JP2015175003A - Surface treatment liquid for galvanized steel plate, surface treated galvanized steel plate, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treatment liquid that does not contain a chromium compound, makes it possible to obtain a surface-treated galvanized steel plate having both corrosion resistance and black discoloration resistance at high level with a thin film, and enables proper thin film formation by any simple drying means such as dryer drying.SOLUTION: There is provided a surface treatment liquid that contains a silane coupling agent (a1) having a glycidyl group, a silane compound (A) obtained from tetraalkoxysilane (a2) and phosphonic acid (a3) and having a hydrolyzable group, a zirconium carbonate compound (B), a vanadic acid compound (C), and water at a specific ratio, has its pH adjusted to 7.2-8.0 with carbonic acid as a pH adjuster, and does not contain any fluorine compound.

Description

  The present invention relates to a surface treatment liquid for a zinc-based plated steel sheet, a surface treatment liquid not containing hexavalent chromium, an environment-friendly surface-treated zinc-based plated steel sheet treated with this surface treatment liquid, and a method for producing the same. .

  Conventionally, for the purpose of improving the corrosion resistance (white rust resistance, red rust resistance) on the surface of galvanized steel sheets used for steel sheets for household appliances, steel sheets for building materials, and steel sheets for automobiles, chromic acid, dichromic acid or Steel sheets subjected to chromate treatment with a surface treatment solution containing salts as main components have been widely used. However, due to recent global environmental problems, there is an increasing demand for adopting non-polluted surface-treated steel sheets that do not depend on chromate treatment, so-called chromium-free treated steel sheets.

  Many technologies related to chromium-free treated steel sheets have already been proposed. Technologies aiming at the passivating action of molybdic acid and tungstic acid belonging to the same group IVA as chromic acid, such as Ti, Zr, V, Mn, Ni, Co, etc. Using technology using metal salts of rare earth elements such as transition metals and La, Ce, technology based on chelating agents such as polyphenolic carboxylic acids such as tannic acid and compounds containing S and N, using silane coupling agents A technique for forming a polysiloxane film or a technique combining these techniques has been proposed.

Specific examples are as follows.
(1) Technology for forming a film from a treatment liquid containing a coating agent obtained by reacting an organic resin such as a polyvinylphenol derivative, an acid component, and an epoxy compound, a silane coupling agent, and a vanadium compound (Patent Document 1) ~ 4)
(2) Technology for forming a film containing an aqueous resin, a thiocarbonyl group, a vanadic acid compound, and phosphoric acid (Patent Document 5)
(3) Technology for forming a film from a treatment liquid containing a metal compound such as Ti and inorganic and organic acids such as fluoride and phosphate compounds (Patent Documents 6 to 12)
(4) Technology to form a composite film of rare earth elements such as Ce, La, Y, etc. and Ti, Zr elements, and to concentrate the oxide layer on the plating interface side and the hydroxide layer on the surface side in the film (patent Document 13) and technology for forming a composite film of Ce and Si oxide (Patent Document 14)

(5) Technology for forming an organic composite coating comprising a phosphoric acid and / or phosphoric acid compound film containing an oxide in the lower layer and a resin film on the upper layer (Patent Documents 15 and 16)
(6) Technology for forming a composite film comprising a specific inhibitor component and a silica / zirconium compound (Patent Document 17)
(7) Technology for forming a composite film comprising a water-soluble zirconium compound, a tetraalkoxysilane, a compound having an epoxy group, a chelating agent, vanadic acid, and a predetermined metal compound (Patent Document 18)
(8) Technology for forming a composite film composed of a specific silane compound, zirconium carbonate compound, vanadic acid compound, and nitric acid compound (Patent Document 19)

JP 2003-13252 A JP 2001-181860 A JP 2004-263252 A Japanese Patent Laid-Open No. 2003-155542 Japanese Patent No. 3549455 Japanese Patent No. 3302677 JP 2002-105658 A JP 2004-183015 A JP 2003-171778 A JP 2001-271175 A JP 2006-213958 A JP 2005-48199 A JP 2001-234358 A Japanese Patent No. 3596665 JP 2002-53980 A JP 2002-53979 A JP 2008-169470 A JP 2010-255105 A JP 2013-60647 A

  Films formed by these technologies aim to suppress the occurrence of zinc white rust by the combined addition of organic or inorganic components. For example, the technologies (1) and (2) above are mainly used. Corrosion resistance is ensured by adding an organic resin. However, such an organic resin film has a problem of discoloration due to resin deterioration in an outdoor environment or a high temperature and high humidity environment. Moreover, high temperature baking is indispensable for film formation, and when manufactured by simple dryer drying, corrosion resistance cannot be ensured.

In the techniques (3) and (4), an inorganic single film that does not contain any organic component has been proposed. However, these metal oxide / metal hydroxide composite films cannot provide sufficient corrosion resistance to the galvanized steel sheet unless the film is thickened. That is, when manufactured by simple dryer drying, drying becomes insufficient, and corrosion resistance cannot be ensured.
The technique (5) has the same problems as the techniques (1) and (2) because a resin film is used as an upper layer in order to ensure corrosion resistance.

  In the technique of (6) above, a passivating action of a vanadate compound and a hardly soluble metal salt by a phosphate compound are used as an inhibitor component, and a composite film of a zirconium compound, fine particle silica, and a silane coupling agent is used as a skeleton film. By forming it, excellent corrosion resistance is expressed. However, sufficient corrosion resistance cannot be imparted to the galvanized steel sheet unless the film is thickened. That is, when manufactured by simple dryer drying, drying becomes insufficient, and corrosion resistance cannot be ensured.

With the technologies (7) and (8) above, it is possible to provide a galvanized steel sheet that is thin and excellent in corrosion resistance. However, sufficient blacking resistance cannot be obtained, and therefore excellent corrosion resistance and blackening resistance are obtained. It was found that both cannot be achieved.
As described above, it has been found that the chromium-free treated steel plates proposed so far cannot achieve both the corrosion resistance of the flat plate portion and the blackening resistance.

Therefore, the object of the present invention is a surface treatment solution for galvanized steel sheet that solves the problems of the prior art as described above, and is highly compatible with corrosion resistance and blackening resistance in a thin film without containing a chromium compound. An object of the present invention is to provide a surface-treated liquid that can provide a surface-treated zinc-based plated steel sheet and that can appropriately form a film even with a simple drying means such as dryer drying.
Another object of the present invention is to provide a surface-treated galvanized steel sheet having a surface treatment film formed with such a surface treatment liquid and a method for producing the same.

As a result of intensive studies to solve the above problems, the present inventors have formulated a specific silane compound, a zirconium carbonate compound, a vanadic acid compound, and water at a specific ratio, and adjusted the pH by carbonic acid. It has been found that the above problems can be solved by forming a surface treatment film on the surface of a zinc-based plated steel sheet using a surface treatment liquid adjusted to a specific range.
The present invention has been made on the basis of such findings and has the following gist.

[1] A silane compound (A) having a hydrolyzable group obtained from a silane coupling agent (a1) having a glycidyl group, a tetraalkoxysilane (a2) and a phosphonic acid (a3), and a zirconium carbonate compound (B) And the vanadic acid compound (C) and water, and the pH is adjusted to 7.2 to 8.0 by carbonic acid as a pH adjusting agent, and satisfies the following conditions (i) to (iv): A surface treatment solution for galvanized steel sheets.
(I) The silane compound (A) is 30 to 70% by mass in the total solid content of the surface treatment liquid.
(Ii) The ratio (B / A) of the mass of the zirconium carbonate compound (B) in terms of ZrO _{2 and the} mass of the silane compound (A) is 0.3 to 2.0.
(Iii) The ratio (C / A) of the V-converted mass of the vanadic acid compound (C) to the mass of the silane compound (A) is from 0.010 to 0.15.
(Iv) Does not contain fluorine compounds (excluding fluorine compounds contained as inevitable impurities).

[2] It has a surface treatment film having a surface treatment film of 100 to 600 mg / m ² formed by applying the surface treatment liquid of [1] above to the surface of a zinc-based plated steel sheet and drying. A surface-treated galvanized steel sheet.
[3] A surface characterized in that the surface treatment liquid of [1] is applied to the surface of a galvanized steel sheet so that the amount of adhesion per side after drying is 100 to 600 mg / m ² and then dried. A method for producing a treated galvanized steel sheet.

  The surface treatment solution for galvanized steel sheet according to the present invention has a dense barrier property without containing a chromium compound, and has a surface treatment zinc system having excellent corrosion resistance and blackening resistance comparable to a chromate treatment material. A plated steel sheet can be obtained, and a film can be appropriately formed by simple drying means such as dryer drying. In addition, the surface-treated zinc-based plated steel sheet of the present invention has excellent corrosion resistance and blackening resistance comparable to chromate-treated materials, and is easy even with surface treatment equipment equipped with simple drying means such as dryer drying. Can be manufactured.

  The zinc-based plated steel sheet to which the surface treatment liquid of the present invention is applied is not particularly limited as long as it contains zinc in the plating film. Typical examples include hot-dip galvanized steel sheet (GI), alloyed hot-dip galvanized steel sheet (GA), hot-dip Zn-5 mass% Al alloy-plated steel sheet (GF), hot-dip Zn-55% mass Al alloy-plated steel sheet ( GL), electrogalvanized steel sheet (EG), electrogalvanized-Ni alloy plated steel sheet, and the like, but are not limited thereto.

The surface treatment liquid for galvanized steel sheet of the present invention is a silane compound having a hydrolyzable group obtained from a silane coupling agent (a1) having a glycidyl group, a tetraalkoxysilane (a2) and a phosphonic acid (a3). (A), a zirconium carbonate compound (B), a vanadic acid compound (C), and water are contained. This surface treatment liquid does not contain a chromium compound such as hexavalent chromium (excluding chromium compounds contained as inevitable impurities).
The silane compound (A) having a hydrolyzable group is obtained by reacting a phosphonic acid (a3) with a low condensate of a silane coupling agent (a1) having a glycidyl group and a tetraalkoxysilane (a2). Compound.
The silane compound (A) is a silane compound having a hydrolyzable group directly bonded to Si element, and the hydrolyzable group forms a silanol group by reacting with moisture. The silane compound (A) may be a group in which all of the groups bonded to the Si element are hydrolyzable groups, or a part of the groups bonded to the Si element may be hydrolyzable groups.

  The silane coupling agent (a1) having a glycidyl group contains a glycidyl group and a lower alkoxyl group having 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms, as a hydrolyzable group in one molecule containing Si. If it exists, it will not specifically limit, For example, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropylmethyl dimethoxysilane, 2- (3,4 epoxy cyclohexyl) ethyl Examples thereof include triethoxysilane, and one or more of these can be used.

The tetraalkoxysilane (a2) contains four lower alkoxyl groups as hydrolyzable groups, and has a general formula Si (OR) ₄ (wherein R is the same or different alkyl group having 1 to 5 carbon atoms). Group) is not particularly limited, and examples thereof include tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane, and one or more of these can be used. Among these, tetraethoxysilane and tetramethoxysilane are preferable from the viewpoint that the corrosion resistance of the galvanized steel sheet is more excellent.
Examples of the phosphonic acid (a3) include hydroxyethylene diphosphonic acid, nitrotris (methylenephosphonic acid), phosphonobutanetricarboxylic acid, and ethylenediaminetetra (methylenephosphonic acid), and one or more of these can be used. .

  The silane compound (A) having a hydrolyzable group includes a low condensate of the above-described silane coupling agent (a1) having a glycidyl group and tetraalkoxysilane (a2). This low condensate has a polysiloxane bond formed by the condensation reaction of the silane coupling agent (a1) and the tetraalkoxysilane (a2) as the main skeleton, and the terminal group bonded to the Si element is hydrolyzed. It may be a functional group, or a part of the group bonded to the Si element may be hydrolyzable.

As the silane compound (A) having a hydrolyzable group, a compound having a condensation degree of 2 to 30 can be used, and a compound having a condensation degree of 2 to 10 is particularly preferable. This is because if the degree of condensation is 30 or less, no white precipitation occurs and a stable silane compound (A) is obtained.
The silane compound (A) having a hydrolyzable group is obtained by combining a low condensate of a silane coupling agent (a1) and a tetraalkoxysilane (a2) with a phosphonic acid (a3) at a reaction temperature of 1 to 70 ° C. It can be obtained by reacting for about 20 minutes to 20 minutes and performing autoclaving.

In the silane compound (A) having a hydrolyzable group, the specific and condensed state of the hydrolyzable group can be measured using gel permission chromatography (GPC), NMR and IR.
The silane compound (A) having a hydrolyzable group is obtained by reacting a silane coupling agent (a1) having a glycidyl group, a tetraalkoxysilane (a2), and a phosphonic acid (a3). It is considered that (a1) and tetraalkoxysilane (a2) are coordinated by hydrolysis with water and phosphonic acid (a3). This hydrolysis reaction and coordination by phosphonic acid (a3) are obtained at the same time, and a silane compound that has extremely high stability at room temperature and can withstand long-term storage is produced.

  Phosphonic acid (a3) is also an effective component for securing corrosion resistance and storage stability. Although the reason is not necessarily clear, it is considered that the phosphonic acid (a3) coordinates to the silane coupling agent (a1) and the tetraalkoxysilane (a2), and the silane compound (A) is a polymer in the surface treatment liquid. It is thought that it has an action to suppress the formation of the material, and the quality at the time of preparation is maintained without deterioration even when the surface treatment liquid is stored for a long time after preparation due to such action. it is conceivable that. In addition, phosphonic acid (a3) is considered to coordinate with the vanadate compound (C) described later, and it is considered that vanadium dissolves in a corrosive environment to form a polysiloxane bond again.

The blending ratio of the silane coupling agent (a1) having a glycidyl group, the tetraalkoxysilane (a2), and the phosphonic acid (a3) is based on 100 parts by mass of the silane coupling agent (a1) from the viewpoint of corrosion resistance. The tetraalkoxysilane (a2) is preferably 25 to 75 parts by mass and the phosphonic acid (a3) is preferably 5 to 30 parts by mass.
Content of the silane compound (A) in a surface treatment liquid shall be 30-70 mass% in the total solid of a surface treatment liquid. If the content of the silane compound (A) is less than 30% by mass, the corrosion resistance cannot be ensured. On the other hand, if the content exceeds 70% by mass, the corrosion resistance decreases.
By mixing with the zirconium carbonate compound (B), the silane compound (A) has a barrier effect that once dried, it does not dissolve in water again.

Examples of the zirconium carbonate compound (B) include salts of zirconium carbonate such as sodium, potassium, lithium, and ammonium (for example, zirconium ammonium carbonate, sodium zirconium carbonate, lithium zirconium carbonate), and one or more of these are used. be able to.
The content of the zirconium carbonate compound (B) is such that the ratio (B / A) of the mass of ZrO ₂ converted to ZrO ₂ (ZrO ₂ converted mass) of the zirconium carbonate compound (B) and the mass of the silane compound (A) is 0. 3 to 2.0, preferably 0.35 to 1.5. If the mass ratio (B / A) is less than 0.3, corrosion resistance cannot be ensured. On the other hand, if the mass ratio (B / A) exceeds 2.0, the corrosion resistance decreases. Moreover, when mass ratio (B / A) exceeds 2.0, blackening-proof property will also fall.

The vanadic acid compound (C) is present in the film formed on the surface of the zinc-based plated steel sheet, uniformly dispersed in a form that is easily dissolved in water, and exhibits a so-called inhibitor effect during zinc corrosion. Further, the vanadic acid compound (C) is considered to be coordinated to the phosphonic acid (a3), and a part of the vanadic acid (C) is ionized and deactivated in a corrosive environment. Demonstrate. Examples of the vanadic acid compound (C) include ammonium metavanadate, sodium metavanadate, vanadium acetylacetonate, and one or more of these can be used.
The content of the vanadic acid compound (C) is such that the ratio (C / A) of the V-converted mass of the vanadic acid compound (C) to the mass of the silane compound (A) is 0.010 to 0.15, Preferably it is set to 0.030-0.10. When the mass ratio (C / A) is less than 0.010, corrosion resistance cannot be ensured. On the other hand, when the mass ratio (C / A) exceeds 0.15, not only the blackening resistance decreases, Since it becomes difficult to dissolve the vanadic acid compound (C), the storage stability is lowered.

The surface treatment liquid needs to have a pH of 7.2 to 8.0. When the pH exceeds 8.0, the zinc-based plating dissolves during the application of the surface treatment solution, and the active surface of zinc is exposed, resulting in a decrease in blackening resistance. On the other hand, when the pH is lower than 7.2, the storage stability of the surface treatment liquid deteriorates.
Moreover, it is necessary to use carbonic acid for pH adjustment of the surface treatment solution. When carboxylic acids such as formic acid, acetic acid, and lactic acid are used for pH adjustment, these components remain in the film, and the blackening resistance and water stain resistance are reduced.
Furthermore, the surface treatment liquid needs to contain no fluorine compound (excluding fluorine compounds contained as inevitable impurities). Examples of the fluorine compound include hydrofluoric acid, titanium fluoride, zirconium fluoride, and zirconium fluoride. The fluorine compound not only lowers the water stain resistance but also reduces the stability of the silane compound, making it impossible to ensure the storage stability of the surface treatment liquid.

A solid lubricant can be added to the surface treatment liquid of the present invention in order to improve the lubricating performance. Examples of solid lubricants include polyethylene wax, oxidized polyethylene wax, oxidized polypropylene wax, carnauba wax, paraffin wax, montan wax, rice wax, Teflon (registered trademark) wax, carbon disulfide, graphite, and the like. The above can be used.
The content of the solid lubricant is preferably 1 to 10% by mass and more preferably 3 to 7% by mass in the total solid content of the surface treatment liquid. When the content of the solid lubricant is 1% by mass or more, an effect of improving the lubrication performance is obtained, and when it is 10% by mass or less, the corrosion resistance of the galvanized steel sheet is not lowered.

In addition, the surface treatment liquid contains a thickener for improving workability, a conductive substance for improving conductivity, a color pigment for improving design properties, a solvent for improving film forming property, and the like. You may add suitably as needed.
The surface treatment liquid can be obtained by mixing the above-described components in water. What is necessary is just to select the solid content concentration of a surface treatment liquid suitably. Moreover, you may add alcohol, a ketone, a cellosolve-type water-soluble solvent, an antifoamer, a fungicidal agent, a coloring agent, etc. to a surface treatment liquid as needed. However, it is important to add these components (that is, components (A) to (C), water, and an additive component other than the solid lubricant) to the extent that the performance obtained in the present invention is not impaired. The total solid content of the liquid is preferably less than 5% by mass.

The surface-treated zinc-based plated steel sheet of the present invention is made of the above-described zinc-based plated steel sheet, and the surface-treated film formed by applying the above-described surface treatment liquid to the zinc-plated steel sheet and drying it. Have.
Coating weight per one side of the surface treatment film is preferably from ^{100~600mg / m 2, 200~500mg / m} 2 is more preferable. When the coating amount per side is less than 100 mg / m ² , there is a concern about insufficient corrosion resistance. On the other hand, when it exceeds 600 mg / m ² , production with simple equipment such as dryer drying becomes difficult.

The surface-treated galvanized steel sheet of the present invention is obtained by applying the above-described surface treatment liquid to the surface of the galvanized steel sheet so that the amount of adhesion per one side after drying is 100 to 600 mg / m ² and then drying. Manufactured by.
As a method of applying the surface treatment liquid to the surface of the galvanized steel sheet, any method such as a roll coating method, a bar coating method, a dipping method, or a spray coating method can be adopted. An optimal method may be selected as appropriate depending on the shape and the like. For example, if the zinc-based plated steel sheet to be treated is a sheet, the roll coating method or bar coating method, or after spraying the surface treatment liquid onto the surface of the zinc-based plated steel sheet, the roll squeezing or gas is sprayed at a high pressure and applied. It is appropriate to use a spray coating method that adjusts the amount. Moreover, when the zinc-based plated steel sheet is a molded product, a method of adjusting the coating amount by immersing it in the surface treatment liquid and pulling it up and blowing off excess surface treatment liquid with compressed air as necessary is suitable.

  In addition, before applying the surface treatment liquid to the galvanized steel sheet, a pretreatment aimed at removing oil or dirt on the surface of the galvanized steel sheet may be performed as necessary. Zinc-coated steel sheets are often coated with rust-preventive oil for rust-prevention purposes, and even if they are not coated with rust-preventive oil, the surface has oil or dirt attached during work. . By performing the above pretreatment, the surface of the zinc-based plating layer is cleaned and easily wetted uniformly. When the surface treatment liquid gets wet uniformly on the surface of the galvanized steel sheet, pretreatment is not particularly necessary. The pretreatment method is not particularly limited, and examples thereof include hot water washing, solvent washing, and alkaline degreasing washing.

  Although there is no restriction | limiting in particular in the heating temperature at the time of drying after apply | coating a surface treatment liquid (maximum ultimate board temperature), Usually, it is about 30-200 degreeC. If the heating temperature is 30 ° C. or higher, moisture does not remain in the film, and if the heating temperature is 200 ° C. or lower, the generation of cracks in the film is suppressed. It is because it does not occur. The heating time is appropriately selected according to the type of zinc-based plated steel sheet used. From the viewpoint of productivity and the like, about 0.1 to 60 seconds is preferable, and about 1 to 30 seconds is more preferable.

  The surface treatment film formed on the surface of the galvanized steel sheet by the surface treatment liquid of the present invention has excellent corrosion resistance and blackening resistance without containing a chromium compound, and can also be a simple drying means such as dryer drying. It is characterized by the ability to form a film properly. The reason why such excellent performance is obtained is not necessarily clear, but is considered to be due to the following effects.

  First, the skeleton of the film formed on the surface of the zinc-based plating layer is composed of the silane compound (A) and the zirconium carbonate compound (B) among the components of the surface treatment liquid. The hydrolyzable group of the silane compound (A) is considered to fix the coating component by reacting with the surface of the zinc-based plating layer and three-dimensionally crosslink with the zirconium carbonate compound (B). Furthermore, it is considered that the glycidyl group of the silane coupling agent (a1) also reacts with the surface of the plating layer, and the bond strength of the film becomes stronger. The surface-treated film thus formed does not dissolve again in water once it is dried and has a barrier effect, so that a galvanized steel sheet having excellent corrosion resistance can be obtained. Further, since the film is not formed by a crosslinking reaction that requires a temperature like a resin, the film can be appropriately formed even by a simple drying means such as dryer drying.

  Among the components of the surface treatment liquid, the vanadic acid compound (C) is present in the film in a form that is easily dispersed in a form that is easily soluble in water, and exhibits a so-called inhibitory effect during zinc corrosion. That is, it is considered that the vanadic acid compound (C) is partially ionized and passivated in a corrosive environment, thereby suppressing zinc corrosion itself. Moreover, since it coordinates to phosphonic acid (a3), after ionization, the hydrolyzable group of the silane compound (A) is three-dimensionally cross-linked, thereby repairing a film defect portion and suppressing corrosion of zinc. Conceivable.

That is, the surface treatment liquid of the present invention forms a dense film with the silane compound (A) and the zirconium carbonate compound (B) to obtain high corrosion resistance, and the vanadate compound (C) as a corrosion inhibitor in the film. By containing, a dense film following the galvanized steel sheet can be formed. Furthermore, it is considered that the active zinc surface is not exposed at the time of film formation and the corrosion resistance and blackening resistance can be made highly compatible by adjusting to a pH region where zinc is hardly dissolved by using carbonic acid.
The surface-treated zinc-based plated steel sheet of the present invention can be applied to various uses, and can be suitably applied to materials used in the fields of architecture, home appliances, automobiles, OA equipment, and the like.

(1) Test plate (galvanized steel plate)
The following commercially available galvanized steel sheets were used as test plates.
(I) Electrogalvanized steel sheet (EG): Plate thickness 0.8 mm, plating basis weight 20/20 (g / m ² )
(Ii) Hot-dip galvanized steel sheet (GI): plate thickness 0.8 mm, plating basis weight 60/60 (g / m ² )
In addition, the plating basis weight is each plating adhesion amount on both surfaces of the steel sheet. For example, the plating basis weight 60/60 (g / m ² ) means that each of both surfaces of the steel sheet has a plating layer of 60 g / m ^2. means.

(2) Pretreatment of test plate (cleaning)
The surface of the test plate (zinc-based plated steel plate) was treated with “Fine Cleaner E6406” manufactured by Nippon Parkerizing Co., Ltd. to remove oil and dirt on the surface. Next, after rinsing with tap water and confirming that the surface of the test plate is 100% wet with water, pour pure water (deionized water), and then dry the moisture in an oven at 100 ° C., This was used as a test plate.

(3) Compound for surface treatment liquid The following were used as the compound for the surface treatment liquid.
(3-1) Production of Silane Compound (A) Production Example 1 (Silane Compound A1)
3-glycidoxypropyltriethoxysilane, tetramethoxysilane, and deionized water were mixed, and ammonia water was added dropwise to precipitate a silane compound. After washing with deionized water, nitrotris (methylenephosphonic acid) was added and stirred to obtain a silane compound A1 having a condensation degree of 4.
Production Example 2 (Silane Compound A2)
A mixture of 3-glycidoxypropyltrimethoxysilane and tetraethoxysilane was added dropwise to a mixture of hydroxyethylenediphosphonic acid and deionized water with stirring at 20 ° C. over 1 hour. Thereafter, aging was performed at 25 ° C. for 2 hours to obtain a silane compound A2 having a condensation degree of 6.
Production Example 3 (Silane Compound A3)
The silane compound A2 of Production Example 2 was further aged at 80 ° C. for 1 hour to obtain a silane compound A3 having a condensation degree of 10.

(3-2) Zirconium carbonate compound (B)
B1: Ammonium zirconium carbonate B2: Sodium zirconium carbonate (3-3) Vanadate compound (C)
C1: ammonium metavanadate C2: vanadyl acetylacetonate (V: 19.2% by mass)

(4) Preparation of surface treatment liquid The above compounds were mixed in water at the ratio shown in Table 1 to obtain a surface treatment liquid for a zinc-based plated steel sheet having a solid content of 15% by mass.

(5) Surface treatment method The above surface treatment solution is adjusted to a predetermined pH, applied to each test plate by bar coating or spraying, and then dried in a hot air oven without washing with water. Formed. The drying conditions were adjusted according to the furnace atmosphere temperature and the time in the furnace.
The bar coat treatment and spray treatment were performed as follows.
Bar coating treatment: The surface treatment solution was dropped onto the test plate and treated with a # 3-5 bar coater. It adjusted so that it might become the predetermined | prescribed film | membrane adhesion amount with the count of the bar coater used and the solid content concentration of the surface treatment liquid.
-Spray treatment: The surface treatment solution was sprayed on the test plate, and the amount of the film was adjusted with a roll coater. It adjusted so that it might become a predetermined | prescribed film | membrane adhesion amount with the conditions of a roll coater, and solid content concentration of a surface treatment liquid.

(6) Method of evaluation test (6-1) Corrosion resistance A test piece having a size of 70 mm × 150 mm was cut out from the test plate on which the surface treatment film was formed, and the back and end portions of the test piece were sealed with vinyl tape, A salt spray test (SST) based on JIS-Z-2371-2000 was performed. The time until the white rust occurrence area ratio in the salt spray test was 5% was measured, and the corrosion resistance was evaluated as follows.
◎: Time until white rust generation area ratio reaches 5% or more 240 hours ○: Time until white rust generation area ratio reaches 5% 120 hours or more, less than 240 hours △: White rust generation area ratio Time until 5% is 72 hours or more and less than 120 hours ×: Time until white rust occurrence area ratio is 5% is less than 72 hours

(6-2) Blackening resistance A test piece having a size of 50 mm × 150 mm was cut out from the test plate on which the surface treatment film was formed, and held in a thermostatic bath at 80 ° C. and 98% RH for 24 hours. The color tone of the test piece before and after holding was measured with a spectrocolorimeter, the color tone was expressed by the L value of the Lab color system, and the blackening resistance was evaluated by the difference ΔL between the L value before and after holding as follows.
A: ΔL ≧ −2
○: −2> ΔL ≧ −4
Δ: −4> ΔL ≧ −6
×: ΔL <−6

(6-3) Water-stain resistance A test piece having a size of 50 mm × 150 mm is cut out from the test plate on which the surface treatment film is formed, and a drop of pure water is dropped on the test piece surface with a dropper, and then placed in an oven at 100 ° C. for 15 minutes. Retained. About this test piece, the trace of pure water was visually observed, and the water resistance was evaluated as follows.
○: No dripping marks are observed.
(Triangle | delta): The dripping trace is observed slightly.
X: The dripping trace is clearly observed.

(6-4) Storage stability of surface treatment liquid After storing the surface treatment liquid in a constant temperature bath at 40 ° C. for 30 days, the appearance of the surface treatment liquid was visually evaluated as follows.
A: No change B: A very small amount of precipitate is observed.
(Triangle | delta): A trace amount precipitation is seen. Or the viscosity became slightly high.
X: A large amount of precipitation is observed. Or it gelled.

The results of the above evaluation tests are shown in Tables 1 to 3 together with the composition and pH of the surface treatment liquid, the pH adjuster, the galvanized steel sheet, and the surface treatment conditions. The drying temperature is the temperature reached on the surface of the test plate.
In the comparative example that does not satisfy the conditions of the present invention, either corrosion resistance or blackening resistance is insufficient. On the other hand, the examples of the present invention are excellent in corrosion resistance and blackening resistance without containing a chromium compound in the surface treatment film, and the surface treatment liquid is also excellent in storage stability.

Claims (3)

A silane compound (A) having a hydrolyzable group obtained from a silane coupling agent (a1) having a glycidyl group, a tetraalkoxysilane (a2) and a phosphonic acid (a3), a zirconium carbonate compound (B), and vanadine Acidic compound (C) and water are contained, pH is adjusted to 7.2-8.0 by the carbonic acid which is a pH adjuster, and it satisfies the following conditions (i)-(iv) Surface treatment solution for galvanized steel sheet.
(I) The silane compound (A) is 30 to 70% by mass in the total solid content of the surface treatment liquid.
(Ii) The ratio (B / A) of the mass of the zirconium carbonate compound (B) in terms of ZrO _{2 and the} mass of the silane compound (A) is 0.3 to 2.0.
(Iii) The ratio (C / A) of the V-converted mass of the vanadic acid compound (C) to the mass of the silane compound (A) is from 0.010 to 0.15.
(Iv) Does not contain fluorine compounds (excluding fluorine compounds contained as inevitable impurities). The surface treatment liquid according to claim 1 is applied to the surface of a galvanized steel sheet and dried, and has a surface treatment film having an adhesion amount per side of 100 to 600 mg / m ^2. Surface treated zinc-based plated steel sheet. The surface-treated zinc according to claim 1, wherein the surface-treated solution is applied to the surface of the galvanized steel sheet so that the amount of adhesion per side after drying is 100 to 600 mg / m ² and then dried. Manufacturing method of a galvanized steel sheet.