KR20030049811A - method of manufacturing Zn electrodeposited steel sheet with good appearance and surface appearance - Google Patents

Abstract

PURPOSE: A plating additive for improving flatness and surface appearance such as glossiness and whiteness of plating layer during electrolytic galvanizing, and a manufacturing method of electrolytic galvanized steel sheet using the additive are provided. CONSTITUTION: The method for manufacturing electrolytic galvanized steel sheet with superior surface appearance and flatness is characterized in that a base metal of cold rolled strip is plated in a chloride based electrolytic galvanizing pot to which a chloride bath electrolytic galvanizing additive is added in a concentration of 0.1 to 8.0 ml/L, wherein the chloride bath electrolytic galvanizing additive is prepared by adding 1.0 to 10.0 g/L of o-vanillin and 1.0 to 10.0 g/L of magnesium to the aqueous solution after preparing an aqueous solution comprising polyethylene glycol (H(OH2CH2)nOH) and aromatic acid in which polyethylene glycol consists polymer of at least two or more of compositions having different n number, constituents having n between 10 to 20 and between 20 to 30 are included, ratio of the constituents is maintained to 1:2 to 1:5, and 10 to 15 wt.% of the constituents is contained.

Description

Method for manufacturing Zn electrodeposited steel sheet with good appearance and surface appearance

The present invention relates to a method for manufacturing a zinc electroplated steel sheet having excellent surface appearance and flatness, and more particularly, a plating bath additive for improving the surface appearance (whiteness, glossiness) and surface flatness of a plating layer in a chloride-based zinc plating bath. It relates to a method for producing a galvanized steel sheet.

In general, zinc electroplating materials are widely used in home appliances, construction, and automotive materials because of their advantages in terms of ease of plating, cost and corrosion resistance. However, in order to improve the productivity of such a steel sheet, high current density plating is essential, and when used for coating, the surface appearance of the plating layer should be excellent.

In addition, the surface flatness should be good when the post-treatment process is carried out for the final product.

Such zinc electroplating baths are used as chloride baths, sulfate baths, cyan baths and neutral salt baths. Among them, the chloride baths are known to be suitable for high current density plating due to their excellent electrical conductivity. The surface appearance is degraded, the surface is rough, and when the phosphate treatment or coating is applied, the surface is dark and the surface reflection is poor.

US Pat. No. 4,075,066 improves the plating properties by adding at least one polyoxalalkylate naphthol and one or more aromatic carboxylic acids or salts for distribution of gloss, ductility and good plating current of the plating layer in ammonia free plating bath.

U.S. Patent 4,146,441 adds a mixture of formaldehyde to improve the glossiness of the plating layer and to expand the range of plating current density in sulfuric acid bath.

U.S. Patent 4,049,510 has been proposed to improve glossiness by adding an amine polymer in a chloride bath.

U.S. Patent No. 3,855,085 improved surface gloss by adding nonionic polyoxyethylene in a chloride bath.

Japanese Patent Application No. 58-48639 includes a method of selectively using ammonium chloride, potassium chloride, sodium chloride, aluminum chloride, barium chloride, calcium chloride, magnesium chloride, etc., and changing plating conditions.

In addition, Japanese Patent No. 61-204389 has a patent to improve the gloss by adding an amino acid, glycine, hydroxyproline, etc., but these are mainly limited to the gloss improvement, which is the surface appearance of the galvanized layer, surface whiteness, adhesion and current It is not suitable to achieve complex quality improvement such as efficiency.

Japanese Patent No. Hei 9-136998 is known to improve the surface appearance by adding 0.01-8 ppm or more of Sn, In, Se, Sb, Ge and the like with low hydrogen overvoltage in a sulfuric acid bath, but no improvement in surface flatness occurs.

The present invention has been made to solve the above problems, to provide a new plating additive for improving the surface appearance (glossiness, whiteness) and flatness of the plating layer during zinc electroplating and to provide a method for producing a galvanized steel sheet using the additive. It is an object of the present invention to add a small amount of the invention additive to the plating bath during zinc electroplating in the chloride bath to change the crystal grain shape and the deposition direction of the plated surface to improve the surface appearance and to prevent the flow of current due to overvoltage. Increasing the throwing power to improve the flatness of the coating layer is characterized by providing an effective method to obtain excellent quality when manufacturing zinc electroplating steel sheet used in post-treatment products (phosphate treatment, chrome treatment, coating treatment).

1 is a table showing the glossiness whiteness and flatness of the surface of the plating material according to the composition of the additive according to the present invention.

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

The object of the present invention is to provide a new plating additive for improving the surface appearance (glossiness, whiteness) and flatness of the plating layer during zinc electroplating, and to provide a method for manufacturing a galvanized steel sheet using the additive. A mixture of two or more kinds of polyethylene glycols having different molecular weights is included, in which an avanillin and magnesium are added at an appropriate ratio, and the additive is added to an appropriate amount of plating bath to effect the plating.

The present invention is prepared while stirring for at least about 300 seconds at a temperature range of 60 ^° C at room temperature while adding water to the mixture containing polyethylene glycol (H (OCH ₂ CH ₂ ) _n OH) and obaniline. Polyethyleneglycols consist of at least two polymers of different n-numbers of composition, and n must contain a component between 10 and 20 and 20 to 30, with a ratio of 1: 2 to 1: 5 and their components 10 At 15% by weight, containing a mixture of ovaniline from 1.0 to 10.0 g / L, in which magnesium (Mg) concentration is formed in the form of magnesium chloride by the addition of 1.0 to 10.0 g / L. When the plating is performed by adding the additive prepared as described above to an acid chloride-based electro zinc plating bath from 0.1 to 8.0 ml / l, an electro zinc plating product having excellent surface appearance and flatness can be prepared as described above. .

Hereinafter, the reason for numerical limitation of the present invention will be described.

If the number of polyethylene glycol n is 10 or less, the effect of miniaturization of the plating grains is weak, the flatness is inferior, and if the number of n is 30 or more, the effect of improving the whiteness and glossiness of the plating layer is reduced. The ratio of the number of components between 10 and 20 and the components between 20 and 30 in the range of 1: 2 to 1: 5 is the same as the reason for setting the lower and upper limits of the number of n. The whiteness improvement function is shown, and the small number of n shows the function of glossiness. When the concentration of these mixtures in the aqueous solution is less than 10% by weight, the microcrystallization efficiency of the plating crystals is small, so that the surface is rough and poor in adhesion.

Less than 1.0 g / L of obanilin improves whiteness and less than 10.0 g / L results in poor adhesion. When the magnesium concentration is 1.0 g / L or less, the surface appearance is not improved, but when the magnesium concentration is 10.0 g / L or more, the surface appearance becomes uneven.

If the addition amount of the plating bath of the additive prepared as described above is less than 0.1ml / l, the surface appearance (glossiness, whiteness) of the coating layer can not be improved, and when it is contained more than 8.0ml / l, surface streaks are generated, The efficiency decreases. When the additives in the above-mentioned range are added to the acid chloride bath during electro zinc plating, a plating layer having excellent glossiness, whiteness and good surface flatness can be obtained. In particular, the additive is added at 0.2 ml / l to 1.0. the best properties in the range of ml / l. The additive of the present invention can be applied to electrogalvanization using acid chloride regardless of the metal type and shape of the plated body, and in particular, it is possible to easily obtain excellent plating quality during continuous electrogalvanization of steel sheets requiring high current density plating. It is a very effective means.

Hereinafter, embodiments of the present invention will be described.

Electroplating was performed using the cold rolled steel sheet as a base metal under the plating solution concentration and plating conditions shown in FIG. 1, and then the results of measuring the glossiness, whiteness, and roughness of the coated steel sheet were compared. The concentration and plating conditions of the plating liquid were Zn: 100 g / L, Cl: 260 g / L, plating amount: 20 g / m ² , temperature 60 ° C., pH: 4.5, and current density of 100 A / dm ² .

In the evaluation of the properties of the plated layer, the glossiness measured by the glossmeter (Erichen) was 16 or more, and the below was poor. The whiteness measured by the color difference meter (JUKI JP7200C) was good and the additive 85 or more. It was shown as bad. The flatness of the plating layer was determined to be good when the surface roughness of the plating material was lower than that of the base metal before plating using a three-dimensional roughness meter.

As shown in the embodiment of Figure 1, the additive of the present invention within the limited range of the invention it can be seen that the plating quality is improved by showing a good gloss, whiteness and surface flatness. That is, the surface gloss, whiteness, and flatness of the polyethylene glycol concentration range from 30 to 30 with the number of n of polyethylene glycol being 10 or more and the ratio of 10 to 20 and 20 to 30 being in the range of 1: 2 to 1: 5. Is maintained at 10-15 weight percent, and the quality of the plating layer when the additive containing the ovalineline at 1.0 to 10.0 g / L and magnesium at 1.0 to 10.0 g / L is contained in the plating bath at 1.0 ml / L to 8.0 ml / L. This is excellent. Therefore, according to the present invention as described above, the surface glossiness, whiteness and flatness of the excellent plating layer in the chloride-based galvanizing bath can be easily produced under the conditions presented.

Claims (3)

An aqueous solution of a mixture containing polyethylene glycol (H (OCH ₂ CH ₂ ) _n OH) and an aromatic acid, wherein the constituent weight ratio of polyethylene glycol including one or more of the number of n in the range of 10-20 and 20-30 is 1 : 2 to 1: 5 by mixing to 10 to 15% by weight in an aqueous solution, and then added to the aqueous solution of the ovaniline 1.0 to 10.0 g / L, magnesium further characterized in that 1.0 to 10.0 g / L Bath zinc electroplating additives. An aqueous solution of a mixture containing polyethylene glycol (H (OCH ₂ CH ₂ ) _n OH) and an aromatic acid, wherein the constituent weight ratio of polyethylene glycol including one or more of the number of n in the range of 10-20 and 20-30 is 1 : 2 to 1: 5 by mixing to 10 to 15% by weight in an aqueous solution, and then added to the aqueous solution of the ovaniline 1.0 to 10.0 g / L, magnesium further characterized in that 1.0 to 10.0 g / L Chlorinated electrogalvanizing bath with zinc electroplating additives added in a concentration of 0.1-8.0 ml / l. An aqueous solution of a mixture containing polyethylene glycol (H (OCH ₂ CH ₂ ) _n OH) and an aromatic acid, wherein the constituent weight ratio of polyethylene glycol including one or more of the number of n in the range of 10-20 and 20-30 is 1 After mixing with 2: 1: 5 to adjust to 10 to 15% by weight in the aqueous solution, zinc chloride electroplating in the aqueous solution of ovaniline 1.0 to 10.0 g / L, magnesium also 1.0 to 10.0 g / L A method for producing an electro-zinc plated steel sheet having excellent surface appearance and flatness, which is plated in a chloride-based electro zinc plating bath to which an additive is added at a concentration of 0.1 to 8.0 ml / l.