KR20060075657A - Chromium free solution for treating steel sheet of automobile fuel tank with excellent corrosion resistance and anti-fuel property and steel sheet treated therewith - Google Patents

Abstract

The present invention relates to a chromium-free solution for automobile fuel tank steel plate and a steel plate treated with chromium, wherein the silicate compound 3 to 15 phr and the silane compound 0.5 to 5 phr in an acrylic or epoxy resin having a number average molecular weight of 1000 or less according to the present invention. And a steel plate treated with a chromium-free solution made by adding 0.2 to 2 phr of a titanium compound, and such a fuel tank steel plate does not contain chromium, which is environmentally friendly and excellent in corrosion resistance and fuel resistance.

Environment-friendly, Automobile Fuel Tank, Chrome-Free, Corrosion Resistance, Fuel Resistance

Description

Chromium Free Solution for Treating Steel Sheet of Automobile Fuel Tank with Excellent Corrosion Resistance and Anti-Fuel Property and Steel Sheet Treated Therewith}

The present invention relates to a chromium-free solution for automobile fuel tank steel plate and a steel plate treated with it, more particularly, it is environmentally friendly because it does not contain chromium, and a chromium-free solution for automobile fuel tank steel plate excellent in corrosion resistance and fuel resistance and a steel plate treated therewith It is about.

As a substitute for Terne plated steel sheet, which is currently used as a fuel tank steel plate for automobiles, steel sheets chromated and resin-treated on zinc and zinc alloy plated steel sheets which do not use lead at all are being developed. Korean Patent Application Nos. 1998-52504 and 1998-52143 disclose steel sheets treated with a phenoxy resin, with a coating containing Cr as the main component of the base. However, the chromium component used in the steel sheet treatment is a substance that is restricted to use because it is harmful to the human body and causes environmental pollution.

In Europe, from July 2007, a regulatory law came into force that completely banned the inclusion of hexavalent chromium (Cr ⁶⁺ ) in vehicles sold. In addition, if the RoHS (Hazardous Substances Control) Act on electrical and electronic components comes into force in July 2006, regulatory measures for chromium are expected to be more stringent. Therefore, it is urgent to develop alternative technologies that do not use chromium.

In order to solve this problem, corrosion inhibitors containing no chromium have been studied, and chromium-free treatment agents using polymers and inorganic materials such as zirconium, silicates and titanium compounds have been developed. Table 1 shows the characteristics of common chromium compounds and chromium-free compounds.

TABLE 1

General comparison between chrome and chrome free

division Cr film characteristics Cr-free film characteristics Remarks Material Inorganic: Organics = 90 ~ 95: 5 ~ 10 Inorganic: Organics = 50 ~ 60: 50-40 Film features Combined with blocking effect and self healing effect by reaction with steel plate The blocking effect of the film formed by the reaction of organic or inorganic material with hardener is dominant Coating Formation Mechanism Reacts rapidly with steel sheet, mainly dehydration and condensation temperature is not a major factor The reaction is slow because it is mainly a curing reaction. The higher the temperature, the denser the coating due to the increased curing density of the coating. High temperature dependence in case of chromium precoat Corrosion Inhibition Mechanism Bipolar reaction suppression Forms an impervious barrier against corrosion currents Film thickness 10 ~ 100mg / m ² 300 ~ 700mg / m ² Film thickness 1 ~ 2mm 3 ~ 5mm Calories required Unit price Low High 생산 in mass production

As shown in the above table, it can be seen that the conventional chromium-free treatment agent has excellent corrosion resistance only when the adhesion amount is higher than that when the chromium compound is used, and when the adhesion amount is high, the conductivity and adhesion between the upper resin and the like are inferior. Since there are problems, the way to overcome them is the most urgent.

Therefore, an object of the present invention, in order to solve the above problems, by treating a zinc or zinc-nickel alloy plated steel plate with a chromium-free solution containing no chromium, it is an environmentally friendly automotive fuel tank steel sheet excellent in corrosion resistance and fuel resistance Is to provide.

According to the invention,

Provided is a chromium-free solution for automotive fuel tank steel sheet having excellent corrosion resistance and fuel resistance by adding silica compound 3 to 15 phr, silane compound 0.5 to 5 phr, and titanium compound 0.2 to 2 phr to an acrylic or epoxy resin having a number average molecular weight of 1,000 or less. .

In addition, an automotive fuel tank steel sheet excellent in corrosion resistance and fuel resistance treated with the chromium free solution of the present invention is provided.

Hereinafter will be described in detail with respect to the present invention.

<Chrome Free Solution>

The chromium free solution for automobile fuel tank steel plate treatment of the present invention is characterized by being composed of a silicate compound, a silane compound, and a titanium compound based on acrylic or epoxy resin.

First, the resin of the chromium free solution according to the present invention will be described. The resin added to the present invention serves as a binder to assist the bonding with other inorganic additive components such as silicate or silane, and an epoxy resin or an acrylic resin is particularly preferable. Epoxy resins contain hydroxyl groups in the resin molecule so that the hydroxyl groups react with the steel sheet and the remaining reactors assist in the bonding of other silicates, silanes and titanium compounds with inorganic additives. In the case of the acrylic resin, similar to the epoxy resin, the hydroxyl group serves to increase the reactivity with the steel sheet. The resin preferably used in the present invention preferably has a number average molecular weight of 1,000 or less, and when the molecular weight is larger than this, the chains of the molecules become large, thereby decreasing the flexibility of the resin itself. When the amount of the resin added to the chromium-free solution is insufficient, the adhesion to the steel sheet and the binder function of the inorganic additives are insufficient, and in the opposite case, since the resin content is large, corrosion resistance is not preferable.

The silicate compound added to the chromium free solution of the present invention has a molecular structure of NaSiO ₃ or NaSi ₅ O ₁₁ , in particular, NaSiO ₃ is preferable, which has a three-dimensional network structure when coating the steel sheet and at the same time the zinc plated steel sheet It shows an excellent binding force. The amount of silicate added is preferably 3 ~ 15phr, when the content of silicate is less than 3phr content is too small and the adhesion and corrosion resistance to the steel sheet is lowered, when more than 15phr is not preferred because the bonding strength with the resin is weak.

The silane compound added to the chromium free solution is preferably gamma glycidoxy propyl triethoxy silane or gamma amino propyl triethoxy silane, and KBM series of Shinko Chemical is particularly preferably used. In addition, the silane compound is hydrolyzed to water to form a siloxane bond, which binds strongly to the steel sheet and at the same time serves as a binder to bind various inorganic materials. The amount of silane compound added is preferably 0.5 to 5 phr. When the content is less than 0.5 phr, the content is small, so that adhesion and corrosion resistance to the steel sheet are insufficient, and in the case of 5 phr or more, physical properties are the same as those below, but economical aspects Not desirable in

Finally, as a component of the chromium-free solution, the titanium compound is made basic by neutralizing HexafluloroTitanic Acid with amine, and then added to the solution. The amine that neutralizes hexafluorotitanic acid is triethylamine. Most preferred. The amount of amine added for neutralization is 3 ~ 10phr based on the weight of hexafluorotitanic acid. If it is less than 3phr, basicity is insufficient and precipitation is formed in the solution.If it is 10phr or more, the amount of amine is too high. The stability of the solution is poor. The amount of titanium compound to be added to the chromium free solution is preferably 0.2 to 2 phr. If the content is less than 0.2 phr, the corrosion resistance is inferior.

<Production of Resin Solution>

After applying the chromium-free solution provided as described above to the automotive fuel tank steel plate, the resin solution is applied thereon to complete the coating of the steel sheet, wherein the resin solution is a phenoxy resin (referred to as the main solution) And 5 to 25 phr of melamine resin as the curing agent, and colloidal silica in an amount of 10 to 20 phr relative to the phenoxy resin content.

In the preparation of such a resin solution, phenoxy resins excellent in corrosion resistance and fuel resistance are most preferred. The glass transition temperature of general resin is around 100 ℃, but the glass transition temperature of phenoxy resin is higher than this, so even if the ambient temperature of fuel tank is higher than this, the chains of resin do not deform and do not deform the chain of resin molecules. Do not. Therefore, the resin molecule chains forming the phenoxy resin make it difficult to penetrate water or gasoline components, which are single molecules, thereby enhancing the corrosiveness of the steel sheet. Therefore, the resin having a high glass transition temperature means that the shielding effect on the steel sheet is that much.

The phenoxy resin has a number average molecular weight of 25,000 to 50,000 is preferable, when the molecular weight is less than 25,000 is difficult to secure the desired physical properties, on the contrary 50,000 or more is impossible due to the limitations of the resin synthesis method.

The content of the melamine resin added to the phenoxy resin is preferably 5-25 phr compared to the phenoxy resin, and in the case of 5 phr or less, since the curing reaction is not completely performed after the resin is coated, there is little effect of fixing the metal powder. On the contrary, when it is 25 phr or more, the curing agents react by excessive addition and adversely affect the coating properties. And the colloidal silica is added to improve the corrosion resistance of the resin film is preferably added 10 ~ 20phr relative to the phenoxy resin content. If the silica content is less than 10phr, the content is too small, there is no corrosion resistance effect, on the contrary, if more than 20phr, the effect of improving the corrosion resistance is inferior to the silica input content.

<Manufacture of fuel tank steel plate>

Hereinafter, an automotive fuel tank steel plate treated with a chromium-free solution according to the present invention will be described.

Automobile fuel tank steel plate of the present invention is a cold-rolled steel sheet is subjected to zinc or zinc-nickel electroplating and then treated with a coated chromium-free solution and coated with a resin solution having excellent fuel resistance on the resin coated steel sheet having a three-layer structure. Characterized in that it is manufactured.

First, zinc or zinc alloy plated steel sheet may be used as the plating layer. In the present invention, Zn-Ni steel sheet, which is a zinc alloy plated steel sheet having excellent corrosion resistance, is more preferable than the plated steel sheet composed of zinc alone. In addition, the chromium-free solution applied after the electroplating has a reaction type or a coating type, and a coating type treatment is more preferable in terms of corrosion resistance.

Chromium coating weight of the pre-solution to be coated on the zinc or zinc alloy coated steel sheet is 200 ~ 1000mg / m ² are preferred, based on the dried, and is most preferably attached in an amount of 300 to 600mg / m ^2. When the adhesion amount is 200 mg / m ² or less, it is difficult to secure desired corrosion resistance and fuel resistance, and on the contrary, when the adhesion amount is 1000 mg / m ² or more, the resin is coated on the upper side, which is not preferable because the resin adhesiveness and weldability deteriorate.

On the other hand, after coating the chromium free solution, the baking temperature is preferably in the range of 160 to 250 ° C based on the MT-metal temperature. When the baking temperature is less than 160 ° C, the resin and the inorganic substance do not react, and some components are washed at the time of washing. It is difficult to secure the desired corrosion resistance due to this drop off, on the contrary, when the temperature is 250 ° C. or more, the expected curing reaction no longer occurs and only a large amount of heat is lost.

The dry thickness of the resin film to be applied after applying the chromium-free solution is preferably 2.0 to 10.0 μm. If the film thickness is 2㎛ or less, it is difficult to secure sufficient corrosion resistance and fuel resistance because the thickness of the coating film is thin. If the thickness is 10㎛ or more, the corrosion resistance and fuel resistance are not affected by the increase in the thickness of the coating film. Weldability falls.

On the other hand, the baking temperature after resin coating is preferably in the range of 180-250 ℃ based on the MT-Metal Temperature. When the baking temperature is lower than 180 ℃, the hardening reaction of the resin is not sufficient. If the adhesion to and decreases, on the contrary, when the temperature becomes higher than 250 ° C, the expected curing reaction no longer occurs and the calorie loss is large.

In general, there are various coating methods such as roll coating, spraying, and dip coating by a roll to apply the steel sheet, but in the case of the present invention, the roll coating method is most preferred. The roll coating method can be applied to both the one side and both sides to the steel sheet applied to the present invention and the reason is as follows. The application form of chromium-free solution and resin applied to the steel plate is performed on all sides without distinction between one side and both sides in case of chromium-free, and in case of resin, both one side and both sides mode according to customer's equilibrium to give functionality I can take it. In other words, since the welding conditions of the customers are different from each other, high current conditions that are easy to weld and customers who frequently exchange electrodes may be used on both sides, but customers who do not frequently replace the low current conditions and electrodes may use it. It is better to use a steel sheet coated with one-sided resin. When the fuel tank is made of steel sheet coated with single-sided resin, the surface coated with resin faces toward the fuel and the surface coated with chrome-free, which is opposite, faces outward. Since the welding is much more easy to weld is an advantage. In addition, since the resin is not coated on the surface of the customer, a thick top coat (about 100 μm) is manufactured to reinforce the corrosion resistance of the fuel tank. Therefore, there is little effect on the corrosion resistance.

Equipment for applying the chromium-free solution and the resin solution of the present invention by a roll coating method is to bury the solution in the drip pan in the pickup roll, transfer it to the transfer roll, and finally in the applicator roll to dry on the steel sheet and dried in an oven to form a final coating Forming method is used, and the amount of adhesion to be attached is controlled by the driving direction of each roll, the rotational speed, and the adhesion pressure between the rolls.

As described above, the automotive fuel tank steel plate to which the chromium-free solution according to the present invention is applied is treated with a solution that does not contain chromium. Therefore, environmental pollution does not occur due to this, and the corrosion resistance and fuel resistance are excellent, and thus the quality of the steel sheet is improved. Significantly improved.

Hereinafter, the present invention will be described in more detail with reference to the following Examples, which do not limit the present invention.

Example

<Standard Steel Sheet Manufacturing Method>

Coating weight is 30g / m ² of electrolytic zinc and alloy-plated steel sheet treated with the Cr-free solution to each of the solution composition on a following steel sheet temperature of 190 ℃ be baked dry and then was cooled and then by applying a resin solution to be a steel sheet temperature of 190 ℃ baking Drying to prepare a resin coated steel sheet having a drying temperature of 2μm.

In this case, the chromium-free solution to be applied is a solution prepared by adding 7 phr of silicate to acrylic resin, 2 phr of silane and 1 phr of titanium compound as the standard composition, and the basic composition of the resin solution is the number average molecular weight in the form of dispersion in water. 5 phr of melamine resin is added to 50,000 phenoxy resin 100, and a resin solution having a solution base composition of 15 phr of colloidal silica having a particle diameter of 20 nm is prepared. Unless otherwise specified, the resin solution prepared by the above mixing ratio is referred to as the standard solution composition, and the method of manufacturing the steel sheet as described above is referred to as a standard steel sheet manufacturing method.

 Example 1

The content of silicate, silane, titanium compound, and resin in the standard solution composition was changed, and the zinc plating amount was plated at 30 g / m 2, followed by 500 mg / m 2 chromium-free treatment, followed by quenching at 190 ° C., followed by cooling. The resin solution was applied by a roll coating method, followed by baking the steel plate at 190 ° C., followed by water cooling to prepare a resin coated steel sheet having a dry resin coating thickness of 2 μm.

And the evaluation of the resin adhesion of the steel sheet was boiled in boiling water for 30 minutes, then taken out, left to stand for 5 minutes and dried, and then the tape was adhered to the steel sheet and peeled and evaluated. The evaluation criteria are as follows.

          ◎: 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

Corrosion resistance was evaluated by the percentage of rust that occurred after 500 hours at 1kg / cm ² spray pressure at 35% in brine concentration at 35 ° C, and the evaluation criteria were as follows. After the cup was made, deteriorated gasoline was added, and 6 months later, the outside of the cup was evaluated for corrosion.

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

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

   ×: corrosion area of 50% or more

Weldability was evaluated by using pneumatic AC spot welding machine to apply constant pressure of 250kg and welding time of 15Cycle, and to maintain constant strength at 7.5kA without spatter. The criteria are two types of welding (◎) and impossible (×). The evaluation criteria were presented in mode.

TABLE 2

Quality Evaluation Results by Composition of Chromium-Free Solution

TABLE 3

Quality Evaluation by Manufacturing Condition Using Chrome Free Solution

As a result of evaluating the composition-specific quality of the chromium-free solution, as shown in Table 2, inventive materials 1 to 12 introducing the chromium-free solution belonging to the present invention compared with the comparative materials 1 to 7 and the adhesion of the steel sheet to the resin, It was evaluated to be excellent in corrosion resistance.

In addition, when the results of Table 3 evaluating the effects of the chromium-free coating production conditions and the amount of chromium film deposition, the baking conditions for producing the chromium-free coating are 160 to 250 ° C. required by the present invention (invention material 13 to 15) was evaluated as having excellent quality characteristics such as weldability, corrosion resistance and adhesion, and the chromium-free coating amount was excellent in quality characteristics such as weldability, corrosion resistance and adhesion in the range of 200 ~ 1,000 ㎎ / ㎡ (Inventive Material 16-18). Was evaluated.

Automotive fuel tank steel plate applied with the chromium-free solution according to the present invention is excellent in corrosion resistance and fuel resistance, and is harmless to the human body and does not cause problems due to environmental pollution because it uses a solution containing no chromium. .

Claims (9)

A chromium-free solution for automotive fuel tank steel sheet having excellent corrosion resistance and fuel resistance, by adding silica compound 3-15 phr, silane compound 0.5-5 phr, and titanium compound 0.2-2 phr to an acrylic or epoxy resin having a number average molecular weight of 1,000 or less. The chromium-free solution for automobile fuel tank steel plate having excellent corrosion resistance and fuel resistance according to claim 1, wherein the silicate compound is NaSiO ₃ or NaSi ₅ O ₁₁ and has a three-dimensional network structure when coating the steel sheet. The chromium free solution for automobile fuel tank steel sheet having excellent corrosion resistance and fuel resistance according to claim 1, wherein the silane compound is gamma glycidoxypropyltriethoxysilane or gamma amino propyltriethoxysilane. The chromium free solution for automobile fuel tank steel sheet having excellent corrosion resistance and fuel resistance according to claim 1, wherein the titanium compound is hexafluorotitanic acid. An automotive fuel tank steel plate having excellent corrosion resistance and fuel resistance treated with the chromium-free solution according to claim 1. The automotive fuel tank steel sheet of claim 5, wherein the adhesion amount after drying of the chromium precoat layer is 200 to 1,000 mg / m ² . 7. The automobile fuel tank steel plate according to claim 6, further comprising a resin solution after the chromium-free solution is treated. According to claim 7, wherein the resin solution is introduced into the water-soluble phenoxy resin having a number average molecular weight of 25,000 ~ 50,000 to 5 ~ 25phr melamine resin compared to the phenoxy resin content, colloidal silica 10 ~ 10 to the phenoxy resin content Automotive fuel tank steel plate with excellent corrosion resistance and fuel resistance, characterized in that the 20 phr injection. The automotive fuel tank steel sheet according to claim 7 or 8, wherein the coating film thickness after drying of the resin solution is 2 to 10 µm.