KR100229210B1 - Zinc electroplating of steel sheet by phosphoric salt treatment - Google Patents

Abstract

The present invention provides a zinc-nickel-based (two-way) used in the conventional phosphate treatment of electro-galvanized steel sheet, so that the manganese is included in the production of electro-galvanized plate to improve the outer space, corrosion resistance and paintability of the core plate In the present invention, a ternary zinc-nickel-manganese phosphate treatment solution is used for a phosphate-treated steel sheet and a method for manufacturing the same. A phosphate treatment solution having a content composition ratio of each ion of 1000-3000 ppm zinc, 50-300 ppm nickel and 300-2000 ppm manganese is used. Characterized in that the concentration of the phosphate treatment solution is in the range of 1.5-5.0%, the phosphate treatment solution temperature is in the range of 40-70 ° C., and the coating secondary content is in the range of 0.5-3.0 g / m 2. The present invention relates to a phosphate-treated electrogalvanized steel sheet excellent in corrosion resistance and paintability, and a method of manufacturing the same.

Description

Method of manufacturing phosphate treated galvanized steel sheet

The present invention is a phosphate treatment galvanized steel sheet which improves the appearance, corrosion resistance and paintability of the steel sheet by including manganese in the phosphate treatment solution in the phosphate treatment technology including zinc-nickel-based (binary) in the electro-galvanized steel sheet It relates to a manufacturing method of.

Zinc is widely used to prevent corrosion of iron due to its versatility and economy, and is widely classified into a hot dip plating method and an electroplating method on the top plate.

In the hot-dip plating method, various coating weights are applied according to the usage of plated steel sheet. In case of 45g / m² (one side) with small coating weight, it is impossible to manufacture due to the characteristics of equipment. have.

On the other hand, the electroplating method has an advantage that the plating deposition amount is 45 g / m 2 or less by controlling each plating cell and ensures uniform adhesion and productivity. Therefore, as an example of various post-treatment techniques, phosphate treatment, chromic acid treatment, organic coating treatment, lubrication treatment, and the like are widely applied, and the coating applied most in the application of this post-treatment technique is a phosphate-treated coating. Phosphate treatment film acts to improve the appearance and corrosion characteristics of the plated steel sheet by the effect of blocking the contact with the outside by forming a strong passivation film by the phosphate on the surface of the plated steel sheet.

Conventional phosphate treatment solutions, iron phosphate, manganese phosphate, and calcium phosphate are commercially available as phosphate treatment solutions, especially for pre-treatment of automotive steel sheet, manganese phosphate-based phosphate for improvement of corrosion resistance and electrodeposition coating properties. To process, or iron-manganese alloy electroplating steel sheet or zinc-iron alloy electroplating steel sheet is used a lot.

In general, phosphate treatment solution used in electro-galvanized steel sheet is mainly composed of phosphate-zinc type, which is characterized by alkali treatment by spraying the so-called binary phosphate treatment to make crystals fine by adding a small amount of nickel. And corrosion resistance is improved.

In the case of the above-described binary phosphate-based zinc-nickel, the sludge of zinc and nickel increases during continuous operation, and thus the adjustment is not easy. Therefore, the whiteness of the plate surface of the phosphate-treated steel sheet is reduced and the film is stained. Frequently problems arise. In general, the crystal structure of the phosphate treated film formed on the galvanized steel sheet has a phosphite (Zn ₃ (Po ₄ ) ₂ 4H ₂ O) form and phosphopyrite (Zn ₂ Fe (Po ₄ ) ₂ 4H ₂ O). In general, the above-described conventional phosphate treatment method is composed of a hofite tissue, and the constituent shape of the coating is formed of needle-like and lobe-shaped tissues. However, most of them consist of a needle-like structure and the grain size is coarse to 6 microns or more, so that pinholes are generated by the generation of hydrogen gas (GAS) during spray coating, resulting in deterioration of product quality or phosphate coating during molding. Due to the powdering phenomenon, the workability is lowered and the workability is poor.

Therefore, in order to refine the crystal of the phosphate film, the titanium salt-based surface modifier was treated on the electrogalvanized steel sheet 1 before the phosphate treatment to form the surface modifier treatment layer 2 as shown in FIG. In this case, however, there is also a problem in attempting to refine the crystal by increasing the concentration of the surface regulator and the treatment temperature. The reason is that increasing the concentration and the treatment temperature of the surface regulator decreases the stability of the solution due to the increase of the solid content. Disadvantages occur, and due to excessive refinement of the crystals, the coating amount of the phosphate-treated coating layer 3 including zinc-nickel, which is binary, is attached to 1 micron or less, which significantly reduces corrosion resistance. Therefore, in order to compensate for the degradation of corrosion resistance due to the pinhole of the phosphate coating, it has been conventionally solved by the passivation coating by chromic acid treatment.

The present invention was created in view of the above-mentioned point to improve productivity and to improve the coating properties, and to allow the nickel and manganese to be evenly dispersed in the coating layer, thereby improving the appearance and corrosion resistance compared to the conventional galvanized phosphated steel sheet. In the present invention, the phosphate-treated steel sheet with improved coating properties, enhanced long-term storage properties, enhanced film adhesion, and excellent paintability have been greatly contributed to quality stabilization of building materials and home appliances. The nickel phosphate solution is prepared so that the manganese content is in the range of 300 to 200 ppm, and then prepared to be adjusted so that the concentration of the mixed phosphate solution is in the range of 1.5 to 5.0%. Spray on a grater; At this time, the solution temperature of the spray is to be in the range 40 ~ 70 ℃, by coating the coating amount by the spray to be 0.5 ~ 3.0g / ㎡, to produce an electro-galvanized steel sheet according to the present invention.

Hereinafter, the present invention will be described in more detail with examples.

1 is a cross-sectional view of a coating layer of a conventional phosphate-treated steel sheet.

2 is a cross-sectional view of the phosphate treated steel film layer prepared according to the present invention.

* Explanation of symbols for main parts of the drawings

1: electro galvanized steel sheet 2: surface conditioner treatment layer

3, 13: phosphate treated film layer

The present invention is to prepare a phosphate treatment solution in which ternary zinc-nickel-manganese is properly mixed in an experimental model equipment using an electrogalvanized steel sheet prepared by a conventional electroplating method, the mixed phosphate treatment concentration is Prepare a phosphate solution with a composition ratio of 1000-3000 ppm zinc, 50-300 ppm nickel, and 300-2000 ppm manganese in a range of 1.5-5.0%.

After the phosphate treatment solution was prepared according to various conditions of the examples described below, a 300 mm × 300 mm electrogalvanized steel test piece was mounted in a model facility, and then degreased and washed with water to activate the steel plate of the phosphate treated film. After the titanium salt-based surface modifier treatment step (surface modifier treatment layer (2) formation step) is carried out to improve the refinement and densification of the grains and to increase the reaction rate of the diluted coating film, the phosphate treatment spray temperature is set to 40. The drying process was performed after forming a phosphate film in the range of ˜70 ° C. and coating amount in the range of 0.5 to 3.0 g / m 2.

On the other hand, the reason why the spray temperature of the phosphate treatment solution is limited to 40 to 70 degrees Celsius is that when the temperature is 40 degrees Celsius or less, the binding strength between zinc and phosphate in the film is weak, so that grain growth is weak and partial staining occurs on the plate surface. Since the appearance is damaged, and the growth of the film is coarse and irregularly formed, the corrosion resistance is remarkably decreased due to the progress of grain boundary corrosion due to excessive local phosphate formation. In addition, when the spray temperature is 70 degrees Celsius or more, the appearance and corrosion resistance of the phosphate-treated product and the densification of the crystal grains have been improved, but after spraying, the sludge of the unreacted solution is promoted. As it has to be repaired frequently, it has been shown to be a factor in lowering productivity and lowering economic feasibility.

Therefore, in order to solve this problem, the zinc content in the phosphate treatment solution was managed more than 500 ppm, resulting in the formation of sludge in the solution, resulting in an increase in the frequency of overflow, thereby increasing the manufacturing cost. In addition, there are disadvantages in that productivity is lowered if the reaction time is kept long for the film formation. In addition, the reason for limiting the content of manganese in the phosphate treatment solution to 300 ~ 2000ppm is that when the content of manganese is 300ppm or less, the reaction time is shortened by the spray method differently from the deposition method, the effect of the addition of manganese It was evaluated to be similar to the conventional treatment method due to its weakness, and the corrosion resistance and paintability were increased when the content of manganese was 2000 ppm or more, but the solution stability was significantly decreased due to the promotion of sludge formation of unreacted manganese.

In the case of the coating amount of the phosphate treated film layer 13, when the coating weight was less than 0.5 g / m 2, the surface roughness of the base galvanized steel sheet was not sufficiently applied, and the corrosion resistance of the coating film was remarkably decreased. If it is abnormal, the corrosion resistance is increased, but the electrical conductivity is evaluated to be poor, and the solution treatment time for controlling the amount of post-attachment takes excessively, and the nonuniformity increases due to the difference in the surface reactivity by spraying, which acts as a factor that hinders the appearance of the product. Appeared to be.

The phosphate treated film of the ternary form according to the present invention shows better corrosion resistance than the coating by the conventional binary treatment method, which is added with nickel and manganese evenly formed throughout the coating, making the grain size fine and uniform to 3 micron or less. It was found that the coating property is improved by improving adhesion and alkali solubility and by substituting with zinc such as Zn _3-X Mex (Po ₄ ) ₂ 4H ₂ O) in the hopitite crystal.

In the following examples, the solution of the mixture of zinc-nickel-manganese titer with a ternary phosphate treatment solution in an appropriate ratio of the present invention was applied to an electrogalvanized steel sheet, and its properties were evaluated. A galvanized product, a conventional binary zinc-nickel phosphate treated electrozinc plated product was used. Characteristics evaluation and comparison items were evaluated for corrosion resistance, surface appearance, whiteness, coating test, wet phase test and adhesion.

Corrosion resistance was compared with the initial red blue color development time in NaCl solution of 5% and 35 degrees Celsius. The surface appearance was measured by the crystal size and denseness of the phosphate treated film, and the whiteness was measured using color meta to measure the surface brightness. , Wet phase test was conducted at 50 degrees Celsius, 95% wet phase atmosphere, compared with the initial red blue development time, after coating to 20 micro thickness, cross-cut the coating film, and after 1000 hours evaluation by the salt spray test, The incidence of bleeding was measured and the results are shown in Table 1.

[Table 1] Evaluation results of various galvanized phosphate treated steel sheets

Example 1-3

In order to apply phosphate treatment solution of zinc-nickel-manganese which is ternary, the phosphate spray treatment temperature is 55 degrees Celsius on the galvanized steel sheet with the content composition ratio of 1000 ppm zinc, 50 ppm nickel and 300 ppm manganese in the phosphate treatment solution. It is a product when the coating film adhesion amount is changed to 0.5, 1.5, and 3.0 g / m <2>, and is processed on the 10 x 300 x 300 (mm) electrogalvanized steel sheet.

EXAMPLES 4-6

It is the same as Example 1-3, but it is a product when it is processed by nickel 100ppm and manganese 1000ppm content composition ratio.

EXAMPLES 7-9

It is the same as Example 1-3, but it is a product when it is processed by nickel content of 300 ppm and manganese 2000 ppm.

[Examples 10-12]

In order to apply phosphate treatment solution of zinc-nickel-manganese which is ternary, the phosphate spray treatment temperature is 65 degrees Celsius on the galvanized steel sheet with the content composition ratio of 2000ppm zinc, 50ppm nickel and 300ppm manganese in the phosphate treatment solution. It is a product when coating-film adhesion amount changes to 0.5, 1.5, and 3.0 g / m <2>, and is processed on the 10 x 300 x 300 (mm) electrogalvanized steel sheet.

[Examples 13-15]

It is the same as Example 10-12, but when processed with nickel 100ppm and manganese 1000ppm content composition ratio.

[Examples 16-18]

It is the same as Example 10-12, but when processed with nickel content of 300 ppm of nickel and 2000 ppm of manganese.

[Examples 19-21]

In order to apply phosphate treatment solution of ternary zinc-nickel-manganese, the phosphate spray treatment temperature is 50 degrees Celsius on the galvanized steel sheet with the content of constituent composition of 3000ppm zinc, 50ppm nickel and 300ppm manganese in the phosphate treatment solution. It is a product when the coating film adhesion amount is changed to 0.5, 1.5, and 3.0 g / m <2>, and is processed on the 10 x 300 x 300 (mm) electrogalvanized steel sheet.

[Examples 22 to 24]

It is the same as Examples 19-21, but when processed with nickel 100ppm and manganese 1000ppm content composition ratio.

[Examples 25-27]

It is the same as Example 19-21, but when processed with the composition ratio of 300 ppm nickel and 2000 ppm manganese.

Comparative Example 1

It is a product when 20g / m2 (single side) of zinc is plated on the steel sheet by the electroplating method.

Comparative Example 2

It is a product when the binary zinc-nickel phosphate treated film was treated with 2.0 g / m 2 after zinc was plated 20 g / m 2 (single side) on the steel sheet by the electroplating method.

According to the present invention, the phosphate-treated coating of the three-way type according to the present invention shows a better corrosion resistance than the coating by the conventional two-way treatment method, which is added to evenly formed nickel and manganese as a whole grain size Fine and uniform to 3 micron or less to improve the adhesion and alkali solubility and to improve the paintability by being substituted with zinc, such as Zn ₃ - _X Mex (Po ₄ ) ₂ 4H ₂ O) in the hophite crystal. In addition, the ternary phosphate treatment solution according to the present invention contains zinc in a composition ratio of 1000 to 3000 ppm, nickel 50 to 300 ppm, and manganese 300 to 2000 ppm, and thus it is possible to uniformly disperse nickel and manganese in the coating layer. Compared with electro zinc plated phosphate treated steel sheet, it is possible to manufacture phosphate treated steel sheet with excellent appearance, corrosion resistance, and paintability. It is expected to contribute greatly to the quality stabilization of building materials and home appliances.

Claims (1)

In the method of manufacturing a phosphate-treated galvanized steel sheet, a phosphate treatment solution containing 1000 to 3000 ppm zinc, 50 to 300 ppm nickel, and 300 to 2000 ppm manganese is prepared, and the concentration of the phosphate treatment solution is 1.5. Preparing in the range of ˜5.0%; And the film layer so that the coating amount may be in the range of 0.5 to 3.0 g / ㎡ on the surface treatment agent treatment layer (2) pre-treated on the electrogalvanized steel sheet (1) with the temperature of the phosphate treatment solution in the range of 40 ~ 70 ℃ Method for producing a phosphate-treated electrogalvanized steel sheet comprising the step of forming a.

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