US20200165741A1

US20200165741A1 - Chemical conversion treatment agent, coating pre-treatment method, and metal member

Info

Publication number: US20200165741A1
Application number: US16/629,484
Authority: US
Inventors: Masato Kishi; Takayuki Ueno
Original assignee: Nippon Paint Surf Chemicals Co Ltd
Current assignee: Nippon Paint Surf Chemicals Co Ltd
Priority date: 2017-07-13
Filing date: 2018-07-12
Publication date: 2020-05-28
Also published as: JP2019019356A; WO2019013282A1; CN110869534A

Abstract

Provided is a chemical conversion treatment agent that has a small impact on the environment and can ensure good post-coating corrosion resistance regardless of the target of treatment. A chemical conversion treatment agent including: at least one type (A) of element selected from the group consisting of zirconium, titanium, and hafnium; at least one type (B) of substance selected from the group consisting of amino group-including silane coupling agents, hydrolysates thereof, and polymers thereof; fluorine (C); and a cationic urethane resin (D). Preferably, the content of (A) is 20-10000 mass ppm in total in terms of metals, and the pH is 1.5-6.5.

Description

TECHNICAL FIELD

The present invention relates to a chemical conversion treatment agent, a pre-coating treatment method, and a metal member.

BACKGROUND ART

Chemical conversion treatment is usually performed for the purpose of improving properties such as corrosion resistance and coating adhesiveness when a surface of a metal material is subjected to cation electrodeposition coating, powder coating, or the like. Chromate treatment is commonly used for chemical conversion in view of its capability of further improving adhesion and corrosion resistance of a coated film. In recent years, the hazardous properties of chromium, however, have been noted, and thus there have been demands for developing a chemical conversion treatment agent which does not contain chromium. As such chemical conversion, widely performed is zinc phosphate treatment.
However, zinc phosphate-based treatment agents contain high concentrations of metal ions and acids, and are highly reactive. This may result in poor waste-treatment economy and poor workability. Further, when a metal surface is treated with a zinc phosphate-based treatment agent, water-insoluble salts may be generated and deposited as precipitates. These precipitates are generally referred to sludge. The removal and disposal of such sludge may add undesirable costs and other problems. Further, phosphate ions may be responsible for increased environmental burden due to eutrophication, and may require additional efforts for waste treatment. Therefore, use of phosphate ions is preferably avoided. Moreover, the treatment of a metal surface with a zinc phosphate-based treatment agent requires surface conditioning. This, disadvantageously, may result in a prolonged process.
As metal-surface treatment agent other than such a zinc phosphate-based treatment agent or a chromate chemical conversion treatment agent, known is a metal-surface treatment agent including a zirconium compound. Such a metal-surface treatment agent including a zirconium compound has a superior property as compared with a zinc phosphate-based chemical conversion treatment agent as described above in that the generation of sludge can be prevented.
Unfortunately, a chemical conversion film obtained by a metal-surface treatment agent including a zirconium compound shows poor adhesiveness, in particular with a coated film obtained by cation electrodeposition coating, and is less often used as a pre-treatment step of cation electrodeposition coating. In such a metal-surface treatment agent including a zirconium compound, a component such as phosphate ions may be used in combination for improving adhesiveness and corrosion resistance. However, when phosphate ions are used in combination, the aforementioned problems such as eutrophication may occur. Moreover, an iron-based base material treated with such a metal-surface treatment agent may have a problem in that neither sufficient coating adhesiveness nor post-coating corrosion resistance can be obtained.
A non-chromate metal-surface treatment agent is also known which includes a zirconium compound and an amino group-containing silane coupling agent. However, surface treatment with such a non-chromate metal-surface treatment agent as an application-type treatment agent used in the field of so-called coil coating is not comparable with post-treatment water-washing. Further, such a non-chromate metal-surface treatment agent is not intended for a target workpiece having a complicated shape.
Furthermore, for an article, such as an automobile body and parts, composed of a metal material such as iron, zinc, and aluminum, the entire metal surface may need to be treated in a single treatment. Accordingly, a pre-coating treatment method is desired to be developed, by which chemical conversion can be performed without causing any problem even in such a case. Meanwhile, a pre-coating treatment method is also desired to be developed, by which chemical conversion can be performed without causing the aforementioned problems even in coating other than cation electrodeposition coating using a powder coating material, a solvent coating material, a water-based paint, and the like.
In an attempt to solve the above problems, a pre-coating treatment method is known, the method involving treating a target workpiece with a chemical conversion treatment agent including at least one selected from the group consisting of zirconium, titanium, and hafnium; fluorine; and at least one selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, polymers thereof to form a chemical conversion film (for example, see Patent Document 1 below).
The above pre-coating treatment method is compatible with any common coating methods, and can provide similar adhesiveness and post-coating corrosion resistance as a case where a zinc phosphate-based chemical conversion treatment agent is used. However, post-coating corrosion resistance obtained was less than satisfactory, depending on a treatment target and applications thereof.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2004-218070

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

The present invention is made in view of the above circumstances. An object of the present invention is to provide a chemical conversion treatment agent which may cause less environmental burden, and can ensure good post-coating corrosion resistance regardless of treatment targets.

Means for Solving the Problems

The present invention relates to a chemical conversion treatment agent including at least one (A) selected from the group consisting of zirconium, titanium, and hafnium; at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof; fluorine (C); and a cationic urethane resin (D).
Further, it is preferred that the total content of (A) is 20 to 10000 ppm by mass in terms of metal, and pH is 1.5 to 6.5.
Moreover, it is preferred that the total content of (B) is 5 to 5000 ppm by mass in the solid content concentration, and the content of (D) is 5 to 5000 ppm by mass in the solid content concentration, and, the solid content mass ratio ((B)/(D)) of (B) to (D) is 0.0002 to 5000.
Moreover, it is preferred to further contain at least one adhesiveness and corrosion resistance-conferring agent selected from the group consisting of magnesium ions, zinc ions, calcium ions, aluminum ions, gallium ions, indium ions, and copper ions.
The present invention also relates to a pre-coating treatment method including treating a target workpiece with the above chemical conversion treatment agent.
Further, the present invention relates to a metal member treated by the above pre-coating treatment method.

Effects of the Invention

The present invention can provide a chemical conversion treatment agent which may cause less environmental burden, and can ensure good post-coating corrosion resistance regardless of treatment targets.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

Below, the embodiments of the present invention will be described. It is noted that the present invention shall not be limited to the following embodiments.
<Chemical Conversion Treatment Agent>
A chemical conversion treatment agent according to the present embodiment can form a chemical conversion film on a metal surface as a target workpiece, and confer preferred post-coating corrosion resistance on the metal surface. There is no particular limitation for a metal as a target workpiece, but any metals such as iron, zinc, and aluminum may be used. Further, the chemical conversion treatment agent according to the present embodiment is preferably used in particular for iron-based highly high tension steel sheets and hot-rolled steel sheets. Such an iron-based highly high tension steel sheets and hot-rolled steel sheets are widely used in suspension related parts of automobiles and the like. However, a uniform chemical conversion film may be difficult to be formed on a surface thereof due to an oxide film which may be formed on the surface. The chemical conversion treatment agent according to the present embodiment, which is substantially free of phosphate ions and hazardous heavy metal ions, can form a uniform chemical conversion film even on the surfaces of a highly high tension steel sheet and a hot-rolled steel sheet. This can ensure good post-coating corrosion resistance of a target workpiece.
The chemical conversion treatment agent according to the present embodiment includes at least one (A) selected from the group consisting of zirconium, titanium, and hafnium; at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof; and fluorine (C); and a cationic urethane resin (D).
The at least one (A) selected from the group consisting of zirconium, titanium, and hafnium corresponds to a component for forming a chemical conversion film. Formation of a chemical conversion film including at least one selected from the group consisting of zirconium, titanium, and hafnium on a base material can improve corrosion resistance and abrasion resistance of the base material, and further can enhance adhesiveness with a coated film.
For example, when a metal base material is surface treated with a chemical conversion treatment agent containing zirconium, metal ions which are eluted into the chemical conversion treatment agent due to a dissolution reaction of metal may extract fluorine from ZrF62-, or an interface pH may be increased. These may result in generation of hydroxides or oxides of zirconium. These hydroxides or oxides of zirconium are thought to be deposited on a surface of a base material. As described above, the chemical conversion treatment agent according to the present embodiment, which is a reactive chemical conversion treatment agent, can be used even for dipping treatment of a target workpiece having a complicated shape. Moreover, surface treatment performed with the above chemical conversion treatment agent can produce a chemical conversion film adhering firmly on a target workpiece by virtue of a chemical reaction. This also can allow post-treatment water-washing to be performed.
There is no particular limitation for a source of the above zirconium, but examples of the source include, for example, alkali metal fluorozirconate such as K2ZrF6; fluorozirconate such as (NH4)2ZrF6; soluble fluorozirconate such as fluorozirconate acid such as H2ZrF6; zirconium fluoride; zirconium oxide; and the like.
There is no particular limitation for a source of the above titanium, but examples of the source include, for example, fluorotitanate such as alkali metal fluorotitanate, (NH4)2TiF6; soluble fluorotitanate such as fluorotitanate acid such as H2TiF6; titanium fluoride; titanium oxide; and the like.
There is no particular limitation for a source of the above hafnium, but examples of the source include, for example, fluorohafnate acid such as H2HfF6; hafnium fluoride; and the like. A source of the at least one selected from the group consisting of zirconium, titanium, and hafnium is preferably a compound having at least one selected from the group consisting of ZrF62-, TiF62-, and HfF62- in view of high film-forming capability.
The total content of the at least one selected from the group consisting of zirconium, titanium, and hafnium included in the chemical conversion treatment agent according to the present embodiment is preferably within a range between a lower limit of 20 ppm by mass and an upper limit of 10000 ppm by mass in terms of metal. When the amount is less than 20 ppm by mass, the resulting chemical conversion film may have insufficient performance. On the other hand an amount of more than 10000 ppm by mass can not provide additional effects, and is thus economically disadvantageous. The above lower limit is more preferably 50 ppm by mass, and even more preferably 100 ppm by mass. The above upper limit is more preferably 2000 ppm by mass, and even more preferably 500 ppm by mass.
The at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof is a compound having at least one amino group in a molecule thereof and also having a siloxane bond. The above at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof can interact with both a chemical conversion film and a coated film. This can improve adhesiveness between them.
This effect can be obtained presumably because a group which can undergo hydrolysis to produce silanol is hydrolyzed and adsorbed on a surface of a metal base material via hydrogen bond, and an amino group can act to enhance adhesiveness between a chemical conversion film and a metal base material. As described above, the at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof is thought to act on both a metal base material and a coated film to show an effect of improving mutual adhesiveness.
There is no particular limitation for the above amino group-containing silane coupling agent, but examples thereof can include, for example, publicly known silane coupling agents such as N-2(aminoethyl)3-aminopropylmethyldimethoxysilane, N-2(aminoethyl)3-aminopropyltrimethoxysilane, N-2(aminoethyl)3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N,N-bis[(3-(trimethoxysilyl)propyl)]ethylenediamine, and the like. Commercially available amino group-containing silane coupling agents KBM-602, KBM-603, KBE-603, KBM-903, KBE-9103, KBM-573 (Shin-Etsu Chemical Co., Ltd.), XS1003 (Chisso Corp.), and the like may also be used.
Hydrolysates of the above amino group-containing silane coupling agent can be prepared by conventionally known methods, for example, by a method including dissolving the above amino group-containing silane coupling agent in ion-exchanged water, and adjusting it to be acidic with any acid, and the like. As a hydrolysate of the above amino group-containing silane coupling agent, a commercially available product such as KBP-90 (Shin-Etsu Chemical Co., Ltd., Active ingredient: 32%) may also be used.
There is no particular limitation for a polymer of the above amino group-containing silane coupling agent, but examples thereof can include, for example, commercially available products such as Sila-Ace S-330 (γ-aminopropyltriethoxysilane; Chisso Corp.), Sila-Ace S-320 (N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; Chisso Corp.).
The total blending amount of the at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof in the chemical conversion treatment agent according to the present embodiment is preferably within a range between a lower limit of 5 ppm by mass and an upper limit of 5000 ppm by mass in terms of the solid content concentration. An amount of less than 5 ppm by mass can not provide sufficient coating adhesiveness. An amount of more than 5000 ppm by mass can not provide additional effects, and is thus economically disadvantageous. The above lower limit is more preferably 10 ppm by mass, and even more preferably 50 ppm by mass. The above upper limit is more preferably 1000 ppm by mass, and even more preferably 500 ppm by mass.
Fluorine (C) can serve as an etching agent for a base material. There is no particular limitation for a source of fluorine (C), but examples of the source can include, for example, fluorides such as hydrofluoric acid, ammonium fluoride, fluoroboric acid, ammonium hydrogen fluoride, sodium fluoride, and sodium hydrogenfluoride. Further, complex fluorides include, for example, hexafluorosilicate, and specific examples thereof can include hydrosilicofluoric acid, zinc hydrofluorosilicate, manganese hydrofluorosilicate, magnesium hydrofluorosilicate, nickel hydrofluorosilicate, iron hydrofluorosilicate, calcium hydrofluorosilicate, and the like.
The cationic urethane resin (D) will form a uniform chemical conversion film on a metal surface as a target workpiece. The cationic urethane resin (D) has a cationic functional group. Cationic functional groups include, for example, an amino group, an ammonium group, a methylamino group, an ethylamino group, a dimethylamino group, a diethylamino group, a trimethylamino group, a triethylamino group, and the like. Among these, prepared is a quaternary ammonium group. Moreover, there is no particular limitation for a polyol, isocyanate components of a urethane resin of the cationic urethane resin (D), and a method of polymerization, but conventionally known components and methods may be used. As the cationic urethane resin (D), the followings may be used: for example, commercially available products such as F2667D (DKS Co. Ltd., Effective concentration: 25%), Superflex 620 (DKS Co. Ltd., Effective concentration: 30%), and Superflex 650 (DKS Co. Ltd., Effective concentration: 26%).
Inclusion of the cationic urethane resin (D) alone in a chemical conversion treatment agent can not provide preferred effects such as post-coating corrosion resistance. However, when it is included in a chemical conversion treatment agent in combination with the at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof, a uniform chemical conversion film can be formed on a surface of a metal surface as a target workpiece, ensuring a preferred post-coating anticorrosion properties of that metal member as a target workpiece. Further, the cationic urethane resin (D) does not undergo a competing reaction with the at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof, and thus may be preferably used without inhibiting the functionality of the amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof (B).
The blending amount of the cationic urethane resin (D) in the chemical conversion treatment agent according to the present embodiment is preferably within a range between a lower limit of 5 ppm by mass and an upper limit of 5000 ppm by mass in terms of the solid content concentration. An amount of less than 5 ppm by mass can not provide sufficient coating adhesiveness. An amount of more than 5000 ppm by mass can not provide additional effects, and is thus economically disadvantageous. The above lower limit is more preferably 10 ppm by mass, and even more preferably 50 ppm by mass. The above upper limit is more preferably 1000 ppm by mass, and even more preferably 500 ppm by mass.
In the chemical conversion treatment agent according to the present embodiment, the mass ratio ((B)/(D)) of the at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof to the cationic urethane resin (D) is preferably 0.0002 to 5000. A mass ratio ((B)/(D)) falling within the above range can achieve preferred post-coating corrosion resistance of a target workpiece on which a chemical conversion film is formed. The mass ratio ((B)/(D)) is more preferably 0.01 to 100, and even more preferably 0.5 to 2.
Preferably, the chemical conversion treatment agent according to the present embodiment is substantially free of phosphate ions. The phrase “substantially free of phosphate ions” means that phosphate ions may be included in an amount such that they do not function as a component of a chemical conversion treatment agent. The chemical conversion treatment agent used in the present embodiment is substantially free of phosphate ions. Therefore, essentially no phosphorus is used which is potentially responsible for increased environmental burden. Further, generation of sludge such as iron phosphate and zinc phosphate can be prevented, which otherwise may be generated when a zinc phosphate-based treatment agent is used.
The chemical conversion treatment agent according to the present embodiment preferably has a pH falling within a range between a lower limit of 1.5 and an upper limit of 6.5. A pH of lower than 1.5 may result in excessive etching, and a sufficient film can not be formed. A pH of more than 6.5 may result in insufficient etching, and can not provide a good film. The above lower limit is more preferably 2.0, and the above upper limit is more preferably 5.5. The above lower limit is even more preferably 2.5, and the above upper limit is even more preferably 5.0. In order to adjust a pH of the chemical conversion treatment agent according to the present embodiment, an acidic compound such as nitric acid and sulfuric acid and a basic compound such as sodium hydroxide, potassium hydroxide, and ammonia may be used.
Preferably, the chemical conversion treatment agent according to the present embodiment further includes at least one selected from the group consisting of magnesium ions, zinc ions, calcium ions, aluminum ions, gallium ions, indium ions, and copper ions as an adhesiveness and corrosion resistance-conferring agent. Inclusion of the above adhesiveness and corrosion resistance-conferring agent can provide a chemical conversion film having better adhesiveness and corrosion resistance.
The content of the above at least one selected from the group consisting of magnesium ions, zinc ions, calcium ions, aluminum ions, gallium ions, indium ions, and copper ions is preferably within a range between a lower limit of 1 ppm by mass and an upper limit of 5000 ppm by mass. When the above content is less than the above lower limit, sufficient effects can not be obtained. This is not preferred. When the above content is more than the above upper limit, additional effects can not be obtained. This is economically disadvantageous, and may also decrease post-coating adhesiveness. The above lower limit is more preferably 25 ppm by mass, and the above upper limit is more preferably 3000 ppm by mass.
The above chemical conversion treatment agent may be used in combination with any component in addition to the above components, if needed. Components which can be used can include silica and the like. It is possible to increase post-coating corrosion resistance by adding such a component.
<Pre-Coating Treatment Method>
There is no particular limitation for chemical conversion in the pre-coating treatment method according to the present embodiment, but it may be performed by contacting a chemical conversion treatment agent with a metal surface under common treatment conditions. The treatment temperature upon the above chemical conversion is preferably within a range between a lower limit of 20° C. and an upper limit of 70° C. The above lower limit is more preferably 30° C., and the above upper limit is more preferably 50° C. The chemical conversion time for the above chemical conversion is preferably within a range between a lower limit of 5 seconds and an upper limit of 1200 seconds. The above lower limit is more preferably 30 seconds, and the above upper limit is more preferably 120 seconds. There is no particular limitation for a method of conversion treatment, but examples thereof can include, for example, the dipping method, the spray method, the roll coating method, and the like.
In the pre-coating treatment method according to the present embodiment, it is preferred that a metal surface may be subjected to degreasing treatment, post-degreasing water-washing treatment before performing the above chemical conversion, and subjected to post-chemical conversion waster-washing treatment after the above chemical conversion. The above degreasing treatment may be performed in order to remove oils and stains adhering on a surface of a base material, and usually performed by dipping treatment at 30 to 55° C. for about several minutes with a degreaser such as phosphorus-free/nitrogen-free degreasing wash liquid. Preliminary degreasing treatment may be performed, if needed, prior to degreasing treatment.
The above post-degreasing water-washing treatment may be conducted by performing spray treatment using a large amount of wash water once or more times in order to wash out a degreaser with water after degreasing treatment. The above post-chemical conversion water-washing treatment may be performed once or more times in order to avoid negative effects on adhesiveness, corrosion resistance, and the like after various subsequent coatings. In that case, the final water-washing is properly performed with pure water. In this post-chemical conversion water-washing treatment, water washing may be performed by either one of spray water-washing or dip water-washing or in combination of these. After the above post-chemical conversion water-washing treatment, drying may be performed in accordance with a known method, if needed, and then various coatings may be applied.
The pre-coating treatment method according to the present embodiment does not require surface conditioning treatment which is required in a conventionally used practical method involving treatment with a zinc phosphate-based chemical conversion treatment agent. This enables chemical conversion of a metal base material to be performed in fewer steps.
There is no particular limitation for a metal base material used in the present embodiment, but examples thereof can include iron-based base materials, aluminum-based base materials, and zinc-based base materials. Iron-, aluminum-, and zinc-based base materials mean an iron-based base material in which the base material includes iron and/or an alloy thereof, an aluminum-based base material in which the base material includes aluminum and/or an alloy thereof, and a zinc-based base material in which the base material includes zinc and/or an alloy thereof, respectively.
Further, the pre-coating treatment method according to the present embodiment is preferably used in particular for an iron-based highly high tension steel sheet and hot-rolled steel sheet. An oxide film having fine surface unevenness may be formed on a hot-rolled steel sheet, and the oxide film is also of a porous state in which a large number of pores are present. For this reason, the surface is very difficult to be covered with a uniform chemical conversion film. An ununiform chemical conversion film formed on a surface may cause different potentials between a coated portion and an uncoated portion, preventing formation of a uniform electrodeposition coated film upon electrodeposition coating. Consequently, a pre-coating treatment method using a conventional chemical conversion treatment agent including zirconium and others can not ensure post-coating corrosion resistance comparable to that in a case where a zinc phosphate-based chemical conversion treatment agent. Similarly, an oxide film having fine surface unevenness may also be formed on a highly high tension steel sheet, and a large amount of dissimilar metals may also be included in the highly high tension steel sheet. These may cause the above different potentials to be more significant, resulting in even less uniform covering with a chemical conversion film. Therefore, ensuring post-coating corrosion resistance may be more difficult. However, the pre-coating treatment method according to the present embodiment can form a uniform chemical conversion film even on an iron-based highly high tension steel sheet and hot-rolled steel sheet, and can ensure post-coating corrosion resistance comparable to that in a case where a phosphate ion-containing chemical conversion treatment agent is used. The mechanism by which such an effect can be obtained is not clearly understood. Nonetheless, one possibility is that the cationic urethane resin (D) may preferentially cover depressed portions and pores of an oxide film through the interaction between the cationic groups of the cationic urethane resin (D) included in a chemical conversion treatment agent and a surface of a steel sheet.
The film content of a chemical conversion film obtained by the pre-coating treatment method according to the present embodiment is preferably within a range between a lower limit of 0.1 mg/m2 and an upper limit of 500 mg/m2 in terms of the total amount of metal included in a chemical conversion treatment agent. An amount of less than 0.1 mg/m2 can not provide a uniform chemical conversion film, and is thus not preferred. An amount of more than 500 mg/m2 can not provide additional effects, and is thus economically disadvantageous. The above lower limit is more preferably 5 mg/m2, and the above upper limit is more preferably 200 mg/m2.
<Metal Member>
A metal base material treated by the above pre-coating treatment method may be subjected to laser processing, press working, and the like to obtain a metal member formed and processed depending on various purposes. Alternatively, a pre-formed and processed metal member may be subjected to the above pre-coating treatment method. There is no particular limitation for the applications of a metal member according to the present embodiment, but examples of thereof include metal members of automobiles such as a door, a bonnet, a roof, a hood, a fender, a trunk room, and the like. Further, they also include metal members used for motorcycles, buses, bicycles, and the like. A metal member treated by the pre-coating treatment method according to the present embodiment may preferably be used in those applications as described above in which a high level of post-coating corrosion resistance is required in view of safely and aesthetics.
There is no particular limitation for coating which can be performed on a metal member treated by the above pre-coating treatment method, but coating may be performed with a conventionally known coating material such as a cationic electrodeposition coating material, a solvent coating material, a water-based coating material, and a powder coating material. For example, there is no particular limitation for the above cationic electrodeposition coating material, but a conventionally known cationic electrodeposition coating material including an aminated epoxy resin, aminated acrylic resin, a sulfonated epoxy resin, and the like may be applied. Amount these, a cationic electrodeposition coating material including a resin having a functional group which shows reactivity or compatibility with an amino group is preferred in order to enhance adhesiveness between an electrodeposition coated film and a chemical conversion film, considering that at least one selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof is blended in a chemical conversion treatment agent.
The present invention shall not be limited to the above embodiments. Modifications, improvements, and the like can be made within a scope of the present invention as long as an effect of the present invention can be achieved.

EXAMPLES

Next, the present invention will be described in more detail with reference to Examples, but the present invention shall not be limited to these Examples. It is noted that the term “ppm” as used in Examples and Comparative Examples refers to “ppm by mass.”

Example 1

A commercially available cold-rolled steel plate (SPC 270, Nippon Testpanel Co., Ltd., 70 mm×150 mm×0.8 mm) as a base material was subjected to pre-coating treatment under the following conditions.

(1) Pre-Coating Treatment

Degreasing treatment: Dipping treatment was performed at 40° C. with 2% by mass of “Surfcleaner 53” (a degreaser from Nippon Paint Surf Chemicals Co., Ltd.). Post-degreasing water-washing treatment: Spray treatment was performed with tap water for 30 seconds. Chemical conversion treatment: Zircon hydrofluoric acid and KBM-603 (N-2(aminoethyl)3-aminopropyltrimethoxysilane, Effective concentration: 100%, Shin-Etsu Chemical Co., Ltd.) as an amino group-containing silane coupling agent; and F2667D (DKS Co. Ltd., Effective concentration: 25%) as a cationic urethane resin were used to prepare a chemical conversion treatment agent including zirconium (A) in a concentration of 100 ppm by mass, an amino group-containing silane coupling agent (B) in a concentration of 100 ppm by mass in terms of the solid content, and a cationic urethane resin (D) in a concentration of 100 ppm by mass. Sodium hydroxide was used to adjusted pH to 4. The temperature of the chemical conversion treatment agent was adjusted to 40° C., and a base material was dip-treated for 60 seconds. The film amount in the initial stage of the treatment was 13.4 mg/m2.
Post-chemical conversion water-washing treatment: Spray treatment was performed with tap water for 30 seconds. Further, spray treatment was performed with ion-exchanged water for 10 seconds. Then, electrodeposition coating was performed in a wet condition. A cold-rolled steel sheet after water washing was dried at 80° C. for 5 minutes in an electric drying furnace, and then the film amount was analyzed as the total amount of metal contained in a chemical conversion treatment agent with a “ZSX PrimusII” (an X-ray analyzer from Rigaku Corporation).

(2) Coating

A cold-rolled steel plate was treated with a chemical conversion treatment agent at 1 L per m2, and then electrodeposition-coated with “Powernics 310” (a cationic electrodeposition coating material from Nipponpaint Industrial Coatings Co., Ltd.) so as to obtain a dry coating thickness of 20 μm, and washed with water, and then heated for baking at 170° C. for 20 minutes to obtain a test plate.

Examples 2 to 7

Test plates were prepared as in Example 1 except that the metal base material was changed to a cold-rolled steel plate (SPC 780 from Nippon Testpanel Co., Ltd., 70 mm×150 mm×0.8 mm), hot-rolled steel plates (SPH 270, SPH 440, SPH 590 from Nippon Testpanel Co., Ltd., 70 mm×150 mm×0.8 mm), a zinc-based plated steel sheet (GA 270 from Nippon Testpanel Co., Ltd., 70 mm×150 mm×0.8 mm), or a 6000-series aluminum plate (Nippon Testpanel Co., Ltd., 70 mm×150 mm×0.8 mm). It is noted that the types of base materials shown in Tables 1 and 2 are as follows: SPC represents the above cold-rolled steel plate; and SPH represents the above hot-rolled steel plates; and GA represents the above zinc-based plated steel sheet; and AL represents the above 6000-series aluminum plate.

Examples 8 to 13

Test plates were prepared as in Example 1 except that the above cold rolled steel plate or hot-rolled steel plates were used as a metal base material, and the concentrations of the silane coupling agent (B) and the cationic urethane resin (D) were 1 ppm by mass, 5 ppm by masses, and 50 ppm by masses, respectively as shown in Table 1.

Examples 14 and 15

Test plates were prepared as in Example 1 except that the above hot-rolled steel plates were used as a metal base material, and Superflex 620 (DKS Co. Ltd., Effective concentration: 30%) or Superflex 650 (DKS Co. Ltd., Effective concentration: 26%) was used as the cationic urethane resin (D) as shown in Table 1.

Examples 16 to 21

Test plates were prepared as in Example 1 except that the above cold rolled steel plate or hot-rolled steel plates were used as a metal base material, and KBM-603 (N-2(aminoethyl)3-aminopropyltrimethoxysilane, effective concentration 100%, Shin-Etsu Chemical Co., Ltd.) or KBM-903 (3-aminopropyltrimethoxysilane, effective concentration: 100%, Shin-Etsu Chemical Co., Ltd.) was used as the silane coupling agent (B) as shown in Table 1, and the concentrations of the silane coupling agent (B) and the cationic urethane resin (D) were as shown in Table 1.

Examples 22 to 25

Test plates were prepared as in Example 1 except that the concentration of zirconium (A) was 500 ppm by masses, and the above cold-rolled steel plate or hot-rolled steel plates were used as a metal base material, and KBE-903 (3-aminopropyltriethoxysilane, effective concentration: 100%, Shin-Etsu Chemical Co., Ltd. or XS1003 (N,N-bis[(3-(trimethoxysilyl)propyl)]ethylenediamine, effective concentration: 50%, Nichibitrading Co., Ltd., Inc.) was used as the silane coupling agent (B) as shown in Table 1, and the concentrations of the silane coupling agent (B) and the cationic urethane resin (D) were as shown in Table 1.

Examples 26 to 37

Test plates were prepared as in Example 1 except that the above cold rolled steel plate or hot-rolled steel plates were used as a metal base material, and zinc nitrate (Zn) was used as an adhesiveness and corrosion-resistance conferring material shown in Tables 1 and 2, and the concentrations of zirconium (A), the silane coupling agent (B), and the cationic urethane resin (D) were as shown in Tables 1 and 2.

Examples 38 to 41

Test plates were prepared as in Example 1 except that the above cold rolled steel plate or hot-rolled steel plates were used as a metal base material as shown in Table 2, and the concentrations of the silane coupling agent (B) and the cationic urethane resin (D) were as shown in Table 2.

Comparative Examples 1 to 8

Test plates were prepared as in Example 1 except that the above cold rolled steel plate or hot-rolled steel plates were used as a metal base material as shown in Table 2, and the concentration of the silane coupling agent (B) or the cationic urethane resin (D) was as shown in Table 2.

Reference Example 1

A test plate was prepared as in Example 1 except that a chemical conversion treatment agent was prepared without including the cationic urethane resin (D) in the chemical conversion treatment agent.

Reference Examples 2 and 3

Test plates were prepared as in Example 1 except that the above cold rolled steel plate or hot-rolled steel plates were used as a metal base material, and surface conditioning was performed with Surffine GL1 (Nippon Paint Surf Chemicals Co., Ltd.) at room temperature for 30 seconds after post-degreasing water-washing treatment, and then chemical conversion treatment was performed by dipping treatment using Surfdine SD-6350 (a zinc phosphate-based chemical conversion treatment agent from Nippon Paint Surf Chemicals Co., Ltd.) at 35° C. for 2 minutes instead of using the above chemical conversion treatment agents as shown in Table 2.
The following evaluation tests were performed for the test plates obtained as described above from Examples 1 to 41, Comparative Examples 1 to 8, and Reference Examples 1 to 3.
[Secondary Adhesiveness tests (SDT)] The resulting test plates were each nicked deep enough to reach an underlying material along two parallel and longitudinal lines, and then dipped under a 5% NaCl aqueous solution at 50° C. for 480 hours. Subsequently, a cut portion was exfoliated off with a tape, and the exfoliation state of a coating material was observed. The exfoliation state was evaluated in accordance with the following evaluation criteria, and an evaluation score of 2 or more was considered as acceptable. The results were shown in Tables 1 and 2.
1: Not exfoliated
2: Somewhat exfoliated
3: Exfoliation width is 3 mm or more
[Salt-water spray tests (SST)] The resulting test plates were each cross-cut deep enough to reach an underlying material, and continuously sprayed with a 5% NaCl aqueous solution for 240 hours in a salt-water spry test chamber maintained at 35° C. Subsequently, the width of a blister from a cut portion was measured. Those having a blister width comparable to or less than that in a case where a zinc phosphate-based surface treatment agent was used as shown in Reference Examples 2, 3 were considered as acceptable. The results were shown in Tables 1 and 2.
[Combined cyclic corrosion tests (CCT)] The resulting test plates were each cross-cut deep enough to reach an underlying material, and then combined cyclic corrosion tests were performed. Combined tests were performed for 100 cycles by a test method in accordance with JASO M609-91. After the tests, the width of a blister from a cut portion was measured. Those having a blister width comparable to or less than that in a case where a zinc phosphate-based surface treatment agent was used as shown in Reference Examples 2, 3 were considered as acceptable. The results were shown in Tables 1 and 2.

	TABLE 1

	Silane	Cationic

			Adhesiveness and	coupling	urethane
			corrosion-	agent(B)	resin(D)

			resistance		Silane		Silane
		Zirconium	conferring agent		coupling		coupling

concentration(A)

Concentration

agent

		(ppm)	Types	(ppm)	Types	(ppm)	Types	(ppm)

Examples	1	100	None	0	KBM-603	100	F2667D	100
	2	100	None	0	KBM-603	100		100
	3	100	None	0	KBM-603	100		100
	4	100	None	0	KBM-603	100		100
	5	100	None	0	KBM-603	100		100
	6	100	None	0	KBM-603	100		100
	7	100	None	0	KBM-603	100		100
	8	100	None	0	KBM-603	1		1
	9	100	None	0	KBM-603	1		1
	10	100	None	0	KBM-603	5		5
	11	100	None	0	KBM-603	5		5
	12	100	None	0	KBM-603	50		50
	13	100	None	0	KBM-603	50		50
	14	100	None	0	KBM-603	100	Superflex	100
							620
	15	100	None	0	KBM-603	100	Superflex	100
							650
	16	100	None	0	KBM-603	1	F2667D	5000
	17	100	None	0	KBM-603	1		5000
	18	100	None	0	KBM-903	5000		1
	19	100	None	0	KBM-903	5000		1
	20	100	None	0	KBM-603	5000		5000
	21	100	None	0	KBM-603	5000		5000
	22	500	None	0	χS-1003	100		100
	23	500	None	0	XS-1003	100		100
	24	500	None	0	KBE-903	5000		5000
	25	500	None	0	KBE-903	5000		5000
	26	100	Zn	500	KBM-603	100		100
	27	100	Zn	500	KBM-603	100		100
	28	20	Zn	500	KBM-603	400		400

				Film
			Base	amount			SST	CCT
		((B)/(D))	material	(mg/m²)	Coating	SDT	(mm)	(mm)

Examples	1	1	SPC270	13.4	Powernics1010F	1	1.5	6.9
	2	1	SPC780	26.6		1	1.7	7.3
	3	1	SPH270	17.6		1	1.7	5.1
	4	1	SPH440	21.8		1	2.0	7.2
	5	1	SPH590	25.3		1	1.9	9.9
	6	1	GA270	15.5		1	0.8	0.3
	7	1	AL(6000series)	10.2		1	0.2	0.2
	8	1	SPC270	23.4		2	1.8	8.7
	9	1	SPH270	25.5		2	2.1	9.9
	10	1	SPC270	19.3		2	2.0	8.9
	11	1	SPH270	22.2		2	2.2	9.2
	12	1	SPC270	14.7		1	1.8	7.3
	13	1	SPH270	16.2		1	1.6	6.5
	14	1	SPH270	15.9		1	2.0	7.4
	15	1	SPH270	18.4		1	2.2	7.6
	16	0.0002	SPC270	13.4		1	1.5	7.0
	17	0.0002	SPH270	16.9		1	1.6	5.3
	18	5000	SPC270	11.1		1	1.4	6.8
	19	5000	SPH270	16.8		1	1.5	5.8
	20	1	SPC270	9.5		1	1.8	8.3
	21	1	SPH270	10.1		1	1.7	7.2
	22	1	SPC270	38.5		1	1.5	6.8
	23	1	SPH270	40.8		1	1.6	5.0
	24	1	SPC270	10.5		1	1.4	7.4
	25	1	SPH270	15.3		1	1.5	6.6
	26	1	SPC270	13.6		1	1.3	5.3
	27	1	SPH270	17.2		1	1.3	4.9
	28	1	SPC270	10.3		1	1.8	6.9

	TABLE 2

	Silane	Cationic

	Adhesiveness and	coupling	urethane
	corrosion-	agent(B)	resin(D)

		resistance		Solid		Solid
	Zirconium	conferring agent		content		content

concentra-

Concen-

concen-

Film

tion(A)

tration

((B)/

Base

amount

SST

CCT

(ppm)

Types

(ppm)

Types

(ppm)

Types

(ppm)

(D))

material

(mg/m²)

Coating

SDT

(mm)

Exam-	29	20	Zn	500	KBM-603	400	F2667D	400	1	SPH270	11.2	Powernics	1	1.9	7.1
ples	30	10000	Zn	500	KBM-603	400		400	1	SPC270	18.4	310	1	2.2	8.3
	31	10000	Zn	500	KBM-603	400		400	1	SPH270	20.3		1	2.1	8.8
	32	200	Zn	500	KBM-603	400		400	1	SPC270	15.2		1	1.3	4.7
	33	200	Zn	500	KBM-603	400		400	1	SPH270	19.7		1	1.6	4.5
	34	200	Zn	500	KBM-603	200		400	0.5	SPC270	16.8		1	0.9	4.9
	35	200	Zn	500	KBM-603	200		400	0.5	SPH270	21.2		1	0.9	5.0
	36	200	Zn	500	KBM-603	400		200	2	SPC270	15.5		1	1.3	4.9
	37	200	Zn	500	KBM-603	400		200	2	SPH270	20.2		1	0.9	5.0
	38	100	None	0	KBM-603	1		100	0.01	SPC270	15.6		2	2.1	8.8
	39	100	None	0	KBM-603	1		100	0.01	SPH270	16.3		2	2.0	9.1
	40	100	None	0	KBM-603	100		1	100	SPC270	16.2		1	2.1	7.1
	41	100	None	0	KBM-603	100		1	100	SPH270	17.8		1	2.0	11.0
Compar-	1	100	None	0	KBM-603	0	F2667D	100	—	SPC270	22.7	Powernics	3	2.1	10.5
ative	2	100	None	0	KBM-603	0		100	—	SPC780	28.5	310	3	2.3	11.9
Exam-	3	100	None	0	KBM-603	0		100	—	SPH270	26.4		3	2.4	11.9
ples	4	100	None	0	KBM-603	0		100	—	SPH440	30.3		3	2.2	15.3
	5	100	None	0	KBM-603	0		100	—	SPH590	34.1		3	2.5	14.2
	6	100	None	0	KBM-603	100		0	—	SPH270	21.4		1	2.0	13.5
	7	100	None	0	KBM-603	0		5000	—	SPC270	18.7		3	1.9	10.1
	8	100	None	0	KBM-603	0		5000	—	SPH270	22.1		3	2.0	14.3
Reference	1	100	None	0	KBM-603	100	F2667D	0	—	SPC270	18.7	Powernics	1	2.0	7.1

Example

2

Zinc phosphate treatment

SPC270

2100

310

2

2.3

9.2

	3									SPH270	2500		2	2.5	11.3

Comparison of Examples 1 to 41 with Comparative Examples 1 to 5, 7, and 8 shows that the metal base materials treated by the chemical conversion treatment agents from Examples 1 to 41 have superior secondary adhesiveness (SDT) as compared with the metal base materials treated by the chemical conversion treatment agents from Comparative Examples 1 to 5, 7, and 8. These results demonstrate that inclusion of the at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof in a chemical conversion treatment agent can confer preferred post-coating corrosion resistance on a metal base material treated by the chemical conversion treatment agent. Further, neither the metal base materials treated with the chemical conversion treatment agents from Comparative Examples 1 and 3 nor the metal base materials treated with the chemical conversion treatment agents from Comparative Examples 7 and 8 show preferred secondary adhesiveness (SDT). This indicates that an increased content of the cationic urethane resin (D) can not provide preferred results when a chemical conversion treatment agent does not contain the at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof, and also indicates that preferred post-coating corrosion resistance can be conferred on a metal base material by pre-coating treatment of the metal base material with a chemical conversion treatment agent including the at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof in combination with the cationic urethane resin (D).
Comparison of Examples 1 to 41 with Comparative Example 6 shows that the metal base materials treated with the chemical conversion treatment agents from Examples 1 to 41 have superior results from the combined cyclic corrosion tests (CCT) as compared with the metal base material treated with the chemical conversion treatment agent from Comparative Example 6. These results indicate that inclusion of the cationic urethane resin (D) in a chemical conversion treatment agent can confer preferred post-coating corrosion resistance on a metal base material treated with the chemical conversion treatment agent.
Comparison of Examples 1 to 41 with Reference Examples 1 to 3 shows that the metal base materials treated with the chemical conversion treatment agents from Examples 1 to 41 have comparable or superior results from the salt-water spray tests (SST), the combined cyclic corrosion tests (CCT) as compared with the metal base materials treated with the chemical conversion treatment agents from Reference Examples 1 to 3. These results indicate that the metal base materials treated with the chemical conversion treatment agents according to the embodiments of the present invention have comparable or superior post-coating corrosion resistance as compared with the metal base material treated by the conventional pre-coating treatment method used for a cold-rolled steel plate from the reference example 1 and the metal base materials subjected to the conventional zinc phosphate treatment from Reference Examples 2 to 3.
Further, comparison of Examples 1 to 7 shows that the metal base materials treated with the chemical conversion treatment agents from Examples 1 to 7 each have preferred post-coating corrosion resistance. These results indicate that the chemical conversion treatment agents according to the embodiments of the present invention can unsure excellent post-coating corrosion resistance regardless of the types of treatment targets.

Claims

1. A chemical conversion treatment agent, comprising: at least one (A) selected from the group consisting of zirconium, titanium, and hafnium;

at least one (B) selected from the group consisting of an amino group-containing silane coupling agent, hydrolysates thereof, and polymers thereof;

fluorine (C); and

a cationic urethane resin (D).

2. The chemical conversion treatment agent according to claim 1, wherein the total content of (A) is 20 to 10000 ppm by mass in terms of metal, and

pH is 1.5 to 6.5.

3. The chemical conversion treatment agent according to claim 1, wherein the total content of (B) is 5 to 5000 ppm by mass in terms of a solid content concentration, and

the content of (D) is 5 to 5000 ppm by mass in terms of a solid content concentration, and

the solid content mass ratio ((B)/(D)) of (B) to (D) is 0.0002 to 5000.

4. The chemical conversion treatment agent according to claim 1, further comprising at least one adhesiveness and corrosion resistance-conferring agent selected from the group consisting of magnesium ions, zinc ions, calcium ions, aluminum ions, gallium ions, indium ions, and copper ions.

5. A pre-coating treatment method, comprising: treating a target workpiece with the chemical conversion treatment agent according to claim 1.

6. A metal member treated by the pre-coating treatment method according to claim 5.