CN101688309A - Aqueous fluid for surface treatment of zinc-plated steel sheets and zinc-plated steel sheets - Google Patents

Abstract

The present invention provides an aqueous treatment liquid for galvanized steel sheet and a galvanized steel sheet with a film formed by the treatment liquid on the surface, wherein the aqueous treatment liquid contains: (A) ammonium zirconium carbonate, (B) 4-valent vanadium compound, ( C) the organic phosphonic acid or its ammonium salt shown in formula (I), (D) the glass transition temperature Tg (°C) converted from the glass transition temperature Tg (K) calculated according to the mathematical formula (1) is 0 Anionic water-dispersible acrylic resin and water at ~60°C, and the ratio of (D) in the total solid content is 1 to 60% by mass, and the ratio of (B) in the total solid content is 0.5 to 0.5% in terms of V. 8% by mass, the mass ratio of V/(C) is 0.05-1.0, the mass ratio of Zr/(V+(C)) after converting (A) into Zr is 0.1-6.0, and the pH is 7-10. The galvanized steel sheet is excellent in corrosion resistance, alkali resistance, appearance, anti-condensation property, paintability and grounding property. This treatment solution can be used in the same treatment equipment as that used in the temporary anti-rust chromate treatment in the galvanizing line.

Description

Water-based surface treatment liquid for galvanized steel sheet and galvanized steel sheet

technical field

The invention relates to an aqueous surface treatment liquid for galvanized steel sheets and galvanized steel sheets.

Background technique

At present, from the viewpoint of ensuring corrosion resistance, the steel sheet surface of a galvanized steel sheet is often galvanized. In addition, in order to improve corrosion resistance, alloyed galvanized steel sheets to which various metals are added are also used.

In addition, places affected by acid rain and soot such as industrial areas or places affected by flying sea salt particles such as coastal areas have very harsh environments, and galvanized steel sheets with better corrosion resistance are desired. Therefore, hot-dip Zn-5%Al alloy steel sheets, hot-dip galvanized-Al-Mg alloy steel sheets, hot-dip galvanized-55%Al alloy steel sheets, aluminum-coated steel sheets, and hot-dip galvanized-55%Al alloy steel sheets with further improved corrosion resistance of galvanized steel sheets have also been proposed. steel plate etc.

However, even the various galvanized steel sheets obtained in this way may not have sufficient corrosion resistance (white rust resistance) and may not have sufficient adhesion to paint when used as a painted steel sheet. Therefore, as a countermeasure , The surface of galvanized steel sheet is usually treated with hexavalent chromium called temporary anti-rust chromate treatment. It is the mainstream to carry out the temporary anti-rust chromate treatment in the following method: In the hot-dip galvanized steel sheet production line (CGL: Continuous Galvanizing Line, continuous galvanizing line), spray with chromic acid (6 Chromate treatment liquid with chromium valence) as the main component, adjust the coating amount by using roller or air throttling device, and dry it with oven (called spray wringer, shower wringer) )).

In the case of chromate treatment, although the surface treatment film is a thin film, it is excellent in corrosion resistance. However, there is a problem that a large amount of hexavalent chromium is contained. In particular, the awareness of environmental issues has recently increased, and the direction is to abolish chromate treatment. At this time, a chromium-free surface treatment that does not contain not only harmful hexavalent chromium but also does not use trivalent chromium is desired.

Under such circumstances, many improvements have been made to surface treatment methods that do not use hexavalent chromium. For example, Patent Document 1 proposes a zinc-based coated steel obtained by coating and drying a composition containing an aqueous resin, water, and sulfide ions, and Patent Document 2 proposes a compound containing a specific bond, A galvanized steel sheet coated with a water-dispersed metal surface treatment composition of silica and resin emulsion. Patent Document 3 proposes to use an aqueous treatment solution containing a specific aqueous dispersion resin, silica particles, and an organic corrosion inhibitor. Film, conductivity, corrosion resistance, solvent resistance and paintability are excellent metal surface treatment materials, proposed in Patent Document 4 with non-ionic aqueous resin dispersion, hydrolyzable titanium, organic phosphoric acid compound and vanadium A surface-treated metal sheet obtained by treating a metal material with a surface treatment composition of a chemical compound, which is excellent in corrosion resistance and paintability, and Patent Document 5 proposes a water-soluble zirconium containing an ionomer resin and a carboxyl group. A water-dispersible antirust coating composition of a compound and/or a water-soluble titanium compound. That is, these gazettes propose a method of directly covering the surface of the galvanized layer with a chromium-free organic film (resin film).

On the other hand, Patent Document 6 proposes a metal plate having a film containing a titanium compound and/or a zirconium compound, a phosphoric acid compound, and a guanidine compound, and having excellent corrosion resistance and alkali resistance, and Patent Document 7 proposes a metal plate containing a water-soluble A galvanized steel sheet with excellent corrosion resistance that has been surface-treated with phosphate compounds, chelating agents, and anti-corrosion agents. Patent Document 8 proposes a surface-treated metal material that has a film formed by a metal surface treatment agent containing a metal compound such as a vanadium compound and a metal compound such as zirconium, and is excellent in corrosion resistance, fingerprint resistance, and paintability. A steel sheet having a coating composed of a tetravalent vanadium compound, a Si compound, and a phosphoric acid compound, excellent in corrosion resistance and electrical conductivity, and having a good coating appearance has been obtained. These are all materials coated with a chromium-free coating mainly composed of inorganic components, and it is considered that the corrosion resistance can be further improved by using a water-based resin in combination.

However, in the above-mentioned prior art, especially in the method of coating with an organic film, it cannot be said that the adhesion of the organic film to the galvanized layer is sufficient. The problem of easy peeling at the interface with the plating layer.

In addition, welding is often performed in joining galvanized steel sheets, and the surface-treated steel sheet coated with a film needs to have electrical conductivity to ensure weldability. In addition, in home appliances, it is necessary to exhibit the required grounding property as a finished product. In view of the above, the above-mentioned galvanized steel sheet is also required to have electrical conductivity. However, most of the galvanized steel sheets on which the resin coating has been formed so far require a coating amount of 1 g/m ² or more in order to obtain corrosion resistance, and thus the desired electrical conductivity cannot be obtained.

In addition, in the prior art, when the surface is a hot-dip galvanized steel sheet with a beautiful surface, if a film with many inorganic components is formed, fine cracks will occur on the film, and the appearance of the film will appear whitish (whitening), or the appearance of the film will appear white. to the problem of iridescent interference colors. In particular, when this whitening occurs, the illusion of white rusting on the surface of the galvanized layer is caused, and there is a problem that the commercial value is lowered.

In addition, when the galvanized steel sheet is stored, water droplets often occur on the surface of the steel sheet due to condensation. In the prior art, when the water droplets are dried, traces of the water droplets remain, which may cause a problem of lowering the commodity value, but no method for solving this problem has been proposed.

In addition, as mentioned above, the temporary anti-rust chromate treatment is usually poured on the galvanized steel plate by spraying the chromate treatment solution with a sprayer or shower, adjusting the coating amount with a roller or an air throttling device, and using an oven Carry out the drying method to implement. This surface treatment method is very simple and has high productivity. However, the conventional technology proposed so far that does not use chromium may be called aqueous, and the active ingredient concentration (or solid content concentration) of the composition is only 20 to 30% at best even if it is high. That is, in order to apply and dry it to obtain a coating amount of 1 g/m ² (approximately 1 μm), the coating amount of the treatment liquid needs to be 4 to 5 g/m ² . Coating method (especially a method called reverse coating method, which is a method of applying a liquid by rotating a roller in the opposite direction to the moving direction of a plate) tends to be a method of processing. Therefore, there is a problem that existing simple equipment such as a spray wringer and a spray wringer cannot be used, and new equipment investment is required for a galvanizing line (CGL, EGL), but this problem has not been solved.

Patent Document 1: Japanese Patent Application Laid-Open No. 8-67834

Patent Document 2: Japanese Patent Application Laid-Open No. 9-221595

Patent Document 3: Japanese Patent Laid-Open No. 2002-241956

Patent Document 4: Japanese Patent Laid-Open No. 2004-238638

Patent Document 5: Japanese Patent Laid-Open No. 2005-15514

Patent Document 6: Japanese Patent Laid-Open No. 2004-2950

Patent Document 7: Japanese Patent Laid-Open No. 2002-155375

Patent Document 8: Japanese Patent Laid-Open No. 2002-30460

Patent Document 9: Japanese Patent Laid-Open No. 2005-48199

Contents of the invention

The present invention was carried out under the above circumstances, and its object is to provide a galvanized steel sheet capable of imparting excellent corrosion resistance, alkali resistance, and appearance, as well as imparting dew condensation resistance and coating properties (coating film adhesion) to a galvanized steel sheet. A water-based surface treatment solution with excellent properties that are well-balanced in properties and grounding properties, and a galvanized steel sheet with a film formed on the surface of the water-based surface treatment solution.

Another object of the present invention is to provide an aqueous surface treatment solution that can be coated even with conventionally used treatment methods (spray wringer, spray wringer, etc.) in galvanized steel sheet manufacturing facilities.

In order to solve the above-mentioned problems, the present inventors conducted intensive studies. As a result, it was found that a galvanized steel sheet surface-treated with an aqueous treatment solution containing the following components (A) to (D) and appropriately adjusting the usage ratio of each component not only has excellent corrosion resistance, alkali resistance and appearance , and also excellent in dew condensation prevention, coating film adhesion and electrical conductivity, thus completing the present invention.

The present invention relates to an aqueous treatment solution for galvanized steel sheets, which contains: (A) ammonium zirconium carbonate, (B) 4-valent vanadium compound, (C) organic phosphonic acid represented by formula (I) or its ammonium salt, (D) an anionic water-dispersible acrylic resin having a glass transition temperature Tg (° C.) converted from the glass transition temperature Tg (K) calculated by the mathematical formula (1) of 0 to 60° C., and water, and , the proportion of (D) in the total solid content (the total solid content refers to the total of the solid content in the components (A) to (D)) is 1 to 60% by mass, and (B) is converted into V in the total solid content The ratio of V/(C) is 0.05 to 1.0, the mass ratio of Zr/(V+(C)) after converting (A) to Zr is 0.1 to 6.0, and the pH is 7 to 6.0. 10.

1/Tg(K)＝∑(Wi/Tgi) (1)

(In the formula, i is an integer greater than 1, Wi represents the mass percentage of i homopolymer, and Tgi represents the Tg (K) of i homopolymer (usually referred to as the FOX formula).

The aqueous treatment liquid preferably contains (E) 0.5 to 20 g/kg of guanidine carbonate.

The aqueous treatment solution preferably further contains (F) 0.5 to 50 g/kg of nitrate ions.

In addition, the present invention relates to a galvanized steel sheet having a film on the surface obtained by applying and drying the aqueous surface treatment liquid.

Invention effect

The galvanized steel sheet surface-treated with the aqueous surface treatment liquid of the present invention is excellent in corrosion resistance, alkali resistance, appearance, anti-condensation property, paintability (coating film adhesion) and grounding property. In addition, the treatment solution of the present invention also has the advantage that it can be used in the same treatment facilities as the conventional temporary anti-rust chromate treatment in the galvanizing line (CGL).

Detailed ways

The aqueous surface treatment liquid (hereinafter sometimes simply referred to as a treatment liquid) of the present invention contains ammonium zirconium carbonate as a component (A). Ammonium zirconium carbonate evaporates carbonic acid and ammonium by drying, and the remaining zirconium polymerizes to form a poorly soluble film, so it is the most preferred among zirconium compounds.

The treatment liquid of the present invention contains a tetravalent vanadium compound as a component (B). When the treatment liquid contains a tetravalent vanadium compound, when the treatment liquid is applied to the surface of the galvanized steel sheet, a passivation film can be formed on the surface of the galvanized steel sheet, thereby improving the corrosion resistance of the galvanized steel sheet. In addition, due to the presence of a coating containing tetravalent vanadium, when a defect is formed in the coating, the nearby quadrivalent vanadium compound is eluted and reduced to trivalent with the corrosion (oxidation) of zinc, and passivation here can also be expected to suppress corrosion. Effect. The tetravalent vanadium compound is not particularly limited, and examples include vanadium (IV) sulfate, vanadium (IV) oxychloride, vanadium (IV) oxide, vanadium (IV) oxalate, vanadium (IV) fluoride, oxyacetylacetonate Vanadium (IV), etc. As the tetravalent vanadium compound, vanadium pentoxide, metavanadic acid, and compounds obtained by reducing their salts 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 a component (C). Organic phosphonic acid or its ammonium salt is required to stably dissolve the quaternary vanadium compound in the treatment solution, and the treatment solution used in the present invention also has a surface oxide film that removes (corrodes) the plating layer when it comes into contact with a galvanized steel sheet , so that the effect of improving the adhesion between the coating film obtained after drying and the surface of the coating layer; and the presence and retention of the 4-valent vanadium compound in the coating film, thereby exerting the effect of white rust inhibition for a long time. That is, it is important that it is a compound having both a chelating effect and a corrosion effect, and the compound having both effects may be other compounds, but the organic phosphonic acid represented by formula (I) or its ammonium salt is most preferable.

The treatment liquid of the present invention contains, as a component, an anionic water-dispersible acrylic resin having a glass transition temperature Tg (° C.) converted from the glass transition temperature Tg (K) calculated by the mathematical formula (1) of 0 to 60° C. ( D). The Tg (°C) is preferably 2 to 55°C, more preferably 5 to 50°C. If the Tg (°C) is lower than 0°C, the desired corrosion resistance cannot be obtained, and if the Tg (°C) exceeds 60°C, the film cannot be formed completely (poor film formation), and not only the desired corrosion resistance cannot be obtained , and the appearance of the film becomes whitish. In addition, the component (D) is an anionic water-dispersible acrylic resin, but is more preferably an acrylic resin that is stably dispersed in water adjusted to be basic with ammonia. The water-dispersible acrylic resin is not particularly limited other than the above. For example, the method of emulsification or the method of superposition is not limited. In addition, as long as it has anionic properties, it may be a water-dispersible acrylic resin emulsified with a nonionic surfactant. .

Next, the usage-amount of components (A)-(D) is demonstrated.

The ratio of the component (D) to the total solid content needs to be 1 to 60% by mass, preferably 3 to 50% by mass, more preferably 5 to 45% by mass. If the ratio is less than 1% by mass, there will be too many inorganic components, and the appearance of the film will become whitish, or iridescent interference colors will be seen, or the corrosion resistance after processing will tend to deteriorate, so it is not preferable. If the ratio exceeds If it is 60 mass %, since alkali resistance will fall, it is unpreferable.

The ratio of the component (B) to the total solids of V in terms of V needs to be 0.5 to 8% by mass, preferably 0.7 to 6.0% by mass, more preferably 1.0 to 5.0% by mass. If the ratio is less than 0.5% by mass, the corrosion resistance will be insufficient, and if the ratio exceeds 8% by mass, the effect will be saturated, and the water-soluble components will increase, resulting in poor dew condensation resistance.

The mass ratio of V/(C) representing the use ratio of V and component (C) when component (B) is converted to V needs to be 0.05 to 1.0, preferably 0.06 to 0.8, more preferably 0.07 to 0.6. If this mass ratio is less than 0.05, easily soluble components will increase, and alkali resistance and/or dew condensation prevention property will fall. On the other hand, if the mass ratio exceeds 1.0, the anti-condensation property will still decrease, or the stability of the treatment liquid will decrease.

The mass ratio Zr/(V+(C)) of the sum of Zr when component (A) is converted to Zr and the sum of V and component (C) when component (B) is converted to V needs to be 0.1 to 6.0, preferably 0.2 to 5.5, More preferably, it is 0.3 to 5.0. If the mass ratio is less than 0.1, the alkali resistance and/or the anti-condensation property will deteriorate, and if it exceeds 6.0, the corrosion resistance itself will deteriorate.

In the treatment liquid of the present invention, it is preferable to contain (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. Therefore, the viscosity of the treatment liquid gradually increases, and finally gels, which may not be able to withstand long-term use. In addition, since vanadium in the tetravalent vanadium compound exists as a metal cation, in order to dissolve it at pH 7-10, it is necessary to use component (C) or other chelating agents, or to form a complex of ammonia or amine compounds. Therefore, if guanidine carbonate is contained, the action of guanidine to replace ammonia can be exhibited while replenishing carbonic acid, thereby maintaining the stability of the treatment liquid for a long period of time. The amount of guanidine carbonate is preferably 0.5 to 20 g, more preferably 1 to 17 g, and still more preferably 1.5 to 15 g per 1 kg of the treatment liquid. If it is less than 0.5 g, there will be no effect, and if it exceeds 20 g, the effect will be saturated, and the residual amount of guanidine in the film will increase, dew condensation prevention and/or paintability will decrease.

In the treatment liquid of the present invention, it is preferable to contain (F) nitrate ions in addition to the components (A) to (D). Nitrate ions are particularly effective in suppressing a phenomenon called blackening. The amount to be added is preferably 0.3 to 30 g, more preferably 0.5 to 20 g, and still more preferably 0.7 to 15 g in terms of nitrate ions per 1 kg of the treatment liquid. If it is less than 0.3 g, the effect of suppressing blackening cannot be obtained, and if it exceeds 30 g, the amount remaining in the film will increase, and the paintability and/or anti-condensation properties will decrease. The supply source of nitrate ions is not particularly limited, and examples thereof include nitric acid, ammonium salts of nitric acid, and salts of nitric acid and metals such as Co, Ni, Zn, Fe, Ti, Zr, Mg, and Ca.

The treatment liquid of the present invention may contain (G) an antifoaming agent in addition to the components (A) to (D). The antifoaming agent is not particularly limited, and stable emulsified products such as petrolatum, fatty acid, and silicone, or water-soluble active dosage forms can be used. If the added amount of the antifoaming agent is small, the antifoaming performance cannot be obtained, and if the added amount of the antifoaming agent is large, the coatability will deteriorate, so it is necessary to add an appropriate amount. The addition amount is not particularly limited, but 0.1 to 3.0 g per 1 kg of the treatment liquid is appropriate.

In addition, the treatment liquid of the present invention may contain a pentavalent vanadium compound, thereby improving corrosion resistance. The amount of the pentavalent vanadium compound added is preferably 0.01 to 40 g, more preferably 0.03 to 30 g, and still more preferably 0.05 to 25 g per 1 kg of the treatment liquid in terms of V. Examples of the pentavalent vanadium compound include metavanadic acid, vanadic acid, salts thereof, vanadium (V) oxide, and the like.

The treatment liquid of the present invention may contain a fluorine-containing compound. Especially in hot-dip galvanized steel sheets with a thick surface oxide film, when the corrosion resistance is improved by fluorine-containing compounds, the reaction layer (passivation layer) with the surface of the material becomes thicker, and the corrosion resistance tends to be improved. However, in the case of adding a fluorine-containing compound, there are problems such as an increase in the amount of Zn and Fe mixed in the treatment solution due to increased corrosion, a decrease in the stability of the treatment solution, and the need to deal with fluorine when the treatment solution is discarded. Therefore, it is preferred The range of fluorine-containing compounds is set after considering the above-mentioned problems. The content of the fluorine-containing compound is not particularly limited, but preferably 0.05-10 g of fluorine is contained in 1 kg of the aqueous treatment liquid, more preferably 0.07-7.0 g, and still more preferably 0.1-5.0 g. As a fluorine-containing compound, ammonium fluoride, ammonium fluorosilicate, ammonium fluorotitanate, ammonium fluorozirconate etc. are mentioned, for example.

The treatment liquid of the present invention may contain silicon-based substances such as liquid-phase silica, fumed silica, silane coupling agent, alkali metal silicate, and water glass. Liquid-phase silica is obtained by removing metal ions of silicates such as sodium silicate, potassium silicate, and lithium silicate by ion exchange, and then gelling. It is also called colloidal silica. Colloidal silica may also include fumed silica dispersed in water. Fumed silica is produced by burning and oxidizing silicon chloride in air. Corrosion resistance and/or paintability tend to improve by containing a silicon-based substance. The amount of the silicon-based substance used is preferably 0.03 to 5.0, more preferably 0.05 to 3.0, and even more preferably 0.08 in terms of the mass ratio Si/Zr of Si when the silicon-based substance is converted to Si and to Zr when the component (A) is converted to Zr. ~2.0. If the usage-amount is less than 0.03, no addition effect will be seen, and if the usage-amount exceeds 5.0, a hard and brittle film will be formed or corrosion resistance will tend to fall.

Examples of liquid-phase silica include Snowtex C, Snowtex CS, Snowtex CM, Snowtex O, Snowtex OS, Snowtex OM, Snowtex NS, Snowtex N, Snowtex NM, Snowtex S, Snowtex 20, Snowtex 30, Snowtex 40, Adelite AT-20N, Adelite AT-20A, Adelite AT-20Q, etc., can also be processed into a special chain shape Snowtex UP, Snowtex OUP, Snowtex PS-S, Snowtex PS-SO, Snowtex PS-M, Snowtex PS-MO, Snowtex PS-L, Snowtex PS -LO et al. Examples of particulate silica called fumed silica include Aerosil 50, Aerosil 130, Aerosil 200, Aerosil 300, Aerosil 380, Aerosil TT600, Aerosil MOX80, Aerosil MOX 170, and those obtained by dispersing them in water can also be used. substance.

Examples of the silane coupling agent include: trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane , methyltriethoxysilane, methyldimethoxysilane, methyldiethoxysilane, dimethylethoxysilane, cyclohexylmethyldimethoxysilane, n-hexyltrimethoxysilane, Phenyltrimethoxysilane, Phenyltriethoxysilane, Isobutyltrimethoxysilane, Vinylmethoxysilane, Vinylethoxysilane, Vinyltrimethoxysilane, Vinyltriethoxy Silane, β-(3,4 epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ -Glycidoxypropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl Trimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-mercaptopropyl Methyldimethoxysilane, γ-acryloxypropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, bis(triethoxysilylpropyl) tetrasulfide γ-triethoxysilyl-N-(1,3-dimethyl-butylene)propylamine, N-(vinylbenzylamino)-β-aminoethyl-γ-aminopropyltrimethyl Oxysilane, etc. Particularly preferred are silane coupling agents called aminosilanes and epoxysilanes having an amino group or an epoxy group as a functional group 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 silicates.

The treatment liquid of the present invention may contain a lubricant, and the lubricant is effective for improving the lubricity of the surface treatment coating to prevent damage or to reduce damage to the galvanized steel sheet during processing. Examples of lubricants include solid lubricants such as polyethylene wax, oxidized polyethylene wax, oxidized polypropylene wax, carnauba wax, paraffin wax, montan wax, and Teflon (registered trademark). When compounding a lubricant, the compounding amount is preferably 0.5 to 50 g, more preferably 1 to 40 g, and still more preferably 3 to 30 g per 1 kg of the treatment liquid. If it exceeds 50 g, not only cannot it be added stably, but the effect of the present invention may be hindered.

Each of the above components contained or may be contained in the treatment liquid of the present invention may 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 lower than 7, the component (A) ammonium zirconium carbonate cannot be dissolved stably, and the stability of the treatment liquid will deteriorate. If the pH exceeds 10, the smell of ammonia will become prominent, and workability will deteriorate. Preference is given to using ammonia, guanidine carbonate, carbonic acid to adjust the pH.

As a galvanized steel sheet for coating the treatment solution of the present invention, there may be mentioned: hot-dip galvanized steel sheet (GI), alloyed hot-dip galvanized steel sheet (GA) obtained by alloying GI (annealed GI material Diffuse Fe of the base material into the zinc coating to alloy), hot-dip Zn-5%Al alloy steel sheet (GF), hot-dip Zn-55%Al alloy steel sheet (GL), electrogalvanized steel sheet (EG), Electroplating Zn-Ni alloy steel plate (Zn-Ni), etc.

The treatment solution of the present invention is applied by coating and drying on a galvanized steel sheet. The coating and drying methods are not particularly limited, and common methods can be used. As the coating method, for example: the method of spraying the treatment liquid with a sprayer or shower and adjusting the coating amount with a roller or an air throttling device, roll coating method, curtain coating method, etc., as the drying method, can include: Hot air method, induction heater method, near-infrared method, etc. The drying temperature is not particularly limited as long as the moisture in the treatment liquid can be evaporated, and is preferably 40 to 250°C, more preferably 50 to 230°C, and even more preferably 60 to 200 ℃.

The amount of the formed dry film is preferably 0.05 to 0.8 g/m ² , more preferably 0.1 to 0.7 g/m ² , and still more preferably 0.15 to 0.6 g/m ² . If the amount 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 properties such as workability, corrosion resistance, and paintability cannot be exhibited in a good balance. On the other hand, if the amount exceeds 0.8 g/m ² , the appearance will become whitish, or the paintability will deteriorate. In addition, if the amount exceeds 0.8 g/m ² , the conductivity and weldability deteriorate, and the peeling amount of the film increases during the press working, which hinders press forming and tends to increase the production cost.

In the present invention, by using the above-mentioned specific components in a specific ratio, a surface-treated galvanized steel sheet excellent in the target corrosion resistance, alkali resistance, appearance, anti-condensation property, paintability, and grounding property can be obtained. The surface-treated galvanized steel sheet can be used as a material with excellent properties in various fields such as construction, electricity, and automobiles.

The mechanism/reason for producing the effect of the present invention is estimated as follows, but this is only speculation, and does not limit the scope or patentability of the present invention thereby.

In the treatment liquid of the present invention, the zirconium in the component (A) and the anionic water-dispersible acrylic resin as the component (D) are considered to form the skeleton of the film, and once dried, they are no longer soluble in water to exert a barrier effect. On the other hand, the tetravalent vanadium compound of the component (B) and the organic phosphonic acid of the component (C) are uniformly dispersed in the film, and exist in a form that is easily soluble in water, so as to improve the corrosion resistance of the galvanized steel sheet The enhanced corrosion inhibitor works.

The corrosion resistance of the present invention is also considered to be caused by the barrier effect and the corrosion inhibitor effect. However, since the acrylic resin itself forming the film skeleton has weak alkali resistance in terms of alkali resistance, it is difficult to exhibit alkali resistance if the resin component is too large. On the other hand, if there are too many inorganic components, the film tends to become hard and brittle. Therefore, the film is prone to cracks, and the appearance of the beautiful galvanized steel sheet becomes whitish, or iridescent interference colors can be seen. The appearance quality is impaired. In the present invention, the tetravalent vanadium compound is considered to be most effective as a corrosion inhibitor.

In addition, since the film formed as described above is composed of water-insoluble components and water-soluble components, it is necessary to appropriately adjust the ratio thereof. That is, sufficient corrosion resistance cannot be obtained even if the film is composed of only insoluble components. Conversely, if a large amount of soluble components are used, the traces of dew condensation will become obvious during condensation, or the components will be washed away by alkaline degreasing. It is difficult to obtain subsequent corrosion resistance.

The amount of the dry film formed by the treatment agent of the present invention may be 0.05 to 0.80 g/m ² as described above, and the target performance can be obtained with a film amount that is generally smaller than that of the prior art. As the treatment liquid of the present invention, a treatment liquid having a solid content concentration of 10 to 20% by mass can be stably prepared. The coating amount in the spray or spray wringer method is usually about 1 g/m ² to about 3 g/m ² , and when 10 to 20% by mass of the treatment liquid is applied by these methods, about 0.1 g/m ² can be obtained. ~ About 0.6g/m ² dry film, it is enough to dry to the extent that the water evaporates. That is, when coating and drying the treatment liquid of the present invention, there is no need for expensive and difficult-to-manage equipment such as a roll coater, and simple equipment such as a sprayer equipment or a spray wringer equipment can be used without reducing the actual production line (CGL, EGL, etc.). ) in the case of productivity of coating and drying. For example, the treatment liquid of the present invention can be used in a galvanizing line (CGL) using the same treatment facilities as those used for the existing temporary anti-rust chromate treatment.

Hereinafter, although an Example demonstrates this invention concretely, these Examples are only illustrations, and the scope of the present invention is not limited by these Examples.

Example

Fabrication of surface-treated galvanized steel sheets as test panels

In the following examples, galvanized steel sheets (GI, GA, EG: GI, GA, and EG with a size of 200mm×300mm and a thickness of 0.8mm were prepared respectively) were subjected to alkaline degreasing to wash off the antirust oil, and washed with water. Rinse off the degreasing solution, rinse with pure water, and then dry with warm air, and use the resulting material as a test panel. Evaluation tests described later were performed using, as test panels, surface-treated galvanized steel sheets in which a film was formed on the surface of the test panel by various aqueous treatment solutions.

Components used in aqueous treatment fluids

Component (A): Commercially available ammonium zirconium carbonate (20% by mass as ZrO ₂ )

ingredient (B)

B-1: Vanadium(IV) oxalate

B-2: Vanadyl(IV) sulfate

B-3: Vanadyl(IV) acetylacetonate

Component (C): Commercially available organic phosphonic acid (manufactured by Daido Pharmaceutical Co., Ltd., Hoslin 303)

ingredient (D)

Use the following water-dispersible acrylic resin synthesized by emulsion polymerization using an anionic or nonionic surfactant (the acrylic resin obtained by using a nonionic surfactant is also a anionic). D-1, 2, 5 and 6 were emulsified using an anionic surfactant at a ratio of 5 parts by mass relative to 100 parts by mass of the resin, and D-3, 4 and 7 were emulsified at a ratio of 15 parts by mass relative to 100 parts by mass of the resin. Proportions Use non-ionic surfactants for emulsification. In addition, the pH was adjusted using ammonia, and the pH was all adjusted to 8.5. In addition, the total solid content was 20% by 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: Tg25°C (BA/AA/MMA/St/AN=37/3/30/10/20; weight ratio) Example

D-4: Tg36°C (BA/AA/MMA/2-HEMA=30/3/64/3; weight ratio) Example

D-5: Tg45°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: Tg70℃ (BA/AA/MMA/2-HEMA/St＝13/3/5 9/5/20; weight ratio)

comparative example

Among the above, BA means butyl acrylate (Tg: -54°C), AA means acrylic acid (Tg: 108°C), MMA means methyl methacrylate (Tg: 105°C), and 2-HEMA means methacrylic acid-2- Hydroxyethyl ester (Tg: 55°C), AN means acrylonitrile (Tg: 105°C), and St means styrene (Tg: 105°C).

Component (E): Commercially available guanidine carbonate (reagent)

Component (F): Commercially available ammonium nitrate (reagent)

Component (G): The following commercially available defoamers

G-1: SNデイフイフオ-マ-JK (manufactured by Sunnopco Co., Ltd.)

G-2: SN Diafo-Ma-430 (manufactured by Sunnopco Co., Ltd.)

G-3: Surfinol 485 (manufactured by Nissin Chemical Industry Co., Ltd.)

Various evaluation tests and evaluation criteria

(1) Corrosion resistance

Cut the surface-treated galvanized steel sheet into a size of 70 mm × 150 mm, seal the back side and the end with glass tape to obtain a test piece, and perform the salt spray test specified in JIS Z2371 on the obtained test piece to reach 5% (area ratio) The time until white rust occurred was evaluated. The evaluation criteria at this time are as follows.

◎: The time until white rust occurs on 5% of the area is 120 hours or more

○: The time until white rust occurs on 5% of the area is 48 hours or more and less than 120 hours

△: The time until white rust occurs on 5% of the area is 24 hours or more and less than 48 hours

×: The time until white rust occurs on 5% of the area is less than 24 hours

On the other hand, the evaluation criteria for GA are as follows.

◎: The time until white rust occurs on 5% of the area is 48 hours or more

○: The time until white rust occurs on 5% of the area is 24 hours or more and less than 48 hours

△: The time until white rust occurs on 5% of the area is 12 hours or more and less than 24 hours

×: The time until white rust occurs on 5% of the area is less than 12 hours

(2) Alkali resistance

The surface-treated galvanized steel sheet was cut into a size of 70 mm × 150 mm, and degreasing called moderate alkaline degreasing (manufactured by Nippon Parker Seisei Co., Ltd., Palculin N364S, 20 g/L, 60° C., spray 2 Minutes later, wash with water, then dry with warm air), seal the back side and the end with glass tape to obtain a test piece, and perform the salt spray test specified in JIS Z2371 on the obtained test piece until white rust occurs on 5% (area ratio) time to evaluate. The evaluation criteria at this time are the same as in the case of corrosion resistance.

(3) Appearance

The surface-treated galvanized steel sheet was cut into a size of 70 mm×150 mm to obtain a test piece, and the surface appearance of the obtained test piece was evaluated. The evaluation criteria at this time are as follows.

◎: No whitening and interference color

○: There is extremely thin whitening, and there is interference color

△: There is whitening and interference color

×: There is conspicuous whitening and noise color

(4) Anti-condensation

Cut the surface-treated galvanized steel sheet into a size of 70mm×150mm to obtain a test piece, and place the obtained test piece in a freezer at -5°C for 1 hour, and then place it in a high-temperature constant-humidity chamber (50°C, humidity 95%) 2 hours. When putting the test piece into the high-temperature constant-humidity chamber, confirm that water droplets (condensation) are formed on the surface of the test piece (if not confirmed, put it in the freezer again for 1 hour, and then put it into the high-temperature constant-humidity chamber). After taking out the test piece from the high-temperature constant-humidity chamber, it was confirmed that the surface of the test piece was dry (if it was not dry, leave it as it is, and wait until the surface was dry). Traces of water droplets (condensation) on the surface of the test piece were visually observed and evaluated. The evaluation criteria at this time are as follows.

◎: No trace of water droplet was observed

○: Slight traces of water droplets were observed

△: Traces of water droplets were observed

×: Obvious traces of water droplets were observed

(5) Paintability

The surface-treated galvanized steel sheet was cut into a size of 70 mm × 150 mm to obtain a test piece, and a melamine-based paint ("Amiraku #1000", manufactured by Kansai Paint Co., Ltd.) was applied to the obtained test piece, and then baked at 160°C to form A coating film with a coating film thickness of 20 μm. The obtained coated sheet was immersed in boiling water for 1 hour, and after 1 hour, 100 grids of 1 mm square were formed on the coating film, the tape was peeled off, and the residual rate was measured. Moreover, after extruding the part in which 100 checkerboards were formed similarly by 5 mm with an ERICHSEN extruder, tape peeling and evaluation were performed. The evaluation criteria at this time are as follows.

◎: Residual rate 91～100%

○: Residual rate 71-90%

△: Residual rate 51-70%

×: residual rate 0 to 50%

(6) Grounding

The interlayer resistance of the surface-treated galvanized steel sheet was measured with an interlayer resistance measuring device. Evaluation was performed according to the following criteria. In addition, the measurement of interlayer resistance was carried out by inserting a needle into the surface-treated surface until it touched the galvanized steel sheet, bringing the electrode into contact with the surface-treated surface, and measuring the resistance value by energizing. Therefore, "interlayer resistance" means the electric resistance between the front surface and the back surface of the film formed.

◎: Less than 1Ω ○: More than 1Ω and less than 2Ω △: More than 2Ω and less than 3Ω ×: More than 3Ω

(7) Resistance to blackening

Cut the surface-treated galvanized steel sheet into a size of 70mm×150mm as a test piece, put the surface-treated sides of two identical test pieces facing each other, wrap them with kraft paper with vinyl coating on one side, and put them in 50°C and 98% humidity in the constant temperature and humidity device. At this time, a weight of 1 kg was placed on the wrapped test piece in order to fix and closely adhere the test piece. After maintaining this state for 10 days, it was taken out, and the appearance of the surface-treated surface of the test piece was observed with the naked eye, and evaluated based on the following criteria.

◎: No change in appearance

○: Discoloration is slightly visible

△: Overall thin blackening or partial blackening can be seen

×: blackening is clearly visible

Example 1

For No.1 in Table 1 below, 6.2 g of B-1 (vanadium (IV) oxalate) was dissolved in pure water and 22 g of (C) organic phosphonic acid, and the pH was raised to 8. Then, (A) 213 g of ammonium zirconium carbonate was added, and 175 g of D-1 water-dispersible acrylic resin was added, stirred and dissolved, G-11 g was added as an antifoaming agent, and pure water was added to make the total amount 1 kg. The pH of this aqueous treatment liquid was 9.0, and the solid content was 10% by mass. Other aqueous treatment liquids having the compositions shown in Table 1 were prepared in the same procedure (all dry solids adjusted to 10% by mass). At this time, the same components as No. 1 were used except for the water-dispersible acrylic resin.

Here, a treatment solution obtained by adding 3 g of (E) guanidine carbonate to the treatment solutions of No. 1 and No. 7 was also prepared, and the treatment solution with (E) added and the treatment solution without (E) added were prepared. Take 100g to 100ml of each solution into a glass beaker, and confirm the stability of the treatment solution while stirring with a stirrer equipped with a water bath set at 40°C until a vortex occurs. As a result, the treatment solution without (E) added Viscosity tends to increase over time and gels after 24 hours. On the other hand, no change was observed in the treatment liquid to which (E) was added even after 24 hours. That is, it can be judged that the addition of (E) improves the stability of the treatment liquid and enables long-term use.

In addition, in the aqueous treatment solution of the present invention, (A) and (D) are solutions adjusted to be alkaline with ammonia, and if the pH is less than 7, they cannot be dissolved or dispersed stably. Therefore, if a solution having a pH of less than 7 is mixed with (A) or (D), the solution will gel or form aggregates (pitting), and a stable aqueous treatment solution cannot be obtained. That is, since an aqueous treatment solution with a pH of less than 7 could not be obtained, the pH of all the aqueous treatment solutions was finally adjusted to 7 or higher.

The water-based treatment solutions in Table 1 were poured onto the surface of the galvanized steel sheet (GI) to wet the entire surface, and then the excess water-based treatment solution was removed with a press roller squeeze machine composed of two flat rubber rollers , heated and dried at the highest attained panel temperature of 60°C to obtain a surface-treated galvanized steel sheet having a film with a coating amount shown in Table 1. Among them, the amount of film less than 0.2g/ ^m2 is diluted with pure water and then coated, and the amount of film exceeding 0.5g/ ^m2 is coated with #4 bar. Table 1 shows the evaluation results of the surface-treated galvanized steel sheets thus obtained.

In addition, the aqueous treatment liquids with numbers above double dashes are so-called examples (except No. 36N4 in Table 5), and the aqueous treatment liquids with numbers below double dashes are so-called comparative examples (other examples are also the same). For example, (D) (anionic water-dispersible acrylic resin) was not used in No. 11, and Tg (° C.) of (D) in No. 13 exceeded the range specified by the present invention.

Table 1

Example 2

In No. 17 of Table 2, 3.3 g of B-1 (vanadium (IV) oxalate) was dissolved in pure water and (C) 15 g of organic phosphonic acid, and the pH was raised to 8 with 28% by mass of ammonia water. Then, add (A) 224g of ammonium zirconium carbonate, then add 200g of D-1 water-dispersible acrylic resin, further add (E) 5g of guanidine carbonate, stir and dissolve, then add G-21g as a defoamer, add water to make the total amount It is 1kg. The pH of this aqueous treatment liquid was 9.5, and the solid content was 10% by mass. Other aqueous treatment liquids having the compositions shown in Table 2 were prepared in the same procedure (all dry solids were adjusted to 10% by mass). At this time, the same thing as No. 17 was used for each component, and the addition amount of each of (E) and G-2 was the same as No. 17.

The water-based treatment solutions prepared above are poured onto the surface of the galvanized steel sheet (GI) to wet the entire surface, and then, the excess water-based treatment solution is removed by a pressure roller water squeezer composed of two flat rubber rollers. , heated and dried at the highest reaching plate temperature of 80°C to obtain a surface-treated galvanized steel sheet. Table 2 shows the evaluation results of the surface-treated galvanized steel sheets thus obtained.

Table 2

Example 3

For No.23 in Table 3, 6.4 g of B-2 (vanadyl (IV) sulfate) was dissolved in pure water and (C) 33 g of organic phosphonic acid, and the pH was raised to 8 with 28% by mass of ammonia water. . Then, add (A) zirconium ammonium carbonate 179g, then add D-1 water-dispersible acrylic resin 175g, further add (E) guanidine carbonate 3g, stir and dissolve, then add G-3 as a defoamer, add water to make the total amount It is 1kg. The pH of this aqueous treatment liquid was 8.6, and the solid content was 10% by mass. Other aqueous treatment liquids having the compositions shown in Table 3 were prepared in the same procedure (all dry solids adjusted to 10% by mass). At this time, the same thing as No. 23 was used for each component, and the addition amount of each of (E) and G-3 was the same as No. 23.

The water-based treatment solutions prepared above are poured onto the surface of the surface-treated galvanized steel sheet (GI) to wet the entire surface, and then, the excess water-based treatment liquid is removed by a pressure roller water squeezer composed of two flat rubber rollers. The treatment solution was heated and dried at a maximum reached plate temperature of 120° C. to obtain a surface-treated galvanized steel sheet. Table 3 shows the evaluation results of the surface-treated galvanized steel sheets thus obtained.

table 3

Example 4

In No. 29 of Table 4, 16.8 g of B-3 (vanadyl (IV) acetylacetonate) was dissolved in 35 g of (C) organic phosphonic acid, and the pH was raised to 8 with 28% by mass of ammonia water. Then, add (A) 121 g of ammonium zirconium carbonate, then add 175 g of D-1 water-dispersible acrylic resin, further add (E) 3 g of guanidine carbonate, stir and dissolve, and then add each of G-1 and G-3 as an antifoaming agent. 0.5g, add water to make the total amount 1kg. The pH of this aqueous treatment liquid was 7.5, and the solid content was 10% by mass. Other aqueous treatment liquids having the compositions shown in Table 4 were prepared in the same procedure (all dry solids were adjusted to 10% by mass). At this time, the same thing as No. 29 was used for each component, and the addition amount of each of (E) and (G) was the same as No. 29.

The water-based treatment solutions prepared above are poured onto the surface of the galvanized steel sheet (EG) to wet the entire surface, and then the excess water-based treatment solution is removed by a pressure roller water squeezer composed of two flat rubber rollers , heated and dried at the highest reaching plate temperature of 120°C to obtain a surface-treated galvanized steel sheet. Table 4 shows the evaluation results of the surface-treated galvanized steel sheets thus obtained.

Table 4

Example 5

The aqueous treatment liquids of Nos. 36, 37, 38, 39, 40, 42, and 43 in Table 5 are the same as the aqueous treatment liquids of Nos. 29 to 35 in Table 4, respectively. The N appended to the No. indicates the addition of (F) ammonium nitrate, which refers to the addition of N 5g/kg, N15g/kg, N210g/kg, N330g/kg in terms of nitrate ions in the aqueous treatment liquid of each No. , N460g/kg.

The water-based treatment solutions in Table 5 were poured onto the surface of the galvanized steel sheet (GI) to wet the entire surface, and then the excess water-based treatment solution was removed with a press roller squeeze machine composed of two flat rubber rollers. , heated and dried at the highest reaching plate temperature of 70°C to obtain a surface-treated galvanized steel sheet. Table 5 shows the evaluation results of the surface-treated galvanized steel sheets thus obtained.

table 5

Example 6

The aqueous treatment liquids of Nos. 45 to 60 in Table 6 are the same as the aqueous treatment liquids of Nos. 1 to 16 in Table 1. The aqueous treatment liquids in which 3 g of ammonium fluorotitanate was added as F to the aqueous treatment liquids of No. 52 and No. 57 were designated as No. 52F and No. 57F.

The water-based treatment solutions in Table 6 were poured onto the surface of the galvanized steel sheet (GA) to wet the entire surface, and then, the excess water-based treatment solution was removed by a roller squeeze machine composed of two flat rubber rollers. , heated and dried at the highest reaching plate temperature of 70°C to obtain a surface-treated galvanized steel sheet. Table 6 shows the evaluation results of the surface-treated galvanized steel sheets thus obtained.

Table 6

These results show that the surface-treated galvanized steel sheet treated with an aqueous treatment solution of a specific component specified in the present invention in a specific ratio has good corrosion resistance and alkali resistance, and has good appearance, anti-condensation performance, and paintability. Both (coating film adhesion) and grounding properties were also excellent.

Claims (4)

1. steel plate galvanized use treatment solution, wherein, contain: (A) zirconium carbonate ammonium, (B) 4 valency vanadium compound, (C) organic phospho acid shown in the formula (I) or its ammonium salt, (D) by the glass transition temperature Tg of calculating according to mathematical expression (1) (K) convert the glass transition temperature Tg that obtains (℃) be 0～60 ℃ anionic water dispersible acrylic resin and water, and, (D) ratio in the total solids composition is 1～60 quality %, (B) be scaled that the ratio in the total solids composition is 0.5～8 quality % behind the V, the mass ratio of V/ (C) is 0.05～1.0, (A) be scaled that the mass ratio of Zr/ (V+ (C)) is 0.1～6.0 behind the Zr, pH is 7～10, described total solids composition is meant the total amount of each solids component in the composition (A)～(D)

1/Tg(K)＝∑(Wi/Tgi) (1)

Formula (1) is commonly referred to the FOX formula, and wherein, i represents the integer more than 1, and Wi represents the quality percentage of i homopolymer, and Tgi represents the Tg (K) of i homopolymer.

2. aqueous treating fluid as claimed in claim 1 wherein, contains (E) Guanidinium carbonate 0.5～20g/kg with respect to this aqueous treating fluid.

3. aqueous treating fluid as claimed in claim 1 or 2 wherein, contains (F) nitrate ion 0.5～50g/kg with respect to this aqueous treating fluid.

4. steel plate galvanized, its surface have by each described aqueous treating fluid in the coating claim 1～3 and make its dry tunicle that obtains.