JPWO2009004684A1 - Aqueous surface treatment solution for galvanized steel sheet and galvanized steel sheet - Google Patents

Abstract

(A) ammonium zirconium carbonate, (B) a tetravalent vanadium compound, (C) an organic phosphonic acid represented by formula (I) or an ammonium salt thereof, (D) a glass transition temperature Tg calculated by formula (1) ( An anionic water-dispersible acrylic resin in which K) is converted to (° C.) is 0 to 60 ° C., and water, and the ratio in the total solid content of (D) is 1 to 60 mass%; The ratio when (B) is converted to V is 0.5 to 8% by mass in the total solid content, the mass ratio of V / (C) is 0.05 to 1.0, and (A) Zr / (V + (C)) mass% when converted to Zr is 0.1-6.0, and the pH is 7-10. Zinc-based galvanized steel sheet that has a coating on the surface. The zinc-based plated steel sheet is excellent in corrosion resistance, alkali resistance, appearance, condensation resistance, paintability, and grounding properties. The treatment liquid can be used in a treatment facility similar to the temporary antirust chromate treatment in the galvanizing production line.

Description

  The present invention relates to an aqueous surface treatment solution for galvanized steel sheet and a galvanized steel sheet.

  Currently, galvanized steel sheets are often galvanized on the steel sheet surface from the viewpoint of ensuring corrosion resistance. In addition, in order to improve corrosion resistance, alloyed galvanized steel sheets with various metals added are also used.

  In addition, places that are affected by acid rain and smoke, such as industrial areas, and places that are affected by incoming sea salt particles, such as coastal areas, are extremely harsh environments, and zinc-coated steel sheets with superior corrosion resistance. Is desired. Accordingly, hot-dip Zn-5% Al alloy-plated steel sheets, hot-dip zinc-Al-Mg alloy-plated steel sheets, hot-dip zinc-55% Al alloy-plated steel sheets, aluminum-plated steel sheets, and the like that have further improved the corrosion resistance of galvanized steel sheets have been proposed. Yes.

  However, even in these various zinc-based plated steel sheets, the corrosion resistance (white rust resistance) may be insufficient, and when used as a coated steel sheet, the adhesion to the paint is also insufficient. A treatment containing hexavalent chromium called temporary rust-proof chromate is generally applied to the surface of the galvanized steel sheet. This temporary rust-proof chromate treatment is carried out by spraying or showering a chromate treatment liquid mainly composed of chromic acid (hexavalent chromium) in a production line (CGL: Continuous Galvanizing Line) of a hot dip galvanized steel sheet. The mainstream method is to adjust the coating amount with an air squeeze and dry with an oven or the like (called spray ringer or shower ringer).

  In the case of chromate treatment, the surface treatment film is a thin film but has excellent corrosion resistance. However, there is a problem of containing a large amount of hexavalent chromium. In particular, recently, awareness of environmental issues has increased, and the chromate treatment is being abolished. At this time, a chromium-free surface treatment not only containing no harmful hexavalent chromium but also using no trivalent chromium is desired.

  Under such circumstances, many improvement studies have been conducted on surface treatment methods that do not use hexavalent chromium. For example, Patent Document 1 discloses a zinc-based coated steel obtained by applying and drying a composition containing an aqueous resin, water and sulfide ions, and Patent Document 2 includes water containing a compound having a specific bond, silica and a resin emulsion. A zinc-based plated steel sheet coated with a dispersion-type metal surface treatment composition is disclosed in Patent Document 3, in which a film is formed with an aqueous treatment liquid containing a specific aqueous dispersion resin, silica particles, and an organic inhibitor, conductivity, corrosion resistance, A metal surface treatment material that is considered to have excellent solvent resistance and paintability is disclosed in Patent Document 4 as a surface treatment composition containing a nonionic aqueous resin dispersion, hydrolyzable titanium, an organic phosphate compound, and a vanadium compound. A surface-treated metal plate treated with a material, which is said to be excellent in corrosion resistance and paintability, is further disclosed in Patent Document 5 as an ionomer resin and a water-soluble diester that reacts with carboxyl groups. Koniumu compound and / or water-dispersible anticorrosive coating composition containing a water-soluble titanium compound have been proposed. That is, these publications propose a method of directly coating the surface of the zinc-based plating layer with an organic film (resin film) containing no chromium.

  On the other hand, Patent Document 6 discloses a metal plate having a film containing a titanium compound and / or a zirconium compound, a phosphoric acid compound and a guanidine compound, which is excellent in corrosion resistance and alkali resistance, and Patent Document 7 discloses water-soluble phosphorus. A galvanized steel sheet that is surface-treated with a treatment agent containing an acid salt compound, a chelating agent, and a corrosion inhibitor and is said to have excellent corrosion resistance is disclosed in Patent Document 8 as a metal surface containing a vanadium compound and a metal compound such as zirconium. A surface-treated metal material that has a film formed of a treatment agent and is excellent in corrosion resistance, fingerprint resistance, and paintability is composed of a tetravalent vanadium compound, a Si compound, and a phosphate compound in Patent Document 9. There has been proposed a steel sheet having an excellent coating appearance, excellent corrosion resistance and electrical conductivity, and having a good coating appearance. These are coated with a chromium-free coating mainly composed of inorganic components, and it is said that the corrosion resistance can be further improved by using an aqueous resin in combination.

  However, in the above-described prior art, particularly the method of coating with an organic film cannot be said to have sufficient adhesion of the organic film to the zinc-based plating layer. There is a problem that it is easy to peel off at the interface.

Furthermore, in the joining of galvanized steel sheets, welding is often performed, and even a surface-treated steel sheet coated with a film needs to have conductivity and ensure weldability. Moreover, in home appliances, it is necessary to exhibit the grounding property necessary for the final product. For these reasons, the galvanized steel sheet is also required to have conductivity. However, in the conventional zinc-based plated steel sheet on which the resin film is formed, the required conductivity is not obtained because the film amount of 1 g / m ² or more is almost required to obtain corrosion resistance.

In addition, in the case of a hot dip galvanized steel sheet with a beautiful surface, when a film with a lot of inorganic components is formed, fine cracks are formed in the film, and the film appearance appears whitish (whitening) or rainbow interference colors appear. There is. In particular, when this whitening occurs, it is mistaken for white rust generated on the surface of the galvanized surface, and there is a problem that the commercial value decreases.

Furthermore, when the zinc-based plated steel sheet is stored, water droplets often occur on the steel sheet surface due to condensation. In the prior art, when the water droplets are dried, the water droplet traces may remain, resulting in a problem that the commercial value is lowered. However, no means for solving this problem has been proposed.

In addition, as described above, the temporary rust-proof chromate treatment is carried out by spraying the chromate treatment solution onto the galvanized steel sheet by spraying or showering, adjusting the coating amount with a roll or air squeeze, and drying in an oven. Is common. This surface treatment method is very simple and has high productivity. However, the conventional technology that does not use chromium that has been proposed so far is sometimes aqueous, and the active ingredient concentration (or solid content concentration) of the composition is 20 to 30% at most. That is, in order to obtain a coating amount of 1 g / m ² (about 1 μm) by applying and drying this, 4 to 5 g / m ² is necessary as the coating amount of the treatment liquid, and in order to control this, a roll There is a tendency to be limited to a coating method (particularly, a method called reverse coating, which is a method of applying a liquid by rotating a roll in the direction opposite to the sheet passing direction). For this reason, conventional facilities such as spray ringers and shower ringers cannot be used, and there is a problem that new capital investment is required in the galvanizing production line (CGL, EGL), but this problem has not been solved. .
JP-A-8-67834 JP-A-9-221595 Japanese Patent Laid-Open No. 2002-241956 JP 2004-238638 A JP 2005-15514 A JP 2004-2950 A JP 2002-155375 A JP 2002-30460 A JP 2005-48199 A

The present invention has been made under such circumstances, and its object is to provide excellent corrosion resistance, alkali resistance and appearance to galvanized steel sheets, as well as condensation resistance and paintability (coating adhesion). Another object of the present invention is to provide a water-based surface treatment liquid capable of imparting excellent properties in a well-balanced manner with respect to grounding properties, and a zinc-based plated steel sheet having a film derived from the water-based surface treatment liquid on the surface.
It is another object of the present invention to provide an aqueous surface treatment solution that can be applied and treated by a treatment method (shower ringer, spray ringer, etc.) that has been conventionally used in a galvanized steel sheet manufacturing facility.

The present inventors diligently studied to solve the above problems. As a result, the galvanized steel sheet containing the following components (A) to (D) and surface-treated with an aqueous treatment liquid in which the proportion of use between the components is appropriately adjusted has only excellent corrosion resistance, alkali resistance and appearance. In addition, the inventors have found that the film has excellent dew condensation resistance, coating film adhesion and electrical conductivity, and completed the present invention.
In the present invention, (A) ammonium zirconium carbonate, (B) a tetravalent vanadium compound, (C) an organic phosphonic acid represented by formula (I) or an ammonium salt thereof, (D) calculated by formula (1) It contains an anionic water-dispersible acrylic resin having a glass transition temperature Tg (° C.) converted from the glass transition temperature Tg (K) of 0 to 60 ° C. and water, and the total solid content of (D) (the total solid content is The proportion in the components (A) to (D) is 1 to 60% by mass, and the proportion when (B) is converted to V is the total solid content. The mass ratio is 0.5 to 8 mass%, the mass ratio of V / (C) is 0.05 to 1.0, and the mass ratio of Zr / (V + (C)) when (A) is converted to Zr. Is 0.1 to 6.0, and pH is 7 to 10. Aqueous treatment solution for galvanized steel sheet

(In the formula, i is an integer of 1 or more, Wi is a mass fraction of i homopolymer, and Tgi is Tg (K) of i homopolymer (generally referred to as FOX formula)).
About.

The aqueous processing solution preferably contains 0.5 to 20 g / kg of (E) guanidine carbonate.
The aqueous treatment liquid preferably also contains (F) nitrate ions in an amount of 0.5 to 50 g / kg.
The present invention also relates to a galvanized steel sheet having on its surface a coating obtained by applying and drying the aqueous surface treatment liquid.

  The zinc-based plated steel sheet surface-treated with the water-based surface treatment liquid of the present invention is excellent in corrosion resistance, alkali resistance, appearance, condensation resistance, paintability (coating film adhesion) and grounding properties. Furthermore, the treatment liquid of the present invention has an advantage that it can be used in a treatment facility similar to the conventional temporary rust-proof chromate treatment in the galvanizing production line (CGL).

The aqueous surface treatment liquid of the present invention (hereinafter sometimes simply referred to as a treatment liquid) contains ammonium zirconium carbonate as the component (A). Zirconium ammonium carbonate is most preferable among zirconium compounds because carbonic acid and ammonium are volatilized by drying, and the remaining zirconium is polymerized to form a hardly soluble film.

  The treatment liquid of the present invention contains a tetravalent vanadium compound as component (B). By containing the tetravalent vanadium compound in the treatment liquid, when the treatment liquid is applied to the surface of the galvanized steel sheet, a passive film is formed on the surface of the galvanized steel sheet, thereby improving the corrosion resistance of the galvanized steel sheet. Can be improved. Furthermore, when a film containing tetravalent vanadium is present, when a film defect occurs, the nearby tetravalent vanadium compound is dissolved and reduced to trivalent along with the corrosion (oxidation) of zinc. It can also be expected to suppress the corrosion. The tetravalent vanadium compound is not particularly limited. For example, vanadium oxysulfate (IV), vanadium oxychloride (IV), vanadium oxide (IV), vanadyl oxalate (IV), vanadium fluoride (IV), vanadium. Examples thereof include oxyacetylacetonate (IV). As the tetravalent vanadium compound, vanadium pentoxide, metavanadic acid and salts thereof reduced to tetravalent can also be used.

  The treatment liquid of the present invention contains an organic phosphonic acid represented by formula (I) or an ammonium salt thereof as component (C). The organic phosphonic acid or its ammonium salt is necessary for stably dissolving the tetravalent vanadium compound in the treatment liquid. Further, when the treatment liquid used in the present invention comes into contact with the galvanized steel sheet, the surface oxidation of the plating is performed. The effect of improving the adhesion between the film obtained by removing (etching) the film and subsequent drying, and the plating surface, and retaining the tetravalent vanadium compound in the film, and suppressing white rust Has the effect of exerting over a long period of time. That is, it is important that the compound has both a chelating effect and an etching effect, and there are other compounds having both such effects, but the organic phosphonic acid represented by the formula (I) or its ammonium salt is most preferable.

  As the component (D), the treatment liquid of the present invention is an anionic water-dispersible acrylic having a glass transition temperature Tg (° C.) of 0 to 60 ° C. converted from the glass transition temperature Tg (K) calculated by the formula (1). Contains resin. This Tg (° C.) is preferably 2 to 55 ° C., more preferably 5 to 50 ° C. If Tg (° C.) is less than 0 ° C., the required corrosion resistance cannot be obtained, and if it exceeds 60 ° C., the film cannot be formed (film formation failure), the necessary corrosion resistance cannot be obtained, and the film appearance becomes whitish. End up. The component (D) is a water-dispersible acrylic resin having an anionic property, but is preferably an acrylic resin that is stably dispersed in water rendered alkaline by ammonia. Regarding the water-dispersible acrylic resin, there is no particular limitation other than the above, for example, the emulsification method and the polymerization method are not limited, and if it has anionic property, it is emulsified using a nonionic surfactant. It may be a thing.

Next, the usage-amount of component (A)-(D) is described.
The ratio of component (D) in the total solid content is required to be 1 to 60% by mass, preferably 3 to 50% by mass, and more preferably 5 to 45% by mass. If it is less than 1% by mass, the amount of inorganic components becomes excessive, the film appearance becomes whitish, rainbow interference colors appear, and the corrosion resistance after processing tends to be inferior. Since alkalinity falls, it is not preferable.

  When the component (B) is converted to V, the proportion of V in the total solid content needs to be 0.5 to 8% by mass, preferably 0.7 to 6.0% by mass, It is more preferable that it is 1.0-5.0 mass%. If it is less than 0.5% by mass, the corrosion resistance is insufficient, and if it exceeds 8% by mass, the effect is saturated and more components are soluble in water, resulting in poor condensation resistance.

  The mass ratio of V / (C) representing the use ratio of V to component (C) when component (B) is converted to V must be 0.05 to 1.0, and 0.06 It is preferable that it is -0.8, and it is more preferable that it is 0.07-0.6. If it is less than 0.05, the amount of easily soluble components increases, and the alkali resistance and / or condensation resistance is lowered. On the other hand, if it exceeds 1.0, the condensation resistance also decreases, or the stability of the treatment liquid decreases.

  Zr / (V + (C)), which is a mass ratio of Vr when component (A) is converted to Zr and V and component (C) when component (B) is converted to V, is 0.1 to 6 0.0 is necessary, 0.2 to 5.5 is preferable, and 0.3 to 5.0 is more preferable. If it is less than 0.1, the alkali resistance and / or condensation resistance is inferior, and if it exceeds 6.0, the corrosion resistance itself is inferior.

  The treatment liquid of the present invention preferably contains (E) guanidine carbonate in addition to the components (A) to (D). The treatment liquid of the present invention contains ammonium zirconium carbonate as the component (A) and a tetravalent vanadium compound as the component (B). Zirconium ammonium carbonate polymerizes with the volatilization of carbonic acid and ammonium. For this reason, the viscosity of the treatment liquid gradually increases and eventually gels, which may not withstand long-term use. In addition, since vanadium in the tetravalent vanadium compound exists as a cation metal ion, in order to dissolve it at pH 7 to 10, the component (C) or other chelating agent is used, or ammonia or an amine compound. It is necessary to make this complex. Therefore, when guanidine carbonate is contained, carbonic acid can be replenished, and guanidine can replace ammonia to maintain the stability of the treatment liquid over a long period of time. The guanidine carbonate is preferably 0.5 to 20 g, more preferably 1 to 17 g, and even more preferably 1.5 to 15 g per kg of the treatment liquid. If it is less than 0.5 g, there is no effect, and if it exceeds 20 g, the effect is saturated, and the amount of guanidine remaining in the film increases, resulting in a decrease in condensation resistance and / or paintability.

  The treatment liquid of the present invention preferably contains (F) nitrate ions in addition to the components (A) to (D). Nitrate ions are particularly effective in suppressing a phenomenon called blackening. The addition amount is preferably 0.3 to 30 g, more preferably 0.5 to 20 g, and even more preferably 0.7 to 15 g as nitrate ions per kg of the treatment liquid. If it is less than 0.3 g, the blackening suppressing effect cannot be obtained, and if it exceeds 30 g, the remaining amount in the film increases, and the paintability and / or condensation resistance decreases. Non-limiting examples of nitrate ion sources include nitric acid, ammonium salts of nitric acid, nitric acid salts with metals such as Co, Ni, Zn, Fe, Ti, Zr, Mg, and Ca.

  In addition to the components (A) to (D), the treatment liquid of the present invention can contain (G) an antifoaming agent. Although it does not specifically limit as an antifoamer, The thing which emulsified mineral oil, fatty acid, silicone, etc. stably, and the thing of a water-soluble activator type can be used. If the addition amount of the antifoaming agent is small, the defoaming property cannot be obtained. If too much is added, the paintability is inferior. Although it does not specifically limit, 0.1-3.0g per kg of process liquid is suitable.

  The treatment liquid of the present invention may also contain a pentavalent vanadium compound, thereby improving the corrosion resistance. The addition amount of the pentavalent vanadium compound is preferably 0.01 to 40 g, more preferably 0.03 to 30 g, and more preferably 0.05 to 25 g per kg of the treatment liquid in terms of V. Examples of the pentavalent vanadium compound include metavanadic acid, vanadic acid and salts thereof, and vanadium oxide (V).

The treatment liquid of the present invention may contain a fluorine compound. In particular, in a hot dip galvanized steel sheet having a thick surface oxide film, when the etching property is increased by a fluorine compound, the reaction layer (passive layer) with the surface of the material becomes thick, and the corrosion resistance tends to be improved. However, in the case of adding a fluorine compound, the amount of Zn and Fe mixed in the processing liquid increases due to the increase in etching property, and the stability of the processing liquid is lowered. Since there is a problem that it is necessary, it is preferable to set the range in consideration of these. Although not limited, the content of the fluorine compound is preferably 0.05 to 10 g, more preferably 0.07 to 7.0 g, and even more preferably 0.1 to 5.0 g as fluorine in 1 kg of the aqueous treatment liquid. preferable. Examples of the fluorine compound include ammonium fluoride, ammonium silicofluoride, ammonium titanium fluoride, and zircon ammonium fluoride.

The treatment liquid of the present invention may contain a silicon-based material such as liquid phase silica, gas phase silica, silane coupling agent, alkali metal silicate, and water glass. Liquid phase silica is formed by removing metal ions of silicate such as sodium silicate, potassium silicate and lithium silicate by ion exchange, and is also called colloidal silica. Colloidal silica may include those obtained by dispersing gas phase silica in water. Vapor phase silica is produced by burning and oxidizing silicon chloride in air. By including a silicon-based substance, the corrosion resistance and / or paintability tends to be improved. The amount of silicon-based material used is preferably 0.03 to 5.0 as Si / Zr, which is the mass ratio of Si when converted to Si and Zr when component (A) is converted to Zr. 0.05 to 3.0 is more preferable, and 0.08 to 2.0 is even more preferable. If it is less than 0.03, the effect of addition is not observed, and if it exceeds 5.0, it becomes a hard and brittle film, or the corrosion resistance tends to decrease.

  As liquid phase silica, Snowtex C, Snowtex CS, Snowtex CM, Snowtex O, Snowtex OS, Snowtex OM, Snowtex NS, Snowtex N, Snowtex NM, Snowtex S, Snowtex 20, Snow Tex 30, Snowtex 40, Adelite AT-20N, Adelite AT-20A, Adelite AT-20Q, etc. In addition, Snowtex UP, Snowtex OUP, Snowtex PS-S processed into a special chain shape , Snowtex PS-SO, Snowtex PS-M, Snowtex PS-MO, Snowtex PS-L, Snowtex PS-LO, and the like. Examples of fine-particle silica called vapor phase silica include Aerosil 50, Aerosil 130, Aerosil 200, Aerosil 300, Aerosil 380, Aerosil TT600, Aerosil MOX80, and Aerosil MOX170, and those dispersed in water can also be used.

For silane coupling, trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane, methyltriethoxysilane, methyldimethoxysilane, methyldiethoxysilane, dimethylethoxysilane, cyclohexylmethyldimethoxysilane , N-hexyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, isobutyltrimethoxysilane, vinylmethoxysilane, vinylethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, β- (3,4 epoxy cyclohexyl) Ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-g Sidoxypropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyl Triethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-acryloxypropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetra Examples thereof include sulfide, γ-triethoxycysilyl-N- (1,3-dimethyl-butylidene) propylamine, N- (vinylbenzylamine) -β-aminoethyl-γ-aminopropyltrimethoxysilane. Particularly preferred are aminosilanes and epoxysilanes having amino groups and epoxy groups which are functional groups active in water.
Examples of the alkali metal silicate include sodium silicate, potassium silicate, and lithium silicate. Water glass is a concentrated aqueous solution of alkali metal silicate.

The treatment liquid of the present invention may contain a lubricant, which is effective for improving the lubricity of the surface treatment film to prevent scratches and reducing damage to the galvanized steel sheet during processing. It is. Examples of the lubricant include solid lubricants such as polyethylene wax, oxidized polyethylene wax, oxidized polypropylene wax, carnauba wax, paraffin wax, montan wax, and Teflon (registered trademark). When blending a lubricant, the blending amount is preferably 0.5 to 50 g, more preferably 1 to 40 g, and even more preferably 3 to 30 g in 1 kg of the treatment liquid. If it exceeds 50 g, not only can it not be stably added, but the effect of the present invention may be inhibited.

  Each of the above-described components that can be contained or contained in the treatment liquid of the present invention can be used alone or in combination of two or more.

  The pH of the treatment liquid of the present invention is preferably 7 to 10, more preferably 7.5 to 9.5, and even more preferably 7.8 to 9.2. If the pH is less than 7, the component (A) ammonium zirconium carbonate cannot be dissolved stably, and the stability of the treatment liquid becomes poor, and if it exceeds 10, the ammonia odor becomes remarkable and the workability becomes poor. For adjusting the pH, it is preferable to use ammonia, guanidine carbonate, or carbonic acid.

  The zinc-based plated steel sheet to which the treatment liquid of the present invention is applied includes a hot-dip galvanized steel sheet (GI), an alloyed hot-dip galvanized steel sheet (GA) alloyed with this, and the base material Fe is zinc by annealing. Galvanized Zn-5% Al alloy plated steel sheet (GF), hot dip zinc-55% aluminum alloy plated steel sheet (GL), electrogalvanized steel sheet (EG), electrogalvanized- Ni alloy plated steel sheet (Zn—Ni) and the like can be mentioned.

  The treatment liquid of the present invention is applied by applying to a galvanized steel sheet and drying, but the application and drying methods are not particularly limited, and ordinary methods can be used. Examples of the application method include a method of pouring a treatment liquid by spraying or showering, a method of adjusting the application amount by roll squeezing or air squeezing, a roll coating method, a curtain flow coating method, etc., and a drying method as a hot air method , Induction heater method, near infrared method and the like. The drying temperature is not particularly limited as long as it can evaporate the water in the treatment liquid, but is preferably 40 to 250 ° C, more preferably 50 to 230 ° C, and more preferably 60 to 200 ° C as the highest plate temperature (PMT) of the galvanized steel sheet. Is even more preferable.

Preferably the amount of dry film to be formed is 0.05~0.8g / ^{m 2,} more preferably from ^{0.1~0.7g / m 2, 0.15~0.6g / m} 2 Is more preferable. If it is less than 0.05 g / m ² , the treatment liquid of the present invention cannot be uniformly applied to the surface of the steel sheet, and various target characteristics such as workability, corrosion resistance, and paintability cannot be exhibited in a balanced manner. On the other hand, if it exceeds 0.8 g / m ² , the appearance becomes whitish and the paintability becomes inferior. On the other hand, if it exceeds 0.8 g / m ² , the conductivity and weldability will be deteriorated. Furthermore, in the press working, the amount of peeling of the film will increase, resulting in trouble with press molding, as well as the production cost. Tend to be higher.

In the present invention, by using the above-mentioned specific components in a specific ratio, it is possible to obtain a surface-treated galvanized steel sheet excellent in target corrosion resistance, alkali resistance, appearance, condensation resistance, paintability and grounding properties. The obtained surface-treated zinc-based plated steel sheet can be used as a material having excellent performance in various fields such as architecture, electricity, and automobiles.

The mechanism / reason that brings about the effect of the present invention is presumed as follows. However, the mechanism / reason is only a presumption and does not affect the scope or patentability of the present invention.
In the treatment liquid of the present invention, the anionic water-dispersible acrylic resin as the component (D) and zirconium in the component (A) are components that form a film skeleton, and once dried, they do not dissolve in water again. It is considered to exert a barrier effect. On the other hand, the tetravalent vanadium compound of component (B) and the organic phosphonic acid of component (C) are uniformly dispersed in the film and are present in a form that is more soluble in water. It is thought to work as an inhibitor that improves the corrosion resistance of the steel sheet.

  It is believed that the corrosion resistance according to the present invention is brought about by a barrier effect and an inhibitor effect. However, regarding alkali resistance, since the acrylic resin itself that forms the film skeleton is weak against alkali, if there are too many resin components, it becomes difficult to exhibit alkali resistance. On the other hand, if there are too many inorganic components, the film tends to be hard and brittle, so cracks are likely to occur in the film, the appearance of a beautiful galvanized steel sheet becomes whitish, and the interference color that is iridescent is applied. It is seen and the corrosion resistance and appearance quality are impaired. In the present invention, a tetravalent vanadium compound is considered to be most effective as an inhibitor.

  Moreover, since the film formed as described above is composed of a component that is not soluble in water and a component that is easily soluble, it is necessary to appropriately adjust the existence ratio. In other words, even if the film is composed of only insoluble components, sufficient corrosion resistance cannot be obtained.Conversely, if many components that are easily soluble are used, dew marks will become noticeable during condensation, or the components will be washed away by alkaline degreasing. Therefore, it becomes difficult to obtain subsequent corrosion resistance.

As described above, the amount of the dry film by the treatment agent of the present invention may be 0.05 to 0.80 g / m ² , and the desired performance can be obtained with a film amount generally smaller than that of the prior art. As a processing liquid of this invention, the thing of 10-20 mass% by solid content concentration can be prepared stably. The application amount in the spray or shower ringer method is usually about 1 to 3 g / m ² , and when a treatment liquid of 10 to 20% by mass is applied by these methods, the drying amount is about 0.1 to 0.6 g / m ^2. It is possible to obtain a film, and it is sufficient that the drying is enough to evaporate the water. In other words, the application and drying of the treatment liquid of the present invention does not require expensive and difficult management equipment such as a roll coater, and it is possible to use an actual production line (CGL, EGL) with simple equipment such as spray equipment and shower ringer equipment. ) Can be applied and dried without reducing the productivity. For example, the treatment liquid of the present invention can be used in a treatment facility similar to a conventional temporary rust-proof chromate treatment in a galvanizing production line (CGL).

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples. However, these examples are merely illustrative and the scope of the present invention is not limited by these examples.

Production of surface-treated galvanized steel sheet as a test plate In the following examples, galvanized steel sheets (GI, GA, EG: 200 mm × 300 mm each and a plate thickness of 0.8 mm were prepared), The sample was washed with alkali to remove rust-preventing oil, washed with water to remove degreasing liquid, then rinsed with pure water, and then dried with warm air as a test plate. A surface-treated galvanized steel sheet having a film formed on the surface with various aqueous treatment liquids was subjected to an evaluation test described later as a test plate.

Aqueous treating solution Components used <br/> component (A): Commercially available ammonium zirconium carbonate (20% by mass as ZrO ₂₎
Ingredient (B)
B-1: Vanadyl oxalate (IV)
B-2: Vanadium oxysulfate (IV)
B-3: Vanadium oxyacetylacetonate (IV)
Component (C): Commercially available organic phosphonic acid (manufactured by Daido Pharmaceutical Co., Ltd., Phoslin 303)

Ingredient (D)
The following water-dispersible acrylic resin synthesized by emulsion polymerization using an anionic or nonionic surfactant was used (the one using a nonionic surfactant also contains an acrylic acid as the acrylic monomer contains an anionic acid). Will be sex). D-1, 2, 5 and 6 contain 5 parts by mass of an anionic surfactant based on 100 parts by mass of the resin, and D-3, 4 and 7 show a nonionic surfactant based on 100 parts by mass of the resin. And emulsified with a blend of 15 parts by mass. In addition, ammonia is used for pH adjustment, and all pH is adjusted to 8.5. Moreover, all solid content is 20 mass%.
D-1: Tg5 ° C. (BA / AA / MMA / 2-HEMA / St = 49/3/25/3/20: mass ratio) Example D-2: Tg15 ° C. (BA / AA / MMA / St = 43) / 3/29/25: weight ratio) Example D-3: Tg 25 ° C. (BA / AA / MMA / St / AN = 37/3/30/10/20: weight ratio) Example D-4: Tg 36 ° C. (BA / AA / MMA / 2-HEMA = 30/3/64/3: weight ratio) Example D-5: Tg 45 ° C. (BA / AA / MMA / St = 26/3/69/2: weight ratio) Example D-6: Tg-10 ° C. (BA / AA / 2-HEMA / St = 60/4/2/34: weight ratio) Comparative Example D-7: Tg 70 ° C. (BA / AA / MMA / 2-HEMA) / St = 13/3/59/5/20: weight ratio) Comparative Example In the above, BA is butyl acrylate (Ag: acrylic acid (Tg: 108 ° C), MMA: methyl methacrylate (Tg: 105 ° C), 2-HEMA: 2-hydroxyethyl methacrylate (Tg: 55 ° C), AN: acrylonitrile (Tg: 105 ° C.), St represents styrene (Tg: 105 ° C.).

Component (E): Commercially available guanidine carbonate (reagent)
Ingredient (F): Commercially available ammonium nitrate (reagent)
Ingredient (G): The following commercially available antifoaming agent G-1: SN deformer JK (manufactured by San Nopco)
G-2: SN deformer 430 (manufactured by San Nopco)
G-3: Surfynol 485 (manufactured by Nissin Chemical Industry Co., Ltd.)

Various Evaluation Tests and Evaluation Criteria (1) Corrosion Resistance A salt spray test specified in JIS Z2371 was performed on a test piece in which a surface-treated zinc-based plated steel sheet was cut into a size of 70 mm x 150 mm and the back side and end were sealed with cellophane tape. The time until white rust was generated by 5% (area ratio) was evaluated. The evaluation criteria at this time are shown below.
A: 120 hours or more until 5% of white rust occurs: 48 hours or more, less than 120 hours until 5% of white rust occurs: 24 hours or more, less than 48 hours until 5% of white rust occurs: 24: Up to 5% of white rust occurs Less than time On the other hand, the evaluation criteria regarding GA are shown below.
◎: 48% or more until white rust 5% occurrence ○: 24 hours or more until white rust occurrence 5%, less than 48 hours △: 12% or more until white rust occurrence 5%, less than 24 hours ×: 12% until white rust occurrence 5% Less than an hour

(2) Alkali resistance A surface-treated zinc-based plated steel sheet was cut into a size of 70 mm x 150 mm and subjected to degreasing called medium alkaline degreasing (Nippon Parkerizing Co., Ltd., Pulclean N364S, 20 g / L, 60 ° C, after 2 minutes spraying) The test piece with the back side and the end sealed with cellophane tape was subjected to the salt spray test specified in JIS Z2371, and white rust was generated by 5% (area ratio). It was evaluated by the time until. The evaluation criteria at this time are the same as in the case of corrosion resistance.
(3) Appearance The surface appearance of a test piece obtained by cutting a surface-treated zinc-based plated steel sheet into a size of 70 mm × 150 mm was evaluated. The evaluation criteria at this time are shown below.
◎: No whitening or interference color ○: Very thin whitening and interference color △: Whitening or interference color ×: Significant whitening or interference color

(4) Condensation resistance A test piece obtained by cutting a surface-treated zinc-based plated steel sheet into a size of 70 mm × 150 mm is left in a freezer at −5 ° C. for 1 hour, and then placed in a high temperature and humidity chamber (50 ° C., humidity 95%) for 2 hours. I put it in. When placing the test piece in the high temperature and humidity layer, it was confirmed that water droplets (condensation) were generated on the surface of the test piece (if it could not be confirmed, put it in the freezer for 1 hour and then put it in the high temperature and humidity layer) . It was taken out from the high temperature and humidity chamber, and it was confirmed that the surface of the test piece was dry (if it was not dry, it was left as it was and waited until the surface was dry). The water droplet (condensation) trace on the surface of the test piece was visually evaluated. The evaluation criteria at this time are shown below.
◎: Drop marks are not visible ○: Drop marks are very slightly visible △: Drop marks are visible x: Drop marks are remarkably visible

(5) Paintability A melamine-based paint [“Amirac # 1000” manufactured by Kansai Paint Co., Ltd.] was applied to a test piece obtained by cutting a surface-treated zinc-based plated steel sheet into a size of 70 mm × 150 mm, and then baked at 160 ° C. to obtain a coating thickness of 20 μm. The coating film was formed. After the obtained coating piece was immersed in boiling water for 1 hour, 100 squares of 1 mm square grids were put into the coating film after 1 hour, and the tape was peeled off to measure the residual rate. Further, similarly, a portion having 100 square grids was extruded 5 mm by an Erichsen extruder, and then evaluated by peeling the tape. The evaluation criteria at this time are shown below.
A: Remaining rate 91-100%
○: Remaining rate 71-90%
Δ: Remaining rate 51-70%
X: Residual rate 0 to 50%

(6) Grounding property With respect to the surface-treated zinc-based plated steel sheet, interlayer resistance (interlayer electrical resistance) was measured with an interlayer resistance measuring machine. Evaluation was made according to the following criteria. The interlayer resistance measurement is performed by piercing the surface of the surface-treated surface until it reaches the zinc-plated steel sheet, applying an electrode to the surface-treated surface, and energizing to measure the electrical resistance value. Therefore, “interlayer resistance” means the electrical resistance between the front surface and the back surface of the formed film.
◎: Less than 1Ω ○: 1Ω or more, less than 2Ω △: 2Ω or more, less than 3Ω ×: 3Ω or more (7) Blackening resistance Surface-treated galvanized steel sheet is cut into 70mm x 150mm size to make a test piece. The surface-treated surfaces of the test pieces were put together, wrapped with kraft paper with one side coated with vinyl, and placed in a thermo-hygrostat with 50 ° C. and 98% humidity. At this time, a 1 kg weight was placed on the packed test piece in order to fix and adhere the test piece. This state was maintained for 10 days, taken out, and the appearance of the surface-treated surface of the test piece was visually evaluated according to the following criteria.
◎: No change in appearance ○: Slight discoloration is observed △: Light black discoloration or local black discoloration is observed x: Obviously black discoloration is observed

Example 1
No. in Table 1 below. For No. 1, 6.2 g of B-1 (vanadyl oxalate (IV)) was dissolved in pure water and 22 g of the organic phosphonic acid (C), and the pH was raised to 8 with 28% by mass ammonia water. Next, 213 g of ammonium zirconium carbonate (A) was added, 175 g of D-1 water-dispersible acrylic resin was added and dissolved by stirring, 1 g of G-1 was added as an antifoaming agent, and pure water was added. The total amount was 1 kg. The aqueous processing solution has a pH of 9.0 and a solid content of 10% by mass. Other aqueous treatment liquids having the composition shown in Table 1 were prepared in the same procedure (all solid contents were adjusted to 10% by mass). At this time, other than water-dispersible acrylic resin, No. The same ingredients as 1 were used.

Here, the above-mentioned No. 1 and no. Preparations were also prepared by adding 3 g of (E) guanidine carbonate to the treatment liquid of No. 7, and taking 100 g of the treatment liquid with and without addition of (E) in a 100 ml glass beaker, respectively, at 40 ° C. When the stability of the processing liquid was confirmed while stirring to the extent that vortexing was possible with the set water bath stirrer, the processing liquid without adding (E) tended to increase in viscosity over time, After 24 hours, it gelled. In contrast, the treatment liquid to which (E) was added showed no change even after 24 hours. That is, it has been found that the addition of (E) improves the stability of the treatment liquid and can be used for a long time.

In the aqueous treatment liquid of the present invention, (A) and (D) are alkaline liquids made of ammonia, and cannot be stably dissolved or dispersed below pH 7. For this reason, when a liquid having a pH of less than 7 is mixed with (A) or (D), the liquid is gelled or aggregates are formed, and an aqueous treatment liquid cannot be stably obtained. That is, an aqueous processing solution having a pH of less than 7 could not be obtained. For this reason, all aqueous processing solutions were finally adjusted to have a pH of 7 or more.

Pour each aqueous treatment solution in Table 1 over the surface of the zinc-based plated steel sheet (GI), wet the entire surface, and then remove excess aqueous treatment solution with a roll drawing machine that combines two flat rubber rolls. It heat-dried at the reached plate temperature of 60 ° C. to obtain a surface-treated zinc-based plated steel sheet having a coating amount of the coating shown in Table 1. However, the coating amount less than 0.2 g / m ² was applied after dilution with pure water, and the coating amount exceeding 0.5 g / m ² was subjected to # 4 bar coating. Table 1 shows the evaluation results of the surface-treated galvanized steel sheet thus obtained.
In addition, the aqueous treatment liquids with numbers above the horizontal double lines are so-called examples (except for No. 36N4 in Table 5), and the aqueous treatment liquids with numbers below the horizontal double lines are so-called comparative examples ( The same applies to other examples). For example, no. No. 11 does not use (D) (anionic water-dispersible acrylic resin). In No. 13, the Tg (° C.) of (D) is outside the range defined in the present invention.

Example 2
No. in Table 2 For No. 17, 3.3 g of B-1 (vanadyl oxalate (IV)) was dissolved in pure water and 15 g of organic phosphonic acid (C), and the pH was raised to 8 with 28% by mass aqueous ammonia. Next, 224 g of ammonium zirconium carbonate (A) was added, 200 g of water-dispersible acrylic resin D-1 was further added, 5 g of guanidine carbonate (E) was further added, and dissolved by stirring. -2 was added, and water was added to make 1 kg. The aqueous processing solution had a pH of 9.5 and a solid content of 10% by mass. Other aqueous treatment liquids having the composition shown in Table 2 were prepared in the same procedure (all dry solid contents were adjusted to 10% by mass). At this time, each component is No. The same thing as 17 is used, and (E) and G-2 are No. The same amount of addition as 17.

  Pour each aqueous treatment liquid prepared above onto the surface of the zinc-based plated steel sheet (GI), wet the entire surface, then remove excess aqueous treatment liquid with a roll squeezer combined with two flat rubber rolls, A surface-treated zinc-based plated steel sheet was obtained by heating and drying at a maximum plate temperature of 80 ° C. Table 2 shows the evaluation results of the surface-treated galvanized steel sheet thus obtained.

Example 3
No. in Table 3 For No. 23, 6.4 g of B-2 (vanadium oxysulfate (IV)) was dissolved in pure water and 33 g of organic phosphonic acid (C), and the pH was raised to 8 with 28% by mass ammonia water. Next, 179 g of ammonium zirconium carbonate (A) was added, 175 g of water-dispersible acrylic resin D-1 was further added, 3 g of guanidine carbonate (E) was further added, and dissolved by stirring. Further, as an antifoaming agent, 1 g of G-3 was added, and water was added to make 1 kg. The pH of this aqueous processing solution was 8.6, and the solid content was 10% by mass. Other aqueous treatment liquids having the composition shown in Table 3 were prepared in the same procedure (all dry solid contents were adjusted to 10% by mass). At this time, each component is No. 23, and (E) and G-3 are respectively No. 23 and No. 23. The addition amount was the same as 23.

Pour each aqueous treatment liquid prepared above onto the surface of the surface-treated zinc-based plated steel sheet (GI), wet the entire surface, and then remove the excess aqueous treatment liquid with a roll squeezer that combines two flat rubber rolls. And it heat-dried at the highest plate | board temperature of 120 degreeC, and obtained the surface treatment zinc-plated steel plate. Table 3 shows the evaluation results of the surface-treated galvanized steel sheet thus obtained.

Example 4
No. in Table 4 For No. 29, 16.8 g of B-3 (oxyvanadium acetylacetonate (IV)) was dissolved in 35 g of the organic phosphonic acid of (C), and the pH was raised to 8 with 28% by mass aqueous ammonia. Next, 121 g of ammonium zirconium carbonate (A) was added, 175 g of water-dispersible acrylic resin D-1 was further added, and 3 g of guanidine carbonate (E) was further added, dissolved by stirring, and further used as an antifoaming agent. 0.5 g of each of G-1 and G-3 was added, and water was added to make the total amount to 1 kg. The aqueous processing solution had a pH of 7.5 and a solid content of 10% by mass. Other aqueous processing liquids having the composition shown in Table 4 were prepared in the same procedure (all dry solid contents were adjusted to 10% by mass). At this time, each component is No. No. 29 is used, and (E) and (G) are No. The addition amount was the same as 29.

Pour each aqueous treatment liquid prepared above onto the surface of the zinc-based plated steel sheet (EG), wet the entire surface, and then remove excess aqueous treatment liquid with a roll squeezer combined with two flat rubber rolls, A surface-treated galvanized steel sheet was obtained by heating and drying at a maximum temperature of 120 ° C. Table 4 shows the evaluation results of the surface-treated galvanized steel sheet thus obtained.

Example 5
No. in Table 5 The aqueous treatment solutions 36, 37, 38, 39, 40, 42 and 43 are No. 4 in Table 4. It is the same as each of the aqueous treatment liquids 29 to 35. No. N added after the symbol indicates that (F) ammonium nitrate was added. This means that N and N1 were added as 5 g, N2 as 10 g, N3 as 30 g, and N4 as 60 g / kg as nitrate ions.

  Pour each aqueous treatment liquid in Table 5 onto the surface of the zinc-based plated steel sheet (GI), wet the entire surface, and then remove excess aqueous treatment liquid with a roll drawing machine that combines two flat rubber rolls. A surface-treated zinc-based plated steel sheet was obtained by heating and drying at an ultimate sheet temperature of 70 ° C. Table 5 shows the evaluation results of the surface-treated galvanized steel sheet thus obtained.

Example 6
No. in Table 6 The water-based treatment liquids of 45 to 60 are No. 1 in Table 1. It is the same as 1-16 aqueous processing liquid. No. 52 and no. No. 57 was obtained by adding 3 g each of ammonium fluoride fluoride as F to the aqueous processing solution No. 57. 52F and No. 57F.

  Pour each aqueous treatment solution in Table 6 onto the surface of the galvanized steel sheet (GA), wet the entire surface, and then remove the excess aqueous treatment solution with a roll drawing machine that combines two flat rubber rolls. A surface-treated galvanized steel sheet was obtained by heating and drying at a plate temperature of 70 ° C. Table 6 shows the evaluation results of the surface-treated galvanized steel sheet thus obtained.

As is clear from these results, the surface-treated galvanized steel sheet treated with an aqueous treatment liquid using a specific component specified in the present invention in a specific ratio has good corrosion resistance and alkali resistance, and has an appearance, Excellent dew condensation resistance, paintability (coating adhesion) and grounding properties.

Claims (4)

(A) ammonium zirconium carbonate, (B) tetravalent vanadium compound, (C) organic phosphonic acid represented by formula (I) or an ammonium salt thereof, (D) glass transition temperature Tg calculated by formula (1) ( An anionic water-dispersible acrylic resin having a glass transition temperature Tg (° C.) in terms of K) of 0 to 60 ° C. and water, and the total solid content of (D) (the total solid content is from component (A) to (D) refers to the total of each solid content) is 1 to 60% by mass, and the ratio when (B) is converted to V is 0.5 to 8 in the total solid content. The mass ratio of V / (C) is 0.05 to 1.0, and the mass ratio of Zr / (V + (C)) is 0.1 to 0.1 when (A) is converted to Zr. An aqueous treatment solution for galvanized steel sheet having a pH of 6.0 and a pH of 7-10.
(In the formula, i is an integer of 1 or more, Wi is a mass fraction of i homopolymer, and Tgi is Tg (K) of i homopolymer (generally referred to as FOX formula).   (E) The aqueous processing liquid of Claim 1 which contains 0.5-20 g / kg of guanidine carbonate with respect to this aqueous processing liquid.   (F) The aqueous processing liquid of Claim 1 or 2 which contains 0.5-50 g / kg of nitrate ions with respect to this aqueous processing liquid.   A zinc-based galvanized steel sheet having on its surface a coating obtained by applying and drying the aqueous processing solution according to any one of claims 1 to 3.