KR100782719B1 - Cr-free and resin coated steel sheet, preparing methods thereof and resin composition therefor - Google Patents

Abstract

A Cr-free and resin-coated steel sheet, a method of preparing the same, and resin composition used in the method are provided to obtain good adhesion, corrosion-resistance, fuel-resistance, smoke-resistance, and weldability, without containing Cr. A Cr-free and resin-coated steel sheet is reacted with a function group of a resin layer. Simultaneously, phosphoric acid-ester of a Cr-free layer is coupled to a Zn-plated layer or a Zn-Ni plated layer. Silane of the Cr-free layer is reacted with a function group of the resin. In addition, the silane is reacted with a plated layer of a cold-rolled steel plate, specifically, the Zn-plated layer or the Zn-Ni plated layer. As a result, the Cr-free layer is coupled to an upper resin layer and a lower plated layer to improve adhesion between the steel plate and the resin layer.

Description

Chromium-free and resin-treated steel sheet, preparation method thereof and resin treatment liquid used therein {Cr-Free and Resin Coated Steel Sheet, Preparing Methods Thereof and Resin Composition Therefor}

1 is a view showing the concept of improving the adhesion between the plated steel sheet and the resin layer by the phosphate ester, silane and titanium carbonate in the chromium-free layer,

2 is a diagram showing an apparatus used for fuel resistance evaluation.

The present invention relates to a chromium-free surface-treated steel sheet, a method of manufacturing the same and a resin treatment liquid used therein, and more particularly, to a chrome-free surface-treated steel sheet for fuel tanks having excellent adhesion, corrosion resistance, fuel resistance, smoke resistance, and weldability, The manufacturing method and the resin processing liquid used for this are related.

Currently, steel plates that have been chromated and resin-treated on chromate-treated zinc and zinc-alloy plated steel sheets which do not use lead at all as a substitute for Terne-plated steel sheets used as automotive fuel tank steel sheets are being developed. These resin-treated steel sheets mainly exhibit various performances according to the properties of the resin-treated coatings. Korean Republic of Korea Patent Application Nos. 1998-52504 and 1998-52143 have Cr as the main component on the base and the upper resin layer is the phenoxy resin coating. To improve corrosion resistance and fuel resistance. However, the chromium component not only causes various diseases such as cancer, but is regulated as being harmful to the human body, and thus cannot be used.

Therefore, chromium-free corrosion inhibitors have been studied for a long time. The combination of polymer and inorganic material is representative, and various kinds of zirconium, silicate and titanium compounds have recently been studied.

However, since these compounds have a high adhesion amount compared to the chromium deposition amount, they may have excellent corrosion resistance. Therefore, the method of overcoming them is the most urgent because there is a problem such as poor conductivity and adhesion to the upper resin when coated on a steel sheet. Table 1 shows the general characteristics of common chromium compounds and chromium-free compounds.

[Table 1] General comparison between chrome coating and chrome free coating

As described above, resin coated fuel tank steel, which is currently used as fuel tank steel for automobiles, contains a large amount of Cr. However, since June 2007, the use of chromium has been fully regulated. Under strict regulations on the disposal of chromium substances under the law, it is time for strict measures to take effect. Therefore, it is urgent to prepare for this.

Meanwhile, alternative fuels are being developed due to higher anti-rust regulation (10-> 20 years) and rapid increase in fossil fuel prices. These alternative fuels are ethanol fuels produced mainly from sugar cane in South America, which can be mixed with gasoline and used as fuel. On the other hand, biodiesel that can be mixed with diesel is roughly classified into soybean oil mainly in Korea and Japan, biodiesel using waste cooking oil, and rapeseed oil mainly in Europe. do.

In conventional biodiesel, only methyl ester and methyl ester of glycerin obtained by decomposition of soybean oil and / or rapeseed oil by hydrogen-substitution reaction with methanol are used as biodiesel. However, a full improvement in fuel resistance is required for ethanol and biodiesel, which are emerging as new automotive fuels.

Accordingly, an object of the present invention is to provide a steel plate which is free of chromium, is chromium-free (Cr-free) having excellent adhesion, corrosion resistance, fuel resistance, smoke resistance, and weldability and is surface-treated with a resin.

Another object of the present invention is to provide a method for producing a steel sheet which is chromium-free and which is chromium-free having excellent adhesion, corrosion resistance, fuel resistance and weldability, and which is surface treated with a resin.

Still another object of the present invention is to provide a resin treatment liquid used in the steel sheet manufacturing method of the present invention.

According to one aspect of the invention,

Galvanized steel sheets; At least one binder selected from the group consisting of 3-40 parts by weight of silicate, 0.5-10 parts by weight of silane, 0.2-8 parts by weight of titanium compound, urethane resin and epoxy resin per 100 parts by weight of chromium-free treatment liquid on the electrogalvanized steel sheet A chromium-free layer formed of a chromium-free treatment liquid comprising 10-50 parts by weight of a resin and 1-5 parts by weight of phosphate ester; And per 100 parts by weight of phenoxy resin, 3-25 parts by weight of melamine resin, 10-20 parts by weight of colloidal silica, 5-40 parts by weight of metal powder, 1-5 parts by weight of phosphate ester and titanium carbonate 1- There is provided a chromium-free surface-treated steel sheet having a resin layer of a resin treatment liquid containing 5 parts by weight.

According to another aspect of the present invention,

Galvanized steel sheet; At least one binder selected from the group consisting of 3-40 parts by weight of silicate, 0.5-10 parts by weight of silane, 0.2-8 parts by weight of titanium compound, urethane resin and epoxy resin per 100 parts by weight of chromium-free treatment liquid on the galvanized steel sheet Applying a chromium-free treatment liquid comprising 10-50 parts by weight of the resin and 1-5 parts by weight of phosphate ester;

Baking the steel plate coated with the chromium-free treatment liquid at a steel plate temperature of 160 to 250 ° C. to form a chromium free layer;

3-25 parts by weight of melamine resin, 10-20 parts by weight of colloidal silica, 5-40 parts by weight of metal powder, 1-5 parts by weight of phosphate ester and 1-5 parts by weight of carbonate per 100 parts by weight of phenoxy resin on the chromium-free layer. Applying a resin treatment liquid comprising a portion; And

Baking the steel sheet coated with the resin treatment liquid at a steel sheet temperature of 190 to 250 ° C. to form a resin coating layer;

Provided is a method for producing a steel plate treated with chromium-free and resin for a fuel tank comprising a.

According to another aspect of the present invention,

Resin comprising 3-25 parts by weight of melamine resin, 10-20 parts by weight of colloidal silica, 5-40 parts by weight of metal powder, 1-5 parts by weight of phosphate ester and 1-5 parts by weight of titanium carbonate per 100 parts by weight of phenoxy resin Treatment liquid is provided.

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

The chromium-free surface treatment steel sheet for fuel tank containing no chromium of the present invention and having excellent adhesion, corrosion resistance, fuel resistance, smoke resistance, and weldability is a chromium-free layer formed on an electrogalvanized steel sheet and a resin layer formed on the chromium-free layer. Is done.

In the chromium-free surface-treated steel sheet of the present invention, the base steel sheet is not limited thereto. For example, a zinc-plated (Zn) or zinc-nickel (Zn-Ni) electroplated steel sheet or electroplated cold rolled steel sheet. Zinc-nickel alloy plated steel sheets may be used. In particular, Zn-Ni steel sheet, which is a zinc alloy plated steel sheet, is preferred because it is more excellent in corrosion resistance than a plated steel sheet composed of zinc alone. In the electrogalvanized steel sheet, the plating amount of zinc or zinc-nickel is preferably 20-30 g / m 2. If the plating amount is less than 20 g / ㎡, the amount of plating adhesion is small and the sacrificial method is small, and if it exceeds 30 g / ㎡ it is not preferable because the productivity decreases on the production line.

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 treatment liquid excellent in terms of double corrosion resistance.

The chromium-free treatment liquid used to form the chromium-free layer may include silicates, silanes, and titanium compounds as a subject in water; Binder resins made of urethane and / or epoxy resins having excellent adhesion in order to improve the physical properties of the coating, especially adhesion to the steel sheet; And it may include a phosphate ester which is an adhesion improving agent. In addition, a wetting agent and a defoaming agent may be further included as necessary. In the chromium pretreatment solution, the silicate, silane, titanium compound, binder resin, and phosphate ester are dispersed in water, and the balance other than these components is made of water.

In the present invention, as the silicate, NaSiO ₃ and / or NaSi ₅ O ₁₁ may be used, and the silicate forms a three-dimensional network structure when coated on a steel sheet, and at the same time, exhibits excellent bonding strength with the underlying steel sheet (plated steel sheet). . Silicate may be used in 3 to 40 parts by weight per 100 parts by weight of chromium-free treatment liquid. If the silicate content is less than 3 parts by weight, the content is too small to give adhesion to the steel sheet and excellent corrosion resistance, and if it exceeds 40 parts by weight, the bonding strength with the resin is weak, which is not preferable.

Silanes are hydrolyzed in water to form siloxide bonds. Silane forms a strong bond with the steel sheet by the siloxane bond and at the same time serves as a binding (binding) to bind various inorganic materials. 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 aminopropyltri which are well hydrolyzed. Preference is given to using oxysilane (γ-aminopropyltriethoxy silane). In addition, KBM series of Shinwol Chemical is most commonly used as silane. The silane may be used in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of the chromium-free treatment liquid. If the content is less than 0.5 parts 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 parts by weight, the physical properties are the same as those below the content, but are not preferable in terms of economics.

Titanium compound is to act to improve the corrosion resistance by the reaction of the plated layer of the steel sheet, specifically, zinc or zinc and nickel, and the titanium compound used in the chromium-free treatment liquid in the present invention is not limited thereto. Hexafluoro Titanic Acid neutralized with amines may be used. That is, the hexafluoro titanic acid is neutralized with an amine to be basic at pH 9-10, and then added to the chromium-free treatment solution. Triethyl amine may be used as the amine. If the pH is not adjusted to 9-10, the pH may not match and gelation may occur.

The titanium compound may be used in an amount of 0.2 to 8 parts by weight per 100 parts by weight of the chromium pretreatment liquid. If it is less than 0.2 parts by weight, the corrosion resistance is inferior. If it exceeds 8 parts by weight, further improvement in physical properties is not sufficient, so it is not preferable in terms of economics.

Silicate, silane and titanium compounds are mixed and used as the subject of the chromium-free treatment solution. Subsequently to this subject, binder resins and phosphate esters having excellent adhesion are added to improve adhesion. The main reason for doing this is to maintain the silicate and silane, the binder resin and phosphate ester stability added later by reacting the silicate and the silane in advance. In the chromium-free treatment liquid, each component is prepared by mixing in water.

As a binder resin for binding the inorganic silicates, silanes and titanium compounds to each other, 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. Since the epoxy resin contains hydroxyl groups in the resin molecule, the 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.

It is preferable to use a number average molecular weight of 1,000 or more as the binder resin, and the upper limit of the number average molecular weight is not particularly limited, but the binder resin has a number average molecular weight of about 7,000 because the maximum number average molecular weight is about 7,000. Binder resins can be used.

The binder resin may be added in 10 to 50 parts by weight per 100 parts by weight of the chromium-free treatment liquid. If it is less than 10 parts by weight, the resin content is too small to insufficient adhesion to the steel sheet and the function of combining the inorganic additives, and if it exceeds 50 parts by weight is too preferable because the resin content is too much corrosion resistance.

Phosphoric acid-ester is used in order to improve the adhesiveness of a steel plate and a chromium free layer, and the adhesiveness of a steel plate and a resin layer. The mechanism in which the adhesiveness of a steel plate and a chromium free layer and the adhesiveness of a steel plate and a resin layer improve by phosphoric acid ester is shown in FIG. That is, in order to increase adhesiveness, the multiple bond structure of each interface was tried.

As indicated by the dotted line in FIG. 1, the phosphate-ester of the chromium-free layer reacts with the functional group of the resin of the resin layer, and at the same time, is combined with the plating layer of the steel sheet, specifically, the Zn plating layer or the Zn-Ni plating layer, As indicated by the silane of the chromium-free layer also reacts with the functional groups of the resin, and at the same time reacts with the plating layer of the steel sheet, specifically Zn plating layer or Zn-Ni plating layer, so that the chromium-free layer is the upper resin layer and the lower Since the double bond with the plating layer of the chromium-free layer, the adhesion between the steel sheet and the resin layer is improved.

Phosphoric acid-ester may be added at 1.0 to 5.0 parts by weight per 100 parts by weight of the chromium-free treatment liquid. If the content is less than 1.0 part by weight, the content is too small, and thus adhesion between the steel sheet and the upper resin is not sufficient. If the content is more than 5.0 parts by weight, there is no effect on the content increase.

The chromium-free treatment liquid is coated and baked on the plated steel sheet 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 adhesion 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, and if the amount exceeds 1000 mg / m ² , the resin is coated on the upper side, which is not preferable because the resin adhesiveness and weldability deteriorate.

After coating the chromium-free treatment liquid, the baking temperature is baked at 160 to 250 ° 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 with the resin and the inorganic substance. to be.

The chromium-free layer may be applied to one side or both sides of the plated steel sheet. The chromium-free treatment liquid can be applied to the steel sheet by various coating methods such as roll coating by a 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, a facility for applying chromium-free treatment liquid is a method in which a solution in a drip pan is buried in a pick-up 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 film. 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.

After the chromium free layer is formed on the plated steel sheet as described above, a resin layer may be formed on the chromium free layer. The resin layer not only has an effect of improving adhesion after processing, but also hardens the coating film, thereby exhibiting significant corrosion resistance.

The resin treatment liquid may include melamine resin, silica, metal powder, phosphate ester, and titanium carbonate, based on phenoxy resin and added thereto to improve the properties of steel sheet.

Phenoxy resins having excellent corrosion resistance and fuel resistance may be used as the main subject in the resin treatment liquid forming the resin layer as the upper layer. Phenoxy resins not only have excellent fuel resistance and corrosion resistance, but also have different physical characteristics from other resins. The physical property distinguished from other resins of phenoxy resins is high glass transition temperature (Tg). The high glass transition temperature means that the resin chain moves at a higher temperature. At temperatures lower than the glass transition temperature, the chains of the resin itself remain intact without micro brown movement, which is primarily related to external low molecular corrosion factors (moisture, gasoline, etc.). It has a protective effect. In other words, when the chain of the resin itself is micro-brown movement, low molecules easily penetrate between the moving chains, thereby facilitating the penetration of corrosion factors. Therefore, the higher the glass transition temperature of the resin means that the greater the shielding effect on the base metal.

As the phenoxy resin used as the subject, it is preferable to use a number average molecular weight of 25,000 to 50,000. If the number average molecular weight is less than 25,000, it is difficult to obtain the desired physical properties because the molecular weight is too small, and if it exceeds 50,000, the synthesis is impossible due to the limitation of the resin synthesis method. On the other hand, the phenoxy resin can be used to prepare a resin treatment liquid in a water-soluble state dispersed in water.

The melamine resin may be blended in an amount of 3 to 25 parts by weight based on 100 parts by weight of the main phenoxy resin in the resin treatment liquid. In the case of melamine resin, it is preferable to select one having good reactivity, but not limited thereto. For example, Cymel 325 may be used. If the melamine resin is added in less than 3 parts by weight, the curing reaction is not perfect after the resin coating, and the effect of fixing the metal powder is small. If it exceeds 25 parts by weight, the curing agents react with each other due to excessive addition of the melamine resin, which adversely affects the coating properties. It is not desirable because it is crazy.

In addition, in order to improve the corrosion resistance of the resin coating, the colloidal silica may be added in an amount of 10-20 parts by weight per 100 parts by weight of the phenoxy resin. If the amount of colloidal silica is less than 10 parts by weight, the content is too small to show corrosion resistance, and if it exceeds 20 parts by weight, there is no effect of improving the corrosion resistance compared to the content of silica.

Phenoxy resins have excellent corrosion resistance and fuel resistance, but are difficult to weld due to resin thickness. In order to overcome this, metal powder is also blended in the resin treatment liquid. Metal powders that can be blended in the resin treatment liquid of the present invention include Ni, Zn, Al, Cu and SnO. The metal powder may be used in one kind or a mixture of two or more kinds. It is preferable to use the particle | grains whose particle diameter is 0.5-1 micrometer as a metal powder. This is because the lower limit of the particle size of the metal powder is due to the limitation in the manufacture of the metal powder. Also, if the particle diameter exceeds 1.0 µm, the metal powder has a specific gravity and is precipitated in the resin solution. The shape of the metal powder is not particularly limited, but the spherical metal powder is preferable to have a plate shape because the metal powder in the plate has more buoyancy of the solution and floats in the solution for a longer time than the spherical metal powder. . SnO powder is more preferable for use because it has a smaller specific gravity and metal particle diameter than the other metals described above. SnO powder is not only easily dispersed in the resin treatment liquid, but also has excellent weldability at low contents.

The metal powder in the resin treatment liquid may be blended in an amount of 20-50 parts by weight based on 100 parts by weight of the phenoxy resin. The lower the metal powder content, especially less than 20 parts by weight, the poor weldability, the higher the metal powder content, especially more than 50 parts by weight, the metal content in the resin film is too high, the cohesion between the resins weakens the adhesion to the steel sheet Because this is poor.

Further, in order to increase the adhesion between the resin treatment liquid and the steel sheet, phosphate-ester may be blended at 1.0 to 5.0 parts by weight per 100 parts by weight of the resin treatment liquid. If the content of phosphate-ester is less than 1.0 parts by weight, the content is too small, the adhesion between the steel sheet and the upper resin is low, and if it exceeds 5.0 parts by weight there is no effect on the increase in the phosphate-ester content.

In addition, the resin treatment liquid of the present invention further enhances the barrier properties of the resin coating layer to improve fuel resistance, and to further bond the resin layer and the chromium free layer to titanium carbonate, which is a Ti-based organic compound. (Titanium Carbonate, hereinafter referred to as 'Ti-carbonate') may be blended.

As shown in FIG. 1, Ti-carbonate is composed of a Ti metal and a triethylamine ligand bonded thereto, and upon initial heat, isopropoxide (OC3H7) dissociates first to form a lower chromium free layer. After being connected to the heavy binder resin, and further heat is applied, the triethylamine ligand is separated and combined with the phenoxy resin in the resin layer, so that the chromium free layer and the resin layer may be more tightly adhered.

Conventionally, in Korean Patent Application Nos. 2004-114478, 2004-114479 and 2005-130382, the barrier and adhesion are increased by the double bond between the resin and the chromium free layer (silane and phosphate ester). In addition to the phosphate ester, a titanic acid ester is further used to form a stronger film structure by the triple bond between the resin layer and the chromium free layer.

The isopropoxide is easily dissociated at a low temperature of about 100 ° C., and the dissociated isopropoxide is easily decomposed when subjected to continuous heat, so that a lot of smoke and odor are generated. .

The Ti-carbonate may be blended in an amount of 1 to 5 parts by weight based on 100 parts by weight of the phenoxy resin. If the content is less than 1 part by weight, the effect of improving the film adhesion and fuel resistance is insignificant. On the contrary, if the content exceeds 5 parts by weight, the isopropoxide dissociated at low temperature will be pyrolyzed, causing severe smoke and It is not preferable because odor occurs together.

Ti-carbonates are roughly classified under the trade names TE, AA, and LA series manufactured and sold by Dupont. AA and LA are not suitable for use due to poor solution stability, and TE may be used in the present invention.

The resin treatment liquid according to the present invention is an aqueous treatment liquid, and the balance other than the above components is made of water. Solid content 30-50 weight% and water 50-70 weight% in the said resin process liquid. If the solid content in the resin treatment liquid is less than 30% by weight, it is difficult to form a solid film, and thus, may not exhibit a strong adhesion with the chromium-free layer and the steel sheet. There is a problem that can not be. In addition, the aqueous resin treatment solution may be added, if necessary, additives generally used in the preparation of the resin treatment solution, such as antifoaming agent, wetting agent (wetting agent).

The resin layer may be formed by coating and baking a phenoxy resin treatment solution including a melamine resin, silica, metal powder, phosphate ester, and Ti-carbonate on the chromium free layer. The resin layer may be formed on one side or both sides of the chromium free layer as necessary.

The resin treatment liquid is coated so that the dry film thickness of the resin layer is 2.0 to 10.0 μm (mg / m 2). When the film thickness is less than 2 μm, the film thickness is thin, making it difficult to secure sufficient corrosion resistance and fuel resistance. When it exceeds 10 μm, the corrosion resistance and fuel resistance no longer increase as the film thickness increases, but the steel sheets are welded to each other. This is because weldability is deteriorated even if there is a metal powder in the resin coating.

After the resin coating, the baking temperature is set at 190-250 ° C based on the MT-Metal Temperature. If the baking temperature is less than 190 ℃ steel sheet temperature, the curing reaction of resin is not enough, and the adhesion between metal powder and resin decreases during processing. If the baking temperature is higher than 250 ℃ steel sheet temperature, the curing reaction does not occur anymore and the heat loss is large. to be.

The resin treatment liquid may be applied to the steel sheet by various coating methods such as roll coating by a roll, spray method, and deposition method, but the roll coating method is most preferable because it is applicable to one or both sides of the chromium free layer.

Like the chromium-free layer, the resin layer is formed on the chromium-free layer by immersing the solution in the drip pan on the pick-up roll, transferring it to the transfer roll, and finally burying the plated steel plate on the applicator roll, and drying it in an oven to form a final film. do. The dry film thickness of the resin layer can be adjusted by the driving direction of each roll, the rotational speed, and the mutual adhesion pressure of each roll.

The resin treatment liquid is for imparting functionality and may be applied to one or both sides of the chromium free layer depending on the use and requirements of the customer. That is, since the welding conditions of the customers are different from each other, in the case of the customer company which frequently exchanges electrodes with high current conditions that are easy to weld, the resin layer may be formed on both sides of the chromium-free layer. However, in the case of low current conditions and customers who do not frequently replace the electrode, it is better to use a steel sheet having a resin layer formed on one surface of the chromium-free layer.

When manufacturing a fuel tank with a steel plate having a resin layer on one surface, the resin coated surface is directed toward the fuel and the chromium-free layer on the opposite side is directed outwards. There is an advantage that the welding is much easier to weld.

In the chromium-free layer having no resin layer, since a thick top coat (about 100 μm) is generally applied to reinforce the corrosion resistance of the fuel tank, there is little effect on the corrosion resistance.

Thus, according to this invention, the steel plate which comprises the chromium free layer which does not contain Cr formed on the Zn type | system | group or Zn type alloy electroplating steel plate which does not contain Cr component, and the resin layer of chromium free layer is provided. Steel sheet according to the present invention is excellent in adhesion, corrosion resistance, fuel resistance, smoke resistance and weldability is preferred for use as fuel tank steel sheet for automobiles.

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  One

In this embodiment, the physical properties of the steel sheet according to the composition change of the chromium-free treatment liquid were evaluated.

Chromium-free treatment in which the content of silicates, silanes, titanium compounds, urethane resins having a number average molecular weight of 1500, and phosphoric acid esters on zinc-plated electrogalvanized steel sheets with a coating weight of 30 g / m 2 was changed as shown in Table 1 below. The liquid was roll coated on both sides of the steel sheet so that the one-side dry coating film adhesion amount was 700 mg / m 2, and baked at 190 ° C. steel plate temperature and cooled. As a titanium compound, hexafluoro titanic acid adjusted to pH 9 using triethylamine was used. The chromium-free treatment liquid was formulated in water so that the content of each component per 100 parts by weight of the chromium-free treatment liquid was in the amount shown in Table 2 below to prepare a chromium-free treatment liquid.

In preparing the chromium-free treatment solution, the silicate, silane, and titanium compound were first blended, followed by addition of urethane resin and phosphate ester. Thereafter, quality evaluation of the manufactured steel sheet was performed, and the results are shown in Table 2 below.

The quality evaluation evaluated the corrosion resistance and adhesion required for fuel tank steel.

(Corrosion resistance evaluation)

Corrosion resistance was evaluated as the percentage of rust that occurred after 500 hours when only chromium-free was applied at a spraying pressure of 5 wt% in brine at a flat state and 1kg / cm ² at 35 ° C (Example 1). In the case of the fuel tank steel plate coated with and to the resin (Examples 2 to 4), it was evaluated as% of rust generated after 1,000 hours. The evaluation criteria are as follows.

          ◎: Corrosion area 0% ○: Corrosion area below 5%

          □: Corrosion Area 5 ~ 30% △: Corrosion Area 30 ~ 50%

×: corrosion area of 50% or more

(Adhesive evaluation)

The evaluation of the resin adhesion of the steel sheet was carried out in parallel, one after the boiling (boiling adhesion) and the other after the cup processing. Boiling adhesion was evaluated by boiling the steel sheet in boiling water for 30 minutes, then taking it out, leaving it to stand for 5 minutes to dry it, and then sticking the tape to the steel sheet and then peeling off the tape. The evaluation criteria are as follows. When the level is 1 or higher (0 to 5% of the peeled area), the acceptance criteria is used.

◎: 0 to 5% of exfoliated area ○: 5 to 20% of exfoliated area

□: 20 to 50% of exfoliated area △: 50 to 75% of exfoliated area

×: 75 to 100% of exfoliated area

The adhesiveness after cup processing was first evaluated by punching a steel plate with 95 pies, then turning the cup to a height of 25 mm so that the radius of curvature of the processing die was 4, and then peeling the tape against the processed wall. The evaluation criteria are as follows, and when the grade is 1 or more (if the peeled area is 0 ~ 5%), the acceptance criteria is accepted.

◎: 0 to 5% of exfoliated area ○: 5 to 20% of exfoliated area

□: 20 to 50% of exfoliated area △: 50 to 75% of exfoliated area

×: 75 to 100% of exfoliated area

TABLE 2

As can be seen in Table 2, the fuel tank steel plate of the invention example in which the content range of each component constituting the chromium-free treatment liquid falls within the scope of the present invention shows excellent corrosion resistance and adhesion. In Table 2, 15 parts by weight of the silane, 10 parts by weight of the titanium compound, and 8 parts by weight of the phosphate-ester are excellent in physical properties, but a large amount of compounding components are used, which is uneconomical.

Example  2

In this embodiment, the physical properties of the steel sheet were evaluated according to the formation conditions of the chromium-free layer.

The coating weight and baking temperature of the chromium-free solution on the galvanized steel sheet having a plating deposition amount of 30 g / m ² were changed as shown in Table 3 below to form a chromium-free layer.

The chromium-free treatment liquid was prepared by blending each component in water such that 20 parts by weight of silicate, 2 parts by weight of silane, 1 part by weight of titanium compound, 20 parts by weight of urethane resin, and 3 parts by weight of phosphate ester per 100 parts by weight of chromium-free treatment solution. In preparing the chromium-free treatment solution, the silicate, silane, and titanium compound were first blended, followed by addition of urethane resin and phosphate ester. The prepared chromium-free treatment liquid was coated on both sides of the steel sheet by the dry coating film adhesion amount shown in Table 3 below by a roll coating method, followed by baking at the steel plate temperature shown in Table 3 to form a steel plate chromium free layer. As the urethane resin, a number average molecular weight of 1500 was used, and as a titanium compound, hexafluoro titanic acid adjusted to pH 9 using triethylamine was used.

After the chromium-free layer was formed, a resin layer was formed on one surface of the chromium-free layer. The resin layer was formed by baking and drying at 200 ° C with a thickness of 3 microns.

As the resin treatment liquid, 5 parts by weight of melamine resin per 100 parts by weight of phenoxy resin having a number average molecular weight of 50,000, 15 parts by weight of colloidal silica having an average particle diameter of 20 nm, 20 parts by weight of a spherical SnO powder having an average particle diameter of 0.5 μm, What was added and mix | blended each component in the phenoxy resin of the form disperse | distributed in water so that 3 weight part of phosphate esters and 3 weight part of titanium carbonates may be used. Solid content in the resin treatment solution was adjusted with water to 30% by weight.

Thereafter, quality evaluation of the manufactured steel sheet was performed, and the results are shown in Table 3 below. Quality evaluation evaluated the corrosion resistance, adhesion and weldability required for fuel tank steel. Corrosion resistance and adhesion were evaluated as in Example 1 above.

 (Weldability evaluation)

Weldability is maintained using pneumatic AC spot welding machine without pressing spatter and twisting welded steel plate with nipper at pressing force 250kgf, welding time 15 cycle, energizing current 7.5kA. Was evaluated. The case where there was no spatter and the welding surface did not fall was evaluated as the criterion of two modes by making weld (⊙) and otherwise impossible (x).

 TABLE 3

Comparative material having a baking temperature of 260 ° C. in Table 3 has good physical properties, but is not preferable because a large amount of heat is consumed due to the high baking temperature.

Example  3

In this example, the physical properties of the steel sheet according to the composition change of the resin treatment liquid were evaluated.

In the Zn-Ni electro zinc alloy plated steel sheet having a coating weight of 30 g / m ² , 20 parts by weight of silicate, 100 parts by weight of silane, 1 part by weight of titanium compound, number average molecular weight 2,000 A chromium pretreatment solution containing each component in water so that 20 parts by weight of a urethane resin and 3 parts by weight of phosphate ester is applied by roll coating method at a thickness of 600 mg / m2 on one side of the coated steel sheet on both sides of the steel sheet and at 190 ° C. It was baked and cooled with air to form a chrome free layer. In preparing the chromium-free treatment solution, the silicate, silane, and titanium compound were first blended, followed by addition of urethane resin and phosphate ester.

Thereafter, the resin treatment liquid was applied to both surfaces of the chromium-free layer so as to have a dry film thickness of 2 μm, and then baked at 190 ° C. to prepare a resin coated steel sheet. As a titanium compound, hexafluoro titanic acid adjusted to pH 9 using triethylamine was used.

The resin treatment liquid for forming the resin layer is melamine resin per 100 parts by weight of phenoxy resin having a number average molecular weight of 50000 in water, colloidal silica having an average particle diameter of 20 nm, spherical SnO powder having an average particle diameter of 0.5 μm, phosphate ester and Ti-carbonates were prepared by combining the amounts of Table 4, respectively. The phenoxy resin was used in a water-soluble state, and the components of Table 4 were formulated so that the total solid content in the resin treatment liquid was 30% by weight.

Then, the quality of the produced steel sheet was evaluated and shown in Table 4 below. The quality evaluation evaluated the corrosion resistance, adhesion, solution stability, fuel resistance and smoke generation required for fuel tank steel plate. Corrosion and adhesion were evaluated as in Example 1 above and weldability as in Example 2.

(Solution stability)

The solution stability was evaluated as 200 mm of the resin treatment liquid in a 250 mm high measuring cylinder, and after 8 hours, when the thickness of the metal powder deposited on the lower measuring cylinder exceeded 5 mm, the solution stability was poor, and the solution stability was less than 5 mm.

In addition, the solution stability according to the Ti-carbonate content and type change was expressed as the degree of gelation of the whole solution rather than precipitation. It was evaluated as poor when the solution was gelated and good when the solution was stable without gel.

When both the solution stability tested in the measuring cylinder and the solution stability according to the Ti-carbonate content and type change were satisfied, the solution stability was good (◎), and if either of the two was not satisfied, it was indicated as bad (X).

(Fuel resistance)

The fuel resistance was evaluated by high temperature fuel resistance against ethanol and biodiesel. Evaluation of fuel resistance for ethanol was carried out by putting a fuel, a mixture of 85 wt% ethanol (5% H2O) + 15 wt% unleaded gasoline + 20 ppm formic acid (20 ppm was negligible in the mixing ratio), into a prepared cup specimen. To prevent the leakage of fuel, as shown in the device shown in Fig., Place a ring on the cup-processed specimen, cover it with a 10 mm thick glass plate, clip it to both corners, and leave it at 60 ° C for 3 months. The corrosion state of the steel sheet was evaluated. The fuel resistance evaluation for biodiesel was conducted using a mixture of 80% by weight diesel (10% H2O) + 20% by weight BIO diesel as fuel and left for 3 months at 90 ° C. The evaluation was carried out in the same way as the corrosion state of the steel sheet, the evaluation criteria are as follows.

          ◎: Corrosion area 0% ○: Corrosion area below 5%

          □: Corrosion Area 5 ~ 30% △: Corrosion Area 30 ~ 50%

×: corrosion area of 50% or more

(Smoke generation)

The occurrence of smoke was visually evaluated for the occurrence of smoke and indicated by X when smoke occurred and by O when smoke did not occur.

TABLE 4

As shown in Table 4, the steel sheet for a fuel tank having a resin layer formed of a resin treatment liquid satisfying the limit of the present invention exhibits excellent solution stability, fuel resistance, corrosion resistance, adhesion and weldability.

Example  4

20 parts by weight of silicate per 100 parts by weight of chromium-free treatment liquid, 2 parts by weight of silane, 1 part by weight of titanium compound, and 20 parts by weight of urethane resin having a number-average molecular weight of 2,000 parts by weight of chromium-free treated liquid on both sides of the galvanized steel sheet of 30 g / m ² A chromium-free coating liquid containing each component in water so that 3 parts by weight of phosphate and phosphate ester was applied was coated at 500 mg / m2 of dry film on one side, baked at 190 ° C, and cooled to form a chromium-free coating layer on both sides of the steel sheet. I did it. In preparing the chromium-free treatment solution, the silicate, silane, and titanium compound were first blended, followed by addition of urethane resin and phosphate ester.

As the resin treatment liquid for forming the resin layer, 5 parts by weight of melamine resin per 100 parts by weight of phenoxy resin having a number average molecular weight of 50000, 15 parts by weight of colloidal silica having an average particle diameter of 20 nm, and a spherical SnO having an average particle diameter of 0.5 micron The resin treatment liquid prepared by adding and blending each component in order to 20 parts by weight of powder, 3 parts by weight of phosphate ester and 3 parts by weight of titanium carbonate was added to the phenoxy resin dispersed in water. The resin treatment liquid was also adjusted with water so that the solid content was 30% by weight.

Thereafter, the resin treatment liquid prepared above was applied to one surface of the chromium-free layer by a roll coating method so as to have a dry film adhesion amount of Table 5, and then baked at a steel plate temperature of Table 5 to form a resin layer.

Quality evaluation of the prepared steel sheet was performed in Table 5 below. The quality evaluation evaluated the corrosion resistance, adhesion, weldability, and fuel resistance required for fuel tank steel sheets. Corrosion resistance and adhesion were evaluated as in Example 1, weldability as in Example 2 and fuel resistance as in Example 3.

TABLE 5

As shown in Table 5, the fuel tank steel plate in which the resin layer was formed under the resin layer forming conditions (resin layer thickness and baking temperature) of the range according to the present invention exhibits excellent corrosion resistance, adhesion and weldability. Comparative material having a baking temperature of 260 ° C. in Table 5 has good physical properties, but is not preferable because a large amount of heat is consumed due to the high baking temperature.

The chromium-free steel sheet for fuel tank of the present invention is not used at all, and is environmentally friendly compared to the product using Cr, and satisfies the properties such as corrosion resistance, adhesion, weldability, pigment resistance, etc. required for the steel plate for fuel tank. will be.

Claims (18)

Galvanized steel sheets; At least one binder selected from the group consisting of 3-40 parts by weight of silicate, 0.5-10 parts by weight of silane, 0.2-8 parts by weight of titanium compound, urethane resin and epoxy resin per 100 parts by weight of chromium-free treatment liquid on the electrogalvanized steel sheet A chromium-free layer formed of a chromium-free treatment liquid comprising 10-50 parts by weight of a resin and 1-5 parts by weight of phosphate ester; And per 100 parts by weight of phenoxy resin, 3-25 parts by weight of melamine resin, 10-20 parts by weight of colloidal silica, 5-40 parts by weight of metal powder, 1-5 parts by weight of phosphate ester and titanium carbonate 1- A chromium-free surface-treated steel sheet having a resin layer of an aqueous resin treatment liquid containing 5 parts by weight. The chromium-free surface treatment steel sheet as claimed in claim 1, wherein the galvanized steel sheet is an electrogalvanized steel sheet coated with zinc or zinc-nickel with a coating amount of 20-30 g / m 2 on the cold rolled steel sheet. The chromium-free surface treatment steel sheet of claim 1, wherein the chromium-free layer has a dry coating weight of 500-1,000 mg / m 2. The chromium-free surface treatment steel sheet according to claim 1, wherein the chromium-free layer is formed on one or both surfaces of the galvanized steel sheet. The method of claim 1, wherein the silicate is NaSiO ₃ And / or NaSi ₅ O ₁₁ Chrome-free surface treatment steel sheet, characterized in that. The chromium free surface-treated steel sheet according to claim 1, wherein the silane is gamma glycidoxypropyltriethoxysilane and / or gamma amino propyltriethoxysilane. The chromium-free surface treatment steel sheet according to claim 1, wherein the titanium compound is hexafluoro titanic acid adjusted to pH 9-10 with an amine. The chrome-free surface-treated steel sheet for fuel tank according to claim 1, wherein the binder resin has a number average molecular weight of 1,000 or more. The chromium-free surface treated steel sheet according to claim 1, wherein the resin layer has a dry coating thickness of 2 to 10 µm. The chromium-free surface treatment steel sheet of claim 1, wherein the phenoxy resin layer is formed on one surface or both surfaces of the chromium-free layer. The chrome-free surface treatment steel sheet of claim 1, wherein the phenoxy resin has a number average molecular weight of 25,000 to 50,000. The chromium-free surface treatment steel sheet according to claim 1, wherein the metal powder has a particle diameter of 0.5-1 탆. The chromium-free surface treatment steel sheet according to claim 1, wherein the metal powder is at least one selected from the group consisting of Ni, Zn, Al, Cu, and SnO. Galvanized steel sheet; At least one binder selected from the group consisting of 3-40 parts by weight of silicate, 0.5-10 parts by weight of silane, 0.2-8 parts by weight of titanium compound, urethane resin and epoxy resin per 100 parts by weight of chromium-free treatment liquid on the galvanized steel sheet Applying a chromium-free treatment liquid comprising 10-50 parts by weight of the resin and 1-5 parts by weight of phosphate ester; Baking the steel plate coated with the chromium-free treatment liquid at a steel plate temperature of 160 to 250 ° C. to form a chromium free layer; 3-25 parts by weight of melamine resin, 10-20 parts by weight of colloidal silica, 5-40 parts by weight of metal powder, 1-5 parts by weight of phosphate ester and 1-5 parts by weight of carbonate per 100 parts by weight of phenoxy resin on the chromium-free layer. Applying an aqueous resin treatment liquid comprising a portion; And Baking the steel sheet coated with the resin treatment liquid at a steel sheet temperature of 190 to 250 ° C. to form a resin coating layer; Method for producing a surface-treated steel plate with a chrome-free and resin for fuel tank comprising a. Chromium comprising 3-25 parts of melamine resin, 10-20 parts by weight of colloidal silica, 5-40 parts by weight of metal powder, 1-5 parts by weight of phosphate ester and 1-5 parts by weight of titanium carbonate per 100 parts by weight of phenoxy resin Aqueous resin treatment liquid for pretreated steel sheet. The aqueous resin treatment liquid according to claim 15, wherein the phenoxy resin has a number average molecular weight of 25,000 to 50,000. The aqueous resin treatment liquid according to claim 15, wherein the metal powder has a particle diameter of 0.5-1 mu m. The aqueous resin treatment liquid according to claim 15, wherein the metal powder is at least one selected from the group consisting of Ni, Zn, Al, Cu, and SnO.

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