KR100398171B1 - Method for manufacturing zinc electroplating steel sheet and a chemical abradant solution for zinc electroplating steel sheet - Google Patents

Abstract

The present invention relates to a method of manufacturing a galvanized steel sheet having high gloss and bright color on the surface of the steel sheet by chemical polishing the plated steel sheet, and to a chemical polishing solution for chemical polishing the galvanized steel sheet. It consists of a plating step of plating and a chemical polishing step of chemically polishing the plated steel plate, and the chemical polishing step is carried out with abrasive acid having a concentration of 0.5 to 20 g / l and hydrogen peroxide with a concentration of 0.5 to 20 g / l. Since the plated steel sheet is chemically polished for 0.1 seconds to 5 seconds in the chemical polishing solution, the galvanized steel sheet having high surface gloss and bright color can be stably manufactured.

Description

Method for manufacturing zinc electroplating steel sheet and a chemical abradant solution for zinc electroplating steel sheet

The present invention relates to a method for producing electro-galvanized steel sheet having a high gloss and bright color on a plated steel sheet by chemical polishing, and a chemical polishing solution for chemical-polishing the electro-galvanized steel sheet.

In general, galvanized steel sheet has excellent corrosion resistance compared to the general steel sheet is widely used in automobile bodies, home appliances and building materials.

In particular, in the galvanized steel sheet used in home appliances, the home appliance should include a function as an ornament in addition to its own function, so that the surface gloss and color of the home appliance are managed as important quality indicators.

In general, the color of the painted home appliance mainly depends on the color of the paint, but in the case of gloss, the basic gloss of the material steel sheet affects the gloss of the steel sheet after coating, so the higher the basic gloss of the material steel sheet High gloss home appliances can be obtained even after painting.

In particular, in recent years in the home appliance industry, in order to reduce the cost of the product, the steel sheet used for the inner plate of the home appliance is often used in an unpainted state. As such, when the inner plate of the home appliance is used as a non-painted steel sheet, the home appliance industry requires a high base gloss and color because the gloss and color of the steel sheet itself determine the gloss and color of the final product.

On the other hand, galvanized steel sheet is used as it is because the steel plate used for the outer plate of home appliances is coated, but the steel plate used for the inner plate is used as an unpainted state, so that the surface of the galvanized steel plate does not have fingerprints. And phosphate treatment.

At this time, the anti-fingerprint steel sheet is a steel plate coated with a transparent resin of about 0.5 ~ 1.5g / m ² of adhesion amount on the galvanized steel sheet surface, even if the operator touches the steel plate by hand, the surface of the steel sheet does not get fingerprints. Phosphate-treated steel sheet is a steel sheet in which a zinc phosphate coating film having an adhesion amount of 1 to 2 g / m ² is formed on a galvanized steel sheet, and fingerprints are not applied even if an operator touches the steel sheet by hand.

Since the gloss and color of the steel plate subjected to the rubbing or phosphate treatment on the surface of the galvanized steel sheet are greatly influenced by the basic gloss and color of the galvanized steel sheet, the galvanized steel sheet is used to increase the gloss and brighten the color of these steel sheets. You should increase the base gloss of the light and brighten the base color.

As a method of improving the basic gloss of a galvanized steel sheet, it is disclosed in Unexamined-Japanese-Patent No. 58-199889, which is incorporated by reference in this specification. According to the above reference, a method of plating by adding an organic gloss material to a plating solution when performing electro zinc plating is disclosed. That is, according to this method, by adding the polish to the plating solution, the polish can reduce the roughness of the plating layer, and thus the surface gloss can be secured by reducing the rate at which the irradiated light is scattered.

However, when the polish is added to the plating solution, not only the plating efficiency decreases and the surface color changes, but also the stress of the plating layer increases when the additive is vacant in the plating layer, causing cracking of the plating layer when forming the coated steel sheet. Serious problems are caused.

In addition, referring to the contents disclosed in Japanese Patent Application Laid-open No. Hei 4-9495, before galvanizing, the iron plate is electropolished with a high current of 7000 c / dm ² or higher in current carrying amount (current x time) and plated in a sulfuric acid plating bath. A method is disclosed. According to this method, gloss can be enhanced by electrolytic polishing of the surface of the iron plate to reduce the unevenness of the iron plate surface, and also to reduce the roughness of the plating layer by galvanizing the surface.

In this method, however, when the thickness of the galvanized layer is thin, the roughness of the plated layer is high due to the influence of the roughness of the base steel sheet, but the gloss is high when the thickness of the galvanized layer is increased. Since it is irrelevant to the present invention, there is no gloss enhancing effect, and the cost of power consumption increases due to a large amount of current.

The present invention has been made in order to solve the conventional problems as described above, and after manufacturing a conventional galvanized steel sheet without the addition of a brightening agent in the plating bath, the surface of the galvanized steel sheet chemical in solution consisting of acid and hydrogen peroxide solution By polishing, the purpose of the present invention is to provide a method of manufacturing an electro-zinc plated steel sheet which can reduce the surface roughness to increase the surface gloss of the galvanized steel sheet and brighten the color.

Another object of the present invention is to provide a chemical polishing solution for chemical polishing the plated steel sheet so that the surface gloss of the galvanized steel sheet increases and the color becomes bright.

In order to achieve the above object, the galvanized steel sheet manufacturing method according to an embodiment of the present invention is a plating step of electro-galvanizing steel sheet in a conventional manner, and a chemical polishing step of chemical polishing the plated steel sheet In the chemical polishing step, the plated steel sheet is chemically polished for 0.1 to 5 seconds in a chemical polishing solution composed of a polishing acid having a concentration of 0.5 to 20 g / l and a hydrogen peroxide solution having a concentration of 0.5 to 20 g / l. It is characterized by being carried out by.

According to another embodiment of the present invention, the chemical polishing solution for electro-galvanized steel sheet is composed of abrasive acid and hydrogen peroxide mixed with at least one acid selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrofluoric acid, boric acid, acetic acid, and the like. The concentration of malic acid and the concentration of hydrogen peroxide are characterized in that 0.5 to 20 g / l, respectively.

Hereinafter, preferred embodiments of the present invention will be described.

According to an embodiment of the present invention, the galvanized steel sheet manufacturing method is one or more acids selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrofluoric acid, boric acid, acetic acid after electroplating the steel sheet in a conventional manner By uniformly polishing the surface of the galvanized layer by immersing the galvanized steel sheet for 0.1 to 5 seconds in a chemical polishing solution composed of a polishing acid having a concentration of 0.5 to 20 g / l and a hydrogen peroxide solution having a concentration of 0.5 to 20 g / l, Galvanized steel sheet with high surface gloss and bright color can be manufactured stably.

Hereinafter, the reason for limiting the structure and method of the chemical polishing solution in the present invention as described above will be described in detail.

That is, according to the present invention, the chemical polishing solution is basically composed of a polishing acid of 0.5 to 20g / l and hydrogen peroxide solution of 0.5 to 20g / l. At this time, the abrasive acid is used by mixing one or two or more acids selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrofluoric acid, boric acid, acetic acid, but basically any acid that shows an acid.

However, the acid listed above does not have a uniform polishing effect of the surface of the plated steel sheet, and only works with hydrogen peroxide solution at all times.

Likewise, even if hydrogen peroxide is added without adding acid, there is no polishing effect, and therefore, acid and hydrogen peroxide must be added together to have a chemical polishing effect.

The reason why the lower limit of acid concentration in the chemical polishing solution composed of acid and hydrogen peroxide solution is 0.5g / l is less than that because of acid polishing effect, but it takes a long time for polishing, so chemical It is not economical to keep the length of the polishing tank relatively long.

The reason why the upper limit of the acid concentration is limited to 20 g / l is as follows. As the acid concentration increases, the polishing effect per unit time increases. Therefore, when the acid concentration is too high, the gloss of the plated steel is high and the color is bright, but the amount of zinc to be polished increases, so that the amount of zinc plating of the final product is decreased, and the aging degree of the chemical polishing solution is also increased. The disadvantage is that the exchange cycle is faster.

Therefore, the acid concentration in the chemical polishing solution is preferably limited to 0.5 to 20 g / l.

The lower limit of the hydrogen peroxide concentration in the chemical polishing solution consisting of acid and hydrogen peroxide solution was limited to 0.5 g / l for the following reasons.

The role of hydrogen peroxide in the chemical polishing solution gives a uniform polishing effect. Therefore, when the concentration of hydrogen peroxide water is low, the plating layer is dissolved by acid, but there is no polishing effect that does not reduce surface roughness, thereby reducing surface roughness.

On the other hand, the upper limit of the hydrogen peroxide concentration is limited to 20g / l, the higher the concentration of hydrogen peroxide, the better the surface polishing effect, when the hydrogen peroxide concentration of 20g / l maximizes the effect of increasing the gloss and white Therefore, it is preferable to limit the amount to 20 g / l in consideration of economic reasons.

The reason why the polishing time was limited to 0.1 to 5 seconds when chemically polishing the surface of the galvanized steel sheet in the chemical polishing solution proposed in the present invention is as follows.

If the polishing time is 0.1 seconds or less, it is not sufficiently polished under the concentration condition of the chemical polishing solution defined in the present invention. Therefore, the effect of improving gloss and color is weak, and if the polishing time exceeds 5 seconds, the equipment is continuously plated at high speed. In this case, it is not economical because the length of the chemical polishing bath has to be long.

In the present invention, the method for producing the galvanized steel sheet before the chemical polishing treatment is not particularly limited, and any galvanized steel sheet may be used.

In other words, the pretreatment form and method or plating bath system and components may be performed by any method.

In the chemical polishing solution proposed in the present invention, a third element, for example, an organic material and / or an inorganic material, may be added to control the chemical polishing rate or to control the dissolution rate.

In addition, the steel plate subjected to the chemical polishing treatment according to the present invention may be treated with one or a mixture of post-treatment such as phosphate treatment, chromate treatment, anti-fingerprint treatment, anti-rust oil coating treatment, etc. Since the improvement effect appears, there is no restriction | limiting in particular about the post-treatment type.

In the chemical polishing process, the higher the temperature of the polishing solution, the faster the polishing. However, the temperature is not particularly limited in the concentration and time ranges defined in the present invention, since sufficient polishing effect is obtained even at room temperature. It is preferable to carry out at convenient normal temperature.

In addition, in the method of contacting the surface of the galvanized steel sheet with the polishing solution and the steel sheet during chemical polishing, either an immersion method in which the steel sheet is immersed in the solution or a spray type in which the solution is sprayed on the steel sheet is not necessary.

The present invention will be described in more detail with reference to the following Examples.

<Example 1>

After degreasing and pickling the iron plate by a conventional method for producing an electroplated steel sheet, a galvanized steel sheet was manufactured at an adhesion amount of 20 g / m ² .

At this time, a plating bath was used as a sulfuric acid bath, the current density was 60A / dm 2. The electroplated steel sheet was prepared by chemical polishing solution under the conditions shown in Table 1 below, and then subjected to chemical polishing by dipping. The gloss and whiteness of the surface of the galvanized steel sheet were measured, and the amount of plating layer dissolved was measured. It is written in Table 1 below.

The chemical polishing solution was prepared based on 98% H ₂ SO ₄ , 60% HNO ₃ , 36% HCl, 99.9% H ₃ PO ₄ , 99.8% H ₃ BO ₃ , 99.8% HF, 99.5% CH ₃ COOH. And temperature were made into normal temperature (18 degreeC).

As shown in Table 1, according to the present invention (1 to 12) according to the present invention, one or two or more acids selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrofluoric acid, boric acid, acetic acid are mixed and When immersing a galvanized steel sheet for 0.1 to 5 seconds in a chemical polishing solution composed of abrasive acid having a concentration of 0.5 to 20 g / l and hydrogen peroxide solution having a concentration of 0.5 to 20 g / l, the gloss of the coated steel sheet was 44.4 or more and the whiteness was It was excellent above 88.1. At this time, the amount of the plating layer dissolved by the chemical polishing treatment was relatively small at 0.72 g / m ² or less.

However, in the case of the comparative example (1) which did not perform chemical polishing to a plated steel sheet, it can be seen that the plated steel sheet is relatively inferior in glossiness of 24.3 and whiteness of 86.5.

Meanwhile, the concentration of hydrogen peroxide in the chemical polishing solution is within 0.5 to 20 g / l, which is the range defined in the present invention, but chemical polishing is performed with a solution containing less than 0.5 to 20 g / l, which is the acid concentration. In Comparative Examples (2 to 4), it can be seen that the effect of improving glossiness and whiteness is weak.

In the case of Comparative Examples (5 and 7), the concentration of hydrogen peroxide solution is within 0.5 to 20 g / l, which is the range defined in the present invention, but the acid concentration exceeds 0.5 to 20 g / l, which is the range defined in the present invention. As a result of performing chemical polishing, the gloss and whiteness improvement effects were excellent, but the amount of the coating layer dissolved was relatively increased from 1.44 to 1.97 g / m ² .

In the case of Comparative Example (6), when the chemical polishing treatment was carried out with a solution in which the concentrations of acid and hydrogen peroxide water exceeded 0.5 to 20 g / l, which is the range defined in the present invention, glossiness and whiteness improvement effect were excellent. It can be seen that the plating layer dissolution was relatively increased to 1.68 g / m ² .

In the case of Comparative Example (8), the concentration of acid and hydrogen peroxide solution satisfies 0.5 to 20 g / l, which is the range defined in the present invention, but the chemical polishing time is 10 seconds and exceeds 0.1 to 5 seconds, which is the range defined in the present invention. In one case, the glossiness and whiteness improvement effect is excellent, but it can be seen that the dissolution amount of the plating layer was relatively increased to 3.06 g / m ² .

Turn Chemical polishing treatment Chemical polishing solution composition Processing time (seconds) Plating layer dissolution rate (g / m ² ) Glossiness Whiteness Acid concentration (g / l) Hydrogen peroxide concentration (g / l) Invention One U Hydrochloric acid0.5 One One 0.05 46 88.1 2 U Sulfuric acid 1 0.5 One 0.07 49.4 88.2 3 U Nitric acid 3 5 One 0.31 56.7 88.5 4 U Phosphoric Acid 5 10 5 0.25 54.3 88.2 5 U Boric Acid 10 20 2 0.33 59.4 88.2 6 U Foshan 0.5 0.5 0.5 0.15 49.2 88.3 7 U Acetic Acid 15 3 2 0.45 56.8 88.6 8 U Sulfuric acid 20 3 One 0.88 70.5 89.1 9 U Sulfuric acid 2 + nitric acid 3 5 2 0.46 64.3 88.7 10 U Sulfuric acid 3 + acetic acid 10 5 One 0.42 66.3 88.8 11 U Nitrate 5 + Phosphate 10 5 One 0.41 72.3 89.1 12 U Sulfuric acid 10 + boric acid 10 3 0.1 0.11 44.4 89.6 13 U Sulfuric acid 3 + nitric acid 3 + phosphoric acid 3 3 One 0.65 77.2 89.7 Comparative example One radish - - - - 24.3 86.5 2 U Hydrochloric acid 0.2 3 One 0.01 28.2 86.8 3 U Nitrate 0.3 5 3 0.03 29.7 86.7 4 U Sulfuric acid 0.1 + nitric acid 0.1 10 One 0.05 32.1 86.8 5 U Nitric Acid 25 5 2 1.44 74.3 89.7 6 U Nitrate 10 + Sulfuric Acid 15 25 One 1.68 77.8 89.9 7 U Sulfuric acid 10 + boric acid 20 5 3 1.97 79.9 90.1 8 U Sulfuric acid 10 10 10 3.06 84.3 90.2

<Example 2>

After the galvanized steel sheet was prepared under the same conditions as in Example 1, chemical polishing was performed for 3 seconds in a chemical polishing solution containing 5 g / l sulfuric acid, 5 g / l nitric acid, and 5 g / l hydrogen peroxide solution. After the post-treatment such as chromate treatment, fingerprinting, fingerprinting, fingerprinting and phosphate treatment, the gloss and whiteness of the steel sheet were measured, and the results are shown in Table 2.

Turn Chemical polishing treatment Post Processing Type Glossiness Whiteness Invention One U Phosphate Treatment 25.2 81.4 2 U Chromate treatment 65.7 87.7 3 U Fingerprint 45.6 84.9 4 U Chromate + Fingerprint Treatment 39.1 82.1 5 U Phosphating + Fingerprinting 22.1 78.4 Comparative example One radish Phosphate Treatment 7.4 68.5 2 radish Chromate treatment 16.8 75.2 3 radish Fingerprint 10.1 72.6 4 radish Chromate + Fingerprint Treatment 9.2 70.0 5 radish Phosphating + Fingerprinting 5.2 66.7

Zinc phosphate was used as the phosphate treatment solution, and the phosphate adhesion amount was 2 g / m ² . The chromate adhesion amount was 20 mg / m ² . In addition, the chromate + anti-fingerprint was coated with an acrylic resin of 1 g / m ² after the chromate treatment was carried out with an adhesion amount of 20 mg / m ² thereon.

As shown in Table 2, according to the present invention, a phosphate treatment was performed after chemical polishing for 3 seconds in a chemical polishing solution in which 5 g / l sulfuric acid, 5 g / l nitric acid, and 5 g / l hydrogen peroxide were mixed according to the present invention. In the case of 1), the glossiness of 25.2 and whiteness of 81.4 are excellent.

On the other hand, in Comparative Example (1) subjected to phosphate treatment without chemical polishing treatment, it can be seen that the glossiness of the steel sheet was inferior to 7.4 and the whiteness was 68.5.

In the present invention Example (2) subjected to chromate treatment as a post treatment after chemical polishing, the gloss of the steel sheet after chromate treatment was excellent at 65.7 and whiteness at 87.7.

On the other hand, in Comparative Example (2) subjected to chromate treatment without chemical polishing treatment, the glossiness of the steel sheet was inferior to 16.8 and whiteness to 75.2.

In the case of the present invention (3) subjected to the after-treatment as a post-treatment after the chemical polishing, it can be seen that the glossiness of the steel sheet after the to-finish treatment was excellent at 45.6 and 84.9.

In Comparative Example (3), in which the anti-fingerprint treatment was performed without chemical polishing treatment, the glossiness of the steel sheet was 10.1 and the whiteness was inferior to 72.6.

In the present invention Example (4) subjected to chromate + fingerprinting as a post-treatment after chemical polishing, it can be seen that the glossiness of the steel sheet after the treatment was excellent at 39.1 and whiteness at 82.1.

In Comparative Example (4), which was subjected to chromate + anti-fingerprint treatment without chemical polishing treatment, the glossiness of the steel sheet was 9.2 and the whiteness was inferior to 70.

In the present invention Example (5) subjected to phosphate + anti-fingerprint as a post-treatment after chemical polishing, the glossiness of the steel sheet after the treatment was excellent at 22.1 and whiteness of 78.4.

In Comparative Example (5), in which phosphate + anti-fingerprint treatment was not performed without chemical polishing treatment, the glossiness of the steel sheet was inferior to 5.2 and whiteness to 66.7.

As described above, when the galvanized steel sheet is manufactured under ordinary conditions, and the surface of the steel sheet is chemically polished in a chemical polishing solution composed of an acid and hydrogen peroxide solution, the surface of the galvanized steel sheet is finely polished to give a high gloss and bright color. Steel plate can be manufactured, and the surface of galvanized steel sheet is chemically polished, and after phosphate treatment, chromate treatment, anti-fingerprint, phosphate + anti-fingerprint, chromate + anti-finger treatment, high gloss and high whiteness Each steel sheet can be produced.

Claims (8)

A plating step of galvanizing the steel sheet, The chemical polishing step of chemically polishing the plated steel sheet, The chemical polishing step is performed by chemical polishing the plated steel sheet for 0.1 seconds to 5 seconds in a chemical polishing solution composed of a polishing acid having a concentration of 0.5 to 20 g / l and a hydrogen peroxide solution having a concentration of 0.5 to 20 g / l. Electro galvanized steel sheet manufacturing method characterized in that. The method of claim 1, wherein the abrasive acid of the chemical polishing solution is mixed with at least one acid selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrofluoric acid, boric acid, acetic acid, and the like. The method of claim 1, wherein the chemical polishing step is performed by immersing the plated steel sheet in the chemical polishing solution or by spraying the chemical polishing solution on the plated steel sheet electrolytic zinc plated steel sheet production Way. The method of claim 1, further comprising a post-treatment step of phosphating, chromate or rubbing the chemically polished steel sheet. The method of claim 4, wherein the phosphate adhesion amount of the steel sheet by the phosphate treatment during the post-treatment step is 0.5 ~ 2.5 g / m ² method of manufacturing an electro-galvanized steel sheet. 5. The method of claim 4, wherein the amount of chromium deposited on the steel sheet by the chromate treatment during the post-treatment is 5 to 20 mg / m ² . 5. The method of claim 4, wherein the resin adhesion amount of the steel sheet by the fingerprinting during the post-treatment step is 0.2 to 2 g / m ² . In the chemical polishing solution for chemical polishing the galvanized steel sheet, At least one acid selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrofluoric acid, boric acid, acetic acid, etc. is composed of a mixed acid and hydrogen peroxide, The concentration of the abrasive acid and the concentration of the hydrogen peroxide solution is characterized in that 0.5 to 20 g / l, respectively.