JP2976280B2 - Metal pickling composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal pickling composition, and more particularly to a metal pickling composition for removing an oxide film adhered to the surface of a metal steel sheet such as a hot-rolled steel sheet.

[0002]

Normally, a black oxide film such as a mill scale adheres to the surface of a metal steel sheet such as a hot-rolled steel sheet, and the metal steel sheet is subjected to the next process such as rust prevention and plating. To do so, it is necessary to remove the oxide film.

[0003] To remove the oxide film, for example, washing with an aqueous solution of an inorganic or organic acid such as sulfuric acid, hydrochloric acid, phosphoric acid, sulfamic acid, nitric acid, hydrofluoric acid, oxalic acid, citric acid, or a mixed acid thereof; So-called pickling is commonly performed.
However, since the oxide film adheres very firmly to the metal surface, it takes a considerably long time to pickle it to completely remove it.

In addition, when pickling is performed, there is a problem that not only the oxide film but also the metal substrate is dissolved and corroded.
In order to solve such a problem, conventionally, together with an acid, for example, acetylenic alcohols (JP-B-44-132)
43, JP-B-44-13244), imidazolines (JP-B-52-42528), thiourea derivatives, quaternary ammonium salts, organic amines, and other corrosion inhibitors. I have. However,
These corrosion inhibitors have the disadvantage of slowing down the pickling rate, so that the pickling time is further increased and a reduction in work efficiency is inevitable.

[0005] As described above, it is industrially important to promote the pickling while suppressing the corrosion of the metal base and to shorten the time required for the pickling, and various proposals and studies have been made.

[0006] For example, Japanese Patent Application Laid-Open No. 57-198273 describes a method in which various surfactants such as a fluorinated type and a hydrocarbon type are added to an acid. However, in this method, the acid aqueous solution foams due to the addition of the surfactant,
There is a drawback that the foaming causes color unevenness or the like on the surface of the metal steel plate after pickling. Moreover, its pickling accelerating effect is not satisfactory. Also, JP-A-63-20
According to Japanese Patent No. 3780, there is proposed a method in which an oxidizing agent such as nitrate or nitrite and a corrosion inhibitor such as thiourea are added to an acid, but the oxidizing agent exhibits an oxidizing effect which is an original function. Inevitably, corrosion of the metal substrate increases, even in the presence of corrosion inhibitors. JP-A-47-3412
No. 2 discloses a method of adding an inorganic reducing agent such as a sulfite or a thiosulfate, or an organic reducing agent such as ascorbic acid or hydrazine to an acid. Although the inorganic reducing agent has a dissolution accelerating effect on the oxide film, it is not preferable because when added to an acid, a toxic gas such as a sulfurous acid gas or a hydrogen sulfide gas is generated and the working environment is remarkably reduced. In addition, there is a disadvantage that the effect of the corrosion inhibitor is reduced and the amount of corrosion is increased.
The organic reducing agent does not show a sufficient accelerating effect. Furthermore,
JP-A-5-195270 discloses water-soluble polymer compounds such as polyethylene glycol, completely saponified polyvinyl alcohol, and polyvinylpyrrolidone as pickling accelerators. Although these water-soluble polymer compounds have a certain degree of pickling-promoting effect, similar to the case of the surfactants, foaming causes color unevenness or the like on the surface of the pickled metal steel sheet. Further, the acid concentration is increased or the acid temperature is raised within a range in which the performance of the corrosion inhibitor does not decrease, thereby shortening the pickling time, but its effect is hardly sufficient.

[0007] On the other hand, 1-hydroxybenzotriazole derivatives are widely used in the field of iron and steel as a pressure regulator during rolling of a steel sheet, and are also effective as a rust inhibitor (corrosion inhibitor) for metals. Known (for example,
JP-B-53-28864). However, at the time of pickling of a hot-rolled steel sheet, there is no example in which an acid is used in combination with the acid, and in combination with the acid, the 1-hydroxybenzotriazole derivative not only prevents the corrosion of the metal base, but also improves the pickling rate. There is no report on increasing the whiteness of the steel sheet surface after pickling.

Therefore, there is a demand for the development of a technique capable of accelerating the pickling while suppressing the corrosion of the metal base and shortening the time required for the pickling.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has succeeded in obtaining a novel metal pickling composition which meets the above-mentioned demands. The invention has been completed.

That is, the present invention relates to (a) an acid, and (b)
General formula

[0011]

Embedded image

[In the formula, R represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an amino group, a nitro group, a hydroxyl group or a mercapto group. ] The metal pickling composition which contains at least 1 sort (s) selected from the 1-hydroxybenzotriazole derivative represented by these, and its salt as an active ingredient.

According to the present invention, a metal capable of exhibiting an excellent effect of remarkably increasing the pickling speed while preventing corrosion of a metal substrate and further increasing the whiteness and smoothness of the surface of the metal steel plate after the pickling. An acid pickling composition is provided. Further, since the metal pickling composition of the present invention does not foam, the color unevenness or the like does not occur on the surface of the metal steel plate after pickling. Furthermore, the metal pickling composition of the present invention does not adversely affect the next step such as rust prevention treatment, and the metal steel sheet after pickling also has good direct coatability.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The metal pickling composition of the present invention comprises:
(A) an acid; and (b) 1 represented by the above general formula (1)
And at least one selected from hydroxybenzotriazole derivatives and salts thereof as an active ingredient.

In the above formula (1), examples of the alkyl group having 1 to 6 carbon atoms represented by R include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group,
Examples thereof include an n-butyl group, a tert-butyl group, a pentyl group, and a hexyl group.

As the acid used as the component (a) in the composition of the present invention, any of the well-known inorganic acids and organic acids conventionally used for pickling metal steel sheets can be used. Examples thereof include inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid, and hydrofluoric acid, and organic acids such as sulfamic acid, acetic acid, oxalic acid, citric acid, formic acid, tartaric acid, malic acid, hydroxyacetic acid, and gluconic acid. Among these, sulfuric acid, hydrochloric acid, nitric acid, inorganic acids such as phosphoric acid, sulfamic acid,
Organic acids such as citric acid and hydroxyacetic acid are preferred, and inorganic acids such as sulfuric acid and hydrochloric acid are particularly preferred. These acids can be used alone or in combination of two or more.

The concentration of the component (a) in the composition of the present invention may be about the same as in the case of conventional pickling, and may be appropriately selected according to the material of the metal steel sheet to be pickled. Usually, it may be about 1 to 20% by weight, preferably about 5 to 10% by weight in the composition of the present invention.

The 1-hydroxybenzotriazole derivative represented by the general formula (1) and the salt thereof, which is the component (b) in the composition of the present invention, have been conventionally used as a pressure regulator and a rust preventive at the time of rolling a metal steel sheet. It is a widely used compound,
There is no report that acid was used in combination with an acid during pickling of hot-rolled steel sheets, and that the acid was used in combination to improve the pickling rate or increase the whiteness of the steel sheet surface after pickling. Has never been done before.

Specific examples of the 1-hydroxybenzotriazole derivative represented by the general formula (1) include 1-hydroxybenzotriazole, 5-methyl-1-hydroxybenzotriazole, 6-amino-1-hydroxybenzotriazole, Examples thereof include nitro-1-hydroxybenzotriazole, 6-methyl-1-hydroxybenzotriazole and 6-ethyl-1-hydroxybenzotriazole. Among these, 1-hydroxybenzotriazole, 5-methyl-1-hydroxybenzotriazole, 6-methyl-1-hydroxybenzotriazole, 6-ethyl-1-hydroxybenzotriazole and the like are preferable, and 1-hydroxybenzotriazole is particularly preferable. preferable. The salt of the 1-hydroxybenzotriazole derivative represented by the general formula (1) is not particularly limited, but may be an ammonium salt, a hydrazine salt, a monoamine salt,
Examples thereof include diamine salts, triamine salts, hydrochlorides, and sulfates. Such 1-hydroxybenzotriazole derivatives of the general formula (1) and salts thereof can be used alone or in combination of two or more.

The concentration of the 1-hydroxybenzotriazole derivative in the composition of the present invention is not particularly limited and can be appropriately selected from a wide range according to the material of the metal sheet to be pickled. In consideration of the above, the content is usually about 0.001 to 0.5% by weight, preferably about 0.005 to 0.2% by weight in the composition of the present invention.

To the composition of the present invention, various conventionally used corrosion inhibitors and other additives can be appropriately added as long as the excellent effects are not impaired.

The composition of the present invention can be produced by dissolving predetermined amounts of the active ingredients (a) and (b) in water. Alternatively, predetermined amounts of the two kinds of active ingredients may be separately dissolved in water and mixed at the time of pickling.

The pickling using the composition of the present invention can be carried out in the same manner as the conventional pickling. Further, the liquid temperature and the like of the composition of the present invention may be appropriately selected according to the material and the like of the metal steel plate to be pickled.

The composition of the present invention can be applied to pickling of various metal steel sheets such as a hot-rolled steel sheet and a cold-rolled steel sheet. Specific examples of the metal species include, for example, special steels such as carbon steel and stainless steel, iron, copper, copper alloys (brass and the like), and metal materials and products to be pickled.

[0025]

The present invention will be specifically described below with reference to examples and test examples. In the following, “%” means “% by weight” unless otherwise specified.

Example 1 In a 5% aqueous hydrochloric acid solution, 1-hydroxybenzotriazole (hereinafter referred to as "1-HOB") having a concentration of 0.01% and a concentration of 0.1% was added.
It was added so as to be 02% and 0.05% to produce a metal pickling composition of the present invention.

Test Example 1 Using the three kinds of metal pickling compositions obtained in Example 1, pickling (20 ° C. × 15 hours) was performed on a cold-rolled steel sheet (3 × 4 cm) whose surface was cleaned. did. Note that FeCl ₂ was added to the metal pickling composition so that the Fe ion content became 5% in order to approximate the actual use situation. The metal sheet after pickling was examined for corrosion amount (mg / g), appearance, pitting corrosion (pieces), and whiteness. Investigation criteria for the amount of corrosion, appearance, pitting corrosion and whiteness are as follows.

Corrosion amount: Calculated from the following equation.

[0029]

(Equation 1)

Appearance and pitting: visual observation.

Whiteness: colorimetric colorimeter [Product name: SE200]
0, manufactured by Nippon Denshoku Industries Co., Ltd.], and calculated by the following equation.

[0032]

(Equation 2)

In the above formula, L: lightness, a: red to green hue, b: yellow to blue hue.

The results are shown in Table 1 below.

For comparison, 1-HOB was used as a blank.
Using a 5% hydrochloric acid aqueous solution (Fe ion content: 5%) containing no, acid pickling was performed in the same manner as above, and the same items as above were tested for the metal steel sheet after pickling. The results are also shown in Table 1.

[0036]

[Table 1]

From Table 1, it is apparent that the amount of corrosion of the steel sheet after removing the oxides is reduced to 1/5 to 1/20 by adding 1-HOB, the appearance is smooth, and the whiteness is significantly improved. It is.

Example 2 1-HOB was added to 5%, 6%, 7% and 8% hydrochloric acid aqueous solutions at concentrations of 0.01%, 0.02% and 0.0%, respectively.
5%, 0.1%, and 0.2% were added to produce various metal pickling compositions of the present invention.

Test Example 2 The various metal pickling compositions obtained in Example 2 were added to a liquid temperature of 85.
At ℃, a low-grade electromagnetic material, a tin material, a high-temperature rolled magnetic material and a high-temperature rolled tin material (each 3 × 5 cm) to which a black oxide film is adhered are immersed, and the time required for the black oxide film to be removed is visually observed. It was checked by observation. In addition, in order to approximate the actual use situation, FeCl ₂ was added to the metal pickling composition so as to have an Fe ²⁺ ion content of 8%, and FeCl ₂ was added so that the Fe ³⁺ ion content became 0.1%. FeCl ₃ was added.

For comparison, 1-HOB was used as a blank.
5-8% hydrochloric acid aqueous solution (Fe ²⁺ ion content 8
%, Fe ³⁺ ion content of 0.1%), and pickling was carried out in the same manner as described above, and the time for removing the black oxide film was examined by visual observation.

The results are shown in FIGS. FIGS. 1 to 4 are graphs each showing the relationship between the hydrochloric acid concentration, the 1-HOB concentration, and the descaling time (second, the time during which the black oxide film is removed). 1 is a graph when the metal steel plate to be pickled is a low-grade electromagnetic material, FIG. 2 is a graph when the metal steel plate to be pickled is a tin material, and FIG. FIG. 4 is a graph in the case where the metal steel plate to be picked up is an electromagnetic material high temperature rolled material, and FIG.

In FIGS. 1-4, ●: 1-HOB concentration 0
%, ◎: 1-HOB concentration 0.01%, ：: 1-HOB concentration 0.02%, Δ: 1-HOB concentration 0.05%, □: 1
−HOB concentration 0.1%, Δ: 1-HOB concentration 0.2%.

From FIGS. 1-4, it is clear that 1-HOB can enhance the pickling rate.

Example 3 1-HOB was added to a 5% aqueous sulfuric acid solution at a concentration of 0.01% and a concentration of 0.1%.
It was added so as to be 02% and 0.05% to prepare various metal pickling compositions of the present invention.

Test Example 3 A low-grade electromagnetic material was added to the metal pickling composition obtained in Example 3.
The tinplate material, the electromagnetic material high-temperature rolled material, and the tinplate high-temperature rolled material were immersed at room temperature for 26 hours, pickled, taken out, and examined for corrosion amount (mg / g) and whiteness.

For comparison, 1-HOB was used as a blank.
Using a 5% aqueous sulfuric acid solution containing no, acid washing was performed in the same manner as described above, and the corrosion amount (mg / g) and whiteness were examined.

Table 2 shows the results for the amount of corrosion, and Table 3 shows the results for the whiteness. The corrosion amount was measured in the same manner as in Test Example 1.

[0048]

[Table 2]

[0049]

[Table 3]

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship among hydrochloric acid concentration, 1-HOB concentration, and descaling time when a low-grade electromagnetic material is used as a metal steel plate to be pickled.

FIG. 2 is a graph showing a relationship between a hydrochloric acid concentration, a 1-HOB concentration, and a descaling time when a tin plate is used as a metal steel plate to be pickled.

FIG. 3 is a graph showing a relationship between a hydrochloric acid concentration, a 1-HOB concentration, and a descaling time when an electromagnetic material high-temperature rolled material is used as a metal steel sheet to be pickled.

FIG. 4 is a graph showing a relationship between a hydrochloric acid concentration, a 1-HOB concentration, and a descaling time when a tin plate high-temperature rolled material is used as a metal steel plate to be pickled.

Claims (1)

(57) [Claims] (1) an acid, and (b) a general formula: [In the formula, R represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an amino group, a nitro group, a hydroxyl group or a mercapto group. ]
A metal pickling composition comprising as an active ingredient at least one selected from the group consisting of a 1-hydroxybenzotriazole derivative represented by the formula: