JPH10140379A - Corrosion inhibitor for pickling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a corrosion inhibitor for pickling with the rust removing rate increased, good in pickling efficiency and without the corrosion inhibiting effect being lowered in high-temp. pickling by incorporating polyethyleneimine and such a sulfur-contg. compd. as cysteamine into the inhibitor. SOLUTION: This corrosion inhibitor for pickling contains polyethyleneimine and >=1 kind of sulfur-contg. compd. among cysteamine, cystamine, 1,3- thiazolidine and 1,3-thiazolidin-2-one and is effective in the pickling at high temps. The polyethyleneimine is used as the modified polyethyleneimine obtained by the reaction of a part or the whole of the contained primary or secondary amine groups with other compds. or the reaction of ethyleneimine with other polymers. The ratio of the used sulfur compd. to the polyethyleneimine or modified polyethyleneimine is appropriately controlled to 0.2-1 pts.wt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a corrosion inhibitor for pickling. Specifically, it is a corrosion inhibitor for pickling for removing oxide films such as rust and scale on the metal surface, and is an acid that suppresses or prevents metal surface corrosion, hydrogen embrittlement, and pitting corrosion during pickling. The present invention relates to a corrosion inhibitor for washing.

[0002]

2. Description of the Related Art In order to remove an oxide film such as rust and scale adhering to a metal surface, a method of chemically cleaning the metal surface by a chemical solution treatment is known. Of which
The method of washing with an acid aqueous solution is most commonly used because of its low cost and high effect. As the acid, an inorganic acid such as hydrochloric acid, sulfuric acid, phosphoric acid, and hydrofluoric acid is used depending on the situation. However, the acid alone causes adverse effects such as corrosion of the metal substrate, hydrogen embrittlement, blistering, and pitting corrosion, in addition to removing oxide films such as rust and scale. Therefore, for the purpose of suppressing or preventing these,
A compound with high adsorptivity to metal surfaces and high protective film moldability
Added as an inhibitor. Such inhibitors include,
It is known that an organic compound having an unshared electron pair such as nitrogen, oxygen, and sulfur in its structure has a high suppressing ability.
Among them, organic amines containing one or more of primary, secondary, and tertiary amino groups in the molecular skeleton are the main components of the inhibitor, and the amino group in the molecule is an amino group. Many high molecular weight compounds are considered to be more advantageous for film formation.

Polyethyleneimine, a kind of high molecular organic amines, has been widely used as a highly effective and easily handleable drug since its corrosion inhibitory effect was reported in JP-A-49-106440. . However,
The mere addition of polyethyleneimine significantly reduces the corrosion inhibiting effect when used at high temperatures. The pickling at room temperature has a limit on the rust removal rate, and the efficiency of the pickling treatment must be reduced.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a novel corrosion inhibitor for pickling.

Another object of the present invention is to use a polyethyleneimine or a modified polyethyleneimine as a component of a corrosion inhibitor for pickling in pickling at a high temperature at a high rust removal rate and high pickling efficiency. In this case, it is an object of the present invention to solve the problem that the effect of inhibiting corrosion is greatly reduced.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies on a novel corrosion inhibitor for pickling in order to solve the above-mentioned problems. As a result, in pickling at a high temperature, (I) (a) polyethyleneimine And (b) cysteamines, cystamines,
1,3-thiazolidine and 1,3-thiazolidine-
A compound containing at least one sulfur-containing compound selected from the group consisting of 2-ones, or (II) (a ') a part or all of primary or secondary amino groups in polyethyleneimine and other Modified polyethyleneimine obtained by reaction with a compound or reaction of ethyleneimine with another polymer and (b) cysteamines, cystamines,
1,3-thiazolidine and 1,3-thiazolidine-
The compound containing at least one sulfur-containing compound selected from the group consisting of 2-ones has a higher corrosion inhibiting effect at high temperature pickling than the polyethyleneimine or modified polyethyleneimine alone. It has been found that the present invention has been completed.

That is, an object of the present invention is to provide (1) (a)
Polyethyleneimine and (b) at least one selected from the group consisting of cysteamines, cystamines, 1,3-thiazolidines and 1,3-thiazolidine-2-ones
It is achieved by a pickling corrosion inhibitor characterized in that it contains a sulfur-containing compound.

The present invention also relates to (2) the reaction of (a ') a part or all of the primary or secondary amino groups in polyethyleneimine with another compound or the reaction of ethyleneimine with another polymer. The resulting modified polyethyleneimine and (b) cysteamines, cystamines, 1,3-
It is achieved by a pickling corrosion inhibitor characterized by containing at least one sulfur-containing compound selected from the group consisting of thiazolidines and 1,3-thiazolidine-2-ones.

Further, the present invention provides (3) an amount of the sulfur-containing compound (b) of 0.2 to 1 part by weight based on the (a) polyethyleneimine or the (a ′) modified polyethyleneimine. It is also achieved by the pickling corrosion inhibitor described in the above (1) or (2).

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polyethyleneimine (a) used in the present invention includes the above-mentioned JP-A-49-10644.
As described in JP-A No. 0, for example, a polymer of polyethyleneimine obtained by a polycondensation reaction of ethylene dichloride and ethylenediamine or a polymer of polyethyleneimine obtained by heating and ring-opening 2-oxazoline, etc. In addition to those of linear high molecular polymers, not only complete linear high polymers such as polyethyleneimine polymers obtained by ring-opening polymerization of ethyleneimine,
General formula (1)

[0011]

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[0012] It includes a branched high molecular polymer having a structural portion having primary, secondary and tertiary amino groups as shown in the above. The molecular weight of (a) polyethyleneimine that can be used in the present invention is not particularly limited, but as described above, it is considered that the high molecular weight body is more likely to form a protective film on the metal surface, so the number average molecular weight is 300. -10
A thing of 100,000 is preferable.

[0013] The (a ') modified polyethyleneimine used in the present invention refers to the reaction of a part or all of the primary or secondary amino groups in polyethyleneimine with other compounds, or the reaction of ethyleneimine with other compounds. It is obtained by reaction with a polymer. Here, other compounds capable of reacting with part or all of the primary or secondary amino groups in polyethyleneimine are not particularly limited, and examples thereof include aldehyde compounds, ketone compounds, alkyl halide compounds, and isocyanate compounds. Examples include compounds, thioisocyanate compounds, active olefin compounds, epoxy compounds, cyanamide compounds, guanidine compounds, ureas, thioureas, carboxy compounds, acid anhydrides and acyl halide compounds. Other polymers that can react with ethyleneimine are not particularly limited, and include, for example, carboxy-containing acrylic resins, polyalkylene glycols, and the like. Among them, a modified polyethyleneimine obtained by reacting a part or all of primary or secondary amino groups in polyethyleneimine with an epoxy compound or a reaction between ethyleneimine and polyalkylene glycol is preferable. Also,
The reaction weight ratio of polyethyleneimine or ethyleneimine and the modifier (other compound) is polyethyleneimine or ethyleneimine: modifier = 1: 0.01 to 2.0, preferably polyethyleneimine or ethyleneimine: modifier = 1: 0.1 to 1.5. The molecular weight of the modified polyethyleneimine is not particularly limited, but preferably has a number average molecular weight of 3 to 1,000,000 like polyethyleneimine.

(B) cysteamines used in the present invention,
Cystamines, 1,3-thiazolidines and 1,3-
The at least one sulfur-containing compound selected from the group consisting of thiazolidine-2-ones is not particularly limited, but preferably includes those specifically exemplified below.

The cysteamines are represented by the general formula (2)

[0016]

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Wherein R ^{1 to} R ⁴ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms and may be the same or different from each other, specifically, cysteamine ( 2-aminoethanethiol), and their hydrochlorides, sulfates, inorganic salts such as phosphates, acetates,
Organic acid salts such as lactate, alkyl sulfonate and benzoate are exemplified.

The cystamines are represented by the general formula (3)

[0019]

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Wherein R ^{1 to} R ⁴ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, which may be the same or different, specifically, cystamine ( 2,2'-dithiobisethanamine), their inorganic salts such as hydrochloride, sulfate, phosphate, and organic acid salts such as acetate, lactate, alkylsulfonate, and benzoate. Alkylenoxide adducts as disclosed in JP-A-7-10830 are exemplified.

The 1,3-thiazolidines are represented by the general formula (4)

[0022]

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(Wherein, R ^{1 to} R ⁶ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and may be the same or different from each other).
1,3-thiazolidine, 2-methyl-1,3-thiazolidine, 2,2-dimethyl-1,3-thiazolidine, 2-
Methyl-2-ethyl-1,3-thiazolidine, 2-methyl-2-isobutyl-1,3-thiazolidine, 2,2
4-trimethyl-1,3-thiazolidine, 2,2,4
5-tetramethyl-1,3-thiazolidine, 2,2-dimethyl-4-ethyl-1,3-thiazolidine, 2,2-
Dimethyl-5-ethyl-1,3-thiazolidine, 2,4
-Dimethyl-2-ethyl-1,3-thiazolidine, 2,
5-dimethyl-2-ethyl-1,3-thiazolidine,
2,4-dimethyl-2-isobutyl-1,3-thiazolidine, 2,5-dimethyl-2-isobutyl-1,3-thiazolidine and 2,4,5-trimethyl-2-isobutyl-1,3-thiazolidine Is mentioned.

The 1,3-thiazolidine-2-ones are represented by the general formula (5)

[0025]

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(Wherein, R ^{1 to} R ⁴ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and may be the same or different from each other).
1,3-thiazolidine-2-one, 4-methyl-1,3
-Thiazolidine-2-one, 5-methyl-1,3-thiazolidine-2-one, 4,4-dimethyl-1,3-thiazolidine-2-one, 4,5-dimethyl-1,3-thiazolidine-2 -One, 4,4,5-trimethyl-1,3
-Thiazolidine-2-one, 4-ethyl-1,3-thiazolidine-2-one, 5-ethyl-1,3-thiazolidine-2-one, 4,5-diethyl-1,3-thiazolidine-2-one , 4-methyl-5-propyl-1,3-thiazolidine-2-one, 4-ethyl-5-butyl-1,
Examples include 3-thiazolidine-2-one, 4-ethyl-5-propyl-1,3-thiazolidine-2-one and 4-butyl-5-butyl-1,3-thiazolidine-2-one.

The above (b) sulfur-containing compounds include cysteamines, cystamines, 1,3-thiazolidines,
Any one or two or more selected from the group consisting of 3-thiazolidine-2-ones may be used, and the amount of the acid in the pickling corrosion inhibitor is not particularly limited, but preferably (a) polyethyleneimine or (a ') With respect to the blended amount of the modified polyethyleneimine, the total blended amount of the (b) sulfur-containing compound is 0.2 to
Preferably, it is 1.0 part by weight.

The pickling corrosion inhibitor according to the present invention comprises:
In order to effectively exhibit the effect, the amount of (a) polyethyleneimine or (a ') modified polyethyleneimine in the pickling corrosion inhibitor is usually 1 ppm to the pickling solution.
10,000 ppm, preferably 500-2000 ppm
It is desirable to use it by adding so as to fall within the range.

The corrosion inhibitor for pickling according to the present invention comprises:
It can be used for pickling in general, and the type of acid component and the concentration of the acid component in the applicable pickling solution composition are also appropriately selected according to the application. And inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid and hydrofluoric acid. Further, if the concentration of the acid component is too low, the rust removal rate is small and the efficiency of pickling is deteriorated, and if it is too high, the rust removal rate is increased but the corrosion of the metal base is promoted. It is preferably 10% by weight.

By using the corrosion inhibitor for pickling according to the present invention, polyethyleneimine or modified polyethyleneimine can be used as a corrosion inhibitor for pickling at a high temperature in pickling at a high rust removal rate and high pickling efficiency. When used as a component, it is possible to solve the problem that the corrosion inhibiting effect is significantly reduced, and specifically, it is stable even when the pickling temperature under normal pressure is as high as 80 to 100 ° C. Can be used as is. In addition, when the treatment is performed under pressure, it can be used even when the pickling temperature is 100 ° C. or higher.

[0031]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1 A 50% aqueous solution of 10% by weight sulfuric acid as an acid component was placed in a sample tube.
and 250 mg of (a) a 10% by weight aqueous solution of polyethyleneimine as a corrosion inhibitor for pickling, and (b) 2% of a 10% by weight aqueous solution of cysteamine hydrochloride, one of sulfur-containing compounds.
Then, 50 mg of the solution was added to make an acid washing solution, and the solution temperature was 90 ° C.
Here, the added polyethyleneimine is a branched high molecular polymer having primary, secondary and tertiary amino groups in its structure as shown in the general formula (1),
Its number average molecular weight was about 1800. The concentration of polyethyleneimine and cysteamine hydrochloride in the pickling solution is
All were 500 ppm.

Next, the cold-rolled steel sheet (JIS No. G3141SPCC-SD, 5
2 mm × 15 mm × 1 mm) for 5 minutes. The steel plate after immersion was visually washed after washing with water and acetone, and the weight was measured to determine the corrosion inhibition rate by the following equation (1). Table 1 shows the results of the appearance and the corrosion inhibition rate.

[0034]

(Equation 1)

The corrosion degree in the above equation (1) is defined as a weight reduction per unit time and unit surface area of the immersed metal.

Example 2 The appearance and corrosion inhibition rate of a steel sheet by a pickling liquid were determined in the same manner as in Example 1 except that 250 mg of a 10% by weight cystamine hydrochloride aqueous solution was used instead of 250 mg of an aqueous solution of cysteamine hydrochloride. I asked. Table 1 shows the results.

Example 3 An acid washing solution was used in the same manner as in Example 1 except that 250 mg of an aqueous solution of 10% by weight of cysteamine hydrochloride was replaced with 250 mg of an aqueous solution of 10% by weight of 2,2-dimethyl-1,3-thiazolidine. The appearance and corrosion inhibition rate of the steel sheet were determined. Table 1 shows the results.

Example 4 A steel sheet was pickled with a pickling solution in the same manner as in Example 1 except that 250 mg of an aqueous solution of 10% by weight of cysteamine hydrochloride was used instead of 250 mg of an aqueous solution of 10% by weight of cysteamine hydrochloride. The appearance and the corrosion inhibition rate were determined. Table 1 shows the results.

Example 5 50 ml of a 10% by weight aqueous solution of an acid component of sulfuric acid was placed in a sample tube.
Then, 250 mg of (a ') a 10% by weight aqueous solution of modified polyethyleneimine and (b) 10% by weight of cysteamine hydrochloride, one of sulfur-containing compounds, were added as corrosion inhibitors for pickling.
250 mg of an aqueous solution was added to make an acid washing solution, and the solution temperature was 9
0 ° C. Here, the added (a ′) modified polyethyleneimine is obtained by partially cross-linking an ethyleneimine-polyethylene glycol polymer with ethylene glycol diglycidyl ether, and is obtained by mixing ethyleneimine with a modifier (ethylene glycol). The reaction weight ratio was ethyleneimine: denaturant = 1: 1.0, and the number average molecular weight of the modified polyethyleneimine was 100,000. The concentrations of the modified polyethyleneimine and cysteamine hydrochloride in the pickling solution were all about 500 ppm.

Next, a cold-rolled steel plate (JIS No. G3141SPCC-SD, JIS No.
2 mm × 15 mm × 1 mm) for 5 minutes. The steel plate after immersion was visually observed after washing with water and acetone, and the weight was measured to determine the corrosion inhibition rate by the above equation (1). Table 1 shows the results of the appearance and the corrosion inhibition rate.

Example 6 In the same manner as in Example 5, except that 250 mg of a 10% by weight aqueous solution of cystamine hydrochloride was used instead of 250 mg of an aqueous solution of 10% by weight cysteamine hydrochloride, the appearance and corrosion inhibition rate of the steel sheet by the pickling solution were reduced. I asked. Table 1 shows the results.

Example 7 An acid washing solution was used in the same manner as in Example 5, except that 250 mg of an aqueous solution of 10% by weight of cysteamine hydrochloride was replaced with 250 mg of an aqueous solution of 10% by weight of 2,2-dimethyl-1,3-thiazolidine. The appearance and corrosion inhibition rate of the steel sheet were determined. Table 1 shows the results.

Example 8 A steel sheet was pickled with a pickling solution in the same manner as in Example 5 except that 250 mg of a 10% by weight aqueous solution of cysteamine hydrochloride was used instead of 250 mg of an aqueous solution of 10% by weight cysteamine hydrochloride. The appearance and the corrosion inhibition rate were determined. Table 1 shows the results.

Comparative Example 1 The appearance and corrosion inhibition rate of a steel sheet by a pickling solution were determined in the same manner as in Example 1 except that cysteamine hydrochloride was not added. Table 1 shows the results.

COMPARATIVE EXAMPLE 2 A 500% aqueous solution of polyethyleneimine (10% by weight) was added to adjust the concentration of polyethyleneimine in the pickling solution to 1000 ppm, except that cysteamine hydrochloride was not added. The appearance and the corrosion inhibition rate were determined. Table 1 shows the results.

Comparative Example 3 The appearance and corrosion inhibition rate of the steel sheet by the pickling solution were determined in the same manner as in Example 5 except that cysteamine hydrochloride was not added. Table 1 shows the results.

Comparative Example 4 500 mg of a 10% by weight aqueous solution of modified polyethyleneimine
In addition, the modified polyethyleneimine concentration of the
The appearance and corrosion inhibition rate of the steel sheet by the pickling liquid were determined in the same manner as in Example 5 except that the content was set to 0 ppm and cysteamine hydrochloride was not added. Table 1 shows the results.

[0048]

[Table 1]

As shown in Table 1 above, when polyethyleneimine or modified polyethyleneimine was added alone, the addition concentration was 5%.
Even when the content is increased from 00 ppm to 1000 ppm, the corrosion inhibiting effect hardly changes. In contrast, when 500 ppm of a sulfur-containing compound such as cysteamine is added to 500 ppm of polyethyleneimine or modified polyethyleneimine,
The corrosion inhibition rate increased by 10 to 30%. In addition, the appearance of the steel sheet after immersion was slightly discolored to gray and gloss was lost when polyethyleneimine or modified polyethyleneimine alone was added, whereas gloss was slightly lost when polyethyleneimine or modified polyethyleneimine and cysteamine were mixed and added. It was about.

[0050]

According to the present invention, in pickling at a high temperature,
Compared with the case where polyethyleneimine is solely added to the pickling solution, metal corrosion can be further suppressed. This makes it possible to set the pickling temperature to a relatively high temperature as compared with the case of adding polyethyleneimine alone, increase the rust removal rate, and perform pickling efficiently.

Claims (3)

[Claims] 1. A sulfur-containing compound selected from the group consisting of (a) polyethyleneimine and (b) cysteamines, cystamines, 1,3-thiazolidines and 1,3-thiazolidine-2-ones. A corrosion inhibitor for pickling, characterized by comprising: 2. (a ′) a modified polyethyleneimine obtained by reacting a part or all of primary or secondary amino groups in polyethyleneimine with another compound or by reacting ethyleneimine with another polymer; b) Pickling characterized by containing at least one sulfur-containing compound selected from the group consisting of cysteamines, cystamines, 1,3-thiazolidines and 1,3-thiazolidine-2-ones. For corrosion inhibitors. 3. The (a) polyethyleneimine or the polyethyleneimine
The corrosion inhibitor for pickling according to claim 1 or 2, wherein the amount of the sulfur-containing compound (b) is 0.2 to 1 part by weight based on the modified polyethyleneimine (a ').