KR20090073908A - Cr-free sealing solution and method of fabricating phosphated electro-galvanized steel sheet using the same - Google Patents

Abstract

A Cr-free sealing solution and a method of fabricating a phosphate electro-galvanized steel sheet using the same are provided to form a sealing resin on the top of a phosphate layer using Cr-free sealing solution containing inorganic compound like silane and zirconium, thereby improving the anti-corrosion and anti-black staining properties. A Cr-free sealing solution including pure water comprises an inorganic cross-linking agent formed of zirconium-based compound 0.2~9wt.%, a silane coupling agent formed of amino, epoxy or methacryl 0.1~3wt.%, and phosphoric acid inorganic matter 0.3~15wt.%. The inorganic cross-linking agent is selected among zirconia, zirconium hydro fluoric acid, zirconium potassium fluoride, zirconium ammonium fluoride, and zirconium compound sol.

Description

Cr-free Sealing Solution And Method of Fabricating PhosPhated Electro-galvanized Steel Sheet Using The Same}

The present invention relates to a chromium-free sealing solution and a method for manufacturing a phosphate electrogalvanized steel sheet using the same, by preparing a chromium-free sealing solution and using the same to form a resin on the phosphate layer, the corrosion resistance and blackening resistance of the same or higher than those of the conventional materials. It relates to the invention to be able to manufacture a product secured.

The demand for electro-galvanized steel sheet is increasing for building materials and home appliances, and in developed countries for automobiles.

Domestic and foreign cold-rolled product manufacturers and other steel-based SMEs that produce electro-galvanized steel sheets produce products by chemical treatment such as chromate treatment and phosphate treatment as final post-treatment. Double chromate treatment refers to coating a rust preventive film by putting a steel plate in a solution mainly composed of chromic acid or dichromate. Chromate treatment is an inexpensive treatment process that gives galvanized steel sheets excellent paint adhesion and corrosion resistance.

Figure 1 is a schematic diagram showing a phosphate electrogalvanized steel sheet according to the prior art.

Referring to FIG. 1, a zinc (Zn) plating layer 20 is formed on a steel plate 10, and a phosphate (P) layer 30 and a chromium (Cr) layer 40 are formed on the zinc plating layer 20. ) Is sequentially formed to form a phosphate electrogalvanized steel sheet 50.

Here, since chromium is a representative pollutant that causes serious damage to workers and the environment, regulatory laws have been enacted in developed countries and implementation is being carried out worldwide. In addition, in the case of chromate-treated steel sheets, hexavalent chromium (Cr ⁺⁶ ) is generated as wastewater in the process, and thus, wastewater treatment is costly and time-consuming, and its use will soon be banned in accordance with international chrome usage regulations. As it is known, research on chromate has not been carried out until now, and researches to develop materials to replace chromium are being actively conducted worldwide.

To date, research has been conducted to reduce chromium hexavalent and to develop 100% chromium trivalent solution since hexavalent chromium is more toxic than trivalent chromium, but this is basically to remove chromium. Also, 100% chromium trivalent solution did not have the advantage of replacing the existing chromate solution in terms of corrosion resistance and price.

On the other hand, according to a recent research paper, there is an attempt to convert the steel sheet using organic materials other than inorganic materials, and as an organic material, alkoxysilane has recently emerged as a substitute for chromate and phosphate.

Alkoxysilane is represented by the chemical formula of Y-Si (OR), and Y is an organofunctional group such as vinyl, amino, epoxy, mercapto. Penetrates into the paint resin and increases adhesion. OR is an alkoxy group, such as -OCH3, -OC2H5, and the water-soluble SiOH has a chemical bond in the metal layer. Alkoxysilane has an excellent effect of increasing the corrosion resistance and coating adhesion of the film, but is limited in industrial use because the price is several times higher than that of chromate treatment. In addition, because of low productivity, it is difficult to realize in the near future. In addition, many materials are currently being studied as candidates for chromium substitution, but the results are extremely limited.

[Table 1] below compares the characteristics and treatment methods of the chromium (Cr) solution and the chromium-free (Cr-free) solution.

TABLE 1

division Reactive Chrome (Cr) Agent Coating type Cr-free Processing way Squeeze / Spray Roll Coater Processing order Post Plating Treatment Post Plating Treatment Material etching U Almost none Advantages  Excellent primary rust prevention Hypo-allergenic, low-reactivity bath management easy (conductivity measurement) Waste water cost reduction, black resistance Disadvantages Management dimness, black stool in case of poor management Poor corrosion resistance compared to chromium (Cr)

As described above, development of alternative materials having low cost and high corrosion resistance, such as chromium (Cr), and excellent corrosion resistance even at a low adhesion amount (100 mg / m ² or less) is actively underway. However, galvanized steel sheet using a material having corrosion resistance as much as chromium with an adhesion amount similar to chromium of 100 mg / m ² has not been developed yet.

The present invention is 0.2 to 9% by weight of inorganic crosslinking agent composed of zirconium or zirconium-based compound, 0.1 to 3% by weight of silane coupling agent composed of amino, epoxy or methacryl in order to ensure rust resistance in pure water controlled to 1 전도 / ㎝ or less and Chromium-free sealing solution containing chromium-free sealing solution containing 0.3 to 15% by weight of phosphoric acid-based minerals, and by using these to produce a sealing resin on the surface of the phosphate galvanized steel sheet, to ensure excellent rust-proof and black wall properties It is an object of the present invention to provide a solution and a method for producing a phosphate electrogalvanized steel sheet using the same.

Chrome-free sealing solution according to the present invention,

In the sealing solution containing pure water, 0.2 to 9% by weight of inorganic crosslinking agent composed of zirconium or zirconium compounds, 0.1 to 3% by weight of silane coupling agent composed of amino, epoxy or methacryl and 0.3 to 15% by weight of phosphoric acid inorganic It is characterized by including.

Here, the pure water of the sealing solution is characterized in that the electrical conductivity is controlled to 1㎲ / ㎝ or less, the inorganic crosslinking agent of the sealing solution is zirconium oxide, zirconium hydro fluoric acid (zirconium hydro fluoric acid), zirconium potassium fluoride (Zirconium potassium fluoride), zirconium ammonium fluoride (Zirconium ammonium fluoride), or any one selected from the zirconium compound of the sol form, the silane fling agent of the sealing solution is any one selected from amino silane, epoxy silane, acrylic silane and vinyl silane It characterized in that it comprises a, the phosphoric acid-based inorganic concentration of the sealing solution is characterized in that it is adjusted to 2 to 4%, the inorganic crosslinking agent: silane: inorganic material ratio is 2: 1: 1: 3 to 3: 1: It characterized in that the adjustment to 5, the sealing solution is a corrosion inhibitor as silicon (Si), zirconium (Zr), titanium (Ti), aluminum (Al), phosphorus (P) or vanadium (V), characterized in that it comprises one or two more polyvalent compounds, further comprising 0.1 to 0.4% of the neutralizing agent of the sealing solution The neutralizing agent is characterized in that it comprises formic acid or ammonia.

In addition, the phosphate electrogalvanized steel sheet manufacturing method according to the present invention,

Preparing a phosphate galvanized steel sheet, applying the chromium-free sealing solution to the surface of the phosphate galvanized steel sheet, and performing a squeegeeing and drying process on the surface of the phosphate galvanized steel sheet to perform phosphate electroplating. It characterized in that it comprises the step of forming a sealing resin on the surface of the galvanized steel sheet.

Here, the chromium-free sealing solution is characterized in that the coating to a thickness of 0.1 ~ 1㎛, the drying process is characterized in that carried out at a temperature of 20 ~ 70 ℃.

The chromium-free sealing solution according to the present invention and a method for producing a phosphate electrogalvanized steel sheet using the same are used instead of the conventional chromium treatment in the surface treatment of a phosphate electrogalvanized steel sheet using a chromium-free sealing solution containing inorganic compounds such as zirconium and silane. By preparing and forming a sealing resin on the phosphate layer using the same, it provides an effect capable of providing corrosion resistance and blackening resistance equivalent to or higher than that of the existing material.

Hereinafter, with reference to the accompanying drawings and examples will be described in detail with respect to the sealing solution and the method for producing a phosphate electrogalvanized steel sheet using the same according to the present invention.

Figure 2 is a schematic diagram showing a phosphate electrogalvanized steel sheet prepared using a chromium-free sealing solution according to the present invention.

Referring to FIG. 2, a zinc (Zn) plating layer 120 is formed on the steel sheet 100, and a phosphate (P) layer 130 and a sealing resin layer 140 are formed on the zinc plating layer 120. Forming sequentially to form a phosphate electrogalvanized steel sheet 150. At this time, the sealing resin layer 140 is manufactured by using the sealing solution according to the present invention, and the sealing solution according to the present invention is a chromium-free sealing solution containing inorganic compounds such as zirconium and silane. Examples of the specific example thereof are as follows.

(Example 1)

One inorganic crosslinking component and a granulated water-soluble component combined with the crosslinking component exhibit a fine alkali reaction with the phosphate layer of the steel sheet upon coating. Therefore, the pH of the sealing solution according to the present invention is preferably 9 to 10.

In addition, if only an inorganic material, a coupling agent, and an inorganic crosslinking agent are present in the sealing solution according to the present invention, the evaporation rate of the coating layer may be increased during the squeezing process by a roll, and thus drying may be performed at a temperature of 60 ° C. or lower. . When the low temperature drying is possible, the energy saving effect and the cooling time of the coil due to the low temperature work can be shortened, and thus the production speed can be improved.

Therefore, when the sealing solution according to the present invention is used, the rust prevention property can be secured by ideally filling the porous pores of the intrinsic phosphate layer by initiation of crosslinking, reaction with the phosphate layer, and inorganic bonding.

First, the zirconium compound contained in the sealing solution according to the present invention can be used to dissolve zirconium alone at a specific solvent or temperature, or to use a compound form. Zirconium oxide, zirconium hydro fluoric acid, zirconium potassium fluoride, zirconium ammonium fluoride or zirconium compounds in the form of sol may be used. In this case, since it is difficult to add dissociated zirconium and zirconium compounds in a large dilution ratio to exert corrosion resistance, it is necessary to construct an additional inorganic insoluble compound.

Next, by using an ammonium compound or phosphoric acid, polyphosphoric acid, zinc phosphate, phosphoric acid derivatives, phosphorous acid and phosphoric acid compounds thereof, which can make ammonium salts, the corrosion resistance can be exerted and the pH to be secured is also controlled. do.

Next, the silane coupler is adjusted to within 0.1-3 of the total weight percent. As the silane, it is preferable to use one of amino silane, epoxy silane, acryl silane, vinyl silane, and one of the more reactive materials.

These silanes have hydrolyzable groups such as alkoxy groups and organic functional groups such as acrylic, epoxy, vinyl, and mecapto groups, and thus contribute to increasing adhesion and improving adhesion between organic materials such as resin and inorganic materials such as silica, glass, and metal. Can be.

Here, the silane has a property of hydrolyzing in water, and in general, the organic component promotes gelation and the inorganic component has a high specific gravity, but also has a function of settling unstable particles to the bottom of the solution. do. Therefore, the addition ratio of the inorganic binder and the silane, the selection of the inorganic amount and the order of addition greatly affect the properties of the product. For example, if an inorganic binder is added to pure water and the mineral is added after stirring for 30 minutes, the color turns green and the reaction stops.However, if the inorganic material is added to the pure plant and the inorganic binder is added, the liquid turns yellow with precipitation. To rise.

Table 2 below compares the evaluation of the corrosion resistance according to the composition ratio of the chromium-free (Cr-fee) sealing solution.

TABLE 2

division Mixing ratio Zr-based binder: Silane: phosphate inorganic Corrosion resistance 24 hours after deposition Liquid bath 45 degrees 120 hours One 1: 1: 1 100% white blue Good 2 1: 2: 1 100% white blue Mineral precipitation 3 1: 1: 2 80% White Blue Good 4 1: 1: 3 70% White Blue Good 5 1: 1: 5 50% White Blue Good 6 1: 1: 7 50% White Blue Mineral Pre-Deposition (Not Green) 7 2: 1: 5 30% White Blue Good 8 3: 1: 5 25% White Blue Good 9 4: 1: 5 25% White Blue Gel

In this way, when looking at the corrosion resistance according to the mixing ratio of the additives, it can be seen that the ratio of the inorganic binder: silane: inorganic material is close to 2: 1: 3 to 3: 1: 5 indicates good corrosion resistance.

Next, in order to enable the silane solution according to the present invention to form an insoluble coating layer, an additive of amines that induces fixation of the inorganic metal component is added to the sealing solution. When elements such as silicon (Si), zirconium (Zr), titanium (Ti), aluminum (Al), phosphorus (P) and vanadium (V) are added, these are combined to form a composite oxide film. Here, excellent corrosion resistance can be obtained by a zirconium (Zr) component, a SiO2 component, a titanium (Ti) component, or a vanadium (V) component. Therefore, the corrosion inhibitory effect is exhibited to the maximum.

For example, as a result of analyzing the zirconium (Zr) component in the composite oxide film by XRF, the adhesion amount within 20 mg / m 2 can be measured. This is a very small amount, which cannot be measured in Ka, and only a small amount is measured in La. (In order to reduce the error, the calibration curve is made of Al.) Here, as the adhesion amount increases, the corrosion resistance is improved. However, if the amount of adhesion is excessively increased, the amount of solution consumed increases and the manufacturing cost is increased.

Next, up to 3% by weight of organic resin is blended to add lubricity, corrosion resistance and fingerprint resistance to the sealing solution according to the present invention.

At this time, however, if the amount of the organic resin is too large, the resin (cure) is accompanied by an increase in the temperature, it is necessary to pay attention to the cumbersome cleaning, lowering of paint adhesion and burning in welding may occur. Therefore, it is preferable that the organic resin is not added unless the inorganic material is excessively added or sludge is generated.

(Example 2)

The sealing solution according to the present invention has a different characteristic depending on what the solvent is, but there is a possibility that black stools (discoloration due to oxidation of the conductive surface) may occur as the amount of the phosphate-based inorganic substance increases. Therefore, neutralizing the sealing solution with formic acid, ammonia, etc. can obtain a protective effect of reducing black stools. However, even with neutralization, the zinc contamination tends to be relatively high. Therefore, the pollution degree and the blackening phenomenon of the steel sheet in accordance with the increase in the phosphate-based inorganic material at the time of manufacturing the sealing solution was measured, and the blacking phenomenon of the steel sheet was measured while increasing the neutralizing agent to find the optimal sealing solution.

Table 3 compares the evaluation of blackening resistance according to the additive composition ratio of the sealing solution according to the present invention.

TABLE 3

division weight pH Relative evaluation of zinc elution (pollution degree) after 1 hour material deposition Initial L value 96 hours L value ΔL value (black side) ΔL = 2 or less One Phosphate-based inorganic 2.0% 8.4 Less pollution 78.85 78.55 0.30 (good) 2 Phosphate-based inorganic 4.0% 9.1 Pollution 78.91 77.28 1.63 (good) 3 Phosphate-based inorganic 6.0% 9.6 Too much pollution 78.88 76.10 2.78 (bad) 4 Phosphate-based inorganic 8.0% 10.0 Too much pollution 78.76 74.35 4.41 (bad) 5 Phosphate-based inorganic 6.0% + pH neutralizing agent 0.01% 9.4 Too much pollution 78.76 76.22 2.54 (bad) 6 Phosphate-based inorganic 6.0% + pH neutralizing agent 0.02% 9.1 Too much pollution 78.68 77.20 1.48 (good) 7 Phosphate-based inorganic 6.0% + pH neutralizing agent 0.03% 8.8 Too much pollution 78.78 77.51 1.27 (good) 8 Phosphate-based inorganic 6.0% + pH neutralizing agent 0.04% 8.4 Too much pollution 78.76 77.42 1.34 (good)

The chromium-free sealing solution prepared by the above-described manufacturing method is diluted in the range of 1 to 20% using pure water, and used in the following steps.

Figure 3 is a schematic diagram showing a phosphate electrogalvanized steel sheet process using a chromium-free sealing solution according to the present invention.

Referring to FIG. 3, first, a phosphate electrogalvanized steel sheet 200 was formed by performing a phosphate treatment on an electro zinc plated steel sheet prepared to have a thickness of about 0.7 mmt and an amount of zinc deposited on an MQ grade cold rolled steel sheet about 20 g / m 2 (one sided basis). Manufacture.

Next, the phosphate electrogalvanized steel sheet 200 is passed through the coating apparatus 250 for coating the chromium-free sealing solution according to the present invention to produce a phosphate electro-galvanized steel sheet 210 coated with a sealing solution. At this time, the coating device 250 is applied to the sealing solution using a spray method, the sealing solution is preferably applied to a thickness of 0.5 ~ 20 mg / ㎡.

Next, the phosphate galvanized steel sheet 210 coated with the sealing solution is passed through a squeezing device 260, and the phosphate galvanized steel plate 220 passed through the squeezing device 260 is cleaned. A phosphate electrozinc plated steel sheet 230 having a sealing resin formed therein to pass through the apparatus 270 and the drying apparatus 280 to protect the phosphate layer is manufactured. At this time, it is preferable that the dry window is maintained at a temperature of 20 to 70 ° C so that the thickness of the sealing resin is 0.1 to 1 m.

Here, when the thickness of applying the sealing solution is thin, the corrosion resistance is lowered, and when the squeegeeing and cleaning process are performed, the thickness of the coating layer may be uneven. In addition, if the thickness of the application of the sealing solution is too thick, zirconium particles or silane particles in the powder blowing phenomenon may occur on the surface of the steel sheet, because the stain may occur at the edge of the steel sheet should be careful.

In addition, the inorganic material used in the sealing solution according to the present invention does not affect the spot weldability, and does not significantly affect the paint adhesion, and thus has suitable properties as a coating agent.

Figure 4 is a graph measuring the conductivity according to the concentration of the chromium-free sealing solution according to the present invention.

Referring to Figure 4, it can be seen that the electrical conductivity increases as the concentration of the sealing solution is increased.

The electrical conductivity can be measured to match the solution concentration in the solution stirred tank of the line.

As described above, the sealing solution according to the present invention prepares a chromium-free sealing solution containing inorganic compounds such as zirconium and silane instead of the conventional chromium treatment in the surface treatment of phosphate electrogalvanized steel sheet, and using the phosphate layer on the upper surface of the phosphate layer. By forming a resin in the product to be able to manufacture a product having more than equivalent corrosion resistance and blackening resistance than existing materials.

1 is a schematic view showing a phosphate electrogalvanized steel sheet according to the prior art.

Figure 2 is a schematic diagram showing a phosphate electrogalvanized steel sheet prepared using a chromium-free sealing solution according to the present invention.

Figure 3 is a schematic diagram showing a phosphate electrogalvanized steel sheet process using a chromium-free sealing solution according to the present invention.

Figure 4 is a graph measuring the conductivity according to the concentration of the chromium-free sealing solution according to the present invention.

Claims (12)

In the sealing solution containing pure water, 0.2 to 9% by weight of inorganic crosslinking agent composed of zirconium or zirconium compounds, 0.1 to 3% by weight of silane coupling agent composed of amino, epoxy or methacryl and 0.3 to 15% by weight of phosphoric acid inorganic Chrome-free sealing solution comprising a. The method of claim 1, Pure water of the sealing solution is chromium-free sealing solution, characterized in that the electrical conductivity is controlled to 1 ㎲ / ㎝ or less. The method of claim 1, The inorganic crosslinking agent of the sealing solution is any one selected from zirconium oxide, zirconium hydro fluoric acid, zirconium potassium fluoride, zirconium ammonium fluoride, or a zirconium compound in the form of a sol. Chrome-free sealing solution characterized in that. The method of claim 1, The silane sealing agent of the sealing solution is chromium-free sealing solution, characterized in that it comprises any one selected from amino silane, epoxy silane, acrylic silane and vinyl silane. The method of claim 1, Phosphoric acid-based inorganic concentration of the sealing solution is adjusted to 2 to 4% chromium-free sealing solution, characterized in that. The method of claim 1, The inorganic crosslinking agent: silane: inorganic chromium-free sealing solution, characterized in that the ratio is adjusted to 2: 1: 3 to 3: 1: 5. The method of claim 1, The sealing solution further comprises one or two polyvalent compounds composed of silicon (Si), zirconium (Zr), titanium (Ti), aluminum (Al), phosphorus (P) or vanadium (V) as a corrosion inhibitor. Chrome-free sealing solution characterized in that. The method of claim 1, Chromium-free sealing solution, characterized in that it further comprises 0.1 to 0.4% of the sealing solution. The method of claim 8, The neutralizing agent is chromium-free sealing solution, characterized in that it comprises formic acid or ammonia. Preparing a phosphate electrogalvanized steel sheet; Applying the chromium-free sealing solution according to claim 1 on the surface of the phosphate electrogalvanized steel sheet; And And squeezing and drying the surface of the phosphate galvanized steel sheet to form a sealing resin on the surface of the phosphate galvanized steel sheet. The method of claim 10, The chromium-free sealing solution is a phosphate electro-galvanized steel sheet manufacturing method characterized in that the coating to a thickness of 0.1 ~ 1㎛. The method of claim 10, The drying step is a phosphate galvanized steel sheet manufacturing method characterized in that carried out at a temperature of 20 ~ 70 ℃.

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