JPH11310757A - Water-based surface-treating agent and surface-treated steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a chromium (VI)-free surface-treating agent which can give a treated sheet equivalent in performance to a chromate-treated one and to obtain a surface treated steel sheet on which a coating film of the surface treating agent has been formed. SOLUTION: There is provided a water-based surface-treating agent containing (a) 50-97.9 wt.% (in terms of the sold matter) water-based resin, (b) 2-49.1 wt.% (in terms of the solid matter) colloidal silica, and (c) 0.1-10 wt.% (in terms of the solid matter) ammonium vanadate. It is desirable that the colloidal silica used is at least either of colloidal silica having adsorbed ammonium and colloidal silica coated with aluminum oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to home appliances, construction materials,
The present invention relates to a water-based surface treatment agent and a surface-treated steel sheet which are used for automobiles and do not contain hexavalent chromium and have excellent corrosion resistance.

[0002]

2. Description of the Related Art In the field of surface treatment of steel sheets, a chromate treatment containing hexavalent chromium is frequently used to improve the corrosion resistance of the steel sheets. However, hexavalent chromium is known to be a harmful element, and there is an increasing demand for surface treatment agents and surface-treated steel sheets that do not contain this hexavalent chromium. In addition, electrolytic chromate mainly composed of trivalent chromium may contain a small amount of hexavalent chromium, and may be difficult to use in the future. Chromate treatment is used as a primary rust preventive treatment for steel sheets and plated steel sheets, and as a base treatment for painting and coating. However, development of a chromium-free treatment technology to replace this chromate treatment is desired.

[0003] As a surface treatment technology that does not contain chromium,
There is a phosphate treatment such as a zinc phosphate treatment. However, phosphate treatment is slightly inferior to chromate as a primary rust preventive treatment, and chromium sealing is necessary to ensure corrosion resistance even as a coating base treatment, and is not a sufficient substitute for chromate. It is. JP-A-5-19
No. 5244, “Method for treating metal surface with chromium-free coating type acidic composition” includes a) each of the anionic components,
1) at least four fluorine atoms, 2) at least one element selected from the group consisting of titanium, zirconium, hafnium, silicon and boron, and 3) one or more oxygen atoms as optional components The anion component comprising:
b) a cation component of an element selected from the group consisting of cobalt, magnesium, manganese, zinc, nickel, tin, zirconium, iron, aluminum and copper, wherein the total number of cations is equal to the total number of anions of component a) A cationic component that is at least 1/3, and c) adjusting the pH of the composition to about 0.5.
A chromium-free conversion coating of an aqueous acidic liquid composition comprising a sufficient amount of free acid to keep it within the range of from 5.0 to 5.0 and, optionally, d) a composition that forms an organic resin thin film by direct drying. A metal surface treatment method for forming a surface has been proposed.

Japanese Patent Application Laid-Open No. 145486/1995 entitled "Composition for metal surface treatment and treatment method" includes: a) a fluorine atom and at least one atom of titanium, zirconium, hafnium, silicon and boron. , An ionizable hydrogen atom,
And / or a component comprising an anion containing at least one oxygen atom, provided that the ratio of the number of cations of component b) to the number of anions of component a) is 1/5 or more, and c) a phosphorus-containing organic oxyanion and / or phosphone. A component comprising an acid anion; d) a component comprising one or more of a water-soluble and water-dispersible polymer and a polymer-forming resin; and e) an amount sufficient to maintain the pH of the composition at 0.5 to 5.0. There has been proposed a treatment method for forming a coating layer containing no chromium on a metal surface by using an aqueous composition containing the above acid component.

[0005]

However, any of the chromium-free metal surface treatment methods proposed in the above publications have the same performance as conventional chromate-treated ones, that is, the same corrosion resistance as the chromate-treated one. The film adhesion has not yet been satisfied. The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a surface treatment agent and a surface-treated steel sheet for post-treatment having the same performance as conventional chromate treatment, and for pre-coating. It is.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its gist is as follows.
(1) 50 to 97.9% by weight of an aqueous resin in terms of solid content;
2 to 49.1% by weight of colloidal silica in terms of solid content;
And ammonium vanadate in a solid content of 0.1 to 1
An aqueous surface treating agent characterized by containing 0% by weight;
(2) The aqueous surface treating agent according to (1), wherein the colloidal silica is at least one of colloidal silica on which ammonium is adsorbed and colloidal silica coated with aluminum oxide.

(3) The water-based resin contains a water-soluble or dispersible crosslinker.
Or (2) the aqueous surface treating agent according to (2), (4) the water-soluble or dispersible crosslinking agent is a melamine resin, and the melamine resin contains 0.5 to 15% in terms of solid content. The aqueous surface treating agent according to any one of (1) to (3) above, wherein (5) the aqueous resin is at least one of an acrylic resin, a urethane resin, and an olefin resin.
(1) characterized in that it is a type of emulsion
The aqueous surface treating agent according to any one of (1) to (4),

(6) A surface-treated steel sheet having a film formed on the steel sheet using the aqueous surface treating agent as described in (1) above, (7) a colloidal silica in which colloidal silica has ammonium adsorbed thereon, or The surface-treated steel sheet according to (6), which is at least one kind of colloidal silica coated with aluminum oxide.
(8) The above (6) or (7), wherein the water-based resin contains a water-soluble or dispersible crosslinking agent.
Surface treated steel sheet described in

(9) The method according to (6), wherein the water-soluble or dispersible crosslinking agent is a melamine resin, and the melamine resin contains 0.5 to 15% in terms of solid content. (8) The surface-treated steel sheet according to any of (8),
(10) The surface-treated steel sheet according to any one of (6) to (9), wherein the aqueous resin is at least one kind of emulsion among an acrylic resin, a urethane resin, and an olefin resin. The surface-treated steel sheet according to any one of the above (6) to (10), wherein the steel sheet is a plated steel sheet.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The surface treating agent and the surface treated steel sheet of the present invention will be described below. The aqueous resin includes a water-soluble resin and a dispersed resin such as an emulsion or a suspension. As the type of resin, olefin resin,
Urethane resin, acrylic resin, polycarbonate resin,
Epoxy resins, polyester resins, alkyd resins, phenolic resins, and other resins as baking paints, and the like, from which one or more resins can be selected. Further, these copolymer resins and mixed resins can also be used. The content of the resin is desirably 50 to 97.9% in terms of the weight of the solid content. When the content is less than 50%, the treated film becomes hard, and the processed portion is difficult to peel off or to form a film. 9
If it exceeds 7.9%, the amount of other components contributing to corrosion resistance and the like becomes small, so that the corrosion resistance becomes insufficient.

[0011] The aqueous resin may contain a crosslinking agent resin. As the crosslinking agent, a resin soluble or dispersible in water can be used, and a water-soluble amino resin, a blocked isocyanate compound (urethane resin),
Epoxy resins and the like can be mentioned. In particular, water-soluble amino resins (melamine resins, glycoluril resins, urea resins)
When used, the strength of the film is increased, the corrosion resistance is improved, and the film is more resistant to scratches. Since the optimum amount of the crosslinking agent varies depending on the type, the amount of the crosslinking agent is optional. In the case of a water-soluble melamine resin, the solid content in the treating agent is desirably 0.5 to 15%. If it is less than 0.5%, the strength will not increase, and if it exceeds 15%, the film will be too hard, and the processed portion will be easily cracked or peeled, and the corrosion resistance will be reduced.

The use of at least one emulsion among an acrylic resin, a urethane resin and an olefin resin as the water-based resin improves the corrosion resistance particularly. The colloidal silica is not particularly limited as long as it has few impurities such as sodium and is weakly alkaline. For example, "Snowtex N", "Snowtex NS", "Snowtex NXS", "Snowtex 30", "Snowtex 40", "Snowtex C", "Snowtex S", "Snowtex 20L", "Snowtex XS", "Snowtex XL" (all manufactured by Nissan Chemical Industries, Ltd.), "Adelite AT-20N", "Adelite AT-20A" (all manufactured by Asahi Denka Kogyo) and the like. The amount of colloidal silica to be added is 2 to 49.1% as a weight of solid content in the treating agent. If it is less than 2%, the corrosion resistance decreases and the film strength is insufficient. If it exceeds 49.1%, it becomes too hard and cracks, peeling, etc. of the treated film occur in the processed portion, resulting in poor corrosion resistance.

When at least one of an ammonium ion adsorption type and an aluminum oxide coating type is used as the colloidal silica, the corrosion resistance is particularly improved. In the above example, "Snowtex N", "Snowtex NS",
"Snowtex NXS", "Adelite AT-20"
"N" is an example of the former, and "Adelite AT-20A" is an example of the latter. Ammonium vanadate has a high rust prevention effect.
0.1 to 10% in terms of solid content in the treatment bath. If it is less than 0.1%, corrosion resistance is insufficient, and if it exceeds 10%, economic efficiency is lacking.

The feature of the present surface treating agent is that ammonium vandate and colloidal silica are used in combination. It is considered that ammonium vandate is adsorbed on the surface of colloidal silica and synergistically improves the rust prevention effect. In particular, when the colloidal silica is of an ammonium-in adsorption type or an aluminum oxide coating type, it is considered that the colloidal silica is easily adsorbed and the corrosion resistance is improved.

The pH of the treatment bath is not particularly limited, but is preferably 8 to 10. If the pH is less than 8, the bath life becomes short. If the pH exceeds 10, the base metal is dissolved by the alkali component, and the base metal is eluted into the treatment bath, which may cause a decrease in adhesion and corrosion resistance. In addition, bath stability may decrease. Drugs can be added to adjust the pH of the bath.

The surface treating agent of the present invention may contain a known solvent or a film-forming auxiliary agent for improving the film-forming property and forming a uniform and smooth coating film. For example, alcohol-based, ketone-based, ester-based, and ether-based ones can be used. Adding a solvent requires that water
It is also useful for preventing volatilization at once and preventing the occurrence of armpits.

The surface treating agent of the present invention may contain other components. For example, pigments, surfactants, additives, silane coupling agents and the like. Examples of the pigment include inorganic pigments such as titanium oxide, zinc oxide, zirconium oxide, calcium carbonate, barium sulfate, aluminum oxide, kaolin gray, carbon black, and iron oxide, and organic pigments such as cyanine blue. As the silane coupling agent, for example, γ-aminopropyltrimethoxysilane,
γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, N- (2- (vinylbenzylamino) ethyl) -3-aminopropyltrimethoxysilane, etc. Can be Examples of the additive include an antifoaming agent, a leveling agent, a surface tension adjusting agent, and the like.

The above-mentioned surface treatment agent is applied on a steel plate by a known method, and is dried and baked to form a surface treatment film. The application method is not particularly limited, and a known method can be used. Examples thereof include a method such as roll coating, spraying, air knife, spin coating, curtain coating, and dip coating. If necessary, the surface treatment agent of the present invention can be applied after performing a pretreatment on the surface of the steel sheet by a known method. For example, water washing, hot water washing,
Examples include alkali degreasing, pickling, grinding, brushing, and solvent degreasing.

Examples of the steel sheet to be treated include a cold-rolled steel sheet, a hot-rolled steel sheet, a galvanized steel sheet, a zinc alloy-coated steel sheet in which the alloy element is at least one of Ni, Cr and Fe, the above-described zinc-coated steel sheet, A zinc-based dispersion-coated steel sheet in which metal oxides such as SiO ₂ , TiO ₂ , ZrO ₂ , and BaCrO ₄ are dispersed and precipitated based on a zinc alloy-coated steel sheet;
Hot-dip galvanized steel sheet, alloyed hot-dip galvanized steel sheet, zinc-aluminum alloy-plated steel sheet, chromium-plated steel sheet, nickel-plated steel sheet, tin-plated steel sheet, stainless steel sheet and the like can be mentioned.

The amount of the surface treatment agent deposited after drying is not particularly limited, but is preferably 0.1 to 20 g / m ² , more preferably 0.2 to 10 g / m ² . If it is less than 0.1 g / m ² , corrosion resistance cannot be ensured, and if it exceeds 20 g / m ² , the drying time becomes long and efficient production is difficult. Further, the film adhesion of the Erichsen-processed portion and the coating film adhesion of the Erichsen-processed portion after the top coat has been applied are reduced. Further, the corrosion resistance of the Erichsen processed part may be reduced. The conditions for drying and baking the surface treatment agent are not particularly limited, but it is desirable that the reached plate temperature be 40 to 250 ° C. If the temperature is lower than 40 ° C., it takes a long time for drying, which is not reasonable for industrial production. Also, when the temperature exceeds 250 ° C., a drying oven having a high capacity is required, which is not desirable. Further, the film may be excessively hardened, and the film may be hardened, and the workability and the corrosion resistance of the processed portion may be reduced. The method of drying is not limited, but hot air heating,
Known methods such as induction heating, near-infrared heating, far-infrared heating, and indirect heating can be applied. A method may be used in which the steel sheet is preheated, applied while hot, and dried with residual heat.

It is also possible to treat the same surface a number of times with the surface treatment agent according to the invention. That is, it is also possible to form a multi-layered film by forming the first layer on a steel sheet by the above-described method and then forming the second layer by the same method. In this case, the adhesion amount after drying may exceed 20 g / m ² . The formation of each layer need not necessarily be performed under the same conditions.

[0022]

EXAMPLES The present invention will be described with reference to examples. A 0.8 mm thick electrogalvanized steel sheet having a coating weight of 20 g / m ² per side was degreased with a 2% strength solution of Surf Cleaner 155 (manufactured by Nippon Paint Co., Ltd.) at 60 ° C. for 10 seconds, washed with water and dried. . Next, a surface treatment agent having the composition shown in Tables 1 and 2 was applied by a roll coater and dried in a hot air drying oven. The drying conditions are shown in Tables 1 and 2. In addition,
Amino alcohol 2M-AB for pH adjustment of treatment agent
S (DMEA) (manufactured by Kokusan Chemical Co., Ltd.) was used as needed. Also, a hot-dip galvanized steel sheet having a coating weight of 60 g / m ² per side and a thickness of 0.8 mm, a galvannealed steel sheet having a coating weight of 40 g / m ² per side and a thickness of 0.8 mm, 20 g / m ² per side
A surface-treated steel sheet using a 0.8 mm-thick zinc-nickel alloy-plated steel sheet (nickel content: 11% by weight) as a base plate was also prepared and evaluated by the same method. The plating types are shown in Tables 1 and 2. EG is galvanized steel sheet, GI
Is a hot-dip galvanized steel sheet, GA is a galvannealed steel sheet, and ZN is a zinc-nickel alloy-plated steel sheet. Table 1
The contents of the surface treatment agents shown in Table 2 are as follows.

[0023]

[Table 1]

[0024]

[Table 2]

1. Resin type Olefin-based: "HI-TECH S-7024" (manufactured by Toho Chemical) Urethane-based: "Bon Titer HUX-320" (manufactured by Asahi Denka) Acrylic: "AP-1058 (12)" (manufactured by Toa Gosei) Epoxy System: “Polysol 8500” (manufactured by Showa Polymer Co., Ltd.) Polyester system: “Pesresin A-124G” (manufactured by Takamatsu Yushi Co., Ltd.)

2. Crosslinking agent S327: Cymel 327 (manufactured by Mitsui Cytec) 3. Colloidal silica ST-N: "Snowtex N" (manufactured by Nissan Chemical Industries, Ltd.) AT-20N: "Adelite AT-20N" (manufactured by Asahi Denka Kogyo) AT-20A: "Adelite AT-20A" (Asahi Denka Kogyo) ST-S: "Snowtex S" (manufactured by Nissan Chemical Industries, Ltd.) Ammonium vanadate: manufactured by Wako Pure Chemical Industries. Powder. Used by dissolving in processing agent.

The following evaluation was performed on the prepared surface-treated steel sheet. 1. Finished Appearance The appearance of the treated film was visually judged and scored. The rating was 5: uniform, 4: extremely slight unevenness, 3: partially uneven, 2: overall uneven, 1: severe unevenness over the entire surface.

2. Adhesion of the surface-treated film The adhesion was determined by the cross-cut tape method (clearance interval: 1 mm) described in JIS K 5400, 8.5.2. Further, the surface-treated steel sheet was extruded by 7 mm with an Erichsen tester specified in 8.2 of JIS K 5400, and the extruded portion was tape-peeled to examine the adhesion of the film. When it is difficult to determine by visual inspection, 0.1% of methyl violet
% Acetone solution, the film exists in the dyed part, and the film does not exist in the unstained part.
The adhesiveness was determined. The same applies to the evaluation of the appearance of the treated film.

3. Olga Select 100 which is a melamine alkyd paint
(Nippon Paint Co., Ltd.) was applied by spraying to a dry film thickness of 25 μm, dried and baked in a hot-air oven at 150 ° C. for 20 minutes, and the adhesion was confirmed in the same manner as in 2. Also, JIS
7 with the Erichsen tester specified in 8.2 of K 5400
After extruding mm, the Erichsen-processed portion was peeled off with a tape in the same manner as in 2, and the adhesion of the coating film was examined and rated. The rating was 10; no peeling, 8; peeled area of 5% or less, 6; peeled area of more than 5% and 10% or less, 4; more than 10% 3
The peeled area was 0% or less, and the peeled area was more than 30%.
Further, after the surface-treated steel sheet was immersed in boiling water for 30 minutes and allowed to stand for 24 hours, the adhesion of the coating film after the application of the amylac coating film by the above-described method was examined.

4. Fingerprint resistance Fingerprints were attached to the film of the surface-treated steel sheet, and the visibility of the fingerprints was visually judged and scored. The rating was 5: no fingerprint mark was visible, 4: very slight fingerprint mark was visible, 3: fingerprint mark was visible, 2: fingerprint mark was noticeable, 1: fingerprint mark was very noticeable.

5. Condensation resistance Water droplets of distilled water were dropped on the film surface of the surface-treated steel sheet, and left for one day to dry the water. After that, traces were visually judged and scored. The score is 5: no trace, 4: very slight trace, 3: trace remains, 2: trace trace is outstanding,
1: It was determined that traces were very noticeable.

6. Corrosion resistance (SST) Flat plate (seal end and back of steel plate as cut)
Salt water spray test (specified in JIS Z 2371) for a 7 mm Erichsen machined part (the end face and the back face of a steel sheet extruded by 7 mm with an Erichsen test machine are sealed)
And the area ratio (%) of the generated white rust was visually determined.

[7] Solvent resistance Press oil was impregnated into the case and applied on the film of the surface-treated steel sheet. The oil was wiped off with gauze impregnated with ethanol or kerosene, and the marks on the film were visually judged and scored. In order to clean oil stains and the like, an operation of wiping with a solvent such as kerosene or ethanol is sometimes performed. At this time, the test is performed to evaluate whether or not the film is damaged by these solvents. The rating was 5: no trace, 4: extremely slight trace, 3: trace trace, 2: trace trace was noticeable, 1: trace trace was very noticeable.

The evaluation results are shown in Tables 1 and 2. In the comparative inorganic chromate treatment, silica (Snowtex O, manufactured by Nissan Chemical Industries, Ltd.) was added to chromic acid having a reduction ratio of 40% so that chromic acid / silica = 1/3 (weight ratio of solid content). Using an agent, the amount of adhesion was adjusted to 50 mg / m ² as Cr using an air knife, and dried at a drying plate temperature of 60 ° C. was used (Comparative Example No. 43). Further, a treatment agent obtained by adding 5% of strontium chromate and 28% of Snowtex N as a rust preventive agent to 67% by weight of olefin resin in terms of solid content and having an adhesion amount after drying of 1.0 g / m ² was obtained. A surface-treated steel sheet coated with a roll coater and dried at an ultimate sheet temperature of 150 ° C. was also used for comparison (Comparative Example No. 4).
2).

The white rust generation area ratio (plane portion) of the comparatively No. 43 chromate-treated steel sheet and the surface-treated steel sheet in which a film obtained by adding a chromium-based rust-preventive pigment to the resin of No. 42 was 72 hours after spraying with salt water, was as follows. 3% and 5%. Among the examples, except that the coating amount of No. 1 was as low as 0.1 g / m ² , all had the same or higher corrosion resistance, and the surface treatment agent and the surface-treated steel sheet according to the present invention contained harmful hexavalent chromium. It can be seen that the material has no high corrosion resistance. Also,
The dew condensation resistance is also remarkably excellent, and it can be seen that there is no deterioration in performance due to poor appearance or elution of components even after exposure to a dew condensation environment.

In No. 8 of the examples, the adhesion of the film was 15 g /
m ² , which is out of the preferable range, and the top coat adhesion (2
Next) and the corrosion resistance of the Erichsen part is slightly inferior. No. 18 of the comparative example was a level at which silica was not added, and was inferior in corrosion resistance, adhesion, and solvent resistance. Comparative Examples No22 and No23 have a low resin content, and in particular, No23 also has an excessive amount of added silica, and the appearance, adhesion, topcoat adhesion,
Poor corrosion resistance. In Comparative Example No. 24, no ammonium vanadate was added, and adhesion and corrosion resistance were poor. Comparative Example N
o29, the added amount of ammonium vanadate is too large,
Poor adhesion and appearance. Comparative Example No. 30 had neither silica nor ammonium vanadate added, and had poor adhesion and corrosion resistance.

A comparison between Example No. 41 and Nos. 5, 9 and 10 shows that the silica type is ammonia adsorption type (ST-N, A
T-20N) or aluminum oxide coated type (AT-20)
It can be seen that A) has better corrosion resistance than other silicas (ST-S). Nos. 11, 36, 37, 38, 39, and 40, which are examples including a cross-linking agent in an aqueous resin, are referred to as No. 15, which is an example not including a corresponding cross-linking agent, respectively.
As compared with 31, 32, 33, 34 and 35, it can be seen that the examples containing the crosslinking agent have better corrosion resistance and better solvent resistance.

When the types of resins are compared, olefins,
It turns out that acrylic type and urethane type are good. For example, it is good to compare No5, 31, 32, 33, 34, 35. The storage stability of the treating agents shown in the examples was good, and there was no change in quality at room temperature for 3 months or more and at 40 ° C. for 2 weeks or more. In addition, it was confirmed that the performance as a surface-treated steel sheet did not change over time after storage for one year. Even when the plating type of the original plate is changed,
ADVANTAGE OF THE INVENTION According to this invention, the surface treatment steel plate excellent in corrosion resistance, dew condensation resistance, and an overcoat film adhesion is obtained.

[0039]

As described above, the surface treating agent and the surface-treated steel sheet according to the present invention can be prepared by combining conventional chromate treatment and chromium-based rust preventive treatment by combining ammonium vanadate containing no hexavalent chromium and silica in an aqueous resin. Compared to pigment-containing treatment agents and coatings, it has excellent dew condensation resistance and almost the same corrosion resistance. That is, the present invention provides a surface treatment agent and a surface-treated steel sheet having low pollution and excellent rust prevention ability.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Motoo Kamiya, 4-1-1-15 Minamishinagawa, Shinagawa-ku, Tokyo Japan Paint Co., Ltd. Tokyo Office (72) Inventor Satoshi Kobori 4-chome Minamishinagawa, Shinagawa-ku, Tokyo 1-115 Nippon Paint Co., Ltd. Tokyo Office (72) Inventor Masateru Takimoto 2-1-2 Oyodo Kita, Kita-ku, Osaka-shi, Osaka Nippon Paint Co., Ltd. Osaka Office (72) Inventor Toshiaki Shimakura Shinagawa-ku, Tokyo 4-1-1-15 Minamishinagawa Japan Paint Co., Ltd. Tokyo Office

Claims (11)

[Claims] 1. An aqueous resin having a solid content of 50 to 97.9.
% By weight, colloidal silica is 2 to 49.1 in terms of solid content.
An aqueous surface treating agent comprising 0.1% to 10% by weight of ammonium vanadate in terms of solid content. 2. The aqueous surface treating agent according to claim 1, wherein the colloidal silica is at least one of colloidal silica on which ammonium is adsorbed and colloidal silica coated with aluminum oxide. 3. The aqueous surface treating agent according to claim 1, wherein the aqueous resin contains a water soluble or dispersible crosslinking agent. 4. The method according to claim 1, wherein the water-soluble or dispersible crosslinking agent is a melamine resin, and the melamine resin contains 0.5 to 15% in terms of solid content. The aqueous surface treating agent according to any one of the above. 5. The aqueous surface treating agent according to claim 1, wherein the aqueous resin is at least one kind of emulsion among acrylic resin, urethane resin and olefin resin. 6. A surface-treated steel sheet having a film formed on the steel sheet using the aqueous surface treating agent according to claim 1. 7. The surface-treated steel sheet according to claim 6, wherein the colloidal silica is at least one of colloidal silica on which ammonium is adsorbed and colloidal silica coated with aluminum oxide. 8. The surface-treated steel sheet according to claim 6, wherein a water-soluble resin contains a water-soluble or dispersible crosslinking agent. 9. The method according to claim 6, wherein the water-soluble or dispersible crosslinking agent is a melamine resin, and the melamine resin contains 0.5 to 15% in terms of solid content. The surface-treated steel sheet according to any one of the above. 10. The surface-treated steel sheet according to claim 6, wherein the aqueous resin is at least one kind of emulsion among acrylic resin, urethane resin and olefin resin. 11. The surface-treated steel sheet according to claim 6, wherein the steel sheet is a plated steel sheet.