (a),
1-hexyn-3-ol (1000 mg / liter)
Added alone (b) and 2-undecyl-1-
Each was prepared by adding only hydroxyethyl imidazoline (1000 mg / liter) (c). S
An iron piece of S400 (JIS G 3101) was polished with sandpaper No. 2000, and then cleaned with acetone to prepare a test piece with a surface area of 0.78 cm ² . The test pieces were dipped in the solutions (a), (b) and (c), respectively, and
After a minute, a potential-current curve was obtained. As a result, the degree of polarization of the cathode and the anode in the solution (a) was more remarkable than that in both the solutions (b) and (c). That is, it is understood that the addition of the composition of Example 2 to the acid cleaning solution promotes polarization. The results of this polarization degree measurement are shown in FIG.

Corrosion Inhibition Test The composition of the present invention was used to test the corrosion inhibition action against an organic acid cleaning solution under the following conditions.

Mild steel sheet SB42 (JIS G 3103)
After polishing (3.5 × 2.5 × 0.3 cm) with No. 400 sandpaper, it was washed with water and then with isopropyl alcohol to prepare a test iron piece. 35g malonic acid and 1
5 g of ascorbic acid was added to 1 liter of water to prepare an organic acid cleaning solution. This organic acid cleaning solution was maintained at 60 ° C., and after adding a predetermined amount of the compositions of Examples 1 to 4, the test pieces were immersed for 24 hours to obtain a corrosion rate (weight reduction mg / cm ² / h).
r) was measured. At the same time, a blank test (only the acid cleaning solution) was performed, and the corrosion inhibition rate was calculated by the following formula.

[0037]

[Equation 1]

The test results are shown in Table 1.

[0039]

[Table 1]

In Comparative Example 1, 1-hexyn-3-ol was used alone. In Comparative Example 2, 2-undecyl-1-hydroxyethylimidazoline was used alone.

Using a test iron piece prepared in the same manner as described above, the composition of the present invention was tested against an organic acid cleaning solution prepared by adding 20 g of glycolic acid and 10 g of formic acid to 1 liter of water. The test was performed by adding a predetermined amount of the compositions of Examples 1 to 4 to the organic acid cleaning liquid kept at 60 ° C., and then dipping the test piece for 4 hours. The test results are shown in Table 2.

[0042]

[Table 2]

In Comparative Example 3, 1-hexyn-3-ol was used alone. In Comparative Example 4, 2-undecyl-1-hydroxyethylimidazoline was used alone.

Using a test iron piece prepared in the same manner as described above, the composition of the present invention was tested against an organic acid cleaning solution prepared by adding 15 g of citric acid and 15 g of glycolic acid to 1 liter of water. The test was performed by adding a predetermined amount of the compositions of Examples 1 to 4 to the organic acid cleaning liquid kept at 60 ° C., and then dipping the test piece for 4 hours. The test results are shown in Table 3.

[0045]

[Table 3]

In Comparative Example 5, 1-hexyn-3-ol was used alone. In Comparative Example 6, 2-undecyl-1-hydroxyethylimidazoline was used alone.

As described above, the composition of the present invention has a very high corrosion inhibition rate as compared with the case of no addition (blank test) and the comparison test (addition of either (A) alkynol or (B) amine). Are better. It was found that the use of either the component (A) or the component (B) alone did not have a sufficient inhibitory effect, and that the combination of both components act synergistically.

[0048]

The corrosion-inhibiting composition of the present invention effectively suppresses corrosion of ferrous metals during pickling when used in combination with an organic pickling solution without containing undesirable elemental sulfur or halogen.
Industrially, the utility value is extremely high.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a corrosion potential and a corrosion current of a composition of the present invention. In the figure, solid line: acid cleaning solution (no addition), one-dot chain line: (b) solution, two-dot chain line: (c) solution, dotted line: (a) solution

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazushi Fujiwara 4-124, Shigino Nishi, Joto-ku, Osaka City, Osaka Prefecture Asahi Kagaku Kogyo Co., Ltd. (72) Hiroshi Sasaki 4 Kagino-nishi, Joto-ku, Osaka City, Osaka Prefecture 1-24, Asahi Kagaku Kogyo Co., Ltd. (72) Inventor, Seiji Furukawa 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Kogyo Co., Ltd. (72) Inventor, Hiroo Yoshikawa 2 Kitahama, Chuo-ku, Osaka-shi, Osaka 2-22, Kurita Engineering Co., Ltd.

Claims (1)

[Claims] 1. An alkynyl alcohol (A) and (B)
And a weight ratio of the component (A) and the component (B) is 9: 1 to 1: 9, and the alkynyl alcohol is represented by the general formula: (In the above formula, R represents a hydrogen atom or an optionally branched alkyl group having 1 to 10 carbon atoms; R ₁ , R ₂ and R ₃ independently represent a hydrogen atom or 1 to 10 carbon atoms. And may each be the same or different; R ₄ and R ₅ are independently a hydrogen atom or a branched alkyl group having 1 to 10 carbon atoms. A good alkyl group, which may be the same or different; m represents 0 or an integer of 1 to 10; l and i may be the same or different, 0 or 1 to 10 Is an integer; and n and k may be the same or different and represent an integer of 1 to 10.) is one or two or more of the compounds represented by Formula [2] (In the above formula, R ₆ represents an optionally branched alkyl group having 11 to 18 carbon atoms; R ₇ is a hydrogen atom and 1 carbon atom
To 20 optionally branched alkyl groups having 6 to 6 carbon atoms
20 aryl groups, benzyl groups or heterocyclic groups are shown;
R ₈ represents a hydrogen atom, a hydroxylethyl group, a benzyl group or an optionally branched alkyl group having 1 to 20 carbon atoms. ) 1 type or 2 types or more of the compound represented by these), The corrosion inhibiting composition for organic acid cleaning characterized by the above-mentioned.