JP2022100934A - Scale remover and manufacturing method of metal material - Google Patents

Abstract

To provide a scale remover which can remove scale while keeping plating film.SOLUTION: A scale remover contains a chelating agent, an organic acid, a fluorochemical and a surfactant. The chelating agent contains an aminocarboxylic acid type chelating agent. The aminocarboxylic acid type chelating agent has equal to or more than 2 carboxyalkyl groups binding to nitrogen atom in the molecule. The carboxyalkyl group is structured by linear alkylene groups. Equal to or more than 2 of the carboxyalkyl group are carboxymethyl groups.SELECTED DRAWING: Figure 1B

Description

The present invention relates to a scale remover and a method for producing a metal material.

Welding of metal materials is generally performed at high temperatures. Therefore, the periphery of the welded portion surface is oxidized and discolored. This discoloration is called scale. The scale causes a change in the appearance of the metal material and inhibits the formation of a chemical conversion film. Therefore, the corrosion resistance of the metal material tends to decrease.

Therefore, Patent Document 1 proposes a scale remover containing organic phosphonic acid or a salt thereof.

Japanese Unexamined Patent Publication No. 2010-70805

However, it was found that when a scale remover containing an organic phosphonic acid or the like was applied to a metal material having a plating film, the plating film was dissolved.

An object of the present invention is to provide a scale remover capable of removing scale while maintaining a plating film.

In order to solve the above problems, the present invention provides the following aspects.
[1]
Containing a chelating agent, an organic acid, a fluorine compound, and a surfactant,
The chelating agent contains an aminocarboxylic acid type chelating agent.
The aminocarboxylic acid type chelating agent has two or more carboxyalkyl groups bonded to a nitrogen atom in the molecule.
The carboxyalkyl group is composed of a linear alkylene group.
A scale remover in which two or more of the carboxyalkyl groups are carboxymethyl groups.

[2]
The scale removing agent according to the above [1], wherein the aminocarboxylic acid type chelating agent has three or more carboxymethyl groups bonded to a nitrogen atom in the molecule.

[3]
The scale removing agent according to the above [1] or [2], wherein the aminocarboxylic acid type chelating agent contains nitrilotriacetic acid.

[4]
The mass ratio of the content _CC1 of the aminocarboxylic acid type chelating agent to the content _CA of the organic acid: _CC1 / _CA is 10/90 to 90/10, the above [1] to [ 3] The scale remover according to any one of.

[5]
The scale removing agent according to any one of [1] to [4] above, wherein the content C _C1 of the aminocarboxylic acid type chelating agent is 3,000 mass ppm or more and 60,000 mass ppm or less.

[6]
The scale remover according to any one of [1] to [5] above, wherein the content _CA of the organic acid is 3,000 mass ppm or more and 60,000 mass ppm or less.

[7]
The scale remover according to any one of the above [1] to [6], wherein the organic acid contains an alkylcarboxylic acid.

[8]
The scale remover according to the above [7], wherein the alkylcarboxylic acid has two or more carboxy groups.

[9]
The scale remover according to any one of the above [1] to [8], which is used for a metal material having a plating film.

[10]
Equipped with a process to bring the scale remover into contact with the metal material,
The scale remover contains a chelating agent, an organic acid, a fluorine compound, and a surfactant.
The chelating agent contains an aminocarboxylic acid type chelating agent.
The aminocarboxylic acid type chelating agent has two or more carboxyalkyl groups bonded to a nitrogen atom in the molecule.
The carboxyalkyl group is composed of a linear alkylene group.
A method for producing a metal material, wherein two or more of the carboxyalkyl groups are carboxymethyl groups.

[11]
The method for producing a metal material according to the above [10], wherein the metal material is immersed in the scale removing agent in the contacting step.

[12]
The method for producing a metal material according to the above [11], wherein the metal material is immersed in the scale removing agent at 40 ° C. or higher and 70 ° C. or lower within 1 minute or more and 50 minutes or less.

[13]
The method for producing a metal material according to any one of [10] to [12] above, wherein the metal material includes a metal material having a plating film.

[14]
The method for producing a metal material according to the above [13], wherein the metal material having the plating film includes a galvanized steel sheet.

According to the present invention, it is possible to provide a scale removing agent capable of removing scale while maintaining a plating film.

It is an image (magnification 5 times) taken through a magnifying glass around the weld bead portion of the test piece prepared in Example 1. It is an image (magnification 5 times) which took the part corresponding to FIG. 1A after being treated with a scale remover through a magnifying glass. 6 is a scanning electron microscope (SEM) image (magnification 1,500 times) around the weld bead portion of the test piece prepared in Example 1 after chemical conversion treatment.

The scale is a metal oxide produced by combining a metal component with oxygen in the air when welding a metal material such as a steel plate. The scale may contain carbon as well as metal oxides. Scales are also called weld burns.

Similarly, when welding a metal material having a plating film, a scale is formed on the plating film. If a scale remover containing a phosphonic acid-based chelating agent is used to remove this scale, the plating film will also be dissolved.

Therefore, in the present embodiment, a scale removing agent containing a specific aminocarboxylic acid type chelating agent and a method for producing a metal material using the scale removing agent are proposed. According to the scale removing agent according to the present embodiment, scale can be removed while maintaining the plating film.

A. Scale remover The scale remover according to the present embodiment contains a chelating agent, an organic acid, a fluorine compound, and a surfactant. The chelating agent contains a specific aminocarboxylic acid type chelating agent (hereinafter, referred to as a first chelating agent) having two or more carboxyalkyl groups bonded to a nitrogen atom in the molecule. The above carboxyalkyl group is composed of a linear alkylene group. Two or more of the above carboxyalkyl groups are carboxymethyl groups.

The pH of the scale remover is 6 or more and 8 or less. As described above, even a substantially neutral scale remover can efficiently remove scale by containing a chelating agent, an organic acid, a fluorine compound and a surfactant. Furthermore, discoloration of metal materials and environmental load are suppressed.

The scale remover is prepared by adding each of the above components to an aqueous solvent and mixing them. Examples of the aqueous solvent include various types of water such as pure water, ion-exchanged water, tap water, and industrial water. If necessary, the scale remover may contain a small amount of a water-miscible organic solvent (for example, alcohols) together with water.

[Chelating agent]
The scale remover according to the present embodiment contains a chelating agent. The chelating agent strips and captures the scale from the surface of the metal material.

The chelating agent contains, in the molecule, a first chelating agent having two or more carboxyalkyl groups attached to a nitrogen atom. The carboxyalkyl group in the first chelating agent is composed of a linear alkylene group. Further, the two or more carboxyalkyl groups are carboxymethyl groups.

(First chelating agent)
The first chelating agent has two or more carboxymethyl groups ( _-CH2 -COOH) bonded to a nitrogen atom in the molecule. Two or more carboxymethyl groups may all be bonded to the same nitrogen atom, each may be bonded to a different nitrogen atom, two carboxymethyl groups may be bonded to the same nitrogen atom, and the other. The carboxymethyl group of the above may be bonded to another nitrogen atom.

The first chelating agent has an amino group and a carboxy group. By both, the first chelating agent is adsorbed on the metal material. Since the carboxy group has an etching ability, it contributes to the removal of scale, but at the same time, it dissolves the plating film. On the other hand, the amino group does not show an etching action and acts to protect the surface of the metal material. Although the reason is not clear, since the carboxyalkyl group bonded to the nitrogen atom does not have a branched structure, the amino group is easily adsorbed on the metal material, and the effect of suppressing the dissolution of the plating film is easily exhibited. It is thought that it will be.

Of the carboxyalkyl groups (-R-COOH) bonded to the nitrogen atom, at least two may be carboxymethyl groups, and the others are not particularly limited. However, each of the carboxyalkyl groups bonded to the nitrogen atom is composed of a linear alkylene group (R = C _n H _2n ). The carbon number n of the alkylene group constituting the above carboxyalkyl group is, for example, about 1 or more and 3 or less.

The first chelating agent has one or more nitrogen atoms in the molecule. The number of nitrogen atoms may be 2 or more. That is, the first chelating agent may be a monoaminopolycarboxylic acid or a polyaminopolycarboxylic acid. The first chelating agent may be an alkali metal salt (typically a sodium salt) of a mono or polyaminopolycarboxylic acid.

In a polyaminopolycarboxylic acid, a plurality of nitrogen atoms may be bonded to each other via an alkylene group. The alkylene group connecting the nitrogen atoms is preferably linear and has 1 or more and 3 or less carbon atoms.

From the viewpoint of suppressing the dissolution of the plating film, the number of carboxymethyl groups bonded to the nitrogen atom in the molecule is preferably 3 or more, and more preferably 4 or more.

The first chelating agent may further have a hydroxy group (—OH). However, the number of hydroxy groups present in the molecule is preferably less than the number of carboxy groups (specifically, carboxyalkyl groups). This suppresses the excessive increase in hydrophilicity of the first chelating agent. Scales are hydrophobic because they usually contain carbon. Since the hydrophilicity of the first chelating agent is not excessively high, the diffusion into the aqueous solvent is suppressed and the scale is easily contacted. As a result, the scale removal effect can be further improved.

The molecular weight of the first chelating agent is not particularly limited. The molecular weight of the first chelating agent is preferably 350 or less, more preferably 300 or less, and particularly preferably 250 or less, in that the effect can be easily obtained with a small amount.

Examples of the first chelating agent include ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriaminetetraacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylenetetraaminehexacetic acid (TTHA), and the like. 1,3-Propanide diaminetetraacetic acid (PDTA), 1,3-diamino-2-hydroxypropane tetraacetic acid (DPTA-OH), hydroxyethyliminodiacetic acid (HIDA), glycol etherdiaminetetraacetic acid (GEDTA), L-glutamic acid Diacetic acid (GLDA) can be mentioned. Some structural formulas of the first chelating agent are shown below.

The first chelating agent may be used alone or in combination of two or more. Of these, NTA, EDTA, and PDTA are preferable because the dissolution of the plating film is easily suppressed. In particular, NTA is preferable. Since NTA, EDTA and PDTA have a relatively small molecular weight, they have high adsorptivity to metal materials. Therefore, these show a higher effect of suppressing the dissolution of the plating film.

The content _CC1 of the first chelating agent is preferably 3,000 mass ppm or more and 60,000 mass ppm or less. As a result, the effect of suppressing the dissolution of the plating film and the effect of removing scale are more likely to be exhibited. The content C _C1 is more preferably 5,000 mass ppm or more, and particularly preferably 7,000 mass ppm or more. The content _CC1 is more preferably 50,000 mass ppm or less, and particularly preferably 30,000 mass ppm or less.

(Second chelating agent)
An aminocarboxylic acid type chelating agent other than the first chelating agent (hereinafter, referred to as a second chelating agent) may be contained. Also in this case, the effect of suppressing the dissolution of the plating film and the effect of removing scale can be exhibited.

From the viewpoint of suppressing the dissolution of the plating film and removing the scale, the content _CC2 of the second chelating agent is preferably 30% by mass or less, more preferably 10% by mass or less of the content _CC1 of the first chelating agent.

The content C _C2 of the second chelating agent is preferably 18,000 mass ppm or less. As a result, it is easy to obtain the effect of removing scale while suppressing the dissolution of the plating film. The content C _C2 is more preferably 15,000 mass ppm or less, and particularly preferably 9,000 mass ppm or less.

Examples of the second chelating agent include an aminocarboxylic acid type chelating agent having an alkylene group having a branched structure and an aminocarboxylic acid type chelating agent having only one carboxyalkyl group bonded to a nitrogen atom. These may be used alone or in combination of two or more.

Examples of the aminocarboxylic acid type chelating agent having a branched alkylene group include methylglycine diacetic acid (MGDA), (S, S) -ethylenediamine disuccinic acid (EDDS), aspartate diacetic acid (ASDA), and glutamic acid diacetic acid. Acetic acid (CMGA) can be mentioned. The structural formulas of MGDA, EDDS and CMGA are shown below.

Examples of the aminocarboxylic acid type chelating agent having only one carboxyalkyl group bonded to a nitrogen atom in the molecule include dihydroxyethylglycine (DHEG). The structural formula of DHEG is shown below.

(Third chelating agent)
A chelating agent other than the aminocarboxylic acid type chelating agent (hereinafter, referred to as a third chelating agent) may be contained. This can improve the scale removal effect.

However, from the viewpoint of suppressing the dissolution of the plating film, the content _CC3 of the third chelating agent is preferably 30% by mass or less, more preferably 20% by mass or less of the content _CC1 of the first chelating agent, and 15 Mass% or less is particularly preferable.

The content C _C3 of the third chelating agent is preferably 5,000 mass ppm or less, more preferably 2,000 mass ppm or less, and particularly preferably 1,500 mass ppm or less. From the viewpoint of scale removal, the content _CC3 of the third chelating agent may be 600 mass ppm or more, and may be 1,000 mass ppm or more.

Examples of the phosphonic acid-based chelating agent include hydroxyethylidene diphosphonic acid (HEDP), nitrilotrismethylenephosphonic acid (NTMP), phosphonobutanetricarboxylic acid (PBTC), and ethylenediaminetetramethylenephosphonic acid (EDTMP). The structural formulas of HEDP, NTMP, PBTC and EDTMP are shown below.

[Organic acid]
Organic acids improve the solubility of the scale and help the chelating agent peel off the scale. On the other hand, it does not excessively reduce the pH of the scale remover.

The organic acid is not particularly limited. From the viewpoint of the scale removing effect, an alkylcarboxylic acid having no aromatic ring is preferable. The hydrocarbon group in the alkylcarboxylic acid may be a chain type or an alicyclic type. The chain hydrocarbon group may be linear or branched. The hydrocarbon group may be saturated or unsaturated. The number of carbon atoms in the hydrocarbon group may be 1 or more and 20 or less, and may be 2 or more and 10 or less. The organic acid may be used alone or in combination of two or more.

Examples of the saturated aliphatic carboxylic acid include monovalent carboxylic acids such as acetic acid, propionic acid, fatty acid, valeric acid, lauric acid, palmitic acid, and stearic acid; oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid. Divalent carboxylic acids such as and the like can be mentioned. Examples of the unsaturated aliphatic carboxylic acid include monovalent carboxylic acids such as acrylic acid, methacrylic acid, oleic acid and linoleic acid; divalent carboxylic acids such as fumaric acid and maleic acid; and trivalent carboxylic acids such as aconitic acid. Carboxylic acid can be mentioned. Examples of the alicyclic carboxylic acid include cyclohexanecarboxylic acid and 1,4-cyclohexanedicarboxylic acid. Of these, an alkylcarboxylic acid having two or more carboxy groups (divalent or higher) is preferable. The number of carboxy groups may be 4 or less.

The organic acid may further have a hydroxy group. As a result, the scale removal effect is likely to be further enhanced. However, the number of hydroxy groups is preferably less than the intramolecular carboxy group. As mentioned above, the scale is hydrophobic. When the number of hydroxy groups is small, the hydrophilicity of the organic acid is not excessively increased, diffusion into an aqueous solvent is suppressed, and it becomes easy to come into contact with scale. As a result, the scale removal effect can be further improved. The number of hydroxy groups may be 1 or 2.

Examples of the alkylcarboxylic acid having a hydroxy group (alkylhydroxycarboxylic acid) include lactic acid, malic acid, and citric acid. Of these, malic acid and citric acid, which are divalent or higher alkyl hydroxycarboxylic acids, are more preferable.

The organic acid content _CA is preferably 3,000 mass ppm or more and 60,000 mass ppm or less. As a result, the scale is removed more efficiently, and the dissolution of the plating film is easily suppressed. The content _CA is more preferably 5,000 mass ppm or more, and particularly preferably 7,000 mass ppm or more. The content _CC1 is more preferably 50,000 mass ppm or less, and particularly preferably 30,000 mass ppm or less.

The mass ratio of the content _CC1 of the first chelating agent to the content _CA of the organic acid: _CC1 / _CA is preferably in the range of 10/90 to 90/10. As a result, the scale is removed more efficiently, and the dissolution of the plating film is easily suppressed. CC1 / CA is more preferably in the range of 30/70 to 70/30, and particularly preferably in the range of _45/55 to _55/45 .

Acids other than organic acids (inorganic acids) may be contained. However, from the viewpoint of suppressing the dissolution of the plating film, it is desirable that the content of the inorganic acid other than hydrofluoric acid is small. The content of the inorganic acid is preferably 200 mass ppm or less, more preferably 100 mass ppm or less, and particularly preferably not more than the detection limit. Examples of the inorganic acid other than hydrofluoric acid include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, and boric acid. These may be used alone or in combination of two or more.

[Fluorine compound]
Fluorine-containing compounds are a source of fluorine ions. Fluorine ions stabilize the metal ions contained in the scale in the scale remover. This makes it easier for the scale to dissolve from the surface of the metal material, and the scale is efficiently removed.

The fluorine-containing compound is not particularly limited as long as it liberates fluorine ions. Examples of the fluorine-containing compound include hydrofluoric acid, sodium acidic fluoride, ammonium acidic fluoride, fluorotitanic acid, fluoroziric acid, fluorosilicic acid, ammonium fluoride, sodium fluoride, potassium fluoride, and hydrogen difluoride. Fluorine is mentioned. These may be used alone or in combination of two or more.

The fluorine ion content _CF is preferably 500 mass ppm or more and 10,000 mass ppm or less as the atomic weight of fluorine. This further enhances the stability of the metal ions contained in the scale in the scale remover. The content C _F is more preferably 1,000 mass ppm or more, and particularly preferably 3,000 mass ppm or more. The content C _F is more preferably 8,000 mass ppm or less, and particularly preferably 7,000 mass ppm or less.

[Surfactant]
Surfactants further enhance scale removal performance. Examples of the surfactant include at least one of anionic surfactant and nonionic surfactant.

The anionic surfactant is not particularly limited, and known ones can be used. Examples of anionic surfactants include phosphate ester-type surfactants, carboxylic acid-type surfactants, sulfonic acid-type surfactants (including sulfosuccinic acid-based surfactants), and sulfate ester-type surfactants. Can be mentioned. These may be used alone or in combination of two or more.

Commercially available products of anionic surfactants include, for example, DOWN TRITON H66 (registered trademark) (Dow Chemical Japan Co., Ltd., potassium phosphate type surfactant), Neogen AS-20 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., sulfone). Acid-type surfactant), Sanmorin OT-70 (manufactured by Sanyo Kasei Co., Ltd., sulfosuccinic acid-based surfactant), Neugen ES-99 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Sunspear PDN-173 (manufactured by Sanyo Kasei Kogyo Co., Ltd., (Carous acid type surfactant).

The nonionic surfactant is not particularly limited, and known ones can be used. Examples of the nonionic surfactant include polyoxyalkylene glycol fatty acid esters, polyalkylene glycol fatty acid esters, and polyoxyalkylene alkyl ethers.

Commercially available nonionic surfactants include, for example, Adecanol UA series (manufactured by ADEKA), Genapol EP 2564 (manufactured by Clariant Japan), Neugen XL100 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and Genagen C 100 (manufactured by Clariant Japan). Made by).

The content _CS of the surfactant is preferably 300 mass ppm or more and 3,000 mass ppm or less. As a result, the scale removal performance is likely to be further improved. The content _CS is more preferably 400 mass ppm or more. The content _CS is more preferably 2,000 mass ppm or less.

[anti-rust]
The scale remover may contain a rust preventive. This enhances the rust resistance of the metal material after the scale is removed until the chemical conversion treatment is performed.

Examples of the rust preventive include so-called P-based, N-based, S-based, and acetylene-based rust preventives. Examples of the P-based rust preventive agent include phosphates. Examples of the N-based organic acid include alkylamines, imidazoles, and triazoles. Examples of the S-based rust preventive agent include santhiol and thiourea. Examples of acetylene-based rust preventives include 3-methyl-1-butyne-3-ol, 3-methyl-1-pentyne-3-ol, and 2,5-dimethyl-3-hexyne-2,5-diol. And 3,6-dimethyl-4-octyne-3,6-diol. Examples of commercially available rust preventives include KORANTIN PM (manufactured by BASF Japan Ltd.).

The content _CR of the rust inhibitor is preferably 50% by mass or more and 300% by mass or less. As a result, the rust resistance of the metal material is likely to be further enhanced.

[Other ingredients]
The scale remover may contain other components as long as the effect is not impaired. Examples of other components include pH adjusters, storage stabilizers, defoamers, antifreeze agents, preservatives, and fungicides.

[Metallic material]
The scale remover is used for metal materials. The scale remover is particularly used for removing weld scales of metal materials having welds. The metal material is not particularly limited, and examples thereof include an iron material, a cold-rolled steel sheet, a hot-rolled steel sheet, a galvanized steel sheet, and an aluminum alloy material.

According to the scale removing agent according to the present embodiment, scale can be efficiently removed while suppressing the dissolution of the plating film. Therefore, in the scale removing agent according to the present embodiment, a metal material having a plating film (typically a zinc-plated steel plate) or a metal material having a plating film and a metal material having no plating film are welded together. Especially suitable for descaling materials.

B. Method for Producing Metal Material A metal material from which scale has been removed can be produced by using the scale removing agent according to the present embodiment. The metal material is produced by a method comprising a step of bringing the scale removing agent according to the present embodiment into contact with the metal material.

(1) Contact step The method of contacting the scale remover with the metal material is not particularly limited. Examples of the contact method include spraying and dipping. Of these, immersion is preferable because of its high contact efficiency. The dipping method is suitable as a method for continuously processing a metal material because the scale removing effect can be obtained in a relatively short time.

In the spraying method, the spraying pressure may be 0.08 MPa or more and 2 MPa or less, and may be 0.1 MPa or more and 1.5 MPa or less.

In the dipping method, ultrasonic waves may be applied to the surface of the metal material while the metal material is immersed in a bath of a scale removing agent. The frequency of the ultrasonic wave may be 25 kHz or more and 100 kHz or less, and may be 30 kHz or more and 50 kHz or less.

In the dipping method, the scale removing agent may be stirred while the metal material is immersed in the scale removing agent bath. This causes the scale remover to flow. The flow rate of the scale remover on the surface of the metal material may be 10 cm / sec or more and 40 cm / sec or less, and may be 15 cm / sec or more and 35 cm / sec or less. The surface flow velocity can be measured using a commercially available surface flow meter (for example, JFE Advantech Co., Ltd., triaxial electromagnetic flow velocity sensor, ACM3-RS, etc.).

The temperature of the scale remover may be 40 ° C. or higher and 70 ° C. or lower. As a result, the effect of removing scale is easily exerted, and the burden on the equipment is reduced. The temperature of the scale remover is preferably 50 ° C. or higher and 70 ° C. or lower, and particularly preferably 55 ° C. or higher and 65 ° C. or lower.

The contact time between the scale remover and the metal material may be appropriately set according to the contact method. The contact time in the spraying method may be, for example, 3 minutes or more and 30 minutes or less, and may be 5 minutes or more and 20 minutes or less. The contact time in the dipping method may be, for example, 1 minute or more and 50 minutes or less, 1 minute or more and 30 minutes or less, and 1 minute or more and 15 minutes or less.

(2) Chemical conversion step After the contact step of the scale removing agent, the surface of the metal material may be subjected to chemical conversion treatment. Since the scale removing agent according to the present embodiment efficiently removes scale, a chemical conversion film is easily formed on the obtained metal material. Examples of the chemical conversion treatment method include zinc phosphate chemical conversion treatment and zirconium chemical conversion treatment.

In the zinc phosphate chemical conversion treatment, a chemical conversion treatment agent containing zinc phosphate is used. The chemical conversion treatment agent containing zinc phosphate is not particularly limited, and conventionally known chemical conversion agents can be used. Preferred chemical treatment agents include zinc ions of 0.5 g / L or more and 2 g / L or less (more preferably 0.7 g / L or more and 1.2 g / L or less), and phosphate ions of 5 g / L or more and 30 g / L or less (more preferably 0.7 g / L or more and 1.2 g / L or less). More preferably, it contains 10 g / L or more and 20 g / L or less), and contains manganese ions of 0.2 g / L or more and 2 g / L or less (more preferably 0.3 g / L or more and 1.2 g / L or less).

Prior to the zinc phosphate chemical conversion treatment, a surface conditioning treatment may be performed on the metal material. As a result, crystals of the zinc phosphate film are easily formed on the surface of the metal material, and a uniform and dense chemical conversion film is easily obtained. The surface treatment agent is, for example, a weak alkaline solution containing a disperse titanium colloid. Titanium colloid becomes the core of the crystal. Crystals are formed from titanium colloid as a starting point and grow.

In the zirconium chemical conversion treatment, a chemical conversion treatment agent containing zirconium ions (zirconium chemical conversion treatment agent) is used. The concentration of zirconium ions in the zirconium chemical conversion treatment agent is preferably 10 ppm or more and 10,000 ppm or less.

The descaled and chemical-treated metal material is particularly preferably used in the manufacture of automobile bodies and parts thereof such as passenger cars, trucks, motorcycles and buses.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are based on mass unless otherwise specified.

[Example 1]
(A) Preparation of scale agent NTA (chelating agent), Adecanol UA90N (nonionic surfactant, manufactured by ADEKA, polyoxyalkylene alkyl ethers), citric acid (organic acid), acidic ammonium fluoride (fluorine compound) and KORANTIN PM (rust preventive, manufactured by BASF Japan) was mixed with water. Then, the pH was adjusted to 6 with an aqueous NaOH solution (40%) to obtain a scale remover. The chelating agent content was 10,000 ppm, the surfactant content was 300 ppm, the organic acid content was 10,000 ppm, the fluorine compound content was 5,000 ppm, and the rust inhibitor content was 300 ppm. ..

(B) Preparation of metal material Two galvanized steel sheets were prepared and welded together. Scale was generated near the weld bead. The welded product produced by this scale was used as a test piece.

(C) Contact with scale remover The scale remover obtained above was placed in a 10 L treatment bath to adjust the temperature to 60 ° C. The test piece was immersed in the treatment bath for 10 minutes. Then, the test piece was taken out and washed thoroughly. After washing, it was dried at 40 ° C. for about 10 minutes.

(D) After degreasing treatment, surface adjustment and chemical conversion treatment (c), the test piece was degreased using a surf cleaner EC90 (manufactured by Nippon Paint Surf Chemicals Co., Ltd.) having a pH adjusted to 11. The treatment temperature was 45 ° C. and the treatment time was 120 seconds. After the degreasing treatment, the test piece was washed with water.
Subsequently, the surface of the test piece was adjusted using Surf Fine 7 (manufactured by Nippon Paint Surf Chemicals Co., Ltd.) whose pH was adjusted to 10. The treatment temperature was room temperature and the treatment time was 30 seconds.
Finally, a test piece was subjected to zinc phosphate chemical conversion treatment using Surfdyne SD5300 (zinc phosphate chemical conversion treatment agent, manufactured by Nippon Paint Surf Chemicals Co., Ltd.). The treatment temperature was 35 ° C. and the treatment time was 120 seconds.

[evaluation]
The test pieces after the treatment (c) or the treatment (d) were evaluated as follows. The evaluation results are shown in Table 1.

(I) Plating retention The plating thickness (Mi) before the treatment (c) and the plating thickness (Mt) after the treatment (c) and before the treatment (d) are measured by a film thickness meter (Fisher Instruments). , DELTASCOPE MP30ES). From this measured value, the plating residual rate was calculated according to the following formula.
Plating residual rate (%) = 100 x plating thickness after treatment (Mt) / plating thickness before treatment (Mi)

The plating residual rate was evaluated according to the following criteria.
Best: Plating residual rate is 90% or more Good: Plating residual rate is 70% or more and less than 90% Possible: Plating residual rate is 50% or more and less than 70% Defective: Plating residual rate is less than 50%

(Ii) Scale removability The scale width (bi) before the treatment (c) and the scale width (bt) after the treatment (c) and before the treatment (d) were measured using a caliper. From this measured value, the scale residual rate was calculated according to the following formula. The scale width is the width of the widest part of the scale generated around the weld bead portion.
Scale residual rate (%) = 100 × scale width after processing (bt) / scale width before processing (bi)

The scale survival rate was evaluated according to the following criteria.
Best: Scale residual rate is less than 30% Good: Scale residual rate is 30% or more and less than 40% Possible: Scale residual rate is 40% or more and less than 50% Defective: Scale residual rate is 50% or more

FIG. 1A is an image (magnification 5 times) of the periphery of the weld bead portion of the test piece prepared in Example 1 taken through a magnifying glass. The dark black part is the scale. FIG. 1B is an image (magnification 5 times) of the portion corresponding to FIG. 1A after being treated with the scale remover, taken through a magnifying glass. As can be seen from FIG. 1B, most of the scale has been removed.

(Iii) The periphery of the weld bead portion after the chemical conversion treatment (d) was observed using an SEM (JSM6510A manufactured by JEOL Ltd.) (magnification 1,500 times). The area ratio (chemical formation rate) of the portion where the chemical conversion film was formed was calculated with the area around the weld bead in the observation field as 100%.

The chemical conversion rate was evaluated according to the following criteria.
Best: Chemical rate is 90% or more Good: Chemical rate is 70% or more and less than 90% Possible: Chemical rate is 50% or more and less than 70% Bad: Chemical rate is less than 50%

FIG. 2 is an SEM image (magnification of 1,500 times) around the weld bead portion after the treatment (d) of the test piece prepared in Example 1. As can be seen from FIG. 2, a chemical conversion film is formed around the entire weld bead portion.

[Example 2-3, Comparative Example 1-4]
A scale remover was prepared in the same manner as in Example 1 except that the chelating agent was changed as shown in Table 1, and the treatment (c) and the treatment (d) were performed and evaluated. The evaluation results are shown in Table 1.

[Example 4-8]
A scale remover was prepared in the same manner as in Example 1 except that the organic acid was changed as shown in Table 2, and the treatment (c) and the treatment (d) were performed and evaluated. The evaluation results are shown in Table 2.

[Example 9-13]
A scale remover was prepared in the same manner as in Example 1 except that the first chelating agent and the third chelating agent (HEDP) were blended as shown in Table 3, and the treatment (c) and treatment were performed. (D) was performed and evaluation was performed. The evaluation results are shown in Table 3.

Since the scale remover according to the present embodiment can remove scale while maintaining the plating film, it is preferably applied to a metal material having a plating film.

Claims (14)

Containing a chelating agent, an organic acid, a fluorine compound, and a surfactant,
The chelating agent contains an aminocarboxylic acid type chelating agent.
The aminocarboxylic acid type chelating agent has two or more carboxyalkyl groups bonded to a nitrogen atom in the molecule.
The carboxyalkyl group is composed of a linear alkylene group.
A scale remover in which two or more of the carboxyalkyl groups are carboxymethyl groups. The scale removing agent according to claim 1, wherein the aminocarboxylic acid type chelating agent has three or more carboxymethyl groups bonded to a nitrogen atom in the molecule. The scale remover according to claim 1 or 2, wherein the aminocarboxylic acid type chelating agent contains nitrilotriacetic acid. The mass ratio of the content _CC1 of the aminocarboxylic acid type chelating agent to the content _CA of the organic acid: _CC1 / _CA is 10/90 to 90/10, claim 1 to 3. The scale remover according to any one item. The scale removing agent according to any one of claims 1 to 4, wherein the content _CC1 of the aminocarboxylic acid type chelating agent is 3,000 mass ppm or more and 60,000 mass ppm or less. The scale remover according to any one of claims 1 to 5, wherein the content _CA of the organic acid is 3,000 mass ppm or more and 60,000 mass ppm or less. The scale remover according to any one of claims 1 to 6, wherein the organic acid contains an alkylcarboxylic acid. The scale remover according to claim 7, wherein the alkylcarboxylic acid has two or more carboxy groups. The scale remover according to any one of claims 1 to 8, which is used for a metal material having a plating film. Equipped with a process to bring the scale remover into contact with the metal material,
The scale remover contains a chelating agent, an organic acid, a fluorine compound, and a surfactant.
The chelating agent contains an aminocarboxylic acid type chelating agent.
The aminocarboxylic acid type chelating agent has two or more carboxyalkyl groups bonded to a nitrogen atom in the molecule.
The carboxyalkyl group is composed of a linear alkylene group.
A method for producing a metal material, wherein two or more of the carboxyalkyl groups are carboxymethyl groups. The method for producing a metal material according to claim 10, wherein in the contacting step, the metal material is immersed in the scale removing agent. The method for producing a metal material according to claim 11, wherein the metal material is immersed in the scale remover having a temperature of 40 ° C. or higher and 70 ° C. or lower within 1 minute or more and 50 minutes or less. The method for producing a metal material according to any one of claims 10 to 12, wherein the metal material includes a metal material having a plating film. The method for producing a metal material according to claim 13, wherein the metal material having the plating film includes a galvanized steel sheet.

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