JP2016089232A - Method for surface-treating zinc-aluminum magnesium alloy plated steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for obtaining a chemical conversion coated zinc-aluminum-magnesium alloy plated steel sheet extremely excellent in corrosion resistance and adhesion to a resin film.SOLUTION: In the method for treating the surface of a zinc-aluminum-magnesium alloy plated steel sheet using a metal surface treatment agent, the metal surface treatment agent includes a predetermined amount of: a compound (A) having a zirconyl ([Zr=O]) structure; a vanadium compound (B); a titanium fluoro complex compound (C); an organophosphorus compound (Da) including a phosphate group and/or a phosphonic acid group; an inorganic phosphorus compound (Db); a specified aqueous acrylic resin (E); and an oxazoline group containing polymer (F) as a hardener. The pH of the metal surface treatment agent is 3-6.SELECTED DRAWING: None

Description

  The present invention relates to a surface treatment method of a zinc-aluminum-magnesium alloy plated steel plate with a chromium-free metal surface treatment agent, and a chemical conversion film treated zinc-aluminum-magnesium alloy plated steel plate obtained by the surface treatment method.

  Metallic materials such as galvanized steel plate materials and aluminum-based materials are oxidized and corroded by oxygen and moisture in the atmosphere, ions contained in the moisture, and the like. As a method of preventing such corrosion, there is a method of forming a chromate film by bringing a treatment liquid containing chromium such as chromate chromate and phosphate chromate into contact with the metal surface. The film formed by the chromate treatment has excellent corrosion resistance and adhesion to the coating film, but contains harmful hexavalent chromium in the treatment liquid, which takes time and cost for wastewater treatment. There's a problem. In addition, since the film formed by the treatment contains hexavalent chromium, problems in terms of environment and safety have been pointed out.

Therefore, an aqueous liquid composition for metal surface treatment and a chemical conversion treatment agent that has corrosion resistance equivalent to that of a conventional chromate chemical conversion film and does not contain chromate (chromium-free) have been proposed (for example, see Patent Documents 1 and 2). .
The metal surface treating agent of Patent Document 1 includes a vanadium compound (A), a metal compound (B) containing a metal selected from cobalt, nickel, zinc, magnesium, aluminum, calcium, strontium, barium and lithium, and optionally A chromium-free metal surface treating agent containing a metal compound (C) containing a metal selected from zirconium, titanium, molybdenum, tungsten, manganese, and cerium, and imparting excellent corrosion resistance, alkali resistance, and interlayer adhesion to a metal material is there.

In addition, the metal surface treatment agent of Patent Document 2 is one or more of four groups selected from a Zr compound that releases zirconyl ions (ZrO ²⁺ ) in an aqueous solution and a Ti compound that releases titanyl ions (TiO ²⁺ ) in an aqueous solution. Contains a transition metal compound (a) and an organic compound (b) having at least two functional groups selected from a hydroxyl group, a carboxyl group, a phosphonic acid group, a phosphoric acid group and a sulfonic acid group in the same molecule. A metal surface treatment agent that has a high adhesion so that the resin coating film does not peel off even when the resin coating film formed after the formation of the chemical conversion film is subjected to severe molding such as deep drawing. It is a chromium-free metal surface treatment agent that can impart properties.
Note that the metal surface treatment agents of Patent Documents 1 and 2 can both contain an aqueous resin that may be water-soluble or water-dispersible.

  On the other hand, since it was proposed in Patent Document 3, it has been known that a hot dip zinc-aluminum-magnesium plated steel sheet using a plating bath containing appropriate amounts of aluminum and magnesium in zinc is excellent in corrosion resistance.

JP 2004-183015 A JP 2013-23705 A US Pat. No. 3,505,043

  However, the metal surface treatment agents of Patent Documents 1 and 2 are not necessarily sufficient in corrosion resistance, adhesion, and the like depending on the object to be treated and applications.

  Accordingly, the present invention provides a chromium-aluminum-magnesium alloy-plated steel sheet with good corrosion resistance, which is excellent in corrosion resistance and capable of forming a film with high adhesion between the plated steel sheet and a resin film such as a paint film or a laminate film. An object of the present invention is to provide a method for obtaining a chemical conversion film-treated zinc-aluminum-magnesium alloy plated steel sheet which is treated with a free metal surface treatment agent and has excellent corrosion resistance and adhesion to a resin film.

As a result of intensive studies to achieve the above object, the present inventors have found that the plating layer is Al: 1.0 mass% or more and less than 4.0 mass%, Mg: 1.0 mass% or more and 10 mass% or less. A zinc-aluminum-magnesium alloy-plated steel sheet containing the balance Zn and inevitable impurities, a compound having a zirconyl ([Zr = O] ²⁺ ) structure, a vanadium compound and a specific metal fluoro complex compound that etches the metal surface, In order to form a corrosion-resistant film, the organic phosphorus compound and the inorganic phosphorus compound are both contained, and a specific amount of the high acid value aqueous acrylic resin and the oxazoline group-containing polymer is contained, and the inorganic component and By treating with a metal surface treatment agent that has a specific range of organic component ratios and adjusted to a specific pH range, it has excellent corrosion resistance and only adhesion to the plated steel sheet. A zinc-aluminum-magnesium alloy-plated steel sheet with excellent corrosion resistance and excellent adhesion to the resin film, in which a film having high adhesion to the resin film such as a coating film or laminate film is formed. I found. The present invention has been completed based on such findings. That is, the present invention is as follows.

[1] A method of treating the surface of a zinc-aluminum-magnesium alloy plated steel sheet with a metal surface treatment agent,
A step of forming a zinc-aluminum-magnesium alloy plating layer on the surface of the steel sheet; and a step of treating the surface of the plating layer with a metal surface treatment agent following the plating layer formation step, the zinc-aluminum The magnesium alloy plating layer is a plating layer containing Al: 1.0% by mass or more and less than 4.0% by mass, Mg: 1.0% by mass or more and 10% by mass or less, the remainder Zn and inevitable impurities; Organophosphorus in which the surface treating agent contains a compound (A) having a zirconyl ([Zr = O] ²⁺ ) structure, a vanadium compound (B), a titanium fluorocomplex compound (C), a phosphate group and / or a phosphonate group A compound (Da), an inorganic phosphorus compound (Db), an aqueous acrylic resin (E), an oxazoline group-containing polymer (F) as a curing agent, and the aqueous acrylic resin ( The solid acid value of E) is 300 mgKOH / g or more, and the content of the aqueous acrylic resin (E) with respect to the metal surface treatment agent is 100 ppm to 30,000 ppm as the concentration of the resin solid content, and the oxazoline Compound (A), vanadium compound in which the content of the group-containing polymer (F) with respect to the metal surface treatment agent is 50 ppm to 5,000 ppm as a solid content and has the zirconyl ([Zr = O] ²⁺ ) structure (B) The mass ratio of the total mass in terms of metal elements of the titanium fluoro complex compound (C) to the solid content of the aqueous acrylic resin (E) and the oxazoline group-containing polymer (F) is (A + B + C) / (E + F) = Zinc-aluminum-magnesium alloy plated steel having a pH of 10/1 to 1/1 and a pH of the metal surface treatment agent of 3-6 How the surface of the treatment with the metal surface treatment agent.

[2] The mass ratio of the solid content of the aqueous acrylic resin (E) and the oxazoline group-containing polymer (F) that is a curing agent is E / F = 20/1 to 2/3, according to the above [1]. A method of treating the surface of a zinc-aluminum-magnesium alloy plated steel sheet with a metal surface treatment agent.
[3] The above [1] or [2], wherein the mass ratio of the organic phosphorus compound (Da) to the inorganic phosphorus compound (Db) is Da / Db = 5/1 to 1/2 in terms of phosphorus element. The method of processing the surface of the zinc-aluminum-magnesium alloy plating steel plate as described in 1 using a metal surface treating agent.
[4] The zinc-aluminum-magnesium alloy plating layer is Si: 0.001% by mass to 2.0% by mass, Ti: 0.001% by mass to 0.1% by mass, and B: 0.001% by mass. % Or more and 0.045% by mass or less, further including one or more of the above-mentioned [1] to [3], the surface of the zinc-aluminum-magnesium alloy plated steel sheet is treated with a metal treating agent. How to handle using.
[5] A zinc-aluminum-magnesium alloy plated steel sheet obtained by the treatment according to any one of [1] to [4].

  According to the present invention, the surface of a zinc-aluminum-magnesium alloy plated steel sheet with good corrosion resistance is treated with a chromium-free metal surface treatment agent that is excellent in corrosion resistance and can form a film with high adhesion to the plated steel sheet and resin film. A method can be provided.

  In the present invention, the surface of a zinc-aluminum-magnesium alloy plated steel sheet (hereinafter sometimes referred to as “metal material”) is treated with a specific chromium-free metal surface treatment agent (hereinafter also referred to as “treatment agent”). A step of forming a zinc-aluminum-magnesium alloy plating layer on the surface of a steel sheet, and a step of processing the surface of the plating layer using a metal surface treatment agent following the plating layer formation step Including.

  The plated steel sheet of the present invention is a zinc-aluminum-magnesium alloy plated steel sheet manufactured using a molten Zn—Al—Mg plating bath. As will be described later, the chemical conversion treatment liquid of the present invention contains a fluorine compound, but by the chemical conversion treatment, a reaction layer containing Al and Mg fluoride is formed on the surface of the plated layer of the plated steel sheet. The adhesion of can be further increased.

The step of forming a zinc-aluminum-magnesium alloy plating layer on the surface of the steel sheet may be obtained by a known method, but aluminum is 1.0% by mass or more and less than 4.0% by mass, and magnesium is 1.0% by mass or more and 10% by mass or more. It is preferably produced by a hot dipping method using an alloy plating bath containing not more than mass%, the balance Zn and inevitable impurities. Further, it is more preferable to add Ti, B, Ti—B alloy or Ti, B-containing compound to the plating bath in order to suppress the formation and growth of the Zn ₁₁ Mg ₂ phase which adversely affects the appearance and corrosion resistance. The addition amount of these metals or compounds is 0.001% by mass to 0.1% by mass and B is 0.001% by mass to 0.045% by mass in terms of metal with respect to the plating bath. It is preferable to do. Ti, when B is within the range, it is possible _to suppress _{the Zn} 11 Mg ₂ phase is generated in the plating layer. Further, in order to improve the adhesion between the base steel and the plating layer during processing, 0.001% by mass or more of Si having an action of suppressing the growth of the Al—Fe alloy layer at the interface between the plating layer and the base steel. It is preferable to add in the range of 0.0 mass% or less.

Therefore, the zinc-aluminum-magnesium alloy plated steel sheet in the present invention can be obtained by forming a zinc-aluminum-magnesium alloy plated layer on the surface of the steel sheet. It is a plating layer containing 0% by mass or more and less than 4.0% by mass, Mg: 1.0% by mass or more and 10% by mass or less, the balance Zn and inevitable impurities. The zinc-aluminum-magnesium alloy plating layer preferably contains 88 to 95% by mass of Zn.
And this zinc-aluminum-magnesium alloy plating layer is Si: 0.001 mass% or more and 2.0 mass% or less, Ti: 0.001 mass% or more and 0.1 mass% or less, B: 0.001 mass%. It is preferable that 1 type or 2 types or more are further included among the above 0.045 mass% or less.

The metal surface treating agent of the present invention includes a compound (A) having a zirconyl ([Zr = O] ²⁺ ) structure, a vanadium compound (B), a titanium fluoro complex compound (C), an organic phosphorus compound (Da), and an inorganic phosphorus compound. (Db), aqueous acrylic resin (E), containing oxazoline group-containing polymer (F) as a curing agent, metal compounds (A), (B), (C), aqueous acrylic resin (E), and curing agent. It is a chromium-free aqueous metal surface treatment agent having a specific mass ratio with the oxazoline group-containing polymer (F).

Fluorine ions released from the titanium fluoro complex compound (C) increase the pH near the surface by etching the surface of the metal material, and the anion of the titanium fluoro complex is generated from the zirconium compound (A) zirconyl ([Zr = O]). ²⁺ ) Reacts with cations and metal cations derived from the metal substrate eluted by etching, and deposits on the surface to form a film having excellent corrosion resistance and high adhesion to the metal material. By containing the vanadium compound (B), a film having improved corrosion resistance can be formed, and by containing both the organic phosphorus compound (Da) and the inorganic phosphorus compound (Db), the corrosion resistance can be improved.
And specific mass ratio with respect to metal compound (A), (B), and (C) water content acrylic resin (E) whose solid content acid value is 300 mgKOH / g or more, and the oxazoline group containing polymer (F) which is a hardening | curing agent. In this case, the adhesion with the metal material, the adhesion with the resin film, and the corrosion resistance are further improved.

The zirconium compound (A) used in the metal surface treatment agent of the present invention is a compound having a zirconyl ([Zr = O] ²⁺ ) structure, and examples of such a zirconium compound (A) include zirconyl ammonium carbonate and zirconyl sulfate. Zirconyl ammonium sulfate, zirconyl nitrate, zirconyl ammonium nitrate, zirconyl formate, zirconyl acetate, zirconyl propionate, zirconyl butyrate, oxalic acid and zirconyl ion salts, malonic acid and zirconyl ion salts, succinic acid and zirconyl ion salts, oxy Examples include zirconium chloride. By being a compound having a zirconyl ([Zr = O] ²⁺ ) structure, the crosslinkability during film formation is improved, and a film having good corrosion resistance can be formed.

  The content of the zirconium compound (A) containing a zirconyl group in the treatment agent is preferably 0.01 to 10% by mass, more preferably 0.1 to 8% by mass, and 0.2 to 8%. It is more preferable that it is mass%, and it is still more preferable that it is 0.5-5 mass%. If the content of the zirconium compound (A) containing a zirconyl group is 0.01% by mass or more, corrosion resistance can be sufficiently imparted, and if it is 10% by mass or less, the flexibility of the film becomes sufficient. Excellent processing adhesion.

  In the metal surface treatment agent of the present invention, the vanadium compound (B) specifically includes metavanadate and its salt, vanadium oxide, vanadium trichloride, vanadium oxytrichloride, vanadium acetylacetonate, vanadium oxyacetylacetonate. , Vanadyl sulfate, vanadium sulfate, vanadium nitrate, vanadium phosphate, vanadium acetate, vanadium biphosphate, vanadium alkoxide, vanadium oxyalkoxide, and the like. Among these, it is preferable to use a compound in which the oxidation number of vanadium is pentavalent. Specifically, metavanadate and its salt, vanadium oxide, vanadium oxytrichloride, vanadium alkoxide, and vanadium oxyalkoxide are preferable.

  The content of the vanadium compound (B) in the treatment agent is preferably 0.01 to 5% by mass, and more preferably 0.1 to 3% by mass. Corrosion resistance can be improved by containing 0.01-5 mass% of vanadium compounds (B).

  Examples of the titanium fluorocomplex compound (C) used in the metal surface treating agent of the present invention include fluorotitanic acid and salts thereof. Since the titanium fluoro complex compound (C) contains fluorine, etching of the metal surface is likely to occur, so that a film having excellent corrosion resistance and high adhesion to the metal material is formed.

  The content of the titanium fluoro complex compound (C) in the treating agent is preferably 0.01 to 10% by mass, more preferably 0.1 to 8.5% by mass, and 0.3 to 7%. More preferably, it is mass%. When the content of the titanium fluoro complex compound (C) is 0.01% by mass or more, sufficient corrosion resistance can be imparted, and when it is 10% by mass or less, excessive etching is prevented, and an inorganic phosphorus compound (Db The metal cations eluted with respect to ()) are prevented from becoming excessive, so that the corrosion resistance is excellent.

  The metal surface treating agent of the present invention can further improve the corrosion resistance by containing both an organic phosphorus compound (Da) and an inorganic phosphorus compound (Db) containing a phosphoric acid group and / or a phosphonic acid group. .

  Examples of such an organic phosphorus compound (Da) include 1-hydroxyethylidene-1,1-diphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, ethylenediaminetetramethylenephosphonic acid, aminotrimethylenephosphonic acid, phenyl Examples thereof include phosphonic acids such as phosphonic acid and octylphosphonic acid, and salts thereof. A combination of these organophosphorus compounds can also be used. Of these, 1-hydroxyethylidene-1,1-diphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, and aminotrimethylenephosphonic acid are preferred.

  Examples of such inorganic phosphorus compounds (Db) include phosphoric acids such as phosphoric acid and phosphorous acid and salts thereof, and condensed phosphoric acids such as pyrophosphoric acid and tripolyphosphoric acid and salts thereof. Here, as a cation for forming a salt of phosphoric acid and a salt of condensed phosphoric acid, any one can be used as long as it forms a salt that is easily soluble in water and the aqueous solution can liberate phosphate ions. Sodium, potassium, ammonium, etc. are mentioned. A combination of these inorganic phosphorus compounds can also be used. As the inorganic phosphorus compound (Db), a salt of phosphoric acid is preferable. In the present specification, “easily soluble in water” means that 1 g of the compound is dissolved in 10 ml of water at 25 ° C. Here, dissolution refers to a state in which it is dissolved in a solvent and is uniform and a state in which it is finely dispersed. Specifically, it means a state in which precipitation does not occur when centrifugation is performed at 12,000 rpm for 30 minutes.

The contents of the organic phosphorus compound (Da) and the inorganic phosphorus compound (Db) are each preferably 0.01 to 10% by mass, and 0.1 to 8% by mass as the content in the treatment agent. Is more preferable, and it is still more preferable that it is 0.3-6 mass%.
The mass ratio of the organic phosphorus compound (Da) and the inorganic phosphorus compound (Db) is preferably Da / Db = 5/1 to 1/2 in terms of phosphorus element. Here, the mass ratio in terms of phosphorus element means the ratio of the mass of phosphorus element contained in each of the organic phosphorus compound (Da) and the inorganic phosphorus compound (Db).
By containing the organophosphorus compound (Da) in the above-mentioned concentration range, the vanadium compound (B) can be stably dissolved in the treatment agent due to the chelating effect. In addition, when the treatment agent contains the inorganic phosphorus compound (Db) in the above-described concentration range, it is possible to efficiently form a film having excellent corrosion resistance with the metal cation eluted by etching. Furthermore, when the organic phosphorus compound (Da) and the inorganic phosphorus compound (Db) are present in the treatment agent at the above mass ratio, both corrosion resistance and water resistance can be achieved.

The aqueous acrylic resin (E) used as the metal surface treating agent of the present invention has a plurality of carboxyl groups obtained by polymerizing monomers having an ethylenically unsaturated double bond, and has a solid content acid value of 300 mgKOH / g or more. It is a polymer. The mass average molecular weight is preferably 1,000 or more and 1,000,000 or less. In this specification, the mass average molecular weight of the resin can be measured by gel permeation chromatography (GPC) using a polystyrene standard sample standard. Moreover, the acid value and hydroxyl value of resin solid content in the present invention can be determined by a method based on JIS K 0070.
Such aqueous acrylic resins include, as monomers, homopolymers obtained by radical polymerization of acrylic acid and methacrylic acid, and copolymers obtained by radical polymerization of these monomers and other ethylenically unsaturated monomers. A polymer can be used. In the case of a copolymer, examples of other ethylenically unsaturated monomers include alkyl (meth) acrylates such as ethyl (meth) acrylate and butyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and 2-hydroxy Examples include hydroxyalkyl (meth) acrylates such as propyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate. The acid value of water-based acrylic resin (E) can be adjusted with the monomer composition used for superposition | polymerization.
The aqueous acrylic resin (E) can be obtained by polymerizing the above monomer by a usual method. For example, a water-based acrylic resin can be obtained by mixing a monomer mixture with a known polymerization initiator (for example, azobisisobutyronitrile), dropping into a Kolben containing a solvent heated to a polymerizable temperature and aging. it can.
As commercially available water-based acrylic resins, “Jurimer AC-10L” (polyacrylic acid, manufactured by Nippon Pure Chemical Co., Ltd.), “PIA728” (polyitaconic acid, manufactured by Iwata Chemical Co., Ltd.), and “Aquaric HL580” (polyacrylic acid, Japan) Catalyst Co., Ltd.).
It is also possible to use a combination of a plurality of types of aqueous acrylic resins.

The aqueous acrylic resin (E) is contained in an amount of 100 ppm to 30,000 ppm as the resin solid content in the treatment agent.
By making it contain in the said density | concentration range, not only adhesiveness with a metal material but adhesiveness with a resin membrane | film | coat and corrosion resistance are further improved. In particular, the effect of improving the adhesion with the resin film is remarkable.

The metal surface treating agent of the present invention further contains an oxazoline group-containing polymer (F) that is a curing agent that reacts with the aqueous acrylic resin (E) to form a crosslinked structure.
The oxazoline group-containing polymer (F) as such a curing agent is an oxazoline group-containing polymer containing in the molecule at least two functional groups capable of reacting with the carboxyl group of the aqueous acrylic resin (E). .

  Specific examples of the oxazoline group-containing polymer include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2- A monomer composed of an addition-polymerizable oxazoline such as oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and other polymerizable monomers used as necessary. An oxazoline group-containing polymer obtained by polymerizing the monomer composition can be exemplified. Commercially available products include “Epocross WS-700” (25% active ingredient, water-soluble type, oxazoline group-containing acrylic resin, manufactured by Nippon Shokubai Co., Ltd.), “Epocross WS-300” (10% active ingredient, water-soluble type, oxazoline) Group-containing acrylic resin, manufactured by Nippon Shokubai Co., Ltd.).

The oxazoline group-containing polymer (F), which is a curing agent, is contained in the treatment agent in a solid content concentration of 50 ppm to 5,000 ppm and is a curing agent that forms a crosslinked structure with the aqueous acrylic resin (E). The mass ratio of the solid content of the group-containing polymer (F) is preferably E / F = 20/1 to 2/3.
By containing in the said concentration range and mass ratio, a water-based acrylic resin (E) and a crosslinked structure are formed, and adhesiveness with a metal material, adhesiveness with a resin film, and corrosion resistance are improved further.

Further, the total mass of metal compound equivalent of the compound (A), vanadium compound (B), titanium fluorocomplex compound (C) having the above zirconyl ([Zr = O] ²⁺ ) structure, aqueous acrylic resin (E), oxazoline The mass ratio with the group-containing polymer is (A + B + C) / (E + F) = 10/1 to 1/1. With metal element conversion, it calculates based on the mass of the zirconium element which a zirconium compound (A) contains, the vanadium element which a vanadium compound (B) contains, and the titanium element which a titanium fluoro complex compound (C) contains. means.
When the inorganic excess composition (A + B + C) / (E + F) is 10/1 or more, a chemical conversion film with poor adhesion and corrosion resistance is obtained, and when (A + B + C) / (E + F) is a composition having a large amount of organic substances of 1/1 or less. It becomes a chemical conversion film having poor corrosion resistance.

  The pH of the metal surface treating agent of the present invention is required to be 3-6. When the pH is higher than 6, etching becomes insufficient, and the adhesion between the metal material and the chemical conversion film becomes insufficient. On the other hand, if the pH is less than 3, the etching becomes excessive and the appearance (powder) of the steel sheet becomes poor. Here, the poor powder property refers to a state in which the steel sheet after chemical conversion treatment has a powder-like appearance, and the film easily falls off by rubbing with a hand or a roll.

The metal surface treating agent of the present invention comprises, in water, at least a compound (A) having a zirconyl ([Zr = O] ²⁺ ) structure according to the present invention, a vanadium compound (B), a titanium fluoro complex compound (C), an organic phosphorus The compound (Da), the inorganic phosphorus compound (Db), the aqueous acrylic resin (E), and the oxazoline group-containing polymer (F) that is a curing agent can be mixed in predetermined amounts. Here, the solid content concentration of the chromium-free metal surface treatment agent of the present invention is preferably 0.1 to 20% by mass, more preferably 1 to 15% by mass with respect to the treatment agent.

  The metal surface treatment agent of the present invention is a chromium-free metal surface treatment agent that substantially does not contain a compound containing not only hexavalent chromium but also trivalent chromium from the environmental and safety aspects. “Containing substantially no chromium-containing compound” means that the content of metallic chromium derived from the chromium compound in the metal surface treatment agent is less than 1 ppm.

  Furthermore, the metal surface treatment agent of the present invention contains a thickener, a leveling agent, a wettability improver, a surfactant, an antifoaming agent, a water-soluble alcohol, a cellosolve solvent, etc., as necessary. May be.

The surface treatment (chemical conversion treatment) using the chromium-free metal surface treatment agent of the present invention can be performed as follows.
There is no particular limitation on the pre-process of the chemical conversion treatment according to the present invention, but usually, before the chemical conversion treatment, a degreasing treatment with an alkaline degreasing solution is performed to remove oil and dirt adhering to the metal material. Accordingly, the surface is adjusted with acid, alkali, nickel compound, cobalt compound or the like. At this time, it is preferable to wash with water after the treatment so that the degreasing liquid or the like does not remain on the surface of the metal material.

  The chemical conversion treatment according to the present invention uses a surface treatment agent of the present invention on the surface of a zinc-aluminum-magnesium alloy-plated steel sheet, roll coating method, air spray method, airless spray method, dipping method, spin coating method, flow coating. The film is formed by a method such as a coating method, a curtain coating method, or a flow coating method, and a chemical conversion film is formed through a drying process. At this time, the treatment temperature is preferably in the range of 5 to 60 ° C., and the treatment time is preferably about 1 to 300 seconds. When the treatment temperature and treatment time are in the above ranges, a desired film can be formed satisfactorily and economically advantageous. The treatment temperature is more preferably 10 to 40 ° C., and the treatment time is more preferably 2 to 60 seconds.

  In addition, the zinc-aluminum-magnesium alloy-plated steel sheet is used for automobile bodies, automobile parts, roofing materials, exterior wall materials, building materials such as columns for agricultural greenhouses, household appliances and parts thereof, guardrails, soundproof walls, drainage grooves, etc. It is applied to sheet coils used in civil engineering products and various molded products.

  The drying step does not necessarily require heat and may be physical removal such as air drying or air blow, but may be heat-dried to improve film formation and adhesion to the metal surface. The temperature in that case is preferably 30 to 250 ° C, more preferably 40 to 200 ° C.

The amount of the chemical conversion film to be formed is preferably 0.001 to 1 g / m ² after drying, and more preferably 0.02 to 0.5 g / m ² . By being 0.001-1 g / m < ² >, sufficient corrosion resistance and adhesiveness with a resin film can be maintained, and it can prevent that a crack arises in a film.

  The chemical conversion film thus formed is excellent in corrosion resistance and also has good adhesion to the following resin film formed on the film.

In the next step, the surface of the metal material (member) to be protected is further improved by forming a resin film layer made of paint, lacquer, laminate film, etc. on the formed chemical film by a known method. Can be protected.
The thickness of the formed resin film layer is preferably 0.3 to 50 μm after drying.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these Examples.

[Production Example 1]
Preparation of Acrylic Resin (1) 775 parts of ion exchange water was charged into a four-necked vessel equipped with a heating / stirring device, and the content liquid was heated to 80 ° C. while stirring and refluxing with nitrogen. Next, while heating, stirring, and refluxing with nitrogen, a mixed monomer solution of 160 parts of acrylic acid, 20 parts of ethyl acrylate and 20 parts of 2-hydroxyethyl methacrylate, 1.6 parts of ammonium persulfate and ion-exchanged water 23. 4 parts of the mixed solution was added dropwise using a dropping funnel over 3 hours. After completion of the dropwise addition, heating, stirring and nitrogen reflux were continued for 2 hours. Heating and nitrogen reflux were stopped, the solution was cooled to 30 ° C. with stirring, and filtered with a 200 mesh comb to obtain a colorless and transparent water-soluble acrylic resin (1) aqueous solution. The obtained acrylic resin (1) aqueous solution had a non-volatile content of 20%, a resin solid content acid value of 623 mg KOH / g, a resin solid content hydroxyl value of 43 mg KOH / g, and a mass average molecular weight of 8400. In addition, the said non volatile matter is the value calculated | required from the residual mass after heating the acrylic resin (1) aqueous solution 2g obtained for 1 hour in 150 degreeC oven.

[Production Example 2]
Preparation of acrylic resin (2) The monomer composition of the acrylic resin was changed to 30 parts acrylic acid, 70 parts ethyl acrylate, 100 parts 2-hydroxyethyl methacrylate in the same procedure as in Production Example 1, Acrylic resin synthesis was performed. While the synthetic resin was being cooled in the vessel, the liquid became cloudy at around 60 ° C., so 28.3 parts of 25% ammonia was added as a neutralizing agent while stirring. The mixture was cooled to 30 ° C. to obtain a light reddish brown acrylic resin (2) aqueous solution. The obtained acrylic resin (2) aqueous solution had a non-volatile content of 19.4%, a resin solid content acid value of 117, a resin solid content hydroxyl value of 216, and a mass average molecular weight of 11,600.

[Production Examples 3-37]
In water, zirconium compound (A), vanadium compound (B), metal fluoro complex compound (C), organic phosphorus compound (Da), inorganic phosphorus compound (Db), aqueous acrylic resin (E), and oxazoline group which is a curing agent A predetermined amount of the containing polymer (F) shown in the following Tables 2 to 4 was added (there may be an additive-free component in the comparative example), and metal surface treatment agents 1 to 35 were prepared with a total amount of 1000 parts by mass.

(Test plate)
Using a cold-rolled steel sheet having a thickness of 0.5 mm as an original sheet, a hot-dip Zn—Al—Mg alloy-plated steel strip having the plating composition shown in Table 1 below is manufactured, and each steel strip is cut to be plated 210 mm × 300 mm. A steel plate was prepared. The plating adhesion amount was 60 g / m ² per side.

[Examples 1-38 and Comparative Examples 1-12]
(Degreasing / Surface treatment)
The plated steel sheet was spray degreased at 60 ° C. for 2 minutes using an alkaline degreasing agent (manufactured by Nippon Paint Co., Ltd., Surf Cleaner 155), washed with water, and dried at 80 ° C. Then, after adjusting the solid content concentration so that it may become the amount of dry film (0.2 g / m < ² >) of the following Tables 5-7, the metal surface treatment agent prepared in said manufacturing example was degreased The coated steel sheet was coated with a bar coater and dried using a hot-air circulating oven so that the metal substrate reached a temperature of 80 ° C. to prepare a test plate on which a chemical conversion film was formed.

(Resin film layer formation)
An epoxy adhesive was applied to the surface of the test plate, and a vinyl chloride film was bonded to obtain a laminated steel plate.

The legends in Tables 2 to 4 are as follows.
(Zirconium compound (A))
A1: Zirconyl nitrate (cation is ZrO ²⁺ )
A2: Zirconyl acetate (cation is ZrO ²⁺ )
A3: Zirconyl sulfate (cation is ZrO ²⁺ )
A4: Zirconyl ammonium carbonate (cation is ZrO ²⁺ )

(Vanadium compound (B))
B1: Ammonium metavanadate B2: Sodium metavanadate

(Metal fluoro complex compound (C))
C1: Titanium ammonium fluoride (anion is TiF ₆ ²⁻ )
C2: zircon ammonium fluoride (anion is ZrF ₆ ²⁻ )

(Organic phosphorus compound (Da))
Da1: 1-hydroxyethylidene-1,1-diphosphonic acid Da2: aminotrimethylenephosphonic acid Da3: 2-phosphonobutane-1,2,4-tricarboxylic acid

(Inorganic phosphorus compound (Db))
Db1: monoammonium dihydrogen phosphate Db2: diammonium monohydrogen phosphate

(Water-based acrylic resin (E))
E1: Low molecular weight polyacrylic acid (“Julimer AC-10L” manufactured by Nippon Pure Chemical Industries, Ltd., solid content acid value: 779 mg KOH / g, mass average molecular weight: 20,000 to 30,000, nonvolatile content: 40%)
E2: High molecular weight polyacrylic acid (“Julimer AC-10H” manufactured by Nippon Pure Chemical Industries, Ltd., solid content acid value: 779 mg KOH / g, mass average molecular weight: 150,000, nonvolatile content: 20%)
E3: Acrylic resin (1) (prepared in Production Example 1; solid content acid value 623 mg KOH / g, mass average molecular weight 8400)
E4: Adekabon titer HUX-232 (Adeka water-based urethane resin, solid content acid value 30 mgKOH / g, non-volatile content 30%)
E5: Acrylic resin (2) (prepared in Production Example 2; solid content acid value 117 mgKOH / g, mass average molecular weight 11,600)

(Oxazoline group-containing polymer (F) as a curing agent)
F1: Oxazoline group-containing acrylic resin (“Epocross WS-300” manufactured by Nippon Shokubai Co., Ltd.)
F2: Oxazoline group-containing acrylic resin (“Epocross WS-500” manufactured by Nippon Shokubai Co., Ltd.)
F3: Multivalent carbodiimide (“Carbodilite SW-12G” manufactured by Nisshinbo Chemical Co., Ltd.)

  A test piece was appropriately cut out from each of the chemical conversion treated steel sheets and each of the laminated steel sheets prepared as described above to make test plates, and the following evaluation tests were performed. The results are shown in Tables 5-7 below.

(Film processing adhesion)
First, a JIS No. 13A test piece was cut out from the laminated steel sheet to which the film was adhered, and 18% elongation was given to the test piece by a tensile tester. Subsequently, two parallel cuts are made at a distance of 15 mm in the longitudinal direction of the test piece with respect to the film of the parallel part of the test piece, and the film between the parallel lines is forcibly separated, The peel strength of was measured. Evaluation was performed according to the following criteria. A score of 3 or higher was accepted.
<Evaluation criteria>
4: Peel strength 50 N / 15 mm or more 3: Peel strength 37.5 N / 15 mm or more and less than 50 N / 15 mm 2: Peel strength 15 N / 15 mm or more and less than 37.5 N / 15 mm 1: Peel strength 15 N / 15 mm or less

(water resistant)
A JIS No. 13A test piece was cut out from the laminated steel sheet to which the film was adhered, immersed in boiling water for 4 hours, and then the film peel strength (N / 15 mm) of the flat portion was measured by the same method as the film processing adhesion test. . Evaluation was performed according to the following criteria. A score of 3 or higher was accepted.
<Evaluation criteria>
4: Peel strength 50 N / 15 mm or more 3: Peel strength 37.5 N / 15 mm or more and less than 50 N / 15 mm 2: Peel strength 15 N / 15 mm or more and less than 37.5 N / 15 mm 1: Peel strength 15 N / 15 mm or less

(Appearance (powder))
The appearance of each test plate after the chemical conversion treatment (whether or not the appearance looks like sprayed powder) was visually evaluated. Evaluation was performed according to the following criteria. A score of 3 was accepted.
<Evaluation criteria>
3: The powder (= film) does not fall off when rubbed with hands or rolls 1: The powder (= film) comes off when rubbed with hands or rolls

(Bath stability)
Each produced test plate was stored in a constant temperature bath at 40 ° C. and 5 ° C. for a certain period (one month), and the presence or absence of thickening or sediment was evaluated. Evaluation was performed according to the following criteria. A score of 3 was accepted.
<Evaluation criteria>
3: After standing for 1 month in a constant temperature bath at 40 ° C. and 5 ° C., neither thickening nor sediment is observed 1: After standing for 1 month in a constant temperature bath at 40 ° C. and 5 ° C., thickening or sedimenting Is accepted

(Corrosion resistance (temporary rust prevention))
The SST test (salt water spray test) was performed by tape-sealing the four corners of the steel sheet subjected to chemical conversion treatment (before lamination adhesion). Evaluation was performed according to the following criteria, and it was judged as acceptable if no white rust was generated for 24 hours or more. Thereafter, the test is continued for a maximum of 72 hours. The higher the numerical value over a long period, the better.
<Evaluation criteria>
Time: Time when white rust did not occur in the flat part-: White rust occurred in the flat part in 24 hours of SST test

The legends in Tables 5 to 7 are as follows.
(Surface conditioner)
Ni: Nickel-based surface conditioner (manufactured by Nippon Paint Co., Ltd., NP conditioner 710)
-: No surface adjustment The adhesion amount of Ni was 5 mg / m ² .

  From Tables 5-7, all the metal surface treating agents according to the examples are superior in corrosion resistance and water resistance than the metal surface treating agents according to the comparative examples, and are zinc-aluminum-magnesium alloy plated steel sheets and laminate films. It can be seen that a film having high adhesion to the resin film is formed.

In Comparative Example 1, zircon ammonium fluoride was used instead of titanium ammonium fluoride, but the water resistance and corrosion resistance were poor.
In Comparative Examples 2 and 3, an aqueous urethane resin having a low acid value or an aqueous acrylic resin having a low acid value was used in place of the high acid value aqueous acrylic resin, respectively, but both had poor adhesion. It was.
In Comparative Example 4, since the pH was higher than 6, etching was insufficient, and adhesion and the like were poor.
Since the comparative example 5 was larger than (A + B + C) / (E + F) = 10/1 (a lot of inorganic substances), the adhesion and corrosion resistance were poor.
Comparative Example 6 did not contain a vanadium compound and was poor in corrosion resistance and powder properties.
Comparative Example 7 did not contain a titanium fluoride compound and had poor corrosion resistance and adhesion.
Comparative Example 8 did not contain an organophosphorus compound, the solubility of the vanadium compound was insufficient, and the corrosion resistance and the like were poor.
Comparative Example 9 did not contain an inorganic phosphorus compound and had poor corrosion resistance.
Comparative Example 10 did not contain an aqueous acrylic resin having a high acid value, and the film-forming property was insufficient, resulting in poor adhesion and powder properties.
In Comparative Example 11, another curing agent (carbodiimide) was used in place of the oxazoline group-containing polymer, but sufficient crosslinking was not obtained, resulting in poor water resistance and corrosion resistance.
In Comparative Example 12, since the Al content of the plated steel sheet was small, etching was excessive and the powder property was poor.

Claims (5)

A method of treating the surface of a zinc-aluminum-magnesium alloy plated steel sheet with a metal surface treatment agent,
Forming a zinc-aluminum-magnesium alloy plating layer on the surface of the steel sheet;
And a step of treating the surface of the plating layer using a metal surface treatment agent following the plating layer forming step,
The zinc-aluminum-magnesium alloy plating layer is a plating layer containing Al: 1.0% by mass or more and less than 4.0% by mass, Mg: 1.0% by mass or more and 10% by mass or less, the balance Zn and inevitable impurities. Yes,
The metal surface treatment agent is
Compound (A) having a zirconyl ([Zr = O] ²⁺ ) structure,
Vanadium compound (B),
Titanium fluoro complex compound (C),
An organophosphorus compound (Da) containing a phosphoric acid group and / or a phosphonic acid group,
Inorganic phosphorus compound (Db),
Aqueous acrylic resin (E),
Containing an oxazoline group-containing polymer (F) as a curing agent,
The acid value of the aqueous acrylic resin (E) is 300 mgKOH / g or more, and the content of the aqueous acrylic resin (E) with respect to the metal surface treatment agent is 100 ppm to 30,000 ppm as the concentration of resin solids. ,
The content of the oxazoline group-containing polymer (F) with respect to the metal surface treatment agent is 50 ppm to 5,000 ppm as a solid content concentration,
And the sum total of the metal element conversion mass of the compound (A) which has the said zirconyl ([Zr = O] < ²⁺ >) structure, a vanadium compound (B), and a titanium fluoro complex compound (C), aqueous acrylic resin (E), and an oxazoline group The mass ratio of the containing polymer (F) to the solid content is (A + B + C) / (E + F) = 10/1 to 1/1,
The pH of the metal surface treatment agent is 3-6.
A method of treating the surface of a zinc-aluminum-magnesium alloy plated steel sheet with a metal surface treatment agent.   The zinc-aluminum according to claim 1, wherein the mass ratio of the solid content of the aqueous acrylic resin (E) and the oxazoline group-containing polymer (F) as the curing agent is E / F = 20/1 to 2/3. -The method of processing the surface of a magnesium alloy plating steel plate using a metal surface treating agent.   The zinc-aluminum according to claim 1 or 2, wherein a mass ratio of the organic phosphorus compound (Da) and the inorganic phosphorus compound (Db) is Da / Db = 5/1 to 1/2 in terms of phosphorus element. -The method of processing the surface of a magnesium alloy plating steel plate using a metal surface treating agent.   The zinc-aluminum-magnesium alloy plating layer is composed of Si: 0.001% by mass to 2.0% by mass, Ti: 0.001% by mass to 0.1% by mass, and B: 0.001% by mass to 0%. The surface of the zinc-aluminum-magnesium alloy plated steel sheet according to any one of claims 1 to 3, further comprising one or more of 0.045% by mass or less, is treated with a metal treating agent. Method.   The zinc-aluminum-magnesium alloy plated steel plate obtained by processing by the method of any one of Claims 1-4.