KR100833073B1 - Zn-mg alloy coated steel sheet excellent in corrosion resistance and painttability, and its manufacturing method - Google Patents

Abstract

A Zn-Mg alloy coated steel sheet having excellent resin paint adhesion and corrosion resistance, and a manufacturing method thereof are provided to improve resin paint adhesion and corrosion resistance of a vacuum deposition-treated Zn-Mg alloy coating film by increasing cohesion of a Zn-Mg alloy costing film and a paint resin coating film. A Zn-Mg based alloy coated steel sheet having excellent resin paint adhesion and corrosion resistance comprises a steel sheet, a Zn-Mg based alloy coating layer formed on an upper portion of the steel sheet, and a molybdenum-silicate coating film formed on an upper portion of the Zn-Mg based alloy coating layer, the molybdenum-silicate coating film having a thickness of 0.05 to 0.5 mum. The molybdenum-silicate coating film comprises 60 to 65% of molybdenum and 40 to 35% of silicate. The Zn-Mg based alloy coating layer has a thickness of 0.5 to 10 mum. The Zn-Mg based alloy coating layer comprises 5 to 15 wt.% of Mg, and the balance of Zn and other inevitable impurities. A manufacturing method of a Zn-Mg based alloy coated steel sheet having excellent resin paint adhesion and corrosion resistance comprises treating a steel sheet having a Zn-Mg based alloy coating layer formed on an upper portion thereof in a molybdenum-silicate solution to form a molybdenum-silicate coating film on an upper portion of the alloy coating layer, the molybdenum-silicate coating film having a thickness of 0.05 to 0.5 mum.

Description

Zn-Mg ALLOY COATED STEEL SHEET EXCELLENT IN CORROSION RESISTANCE AND PAINTTABILITY, AND ITS MANUFACTURING METHOD}

1 is a schematic cross-sectional view of a Zn-Mg alloy plated steel sheet.

2 is a schematic diagram of a Zn-Mg alloy plated steel sheet on which a molybdenum-silicate film is formed.

International Publication WO05 / 106074

International Publication WO01 / 098413

European Patent 1272640

The present invention relates to a Zn-Mg alloy plated steel sheet and a method of manufacturing the same, and more particularly, to a Zn-Mg alloy in which a molybdenum-silicate film is formed on the upper portion thereof, thereby adhering to the resin coating film and further improving plate adhesion. It relates to a plated steel sheet and a method of manufacturing the same.

Zn-Mg-based alloy coated steel sheet exhibits excellent performance in corrosion resistance, weldability, etc., compared to other zinc-based alloy coated steel sheets. However, in the existing hot dip galvanizing method, the fume generated from Mg is a very harmful substance to the human body, which may cause air pollution and cause a problem of worker safety. On the other hand, when manufactured by a method of vapor deposition (evaporation heat, ion beam and sputtering) in a vacuum chamber, an excellent Zn-Mg-based film can be obtained, but it has a difficult point in securing the required adhesion during the coating process performed in a post process.

That is, in the Zn-Mg-based alloy film deposited on the steel sheet, pores of 100 to 500 nanometers are generated as shown in FIG. 1 due to the collision of clusters generated during the film growth of the adsorbed elements in the deposition manufacturing process. Adhesion is not good.

Therefore, it is a well-known technique to use the phosphate coating production technology to improve the adhesion between the alloy plated steel sheet and the coating film of which the resin is the main component. When applying the conventionally known phosphate film production technology to the Zn-Mg-based alloy film produced by vacuum deposition, the phosphate film formation has a non-uniform technical limitations due to the pores contained in the alloy film. Techniques for improving this problem include International Patent Publications WO05 / 106074, WO01 / 098413 and European Patent 1272640. In order to form a phosphate or chemical conversion film on the surface of magnesium, they are immersed in an acidic or alkaline solution that is strong in the previous process, and then the surface is modified and then immersed in a phosphate solution to form a phosphate film. However, contamination occurs during the post-processing by strong acid treatment. In addition, when applied to the surface of the Zn-Mg alloy coating film has a limitation that the adhesion between the coating film and the coating film is not greatly improved due to the difference in reactivity due to the galvanic electromotive force difference between Zn and Mg and the reaction unevenness caused by the pores.

The present invention is to solve the above problems, to increase the bonding strength of the Zn-Mg alloy film and the coating resin film to improve the resin coating adhesion and corrosion resistance of the Zn-Mg alloy film subjected to vacuum deposition.

Zn-Mg alloy plated steel sheet of the present invention for achieving the above object,

A steel plate and a Zn-Mg type alloy plating layer are formed in the upper part of this steel plate, and it has a molybdenum desilicate-silicate film in the upper part of this alloy plating layer.

In the present invention, the molybdenum-silicate film preferably has a thickness of 0.05-0.5 탆.

In the present invention, the Zn-Mg-based alloy plated steel sheet may be a Zn-Mg-based alloy, and according to an embodiment of the present invention, the content of Mg is 5 to 15% by weight, and Zn-Mg made of the remaining Zn and other unavoidable impurities Based alloy plating may be applied. As for the thickness of a Zn-Mg type alloy plating layer, 0.5-10 micrometers is preferable.

Method for producing a Zn-Mg-based alloy plated steel sheet according to the present invention,

The Zn-Mg-based alloy plated steel sheet is treated in a molybdenum-silicate solution to form a molybdenum-silicate film on top of the plated steel sheet.

According to one embodiment of the present invention, the molybdenum-silicate solution may be composed of Mo: 0.1 to 2.0 M, NaOH: 1 to 10 g / L, and colloidal silica: 1 to 20 g / L. The method of forming a film with the above-mentioned solution may be a method of immersing or spraying the solution.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The metal surface has a problem of inferior bonding strength with the resin coating film, and in the case of an alloy containing magnesium, the bonding strength with the resin is significantly inferior due to the production of magnesium oxide. In order to overcome these technical limitations, the present invention is characterized by introducing a silicate having excellent bonding strength between molybdenum and resin having excellent bonding strength with Zn-Mg alloy.

An alloy plated steel sheet to which the molybdenum ni-silicate coating is applied according to the present invention is a Zn-Mg-based alloy plated steel sheet. In the present invention, in order to solve the inferior adhesion force with the resin by Mg in the Zn-based alloy plated steel sheet, it is applicable if Mg is included in the Zn-based alloy plated layer. Of course, it is not particularly limited to the content of Mg in the Zn-Mg-based alloy plating layer, and does not exclude the inclusion of other components in addition to Mg. In addition, it is also applicable that another alloy layer is formed under the Zn-Mg-based alloy plating layer. In the description of the present invention, the base material of the Zn-Mg-based alloy broadly includes Zn and Mg, and the main concept is Zn and Mg in a narrow concept. While Zn-Mg is a main component, inevitable impurities may be included.

According to one embodiment of the present invention, the Zn-Mg-based alloy plating layer has a Mg content of 5 to 15% by weight, and the other Zn and other unavoidable impurities, but is not necessarily limited thereto. The Mg content in the Zn-Mg layer shows the best physical properties of the alloy plated layer when it contains 5 to 15% by weight. In the present invention, the Zn-Mg alloy film forming time is 0.5 to 10 mu m in thickness.

If the thickness of the Zn-Mg alloy plating layer is less than 0.5 µm, the effect of forming the alloy layer is not large. If the thickness of the Zn-Mg alloy plating layer is greater than 10 µm, the coating layer cracks due to the overcoat formation may be feared.

On the surface of the Zn-Mg-based alloy plated steel sheet, a molybdenum-silicate thin film is formed.

The molybdenum-silicate film fills pores in the Zn-Mg alloy plating layer and forms a molybdenum-silicate film to improve adhesion to the resin coating film and impart temporary rust resistance to significantly improve coating adhesion and corrosion resistance. Play a role. A schematic diagram of such a role is shown in FIG. 2.

When molybdenum and silicate are present in the Zn-Mg alloy plating layer, molybdenum is responsible for the bonding force with the Zn-Mg alloy plating layer and the silicate is responsible for the bonding force with the resin. Therefore, when molybdenum and silicate are simultaneously present in the molybdenum-silicate thin film, adhesion is secured.

According to one embodiment of the present invention, the molybdenum-silicate film preferably has a thickness of 0.05 to 0.50 μm. When the thickness of the molybdenum ni-silicate film is less than 0.05㎛ can not be expected to greatly increase the adhesion, if the thickness exceeds 0.5㎛ there is a fear that the film itself cracks.

According to one embodiment of the invention, the molybdenum-silicate coating layer may be composed of a composition of about 60-65% silicate about 40-35%. The coating composition is determined by the concentration condition of the treatment solution. The composition of the film is not necessarily limited to the above conditions, and the film composition is an optimum condition from which the best physical properties can be obtained.

According to the present invention will be described a method of manufacturing a Zn-Mg-based alloy plated steel sheet.

What is necessary is just to perform the method of forming a Zn-Mg alloy plating layer in a steel plate according to a conventional method, and it does not specifically limit in this invention. The conventional method will be described as follows. The Zn-Mg-based alloy plated steel sheet is generally preferably formed by a vacuum deposition method (thermal evaporation method, electron beam method, electromagnetic levitation method, ion plating or sputtering). When the Zn-Mg-based alloy plating is to be formed by vacuum deposition, Zn, Mg, and Zn-Mg alloy targets may be used as targets. The general vacuum evaporation method is a material to be coated by a vaporized target material after vaporizing the material (target) to be deposited in the vacuum chamber by various methods (resistance heating, electron beam, electromagnetic levitation, or plasma ion state). It means the method of forming an adsorption film in a (subject).

Thermal evaporation refers to a method of evaporating and depositing Zn, Mg, or Zn-Mg in a vacuum chamber by direct resistance heating or induction resistance heating. In the electron beam category, an electron beam emitted by an electron gun locally targets a target material. It refers to a method of melting and adsorbing on a subject after evaporation and vaporization. The electromagnetic flotation method refers to a method in which a target material supported by alternating current induction heating is evaporated and adsorbed onto a subject. The ion plating method is to coat a target material by activating the target material in a plasma ion state. The sputtering method refers to a method in which plasma ions physically evaporate a target material so that the accelerated target particles form a film after adsorption on the subject.

As described above, the formation of the molybdenum-silicate film on the Zn-Mg-based alloy plated steel sheet is performed as follows. A film is formed from a solution containing molybdenum and colloidal silica as a main component. The coating may be formed by providing a reaction time with the surface of the Zn-Mg-based alloy coating, and immersion or spraying is preferable. According to one embodiment of the present invention, the temperature of the steel sheet to be treated after the vacuum deposition process: immersed or sprayed in a treatment solution at 100 ~ 400 ℃ hot air drying to form a molybdenum Ni-silicate thin film.

The composition of the treatment solution for molybdenum-silicate coatings used in the present invention is preferably Mo: 0.1 to 2.0 M, NaOH: 1 to 10 g / L, colloidal silica: 1 to 20 g / L. If the concentration of Mo is less than 0.1 M, the desired film composition is impossible, and if it exceeds 2.0 M, the film is excessively produced, which is not preferable. NaOH is mainly added to ensure the solution stability by adjusting the pH in the solution, if less than 1g / L is difficult to secure solution stability, if more than 10g / L white precipitate in the solution is not preferable. Colloidal silica is not preferable because the silica component significantly improves the adhesion between the metal surface and the resin coating, and if it is less than 1g / L, it is difficult to achieve its purpose, and when the silica component exceeds 20g / L, the silicate components are observed.

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

The following examples are examples of the invention and the invention is not limited thereto.

Example 1

After the general cold rolled steel sheet was etched for 20 minutes at a substrate temperature of 250 ° C. by an RF sputtering method, a Zn-Mg alloy plating layer having a film thickness of Table 1 was formed. The Mg content in the Zn-Mg alloy plating layer was prepared while changing the Mg content of the heat evaporation source material.

The Zn-Mg-based galvanized steel sheet obtained above was immersed for 5 seconds in a solution composed of Mo 0.5M, NaOH 10g / L and colloidal silica 10g / L, followed by hot air drying to prepare a Zn-Mg-based alloy plated steel sheet. The resin coating adhesion and corrosion resistance of the prepared specimens were measured, and the results are shown in Table 1 below.

The thickness of the Zn-Mg alloy plating layer was notched in the coating layer, and the thickness of the Zn-Mg alloy plating layer was observed by observing the cross section of the coating layer with a high magnification scanning electron microscope, and the Mg content was dissolved in the 1: 1 hydrochloric acid solution. Was measured by analysis. The resin coating was sprayed with acrylic paint at high speed to adjust the coating thickness to 100 um.

The resin coating adhesiveness of the following Table 1 was evaluated by cross-cutting and then peeling off the scotch tape after cross cutting at 10 × 10 mm intervals. Corrosion resistance was measured for the time until the development of 5% white rust according to ASTM B-117.

division Zn-Mg based alloy plating layer Molybdenum-Silicate Resin adhesion Corrosion resistance (5% white rust occurrence time) Alloy Plating Composition Thickness (um) Processing (hours) Film thickness Example 1 Zn-Mg (Mg 5 wt%) 5 radish - Peeling 15 Example 2 Zn-Mg (Mg10wt%) 5 radish - Peeling 20 Example 3 Zn-Mg (Mg15wt%) 5 radish - Peeling 30 Inventive Example 4 Zn-Mg (Mg 5 wt%) 5 Processing (5 seconds) Less than 0.5um No peeling 40 Inventive Example 5 Zn-Mg (Mg10wt%) 5 Processing (5 seconds) Less than 0.5um No peeling 50 Inventive Example 6 Zn-Mg (Mg15wt%) 5 Processing (5 seconds) Less than 0.5um No peeling 55

As shown in Table 1, Example 3 in Conventional Example 1 measured the resin adhesion and platelet corrosion resistance of the Zn-Mg alloy layer according to the Mg content without molybdenum ni-silicate treatment. In this case, partial peeling occurred at the time of application of the resin coating film, and it was observed that platelet corrosion resistance slightly increased with increasing Mg content.

On the other hand, in the case of the invention examples (4 to 6) in accordance with the present invention, the molybdenum-silicate coating layer is formed on the surface of the Zn-Mg alloy plated steel sheet, it can be seen that the adhesion of the coating resin and the plate resistance significantly improved, Zn It can be seen that it is applied regardless of the Mg content of -Mg alloy plated steel sheet.

The molybdenum-silicate coating layer was measured by dissolving in 1: 1 hydrochloric acid solution and analyzing the solution by chemical analysis. As a result of chemical analysis, a film composed of about 60-65% silicate and about 40-35% silicate was obtained. The coating composition is determined by the concentration condition of the treatment solution.

According to the present invention, the adhesion and corrosion resistance of the coating resin are remarkably improved because the molybdenum ni-silicate coating not only improves adhesion between the resin and the metal interface but also fills pores of the Zn-Mg coating layer to improve corrosion resistance. I think that.

As described above, according to the present invention, a Zn-Mg alloy plated steel sheet excellent in resin coating adhesion and corrosion resistance can be provided.

Claims (8)

A steel plate and a Zn-Mg alloy plating layer are formed on the steel plate, The Zn-Mg-based Zn-Mg-based alloy plating layer has a molybdenum-silicate film on the upper portion, wherein the molybdenum-silicate film has a thickness of 0.05-0.5㎛, Zn-Mg-based excellent adhesion strength and corrosion resistance Alloy plated steel sheet. delete The Zn-Mg-based alloy plated steel sheet having excellent adhesion strength and corrosion resistance according to claim 1, wherein the molybdenum-silicate film is 60-65% silicate 40-35%.  The Zn-Mg-based alloy plated steel sheet having excellent resin adhesion and corrosion resistance according to claim 1, wherein the Zn-Mg-based alloy plated layer has a thickness of 0.5 to 10 µm. The Zn-Mg-based alloy plated steel sheet according to claim 1, wherein the Zn-Mg-based alloy plated layer has a Mg content of 5 to 15% by weight and has excellent resin adhesion and corrosion resistance, which is made of the remaining Zn and other unavoidable impurities. A steel sheet having a Zn-Mg-based alloy plating layer thereon was treated in a molybdenum-silicate solution to form a molybdenum-silicate film on the alloy plating layer, wherein the molybdenum-silicate film had a thickness. A method for producing a Zn-Mg alloy plated steel sheet excellent in resin adhesion and corrosion resistance, characterized in that 0.05-0.5㎛. The method of claim 6, wherein the molybdenum ni-silicate solution, Mo: 0.1 ~ 2.0M, NaOH: 1 ~ 10g / L, colloidal silica: 1 ~ 20g / L resin composition characterized in that the adhesive strength Method for producing Zn-Mg alloy plated steel sheet excellent in corrosion resistance and corrosion resistance. The method of claim 6, wherein the treatment is selected from immersion in the molybdenum-silicate solution or spraying molybdenum-silicate solution, the production of Zn-Mg alloy plated steel sheet having excellent adhesion and corrosion resistance Way.

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