KR20090065020A - Chrome-free treatment agents having boiling resistance and corrosion resistance, producing method using the treatment agent and steel sheets produced by the method - Google Patents

Abstract

A chrome-free treatment agent, a fuel tank steel sheet for baffle and a manufacturing method thereof using the chrome-free treatment agent are provided to obtain a fuel tank steel sheet for baffle with superior boiling and corrosion resistances without including a surface treatment resin layer on the chrome-free layer. A chrome-free treatment agent contains silicate 3-40 weight%, silane 0.5-10 weight%, ammonium phosphate 0.1-2 weight%, titanium phosphate 1-5 weight%, urethane resin and epoxy resin or the resin mixture 10-50 weight%, and the remnant. The silicate is NaSiO3, and NaSi5O11 or their mixture. The silane is gamma - glycidoxy propyl triethoxy silane and gamma - aminopropyltriethoxysilane or their mixture.

Description

CHROME-FREE TREATMENT AGENTS HAVING BOILING RESISTANCE AND CORROSION RESISTANCE, PRODUCING METHOD USING THE TREATMENT AGENT AND STEEL SHEETS PRODUCED BY THE METHOD}

The present invention relates to a chromium-free treatment liquid of a fuel tank steel plate for automobiles, a method for manufacturing a fuel tank steel sheet for baffles, and a fuel tank steel sheet manufactured, more specifically, comprising a steel plate / plating layer / chromium-free layer. The present invention relates to a fuel tank steel plate for baffle having excellent surface properties without including a surface treatment resin layer on the chromium-free layer.

The fuel tank steel plate currently used is developed and produced with one side treatment of resin after chrome-free treatment.

The resin coated steel sheet currently used as a fuel tank steel sheet for automobiles is an eco-friendly steel sheet which does not use lead and chromium at all. These resin coated steel sheets mainly exhibit various performances depending on the physical properties of the resin treated film.

In Korean Patent No. 0782719, a film containing Cr-free component is formed on the base, and a resin layer of phenoxy resin is formed on the upper portion to improve corrosion resistance and fuel resistance. However, such a resin coated steel sheet is so high that the cost of the upper resin layer is rising due to the increase in manufacturing cost of the automobile company, and the situation is avoiding the use of the resin coated steel sheet. Therefore, it is necessary to develop a resin-free fuel tank steel plate in which a chrome-free coating is coated on a zinc-nickel alloy plated steel sheet.

In order to reduce cost, the baffle material is changed from Zn-Ni steel sheet to Zn-based steel sheet as a base steel sheet, which is showing a movement to lower the steel sheet price. Along with this movement, there has been an attempt to develop a product composed of only chromium-free layers by omitting the resin layer formed after chromium-free treatment in view of cost reduction of the automobile company and shortening of the process of the manufacturer.

Previously, the same coating was used for both the steel plate for the body constituting the body of the fuel tank, and the baffle steel plate, which is a partition installed inside the fuel tank to prevent the vehicle from falling when fuel is biased out due to centrifugal force when the vehicle rotates at a high speed. Has come.

Since the resin-free fuel tank steel plate does not have a resin layer but requires the physical properties of a steel plate having a resin layer using only a chromium-free layer, it requires not only an adhesion amount but also an improvement in the compactness of the film, and thus has a slightly different composition from the existing chromium-free layer. Must have

In addition, the chromium-free layer alone must not only meet the properties required for fuel tank steel sheets, but also meet the ever-increasing requirements of customers, such as tougher anti-rust regulations (10-20 years) for automotive steel sheets. .

Furthermore, there should be resistance to alternative fuels caused by the recent surge in fossil fuel prices. These alternative fuels include ethanol fuel produced from South American sugar cane, which can be mixed with gasoline, and biodiesel, which can be mixed with diesel, and biodiesel with soybean oil mainly in Korea and Japan. Biodiesel using waste cooking oil and biodiesel using rapeseed oil mainly used in Europe are roughly classified. The amount of mixing is limited in each country. In Korea, it is allowed to be around 5% except for some vehicles. In addition, the CRDI (Common Rail Direct Injection) engine, which is developed for fuel efficiency and vehicle quietness, injects compressed diesel at very high pressure, which causes the temperature of the fuel to rise to 80 to 100 ° C. It is necessary to improve the fuel resistance of fuel tank steel sheets.

An object of the present invention is to provide a chromium pretreatment liquid based on a pure galvanized steel sheet and excellent corrosion resistance and boiling resistance without forming a resin layer, a fuel tank steel plate for baffle treated with the chromium pretreatment liquid, and a method for manufacturing the steel sheet. It is done.

Furthermore, the present invention is to develop a fuel tank steel plate for baffle using a pure galvanized steel sheet steel sheet.

The present invention to achieve the above object,

As a first aspect, a chromium-free treatment liquid for chromium-free layer formation of a fuel tank steel plate for baffle composed of a galvanized layer and a chromium-free layer, comprising: 3-40% by weight of silicate; Silane 0.5-10% by weight; 0.1-2% by weight of ammonium phosphate; 1-5% by weight of titanium phosphate; 10-50% by weight of urethane resin, epoxy resin or a mixture of these resins; And chromium-free treatment liquid containing the balance water,

As a second aspect, the silicate is NaSiO ₃ , NaSi ₅ O ₁₁ or a mixture of chromium-free treatment, characterized in that

As a third aspect, the silane is a chromium-free treatment liquid, characterized in that γ-glycidoxypropyltriethoxysilane, γ-aminopropyltriethoxysilane or a mixture thereof,

As a fourth aspect, the urethane resin and epoxy resin provides a chromium-free treatment liquid, characterized in that the glass transition temperature (Tg) is 70-130 ℃,

As a fifth aspect, a fuel tank steel plate for a baffle composed of a galvanized layer and a chromium free layer, wherein the chromium free layer comprises: 3-40% by weight of silicate; Silane 0.5-10% by weight; 0.1-2% by weight of ammonium phosphate; 1-5% by weight of titanium phosphate; 10-50% by weight of urethane resin, epoxy resin or a mixture of these resins; And a fuel tank steel plate for a plating layer / chromium-free layer baffle, which is manufactured from a chromium-free treatment liquid containing residual water.

As a sixth aspect, the zinc plated layer is a fuel tank steel plate for plating layer / chromium-free layer baffle, characterized in that the zinc is electroplated with a plating adhesion amount of 20-30g / ㎡ to the cold rolled steel sheet,

As a seventh aspect, the chromium-free layer is a fuel tank steel plate for the plating layer / chromium-free layer baffle, characterized in that the dry coating film adhesion amount 500-1000mg / ㎡

As an eighth aspect, the silicate is NaSiO ₃ , NaSi ₅ O ₁₁ or a mixture of these fuel tank steel plate for chrome-free layer baffle,

In a ninth aspect, the silane is γ-glycidoxypropyltriethoxysilane, γ-aminopropyltriethoxysilane, or a mixture thereof, the fuel tank steel plate for baffle plating / chromium free layer,

As a tenth aspect, the urethane resin and epoxy resin provides a fuel tank steel plate for plating layer / chrome-free layer baffle, characterized in that the glass transition temperature (Tg) is 70-130 ℃,

In an eleventh aspect, silicate 3 to 40% by weight of a chromium-free treatment liquid on an electrogalvanized steel sheet; Silane 0.5-10% by weight; 0.1-2% by weight of ammonium phosphate; 1-5% by weight of titanium phosphate; Applying a chromium-free treatment liquid comprising 10-50% by weight of a urethane resin, an epoxy resin or a mixture of these resins; And calcining the steel plate coated with the chromium-free treatment liquid at a steel plate temperature of 160-200 ° C. to form a chromium-free layer.

As a twelfth aspect, the electrogalvanized steel sheet is a method for manufacturing a fuel tank steel plate for plating layer / chromium-free layer baffle, characterized in that the galvanized amount of 20-30g / ㎡ in cold-rolled steel sheet,

In a thirteenth aspect, the method for producing a fuel tank steel plate for a plating layer / chromium-free layer baffle, wherein the chromium-free layer has a dry coating amount of 500-1000 mg / m 2.

In a fourteenth aspect, the silicate is NaSiO ₃ , NaSi ₅ O ₁₁ or a mixture of them, characterized in that the fuel tank steel plate manufacturing method for plating layer / chrome-free layer baffle, and

In a fifteenth aspect, the silane provides γ-glycidoxypropyltriethoxysilane, γ-aminopropyltriethoxysilane, or mixtures thereof, and provides a method for manufacturing a fuel tank steel plate for a baffle of a plating layer / chromium-free layer. .

According to the present invention, it is possible to obtain a fuel tank steel plate for baffle composed of only steel sheet / plating layer / chromium-free layer and having excellent surface characteristics without including a surface treatment resin layer on the chromium-free layer.

By using the chromium-free treatment liquid according to the present invention, a fuel tank steel sheet excellent in boiling resistance and corrosion resistance at low cost can be obtained.

Baffle fuel tank steel plate according to the present invention has excellent physical properties having the required adhesion, corrosion resistance, fuel resistance and weldability.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The chromium-free surface-treated steel sheet for baffles of fuel tanks, which does not contain chromium of the present invention and does not contain a resin layer and has excellent adhesion, corrosion resistance, fuel resistance, boiling resistance and weldability with the plating layer, is electrogalvanized on cold rolled steel sheet. It consists of a plated layer and a chromium-free layer, and does not include a separate resin layer.

In the chromium-free surface-treated steel sheet of the present invention, the base steel sheet is not limited thereto. For example, an electro galvanized steel sheet electroplated with zinc (Zn) on a cold rolled steel sheet may be used. In the case of using a galvanized steel sheet composed of such zinc alone, it is advantageous in terms of cost reduction. In the electrogalvanized steel sheet, the plating amount of zinc is preferably 20-30 g / m 2. If the plating amount is less than 20 g / m 2, the plating deposition amount is small and the sacrificial method is less.

In the steel sheet according to the present invention, a chromium free layer is formed on the base steel sheet. The chromium-free layer is formed by coating, baking and drying the chromium-free treatment liquid. The chromium-free treatment liquid is generally classified into a reaction type and a coating type, and it is preferable to use a coating type treatment liquid excellent in terms of double corrosion resistance.

The chromium-free treatment liquid used to form the chromium-free layer may include water, silicates and silanes; Titanium phosphate and ammonium phosphate capable of enhancing the bond with the plating layer; And a binder resin made of urethane and / or epoxy resin having excellent adhesion in order to improve the physical properties of the coating, especially adhesion to the steel sheet.

Furthermore, the chromium free treatment liquid of the present invention may further include a wetting agent, a defoaming agent, and the like, as necessary. The main chromium-free treatment liquid, titanium phosphate and ammonium phosphate, and a binder resin are dispersed in water, and remainder except these components is made of water.

As a silicate which is a main component of the chromium-free treatment solution of the present invention, NaSiO ₃ and / or NaSi ₅ O ₁₁ may be used. Plated steel sheet) and excellent bonding strength.

Silicate may be used in an amount of 3 to 40% by weight in 100% by weight of the chromium-free treatment liquid. If the silicate content is less than 3% by weight, the content is too small to give adhesion to the steel sheet and excellent corrosion resistance, and if it exceeds 40% by weight, the bonding strength with the resin is weak, which is not preferable.

Furthermore, silane, one of the main components, is hydrolyzed in water to form a siloxide bond, which forms a strong bond with the steel sheet and binds various inorganic materials at the same time. Do it. The silane used in the chromium-free treatment liquid of the present invention is not particularly limited, but, for example, gamma glycidoxypropyltriethoxy silane and / or gamma aminopropyl tree which are well hydrolyzed. It is preferable to use ethoxysilane ((gamma) -aminopropyltriethoxy silane), As a commercial item, KBM series of Shin-Etsu Chemical can be purchased and used.

The silane may be used in an amount of 0.5 to 10% by weight in 100% by weight of the chromium-free treatment liquid. If the content is less than 0.5% by weight, the content is too small to show adhesion to the steel sheet and excellent corrosion resistance. If the content is more than 10% by weight, no further improvement in physical properties is not preferable in terms of economics.

The silicate, the silane and the titanium compound are mixed and used as the subject of the chromium-free treatment liquid, and it is preferable to add the binder resin having excellent adhesion and titanium phosphate and ammonium phosphate to improve the adhesion after this subject. The main reason for this is to maintain the stability of the binder resin, titanium phosphate and ammonium phosphate added later by reacting the silicate with the silane in advance.

The chromium-free treatment liquid of the present invention contains ammonium phosphate and titanium phosphate as titanium phosphate and ammonium phosphate. These titanium phosphate and ammonium phosphate serve to strengthen the bond between the chromium-free treatment layer and the plating layer formed of the chromium-free treatment liquid of the present invention, and further improve the corrosion resistance. That is, ammonium phosphate is bonded to Zn and silane of the plating layer, and titanium phosphate reacts with Zn of the plating layer to form a multiple bond. Such multiple bonds improve not only corrosion resistance but also adhesion between the chromium free layer and the plating layer.

The ammonium phosphate preferably has a content of 0.1 to 2% by weight in 100% by weight of the chromium-free treatment liquid. If it is less than 0.1% by weight, the effect of improving the corrosion resistance is insufficient, and if it exceeds 2% by weight, solution stability becomes poor, and it is preferable to have the above content range.

Furthermore, the titanium phosphate preferably has a content of 1 to 5% by weight in 100% by weight of the chromium-free treatment liquid. If it is less than 1% by weight, the corrosion resistance is inferior, and if it exceeds 5% by weight, solution stability becomes poor, and it is preferable to have such a content range.

An epoxy resin, a urethane resin, or a mixture thereof having good bonding strength with a steel sheet may be added to the chromium-free treatment liquid of the present invention as a binder resin for linking the inorganic main material, titanium phosphate, and ammonium phosphate to each other. Epoxy resins contain hydroxyl groups in the resin molecule, which hydroxyl groups react with the steel sheet and the remaining reactors serve to bind the inorganic additives. Urethane resin is also suitable for use as binder resin because it reacts with steel sheet and binds inorganic additives like epoxy resin, and also has the advantage that the resin itself is flexible.

Furthermore, the binder resin preferably has a Tg of 70 or more so as to have high resistance to high temperature diesel fuel in an engine such as CRDI. Furthermore, since coating becomes difficult when said Tg exceeds 130 degreeC, it is preferable that it is 130 degrees C or less.

The binder resin may be added in 10 to 50% by weight in 100% by weight of the chromium-free treatment liquid. If it is less than 10% by weight, the resin content to bind is low, insufficient adhesion to the steel sheet and the ability to combine the inorganic additives, stains on the surface of the steel sheet upon washing, and the film is damaged even after applying to the steel sheet is not suitable, 50% by weight It is not preferable to exceed the resin content because the resin content is too high and corrosion resistance and weldability deteriorate.

The chromium-free treatment liquid of the present invention is applied to the plated steel sheet and baked to form a chromium-free layer.

The chromium-free treatment liquid may be applied to the base steel sheet (plated steel sheet) so that the dry coating amount is 500-1,000 mg / m 2. If the adhesion amount is less than 500 mg / m 2, it is difficult to secure desired corrosion resistance and fuel resistance. If the adhesion amount is more than 1000 mg / m 2, weldability is deteriorated, which is not preferable.

After coating the chromium-free treatment liquid, it is baked at a temperature range of 160 to 200 ° C based on the MT (Metal Temperature). If the baking temperature is less than 160 ℃, it is difficult to secure the desired corrosion resistance because some of the components are eliminated when washing the resin and the inorganic material.If the baking temperature exceeds 200 ℃, the curing reaction does not occur any more and the calorie loss is so large. .

The chromium-free layer may be applied to one side or both sides of the plated steel sheet. The chromium-free treatment solution can be applied to the steel sheet by various coating methods such as roll coating by roll, spray method, and deposition method. The roll coating method is most preferable because the chromium treatment liquid can be applied simultaneously to one or both surfaces of the plated steel sheet.

For example, the equipment for applying the chromium-free treatment liquid is a method in which a solution in a drip pan is buried in a pickup roll, transferred to a transfer roll, and finally coated in a plated steel sheet on an applicator roll, and then dried in an oven to form a final coating. The chromium free layer may be formed on the plated steel sheet. The adhesion amount of the chromium-free treatment liquid can be adjusted by the driving direction of each roll, the rotational speed, the mutual adhesion pressure of each roll, and the like.

Thus, according to this invention, the steel plate which consists of the chromium free layer which does not contain Cr formed on the Zn electroplated steel sheet which does not contain Cr component is provided. The steel sheet according to the present invention is excellent in adhesion, corrosion resistance, fuel resistance, boiling resistance and weldability, and is suitable for use as a baffle steel sheet for automobile fuel tanks.

Hereinafter, the present invention will be described in detail by way of examples. The following examples illustrate the invention but do not limit the invention.

Example 1

Incorporating silicate, silane, ammonium phosphate, titanium phosphate, and urethane resin into water in an amount of 20 g / m 2 plated zinc plated electrogalvanized steel sheet in an amount as shown in Table 1 to Inventive Materials 1 to 16 and Comparative Materials 1-10 chromium-free treatment liquids were prepared, and the prepared chromium-free treatment liquid was roll-coated to the steel plate so that dry coating film adhesion amount might be 800 mg / m <2>, and it baked at 160 degreeC steel plate temperature, and cooled.

In preparing the chromium-free treatment liquid, the silicate and the silane were first blended, followed by addition of a urethane resin, ammonium phosphate and titanium phosphate.

Then, the evaluation of the corrosion resistance, solution stability, boiling resistance by performing a quality evaluation on the manufactured steel sheet is shown in Table 1 below.

Example 2

After the zinc plated deposition amount was plated at 20 g / m 2 on the cold rolled steel sheet, 20 wt% of silicate, 2 wt% of silane, 0.5 wt% of ammonium phosphate, 3 wt% of titanium phosphate, and 40 wt% of urethane resin were added thereto. A chromium-free treatment solution was prepared, coated with a dry coating weight, and dried at a steel sheet baking temperature to prepare a fuel tank steel plate for baffle. The dry coating film deposition amount and the steel sheet baking temperature were carried out as described in Invention Materials 17 to 21 and Comparative Materials 11 to 15.

The quality of corrosion resistance, boiling adhesion, and weldability of the prepared steel sheet was evaluated, and the results are shown in Table 2.

Quality evaluation

As a quality evaluation, the solution stability of the chromium-free treatment liquid and the corrosion resistance, adhesion resistance, and weldability required for the fuel tank steel plate for the baffle were evaluated. The evaluation method was performed as follows.

(Solution stability evaluation)

The prepared chromium-free treatment solution was left at room temperature, and after 15 days it was evaluated whether the solution maintains the same properties as the initial state. If it had the same property as an initial state, it was good ((circle)), otherwise, it will display as (x) when gelation progressed.

(Adhesive evaluation)

The evaluation of the resin adhesiveness of the steel sheet was carried out in parallel, one was the adhesion after boiling (boiling adhesion), and the other was the adhesion after cup processing.

Boiling adhesion was evaluated by boiling the steel sheet in boiling water for 30 minutes, taking it out, leaving it to stand for 5 minutes, drying it, and then peeling the tape after adhering the tape to the steel sheet. The evaluation criteria are as follows, and when the grade is 1 or higher (in case of 0 ~ 5% peeled area), the acceptance criteria is used.

◎: peeling area 0-5% ○: peeling area 5-20% □: peeling area 20-50%

(Triangle | delta): Peeling area 50-75% X: Peeling area 75-100%

The adhesiveness after cup processing was first evaluated by punching a steel plate with 95 pies, making the radius of curvature of the processing die 4, and cup processing to a height of 25 mm. The evaluation criteria are as follows, and when the grade is 1 or more (in case of 0 ~ 5% peeled area), the acceptance criteria is used.

◎: peeling area 0-5% ○: peeling area 5-20% □: peeling area 20-50%

(Triangle | delta): Peeling area 50-75% X: Peeling area 75-100%

(Corrosion resistance evaluation)

Corrosion resistance was evaluated as the percentage of rust that occurred after 800 hours when only chromium-free coating was applied at a spraying concentration of 5 wt% in a flat state and 1 kg / cm2 at 35 ° C (Example 1). Is as follows.

◎: corrosion area 0% ○: corrosion area 5% or less □: corrosion area 5-30%

(Triangle | delta): Corrosion area 30-50% X: Corrosion area 50% or more

(Weldability)

Weldability was evaluated by using a pneumatic AC spot welder to maintain the sputtering and constant strength at a pressing force of 250 kg, a welding time of 15 cycles, and a current of 7.5 kV. If the welding is possible on the basis of that, it is indicated by (◎), and if not, it is indicated by (×).

 division Solution composition (% by weight)  Corrosion resistance Solution stability  Boiling resistance Silicate Silane Ammonium phosphate Suzy Titanium phosphate Comparative Material 1 One   3     0.5       20         2 □ ○ △ Invention 1 3 ○ ○ ○ Invention 2 20 ◎ ○ ◎ Invention 3 40 ◎ ○ ◎ Comparative Material 2 50 ◎ ○ ○ Comparative Material 3          20 0.3 △ ○ □ Invention 4 0.5 ○ ○ ○ Invention 5 3.0 ◎ ○ ◎ Invention 6 10.0 ◎ ○ ◎ Comparative Material 4 15.0 ◎ × ◎ Comparative Material 5        3 0.05 □ ○ ◎ Invention Material7 0.1 ○ ○ ◎ Invention Material 8 0.5 ◎ ○ ◎ Invention Material 9 1.0 ◎ ○ ◎ Invention 10 2.0 ◎ ○ ◎ Comparative Material 6 2.5 ◎ × ◎ Comparative Material7     0.5 5 △ ○ □ Invention Material 11 10 ○ ○ ○ Invention Material12 20 ◎ ○ ◎ Invention Material 13 50 ○ ○ ◎ Comparative Material 8 60 □ ○ ◎ Comparative Material 9   20 0.5 ○ ○ □ Invention 14 1.0 ◎ ○ ◎ Invention 15 2.0 ◎ ○ ◎ Invention 16 5.0 ◎ ○ ◎ Comparative Material 10 8.0 ◎ ○ ◎

 division Manufacture conditions  Corrosion resistance  Boiling adhesion  Weldability Baking temperature (PMT, ℃) Amount of adhesion (mg / ㎡) Comparative Material 11 150   800 □ △ ◎ Invention Material 17 160 ◎ ◎ ◎ Invention Material 18 180 ◎ ◎ ◎ Invention 19 200 ◎ ◎ ◎ Comparative Material 12 240 ◎ ◎ ◎ Comparative Material 13   160 100 × ◎ ◎ Comparative Material 14 300 △ ◎ ◎ Invention 20 500 ◎ ◎ ◎ Invention Material 21 1000 ◎ ◎ ◎ Comparative Material 15 1500 ◎ ◎ ×

Thus, by using the chromium-free treatment liquid according to the present invention, it is possible to obtain a fuel tank steel sheet excellent in boiling resistance and corrosion resistance at low cost. The fuel tank steel plate for baffle according to the present invention has excellent physical properties having the required adhesion, corrosion resistance, fuel resistance and weldability.

Claims (15)

A chrome-free treatment liquid for forming a chromium-free layer of a fuel tank steel plate for baffle composed of a galvanized layer and a chromium-free layer, Silicate 3-40% by weight; Silane 0.5-10% by weight; 0.1-2% by weight of ammonium phosphate; 1-5% by weight of titanium phosphate; 10-50% by weight of urethane resin, epoxy resin or a mixture of these resins; And chromium-free treatment liquid containing the balance water. The chromium-free treatment liquid of claim 1, wherein the silicate is NaSiO ₃ , NaSi ₅ O ₁₁ or a mixture thereof. The chromium-free treatment liquid according to claim 1, wherein the silane is γ-glycidoxypropyltriethoxysilane, γ-aminopropyltriethoxysilane, or a mixture thereof. The chromium-free treatment liquid according to claim 1, wherein the urethane resin and the epoxy resin have a glass transition temperature (Tg) of 70-130 ° C. A fuel tank steel plate for baffle composed of a galvanized layer and a chromium free layer, The chromium-free layer is silicate 3-40% by weight; Silane 0.5-10% by weight; 0.1-2% by weight of ammonium phosphate; 1-5% by weight of titanium phosphate; 10-50% by weight of urethane resin, epoxy resin or a mixture of these resins; And a fuel tank steel plate for a plating layer / chromium-free layer baffle, which is manufactured from a chromium-free treatment liquid containing residual water. [6] The fuel tank steel sheet of claim 5, wherein the zinc plated layer is electroplated with zinc at a plating adhesion amount of 20-30 g / m 2 to the cold rolled steel sheet. 6. The fuel tank steel sheet for the plating layer / chromium-free layer baffle according to claim 5, wherein the chromium-free layer has a dry coating amount of 500-1000 mg / m 2. 6. The fuel tank steel plate of claim 5, wherein the silicate is NaSiO ₃ , NaSi ₅ O ₁₁ or a mixture thereof. 6. The fuel tank steel sheet according to claim 5, wherein the silane is γ-glycidoxypropyltriethoxysilane, γ-aminopropyltriethoxysilane, or a mixture thereof. 6. The fuel tank steel sheet for plating / chromium free layer baffle according to claim 5, wherein the urethane resin and the epoxy resin have a glass transition temperature (Tg) of 70 to 130 ° C. 3-40% by weight of silicate in chromium-free treatment liquid on electrogalvanized steel sheet; Silane 0.5-10% by weight; 0.1-2% by weight of ammonium phosphate; 1-5% by weight of titanium phosphate; Applying a chromium-free treatment liquid comprising 10-50% by weight of a urethane resin, an epoxy resin or a mixture of these resins; And Baking the steel plate coated with the chromium-free treatment liquid at a steel plate temperature of 160-200 ° C. to form a chromium-free layer; Fuel tank steel plate manufacturing method for plating layer / chrome-free layer comprising a. 12. The method of claim 11, wherein the galvanized steel sheet is galvanized in a cold rolled steel sheet 20-30g / ㎡ galvanized amount of the plating layer / chrome-free layer fuel tank steel plate manufacturing method for baffles. 12. The method of claim 11, wherein the chromium-free layer has a dry coating thickness of 500-1000 mg / m 2. 12. The method of claim 11, wherein the silicate is NaSiO ₃ , NaSi ₅ O ₁₁ or a mixture thereof. The method of claim 11, wherein the silane is gamma-glycidoxypropyltriethoxysilane, gamma-aminopropyltriethoxysilane, or a mixture thereof.