KR100321040B1 - Solution for forming molybdenum/phosphorus/silicate film and method for forming molybdenum/phosphorus/silicate film using the same - Google Patents

Abstract

PURPOSE: A solution for forming molybdenum/phosphorus/silicate film having excellent corrosion resistance and wettability, and a method for forming molybdenum/phosphorus/silicate film using the same are provided. CONSTITUTION: The method for forming molybdenum/phosphorus/silicate film includes step of heating a solution comprising molybdenum concentration 0.4 to 4.0 g/L, phosphorus concentration 7.0 to 14 g/L, colloidal silica concentration 1.0 to 150 g/L in the temperature range of 40 to 60°C; and immersing galvanized steel sheet in the solution.

Description

Molyphosilicate film forming solution and film forming method using the same

The present invention relates to a forming liquid for forming a molybdate silicate film on a galvanized steel sheet and a forming method using the same, and more particularly, to a film forming solution and a film forming method, in which a molybdate silicate film having excellent corrosion resistance and resin adhesion is obtained. It is about.

The chromate coating treatment to improve the corrosion resistance of galvanized steel sheet is well known in the industry as a well-known production technology, but due to the toxic toxicity of chromium hexavalent ions used in chromate solution, it is relatively less characteristic as the environmental regulations are strengthened in the future. Development of alternative materials is needed. One of the alternative material systems is a morphophosphate coating, and research results have been reported that the morphophosphate coating film has a relatively excellent corrosion resistance.

Japanese Patent Application Laid-Open No. 71-6846 relates to a molybdate coating production technique to which a water-soluble organic compound of 0.05 to 45 wt% is added at a molybdate concentration of 0.5 molar concentration or less, and Japanese Laid-Open Patent Publication 76-2419 discloses a 0.025 to immersion method. It relates to a 0.02 M magnesium or calcium molybdate solution, Japanese Patent Publication No. 76-14141 relates to a molybdate solution containing ammonium sulfate by an immersion method.

However, the above proposals are related to the formation of molybdate film and it is known that the reaction time is required for a long time and the corrosion resistance is not excellent (GB 2B 2070073). On the other hand, Nielsen (Bech-Nielsen) moly phosphate while applying an oxidation current of -2.5 ~ + 5.0V (vs SHE) to the subject under Mo concentration of 2.9 ~ 9.8g / L, Mo / P mole ratio of 0.2 ~ 0.8 Although a manufacturing technique for forming a film is proposed (WO 93/10278), the reaction time takes more than 2 minutes and corrosion resistance is considered to be inferior to the conventional chromate treatment material as a technical limitation.

Accordingly, an object of the present invention is to provide a solution for forming a morphosilicate film excellent in corrosion resistance and resin adhesion by containing a colloidal silica and appropriately controlling the remaining components in forming a solution for forming a morphophosphate film on a steel sheet. I want to.

In addition, another object of the present invention is to provide a method for forming a film obtained by controlling the temperature of the solution appropriately, by applying an immersion method to form a film on a galvanized steel sheet, a morphosilicate film excellent in corrosion resistance and resin adhesion. have.

Molyphos silicate coating is an alternative development agent of the conventional chromate coating treatment, forming a film with Mo-P-Si-OH composition on the surface of the steel sheet, which is used as an external corrosion factor (H ₂ O, Cl, O ₂ ). To form a corrosion barrier to protect the plating film or steel plate surface. Conventionally, studies have been conducted on molybdate coatings mainly composed of Mo components and molybdate films mainly composed of Mo-PO, but the present inventors have added Mo-P-Si-OH by adding Si having excellent corrosion resistance. A technique was established for the subject to form a morphosilicate film.

Starting from the above point of view, the present invention is characterized in that the concentration of molybdenum is 0.4 to 4.0 g / L, the concentration of phosphate is 7.0 to 14 g / L, and the concentration of colloidal silica is 1.0 to 150 g / L. The present invention relates to a molybdate silica film-forming liquid, and the present invention also provides a molybdenum concentration of 0.4 to 4.0 g / L, a phosphoric acid group of 7.0 to 14 g / L, and a colloidal silica concentration of 1.0 to 150 g /. After maintaining a solution of l at 40 ~ 60 ℃, and immersed galvanized steel sheet in the solution to a film forming method for morphosilicate.

Hereinafter, the present invention will be described in detail.

In the present invention, molybdenum is maintained at a concentration of 0.4 to 4.0 g / l in the molybdate silicate film-forming liquid. If the concentration of molybdenum is less than 0.4 g / L, even if the amount of phosphoric acid in the solution changes, the amount of adhesion is small. This means that the molybdenum component, which is the main agent of the film, should be added at least 0.4 g / L in the solution. . On the other hand, when molybdenum in the solution was added in excess of 4.0 g / L, the amount of coating was decreased and the corrosion resistance was poor.

In the present invention, the phosphate group in the molybdate silicate film-forming liquid is maintained at a concentration of 7.0-14 g / L. This is because when the concentration of phosphoric acid is less than 7.0 g / L or more than 14.0 g / L, the amount of coating is reduced and the corrosion resistance is poor.

In the present invention, the colloidal silica is maintained at a concentration of 1.0 to 150 g / L. Colloidal silica is a silicon oxide, which is characterized by a large particle surface area and a large adsorption phenomenon with other molecules because its behavior is governed by the particle quality of the surface of 10 ^2-3 m ² / g. At this time, the surface of the particle mainly contains Si-O-Si defects or -Si-OH bonds, and promotes the formation of basic zinc salt (ZnClZn (OH) ₂ ) which adsorbs to the film to form zinc. Corrosion resistance is improved by the corrosion barrier effect by the, and the hydroxyl bond group in the outer layer of the film by -Si-OH bonds to improve the adhesion to the resin component. In addition, the Si-O component is adsorbed on the molybdate film composed of Mo-PO, so that the Si-O component is adsorbed on the molybdate film composed of Mo-PO, thereby forming a molybdate silicate film in the form of Mo-P-Si-OH. Corrosion factor (H ₂ O, O ₂ ) acts to increase the shielding effect to increase the corrosion resistance.

If the concentration of colloidal silica is less than 10g / L, the adhesion and corrosion resistance are poor. If it exceeds 150g / L, the corrosion resistance is slightly improved but the resin adhesion tends to decrease. It is believed that this is because the van der Waals bond between the resin and the film interface is weakened inversely. From these results, when colloidal silica is added to a solution composed of molybdenum and phosphate groups, corrosion resistance is improved, and it is preferable to limit the concentration of colloidal silica to 5 to 150 g / L.

The molybdate silicate film-forming solution configured as described above can be applied to galvanized steel sheet or cold rolled steel sheet. Next, a method of forming a film by applying the solution to a galvanized steel sheet will be described.

In the present invention, the film is formed by maintaining the molybdate silicate film-forming solution constituted as described above at 40-60 ° C. and immersing the galvanized steel sheet in this solution.

In the case where the molybdate silicate film-forming liquid is less than 40 ° C, the adhesion amount is small, the corrosion resistance is significantly inferior, and in the case where it exceeds 60 ° C, problems occur due to excessive adhesion.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

The solution and the treatment conditions of the components as shown in Table 1 were subjected to chromate treatment, molybphosphate treatment and molybdate silicate treatment on the galvanized steel sheet. In order to evaluate the physical properties of each obtained film, the test was conducted in the following manner, and the results are shown in Table 1 below.

(Adhesive weight measurement)

The weight loss before and after the film was immersed in 1: 3 HCl hydrochloric acid solution for 1 minute was measured and the amount of film adhesion was measured from the value converted into unit area.

(Corrosion resistance measurement)

ASTM B-117 was used to measure the time required to produce 5% white rust.

(Resin adhesion)

Apply 1mm thick acrylic resin for the fingerprint to the coated specimen by the roll coating method, then expose 100 coating cuts to the zinc plated surface at 1mm intervals, and then use scotch tape. The peeling state of the coating film was measured. The peeling state of each coating film was evaluated relative to the 5-point method based on the following criteria.

5: Excellent (no peeling and cracking)

4: Good (part of crack and peeling observation: within 5%)

3: Normal (cracking and peeling observation: within 15%)

2: degradation (cracking and peeling observed: within 35%)

1: Deepening (Extreme Depth: 35%)

Solution (g / L) Amount of adhesion (mg / m ² ) Corrosion resistance (white rust occurrence time) Resin adhesion Processing temperature Comparative example One Chromate Treatment 45 45 5 2 Molybdenum 0.3 5 10 3 50 ℃ Phosphate 3.0 3 Molybdenum 0.3 5 8 3 Phosphate 14.0 4 Molybdenum 5.0 10 10 3 Phosphate 6.0 5 Molybdenum 5.0 15 15 3 Phosphate 14 6 Molybdenum 0.4 25 25 3 Phosphate 7.0 7 Molybdenum 0.4 28 25 3 Phosphate 14.0 8 Molybdenum 4.0 28 25 3 Phosphate 7.0 9 Molybdenum 4.0 30 25 3 Phosphate 14.0 Inventive Example One Molybdenum 4.0 30 25 4 Phosphate 14.0 Colloidal silica One 2 Molybdenum 4.0 40 50 5 Phosphate 14.0 Colloidal silica 10 3 Molybdenum 4.0 45 55 5 Phosphate 14.0 Colloidal silica 150 Comparative example 10 Molybdenum 4.0 45 55 4 Phosphate 14.0 Colloidal silica 160

In Table 1, the following conclusions can be obtained.

That is, in Comparative Example (1), which is the result of measuring the physical properties of the existing chromate-treated specimens on the galvanized steel sheet, it has relatively excellent physical properties with an adhesion amount of 45 mg / m ² , corrosion resistance of 45 hours, and resin adhesiveness 5. On the other hand, the measurement results of the physical properties of the molten phosphate solution immersed in 50 ℃ solution for 40 seconds while changing the concentration of molybdenum and phosphate groups using a galvanized steel sheet as a substrate described in Comparative Example (2) to Comparative Example (9) It was.

As shown in Comparative Example (2) and Comparative Example (3), when the molybdenum concentration was 0.3g / L and the concentration of phosphate group was changed to 3.0 and 14.0, the adhesion amount was 5mg / m ² , so that the molybdate film was not sufficiently formed. Corrosion resistance was also measured to be poor at 10 and 8 hours.

As shown in Comparative Example (4) and Comparative Example (5), when the concentration of phosphate group was changed to 6.0 g / L and 14.0 g / L at the concentration of molybdenum concentration of 5.0 g / L, the adhesion amount was 10, 15 mg / L. m ² , corrosion resistance was measured to 10, 15 hours.

As shown in Comparative Example (9) in Comparative Example (6), as a result of changing the molybdenum concentration to 0.4-4.0 g / L and the concentration of phosphate group to 7.0-14.0 g / L, the adhesion amount was 25-28 mg / m ² , Corrosion resistance improved to 25 hours. From these results, it can be seen that there exists an optimum concentration range of molybdenum and phosphate groups for forming the molybphosphate film. That is, when the galvanized steel plate is immersed in the molybdenum and phosphate solution, the molybdate film is formed. Preferably, the molybdenum film is prepared with 0.4 to 4.0 g / L and 7.0 to 14.0 g / L phosphate. Corrosion resistance of the films presented from Comparative Example (6) to Comparative Example (9) was improved, but the resin adhesiveness was measured to be 3, indicating that the resin adhesiveness was poor. It exists because it is not able to maintain adhesive force with acrylic resin which is organic by existence. In order to improve the adhesive force with the acrylic resin, generation of hydroxyl (-OH) is required at the resin and the film interface. The hydroxyl group formed on the film increases the van der Waals bonding force with the resin, thereby improving the resin adhesion.

Applying this principle, the experiment was performed to add colloidal silica to the molybphosphate solution. Colloidal silica can improve the resin adhesion and corrosion resistance by converting the conventional molybdate film (Mo-PO) to the film structure of the molybdate silicate (Mo-Si-OH) form a -Si-OH defect. Invention Example (1) describes the results of treatment in molybdenum concentration of 4.0 g / L phosphate group concentration of 14.0 g / L colloidal silica concentration of 1.0 g / L. Compared with Comparative Example (9), there is no change in adhesion amount and corrosion resistance, but it can be seen that resin adhesiveness is improved from 3 to 4. This is considered to be because the -Si-OH component formed in the film improved the adhesiveness with resin. In (2) and (3), the results of increasing the concentration of colloidal silica from 10 to 100 g / L are described. As the colloidal silica concentration was increased, adhesion amount and corrosion resistance were improved. This is because Si is a highly hydrophobic material, and it is considered that corrosion resistance is increased by shielding corrosion factors (H ₂ O, Cl ⁻ , O ₂ ) penetrating from the outside. In addition, the resin adhesiveness was also measured as 5, which is believed to improve the resin adhesiveness as the -Si-OH component is formed in the film. On the other hand, Comparative Example (10) was added to 160g / L of colloidal silica, the adhesion amount and corrosion resistance did not increase any more, it was shown that the resin adhesion decreases. From these results, it can be seen that when colloidal silica is added to the molybdate solution, a molybdate silicate film is formed to improve adhesion, corrosion resistance, and resin adhesion, and the concentration of colloidal silica is considered to be preferably 1-150 g / L.

Example 2

Using the same solution as Inventive Example (3) in Example 1 above, the treatment temperature was applied to a galvanized steel sheet by applying 30 ° C, 40 ° C, and 60 ° C.

In order to evaluate the physical properties of each obtained film, the test was carried out in the same manner as in Example 1, and the results are shown in Table 2 below.

Solution (g / L) Amount of adhesion (mg / m ² ) Corrosion resistance (white rust occurrence time) Resin adhesion Processing temperature Comparative example a Molybdenum 4.0 13 14 3 30 ℃ Phosphate 14.0 Colloidal silica 150 Inventive Example a Molybdenum 4.0 45 55 5 40 ℃ Phosphate 14.0 Colloidal silica 150 b Molybdenum 4.0 45 55 5 60 ℃ Phosphate 14.0 Colloidal silica 150

As can be seen in Table 2, in the comparative example (a) treated at 30 ℃ under a solution condition of molybdenum concentration 4,0g / L, phosphate concentration 14.0g / L, colloidal silica 150g / L It is judged that a morphosilicate film was not formed due to 13 mg / m ² and corrosion resistance 14 hours of resin adhesion. As a result, it can be seen that the temperature range for forming the morphosilicate film exists. As shown in Inventive Example (a) and Inventive Example (b), when the solution treatment temperature is 40 ° C. or higher, the morphophosphate film is formed, thereby providing corrosion resistance and resin. The adhesion was shown to be improved. However, when it exceeds 60 ℃ showed an excessive amount of adhesion.

As described above, the present invention forms a molten silicate film of Mo-P-Si-OH type by immersing the steel plate in a solution composed of molybdenum, phosphate groups, and colloidal silica to form a steel plate having excellent corrosion resistance and resin adhesion. It provides an effect that can be produced.

Claims (2)

Molybdenum film forming liquid, characterized in that the concentration of molybdenum is 0.4 ~ 4.0g / L, the concentration of phosphate groups is 7.0 ~ 14g / L, the concentration of colloidal silica is 1.0 ~ 150g / L After maintaining the solution of molybdenum concentration of 0.4 ~ 4.0g / L, phosphate concentration of 7.0 ~ 14g / L, colloidal silica concentration of 1.0 ~ 150g / l at 40 ~ 60 ℃, zinc in the solution A method of forming a molten silicate film by dipping a plated steel sheet to form a film.