KR910000979B1 - Chromated solution of galvanized steel sheet having superior resistance to corrosion and removing of fingerprint - Google Patents

Abstract

A solution having 0.05-0.5 mol/l concentration of chromic anhydride is prepared. Part of the solution is reduced. And the composition of this solution is modified to 0.1-0.5 of ratio of reduced chromic anhydride/ added chromic anhydride. Phosphic acid of 0.3-0.8 mol/l, poly ethylene glycol of 5-50g/l and sulfuric acid of 0.001-0.01 mol/l are added to the solution this chromate solution has superior resistance to corrosion and removing of fingerprint for the treating galvanized steel sheet.

Description

Chromate treatment solution of galvanized steel sheet with excellent anti-fingerprint and corrosion resistance

1 is a graph showing the surface roughness of the comparative example and the illustrative example.

The present invention relates to a chromate treatment solution for forming a chromate treatment solution which is excellent in anti-fingerprint and corrosion resistance, without the occurrence of surface stains, especially in the chromate treatment solution which is carried out as a post-treatment in the production of electro-galvanized steel sheet.

Conventionally, in the case of galvanized steel sheet, chromate treatment has been performed as a post-plating post-treatment to prevent the occurrence of white blue during storage or transportation to demand.

In recent years, the demand for electrogalvanized steel sheet has the drawback of easily attaching fingerprints or contaminants from surroundings by hand contact. The cause of fingerprinting is a problem related to the surface shape (surface roughness) of the plating layer caused by contaminants, such as sweat, adhered to the micro-grooves of the large ridges on the surface of the electroplated steel sheet. It is not removed by the usual chromate treatment. In particular, the attached fingerprints and contaminants are not removed by normal surface cleaning but cause surface damage and reduced corrosion resistance of the contaminant attachment site, which is a serious limitation in the use of unpainted state such as the inner plate of home appliances.

In order to prevent the occurrence of fingerprints, a method of increasing the adhesion amount of the chromate film and a method of applying organic and inorganic composite resins after chromate treatment were developed, and a solution consisting of chromic anhydride and silica sol was developed as a method of changing the chromate film composition. .

In the normal chromate treatment, the anti-fingerprint fragrance effect due to the increase in the adhesion amount of the chromate coating is shown in the amount of chromium deposition of 300-500 mg / m ² or more. There is a problem in the process that is difficult to be carried out in the continuous line, and there is a problem in that the value of the product is lowered due to coloration and staining caused by the deposition of a large amount of chromium. Japanese Patent Application Laid-Open No. 82-169092 relates to a chromate treatment solution in which a chromate treatment solution composed of chromic anhydride and a cationic silica sol is coated on a surface and then dried to form a coating. This method has some effects on corrosion resistance and paintability. However, it is not satisfactory to improve the anti-fingerprint effect of the galvanized steel sheet, especially in the case of adopting the method of removing the filtrate by the roll as a method of adjusting the adhesion amount during the chromate treatment, the surface of the roll is dried when the solution on the roll is dried. There is a problem such as poor workability due to contamination with silicates.

Recently, as a method for improving the rubbing resistance and corrosion resistance of galvanized steel sheet, a lot of methods for applying organic and inorganic composite resins after chromate treatment have been developed (Japanese Patent Laid-Open No. 83-177476, 83-153785). Is as follows.

Carboxyl-based polyethylene resin and colloidal silica (Colloidal Silicasol) were formed by forming a chromate film having a chromium adhesion amount of 10-60 mg / m ² by a conventional chromate solution composed of chromic acid and inorganic acid on the surface of the galvanized steel sheet. ) is applied to a solution to avoid the chromate film and dried to combine the method of attaching the degree of resin ^{0.3mg / m 2 -4mg / m 2} .

In this method, it is difficult to obtain a film of uniform thickness, and in a general electro galvanizing plant consisting of pre-treatment, painting, and post-treatment, an additional process of resin coating, baking, and cooling is required. There is a drawback that an increase problem occurs.

In order to solve the above problems, there is no need for additional organic / inorganic composite resin coating process, and only the normal chromate treatment which is dried after chromate treatment in an electroplating factory, without staining of the surface and damage of surface appearance, An object of the present invention is to provide a chromate treatment solution capable of producing an electrogalvanized steel sheet having a quality of corrosion resistance.

첨가하고 그중 일부를 크롬 3가 이온으로 환원시켜 환원된 무수크롬산/첨가된 무수크롬산의 비가 0.1-0.5로 되도록 조정하고 상기 값으로 조정된 용액에 0.3-0.8mol/

의 인산, 5-50g/

의 폴리에틸렌 글리콜 및 0.001-0.01mol/

의 황산이온을 첨가하여 조성된 전기아연도금강판의 크로메이트처리용액에 관한 것이다. 크로메이트처리방법은 크로메이트처리후 건조하는 통상적인 크로메이트처리방법으로 실시할 수 있다.The present invention is a chromic acid (chromic acid) 0.05-0.5mol /

And some of them were reduced to chromium trivalent ions to adjust the ratio of reduced chromic anhydride / added chromic anhydride to 0.1-0.5 and 0.3-0.8 mol /

Phosphoric Acid, 5-50g /

Polyethylene glycol and 0.001-0.01 mol /

The present invention relates to a chromate treatment solution of an electrogalvanized steel sheet prepared by adding sulfate ions. The chromate treatment method can be carried out by a conventional chromate treatment method which is dried after chromate treatment.

이하에서는 크로메이트피막이 형성되기에는 용액중 크롬농도가 너무 적어 크로메이트처리시간이 많이 소모되며 또한 형성된 피막의 내식성이 충분하지 못하고, 크롬농도가 0.5mol/

이상에서는 크롬에 의한 표면의 착색이 심하게 되며 또한 피액처리시 크롬 6가의 제거를 위한 경비가 많이든다. 첨가된 무수크롬산/환원된 무수크롬산의 비율이 0.1 이하에서는 형성된 크로메이트피막중 흡습성을 가진 크롬 6가의 비율이 많게되어 크로메이트피막의 건조에 시간이 많이 소요되며, 또한 부식장벽효과를 나타내는 크롬 3가의 비율이 적게되어 내식성이 열화되고, 또한 비율이 0.5 이상에서는 용액제조후 시간이 경과함에 따라 용액의 점도가 증가되는 용액의 경시변화가 심하게 되어 작업성면에서 문제로 된다. 인산이온의 첨가량에 따른 피막특성변화는 0.3mol/

이하에서는 크로메이트피막특성이 변화되어 내식성 및 내지문성의 향상이 거의없고, 또한 0.8mol/

이상에서는 표면에 검은 반점이 발생되는 등의 표면외관이 손상된다. 황산이온은 0.001mol/

이하에서는 크로메이트피막형성에 미치는 황산이온의 효과가 적어 피막형성이 완전하지 않아 내식성이 우수하지 못하여 또한 0.01mol/

이상에서는 황산이온에 의한 크롬 6가의 흡착이 많게되어 표면의 착색이 발생하게 되며 또한 과도한 황산이온이 흡착하게 되어 내식성이 감소되므로 크로메이트처리후 수세를 함으로써 황산이온을 제거해야 하는 문제점이 있다.The reason why the solution composition of the present invention has the above range is as follows. Chromium concentration of 0.05 mol /

In the following, the chromium concentration in the solution is too small to form a chromate coating, so that the chromate treatment time is consumed a lot, and the corrosion resistance of the formed coating is not sufficient, and the chromium concentration is 0.5 mol /

In the above, the surface of the chromium is severely colored, and a lot of expenses for the removal of chromium hexavalent when the liquid is treated. If the ratio of added chromic anhydride / reduced chromic anhydride is 0.1 or less, the ratio of chromium hexavalent having hygroscopicity is increased in the formed chromate film, which takes a long time to dry the chromate film, and also the ratio of chromium trivalent, which shows the corrosion barrier effect. In this case, the corrosion resistance is deteriorated and the ratio is 0.5 or more. As the time passes after the preparation of the solution, the change in the solution which increases the viscosity of the solution increases over time, which is a problem in terms of workability. Changes in film properties with the addition of phosphate ions were 0.3 mol /

In the following, the chromate coating properties are changed to show little improvement in corrosion resistance and fingerprint resistance, and 0.8 mol /

In the above, the surface appearance such as black spots on the surface is damaged. Sulfate ion is 0.001mol /

In the following, the effect of sulfate ion on the formation of chromate film is small, the film formation is not complete, so the corrosion resistance is not excellent, and 0.01 mol /

In the above, since the adsorption of chromium hexavalent by sulfate ions increases, coloring of the surface occurs, and excessive sulfate ions are adsorbed, thereby reducing corrosion resistance. Therefore, there is a problem of removing sulfate ions by washing with water after chromate treatment.

이하일 경우에는 수용성 고분자의 첨가효과가 감소되어 내지문성의 향상효과가 적으며, 50g/

이상 첨가할 경우에는 내지문성은 양호하나 형성된 크로메이트피막중 유기물의 비율이 증가하여 크롬화합물에 의한 내식성 향상효과가 감소하게 된다.Polyethylene glycol addition amount 5 g /

In the case of less than, the effect of adding the water-soluble polymer is reduced to lessen the anti-fingerprint effect, 50g /

When added above, the fingerprint resistance is good, but the ratio of organic matter in the formed chromate film is increased, thereby reducing the effect of improving the corrosion resistance by the chromium compound.

The effects of each chemical component of the solution of the present invention on the film formation reaction and the film properties are described as follows. When the plated steel plate is deposited on the chromate solution, a film forming reaction generated in a conventional chromate solution occurs, so that the zinc-dissolved chromium hexavalent ions are reduced to chromium trivalent ions, and the reduced chromium trivalent and chromium trivalent plating solutions are Chromate film formation reactions such as precipitation and chromium hexavalent adsorption occur in the form of a hydrate, and at this time, sulfate ions promote the adsorption of chromium hexavalent to form a dense coating.

When the specimen is removed from the solution and the remaining filtrate is removed from the surface, most of the solution on the surface is removed.However, the solution remains in the fine part of the surface, and by adding an appropriate amount of phosphate and polyethylene glycol in the organic matter. A uniform and excellent film is formed.

As a result of the film formation reaction, a chromate film having a composition similar to that of a normal chromate film is formed over the entire surface of the surface, and the organic and inorganic complex chromate film is formed in the large microbubble that is the fingerprint generation area, thereby reducing the microbubble area and The blocking effect between the plating layer and the surroundings prevents adhesion of fingerprints and contaminants, thereby improving fingerprint resistance and securing excellent corrosion resistance. Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

Table 1 shows the treatment conditions and the treatment solution of the present invention and comparative examples.

TABLE 1a

TABLE 1b

Comparative Example 1 of Table 1 was treated by the method of washing with water after the chromate treatment frequently used in the galvanizing plant, and Comparative Example 2 was applied to the organic and inorganic composite resin after the same chromate treatment as in Comparative Example 1. .

In Comparative Example 3-7 and Inventive Example 1-10, the solution remaining on the surface after chromate treatment was removed by squeezing and then chromated.

Chromate treatment solution composition of Comparative Example 1 consists of chromium ion, fluorine ion, hydrochloric acid ion, Comparative Example 3 is not added to the sulfate ion in the composition of the present invention.

정도로 적정농도범위이상 첨가한 것이다.In Comparative Example 4, polyethylene glycol was not added. In Comparative Example 5, the amount of polyethylene glycol added in the solution composition of the present invention was 60 g / g.

It is added above the concentration range.

로 본 적정범위이하로 첨가한 것이고 비교예 7은 1.0mol/

로 과도하게 첨가한 것이다. 발명예 1은 폴리에틸렌 글리콜 20g/

, 인산이온 0.5mol/

황산이온을 0.002mol/

첨가한 것이고 발명예 2는 폴리에틸렌 글리콜 40g/

인산이온 0.5mol/

황산이온을 0.002mol/

첨가한 경우이다.In Comparative Example 6, the amount of phosphate ion added was 0.2 mol /

It was added below the appropriate range, and Comparative Example 7 is 1.0 mol /

It is excessively added. Inventive Example 1 is 20 g / of polyethylene glycol

Phosphate Ion 0.5mol /

0.002mol /

Inventive Example 2 is a polyethylene glycol 40 g /

Phosphate Ion 0.5mol /

0.002mol /

In the case of addition.

The comparative fingerprints and the inventive examples treated with the above solutions and conditions are shown in Table 2 below, and the fingerprints were measured before and after the thin coating of white and serine on the specimen surface. It is measured by the surface color difference meter and is shown by the difference of the surface color difference (E) value in Lab system of ASTM D 2244, and corrosion resistance is shown by measuring the time until the occurrence of white rust in accordance with JIS Z 2371.

TABLE 2

As shown in Table 2, Comparative Example 1 showed extremely poor fingerprinting and corrosion resistance, and Comparative Example 2 (coating with organic and inorganic complex water in Comparative Example 1) showed excellent fingerprinting and corrosion resistance. As can be seen from Figure 1, a complicated treatment process is required, and in Comparative Example 3 without adding sulfuric acid, the fingerprint resistance was relatively good, but the corrosion resistance was not satisfactory, and the water-soluble polymer of Comparative Example 4 was not added. In this case, it can be seen that both fingerprint and corrosion resistance are not satisfactory.

정도로 다량 첨가한 경우에는 내지문성은 우수하였으나 내식성이 열화되었다. 비교예 6의 인산이온을 적정농도범위이하로 첨가한 경우에는 내지문성의 향상이 거의 없었으며, 인산이온을 1.0mol/

로 과량첨가한 경우(비교예 7)는 표면에 검은 반점이 발생되는 등의 표면외관이 열화되었다.In addition, 60 g / of polyethylene glycol of Comparative Example 5

When the amount was added in a large amount, the fingerprint resistance was excellent but the corrosion resistance was deteriorated. When the phosphate ions of Comparative Example 6 were added below the optimum concentration range, there was little improvement in fingerprint resistance, and 1.0 mol /

In the case of over-addition (Comparative Example 7), the surface appearance such as black spots on the surface was deteriorated.

On the other hand, Example (1-10) of the present invention shows excellent anti-fingerprint properties and excellent corrosion resistance, in particular, Inventive Examples 1-2 and 4-7, the time required until the generation of excellent fingerprint and white rust not observed fingerprints more than 200 hours Showed very good corrosion resistance.

On the other hand, the surface roughness of Comparative Examples 1, 2, 4 and Example 2 of the present invention was measured and shown in FIG. 1 by enlarging the horizontal axis to 5000 times and the vertical axis to 100 times. As shown in FIG. 1, in Comparative Examples 1 and 4 having poor anti-fingerprint, the fine stains that cause fingerprint generation are hardly removed by chromate treatment, but Example 2 of the present invention is applied to organic or inorganic resin after chromate treatment. Similar to the case of Comparative Example 2, which was subjected to the additional step of, it can be seen that the fine chaff is almost removed, thereby improving the rubbing resistance.

As described above, the chromate film produced using the solution of the present invention reduces the convex portion, which is the fingerprint generation portion, and prevents adhesion of fingerprints and contaminants by blocking the plating layer from the atmosphere, thereby preventing the adhesion of fingerprints and contaminants. Since the steel sheet can be produced, there is an excellent effect of simplifying the process and reducing the manufacturing cost.

Claims (1)

In chromate treatment solution of electrogalvanized steel sheet, 0.05-0.5 mol /

Chromic anhydride was added and some of them were reduced to 0.3-0.8 mol / to a solution adjusted to reduce the ratio of reduced chromic anhydride / added chromic anhydride to 0.1-0.5.

Phosphoric Acid, 5-50g /

Polyethylene glycol and 0.001-0.01 mol /

A chromate treatment solution for an electrogalvanized steel sheet excellent in anti-fingerprint and corrosion resistance, characterized by adding sulfuric acid.

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