KR100321374B1 - METHOD FOR MANUFACTURING Zn/Fe ALLOY ELECTROPLATED STEEL SHEET EXCELLENT IN PLATING ADHESION, SURFACE ROUGHNESS AND APPEARANCE - Google Patents

Abstract

PURPOSE: A method for manufacturing a Zn/Fe alloy electroplated steel sheet excellent in plating adhesion, surface roughness and appearance such as color and gloss is provided. CONSTITUTION: The method for manufacturing a Zn/Fe alloy electroplated steel sheet is characterized in that electroplating process is carried out under the plating conditions of a current density of 20-200A/dm¬2, a relative current velocity of 0.5-2.5m/sec between an electroplating solution and cathode, a temperature range of the electroplating solution of 40-70 deg.C and a pH range of the electroplating solution of 1.0-6.0.

Description

Manufacturing method of zinc-iron alloy plated steel sheet with good plating adhesion, surface roughness and surface appearance

The present invention relates to polyethylene glycol and methoxy polyethylene glycol in a chloride-based zinc-iron alloy plating bath composed of one or two or more mixtures of supporting electrolytes such as potassium chloride, calcium chloride, sodium chloride, and ammonium chloride in zinc chloride and iron chloride. And zinc-iron alloy having good plating adhesion and surface roughness and surface appearance by adding an additive composed of aromatic acid to improve the adhesion of the plating layer, and to obtain a plating layer having good surface roughness and surface appearance (whiteness, glossiness). It relates to a method for producing a coated steel sheet.

In general, zinc electroplating is performed to improve corrosion resistance of steel sheets, and zinc electroplating steel sheets are widely used in fields such as home appliances, automobiles, and construction.

However, in order to secure corrosion resistance under severe atmosphere, the thickness of the galvanized layer should be increased, thereby increasing the cost and lowering the quality characteristics such as plating adhesion, processability, weldability, and paintability.

Therefore, in order to improve this problem, zinc-based alloy electroplating has been developed based on automotive steel sheets. Among these, zinc-iron alloy electroplating materials are known as plating systems excellent in corrosion resistance, workability, and paintability.

The zinc-iron plating method has been proposed in various ways depending on the components of the plating bath, but the plating solution based on the acid bath is generally used, and the acid plating solution can be classified into a sulfide bath and a chloride bath.

Chloride baths have better electrical conductivity than sulfide baths, enabling high current density plating, and easier solution management and lower costs than sulfide baths that use insoluble anodes, mainly using soluble anodes.

However, zinc-iron alloy electroplating products of chloride baths using a soluble anode tend to have poor surface appearance, poor glossiness, and the like, and have a poor surface coating and a large coating amount.

Conventionally, in order to improve the surface appearance of zinc-iron alloy plating, Japanese Patent No. 57-114686 discloses polyamine, polyvinyl alcohol, and the like when alloys of iron group metals (Fe, Ni, Co, etc.) are alloy-plated with zinc as a main component. By adding metal co-precipitation to improve workability, economics and gloss, plating adhesion and surface roughness cannot be improved, and Japanese Patent No. 64-47893 adds substituted polyethers as an additive to improve surface uniformity and appearance. Although the color tone was improved, the surface of the plating layer became rough, the iron deposition rate did not increase, and in Japanese Patent No. 64-47892, the addition of polyethylene glycol, which is a nonionic surfactant, resulted in water-adhesion resistance, chemical conversion treatment, Although the upper iron content is improved, the surface appearance is poor.

Accordingly, the present invention provides a plating additive and a plating method for improving the glossiness, surface roughness and plating adhesion of the zinc-iron alloy electroplating, and the plating adhesion property by the interrelationship between the organic compound and the metal ion added in the plating bath. Its purpose is to improve surface roughness and surface appearance of plating.

In the present invention, zinc ions using zinc chloride has a water concentration of 0.5-2.5 mol / liter, iron chloride has a water concentration of 0.1-0.5 mol / liter, iron chloride has a water concentration of 4.0-9.0 mol / liter, Iron ions: (Zinc ions + Iron ions) in water ratio of 0.05-0.3: 1, pH 1.0-6.0 of plating solution, temperature of plating solution 40-70 ℃, converter density 20-200A / dm ² and plating solution and cathode To produce a zinc-iron alloy electroplated steel sheet having an iron content of 5-30% by electroplating under a plating condition of 0.5-2.5m / sec, but with a degree of polymerization of polyethylene glycol (H (OCH ₂ CH ₂ ) nOH n One or more of 10-20 and 20-30 numbers are mixed, and the aromatic acid and methoxy polyethylene are mixed in an aqueous solution of 5-15% of mixed polyethylene glycol having a mixing ratio of 1: 2-1: 5 by weight. number of glycol polymerization degree n of the _{(CH 3 (OCH 2 CH 2} ) nOH) is 2-10% of the 10 to 40 range in that an aqueous solution of polyethylene glycol and methoxy polyethylene As a sum of the addition of organic solvent additives which are composed of an aromatic acid is 0.1-1.0% based on the weight of the mixture to maintain a 8-22% by 0.2-8.0ml / L concentrations to the hayeoseo electroplating.

The reason for numerical limitation is as follows.

The zinc ions of the plating solution cause burns that burn black in the plating due to insufficient concentration of ions to be coated at a molar concentration of 0.5 mol / liter or less, and at 2.5 mol / liter or more, the plating layer is powder-plated. Adhesion is poor and the iron content of the plating layer is reduced, so that weldability and paintability are deteriorated. At a molar concentration of 0.5 mol / liter or more, the iron content of the plating layer is too high, so that workability is lowered and corrosion resistance due to galvanic corrosion is reduced.

When the chlorine ion is 4.0 mol / liter or less, a large amount of burning occurs due to a decrease in electrical conductivity, and when 9.0 mol / liter or more, chlorine ions are precipitated due to solubility problems, thereby decreasing plating workability and making it difficult to manage the plating solution concentration.

Zinc-iron alloy electroplating is excellent in corrosion resistance and workability in the iron content of the coating layer of 4-30% range, the preferred range is 10-20%. Therefore, the iron ions: (iron ions + zinc ions) ratio of less than 0.05, the iron content of the plated layer is lowered to 4 percent or less, and more than 0.3, iron content is more than 30 percent, poor corrosion resistance and workability.

When the temperature of the plating solution is 40 ° C. or lower, the plating layer is dark, the adhesion of the plating layer is poor, and the peeling phenomenon occurs, and the iron content of the plating layer is also lowered.

When the temperature of the plating layer is 70 ℃ or more, the plating streaks are generated, the evaporation of the plating liquid is severely inhibited the working environment and the sludge generation of the zinc anode is severe, it is preferable to limit the temperature of the plating liquid to the range of 40 ℃ to 70 ℃.

The pH of the plating solution is less than 1.0, the plating surface is dark and semi-gloss state, the plating surface is roughened at 6.0 and above, and precipitation of iron hydroxide occurs in the plating solution, so the pH of the plating solution is preferably limited to 1.0-6.0.

The current density in the plating solution 20A / dm ² in the coating, and the speed is slow and cost is increased away from the productivity also reduced the iron content of the plating layer, 200A / dm ² or more in the result of limitations in the diffusion rate of the metal ion-generating burning, etc. Since it is difficult to obtain normal plating quality, it is necessary to limit the current density to 20-200A / dm ² .

When the relative flow velocity of the plating solution and the cathode in the plating solution is 0.5 m / sec or less, the diffusion rate of the metal ions is limited, making high current density plating difficult, and it is difficult to obtain a flow rate of 2.5 m / sec or more because it is difficult for equipment. The range of the genus is preferably limited to 0.5-2.5m / sec.

When the number of polyethylene glycol n as an additive in the plating solution is less than 10, the fineness of the plating crystal grains is poor, roughness is poor, and when the number of n is 30 or more, the surface appearance improvement effect 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 surface appearance improvement function is shown.

When the concentration in these aqueous solutions is 5% or less, the plating crystals have a small effect of miniaturization, and when the concentration becomes 15% or more, the surface appearance improvement effect of the plating layer is reduced.

When n-number of methoxy polyethylene glycol is 10 or less, the surface roughness does not improve because there is little crystal refinement effect of a plating layer, and when 40 or more, surface appearance improvement of a plating layer is difficult. Its concentration is less than 2 percent, the surface roughness effect is weak, and above 10 percent, the surface appearance improvement effect is reduced.

If the sum of polyethylene glycol and methoxy polyethylene glycol is less than 8%, the plating adhesion and micronization effect is weak, and at more than 22%, the plating layer becomes rough.

At less than 0.1 percent of the aromatic acid, the particles are not uniform. At more than 1.0 percent, yellow streaks are formed in the plating layer, and the plating state is also poor.

If the amount of the plating bath added as described above is 0.2ml / l or less, the surface roughness and surface appearance improvement effect due to the refinement of the plating grains cannot be obtained. Is reduced.

When the additives in the above-mentioned range are added to the acid chloride bath during zinc-iron alloy electroplating, the plating grains are finely uniform to improve the surface roughness and to obtain a plating layer having excellent gloss and plating adhesion. In particular, it shows the best characteristic in the addition amount ranging from 1.0 ml / l to 3.0 ml / l.

The additive of the present invention can be applied to zinc-iron alloy electroplating using acid chloride regardless of metal type and shape of the plated body, and particularly, excellent plating quality can be easily obtained when continuous electro-zinc plating of steel sheet requiring high current density plating. It is a very effective means to do this.

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

(Example)

When the cold-rolled steel sheet is used as the base metal, the plating layer composition shows the whiteness, glossiness, surface roughness and plating adhesion when the plating amount is 40g / dm ² according to the plating conditions.

Table 1 Plating conditions for measuring the surface whiteness, glossiness, surface roughness, coating weight according to the additives in the plating solution, PH = 2, temperature = 55 ℃, relative flow rate = 1.5m / sec, current density = 60A / dm Set to ² .

number Additive ml / L Polyethylene glycol Methoxy polyethylene glycol Total concentration (wt%) Aromatic acid (wt%) Plating adhesion Surface roughness Glossiness Whiteness number of n ratio of number of n to other Concentration (wt%) number of n Concentration (wt%) A B A: B One 2.0 15 25 1: 2 12.0 20 5.0 17.0 0.5 Good Good Good Good 2 10 25 1: 3 20 Good Good Good Good 3 15 25 1: 3 20 Good Good Good Good 4 15 30 1: 3 20 Good Good Good Good 5 15 25 1: 5 20 Good Good Good Good 6 15 25 1: 3 20 Good Good Good Good 7 15 25 1: 3 10.0 20 5.0 15.0 Good Good Good Good 8 15 25 1: 3 15.0 20 5.0 20.0 Good Good Good Good 9 15 25 1: 3 12.0 20 5.0 17.0 0.1 Good Good Good Good 10 15 25 1: 3 20 1.0 Good Good Good Good 11 15 25 1: 3 20 0.5 Good Good Good Good 12 15 25 1: 3 20 0.5 Good Good Good Good 13 8 25 1: 3 12.0 20 5.0 17.0 0.5 Bad Bad Good Good 14 15 35 1: 3 12.0 20 5.0 17.0 0.5 Bad Good Bad Bad 15 15 25 1: 1 12.0 20 5.0 17.0 0.5 Bad Bad Bad Bad 16 15 25 1: 6 12.0 20 5.0 17.0 0.5 Bad Bad Bad Bad 17 15 25 1: 3 4.0 20 5.0 9.0 0.5 Bad Bad Good Bad 18 15 25 1: 3 5.0 20 5.0 10.0 0.5 Good Good Good Good 19 15 25 1: 3 15.0 20 5.0 20.0 0.5 Good Good Good Good 20 15 25 1: 3 16.0 20 5.0 21.0 0.5 Bad Good Bad Bad 21 15 25 1: 3 12.0 20 5.0 17.0 0.005 Bad Bad Bad Bad 22 15 25 1: 3 12.0 20 5.0 17.0 1.5 Bad Bad Bad Bad 23 15 25 1: 3 12.0 10 5.0 17.0 0.5 Good Good Good Good 24 15 25 1: 3 12.0 5 5.0 17.0 0.5 Good Good Good Good 25 15 25 1: 3 12.0 40 5.0 17.0 0.5 Good Good Good Good 26 15 25 1: 3 12.0 45 5.0 17.0 0.5 Bad Bad Bad Bad 27 15 25 1: 3 5.0 20 2.0 7.0 0.5 Bad Bad Bad Bad 28 15 25 1: 3 15.0 20 10.0 25.0 0.5 Bad Bad Bad Bad 29 0.1 15 25 1: 3 12.0 20 5.0 17.0 0.5 Bad Bad Bad Bad 30 0.2 15 25 1: 3 12.0 20 5.0 17.0 0.5 Good Good Good Good 31 8.0 15 25 1: 3 12.0 20 5.0 17.0 0.5 Good Good Good Good 32 9.0 15 25 1: 3 12.0 20 5.0 17.0 0.5 Bad Bad Bad Bad

* Whiteness: L value of Color Difference Meter (good: above 65, bad: below 64)

** Glossiness: gloss meter (good: 63 or more, poor: 62 or less)

*** Surface Roughness: Plating Roughness (Rmax)-Disc Roughness (Rmax) (Good: 0.7um or less,

Poor: 0.8um or more)

**** Plating adhesiveness: (good: bend 120 ° and after taping, there should be no plating layer on tape, other: bad)

As shown in Table 1, the plating adhesion, surface roughness, and surface appearance (glossiness, whiteness) are good under the conditions consistent with the present invention, but the plating layer performed under the plating conditions outside the scope of the invention is poor. have.

As described above, the present invention improves the quality by improving the adhesion of the plating layer, the surface roughness, and the surface appearance in the chloride-based plating solution in zinc-iron alloy electroplating, thereby producing an excellent zinc-iron alloy electroplating steel sheet. It is to provide a plating solution and a plating method that can be.

As described above, the present invention improves the adhesion and surface roughness and surface appearance of the plating layer in the chloride-based plating solution in the zinc-iron alloy electroplating, thereby improving the quality and producing an excellent zinc-iron alloy electroplating steel sheet. It has an effect.

Claims (1)

Zinc chloride zinc ion water concentration 0.5-2.5 mol / liter, iron chloride iron ion water concentration 0.1-0.5 mol / liter, chloride ion water concentration 4.0-9.0 mol / liter, iron ion ratio 0.05-0.3: 1 On the basis of the above, one or more types of polyethylene glycol (H (OCH ₂ CH ₂ ) nOH having a degree of polymerization n of 10-20 and 20-30 are mixed, respectively, and the mixing ratio is 1: 2-1: 5 by weight ratio. In the aqueous solution having a concentration of 5-15% of phosphorus mixed polyethylene glycol, the range of the polymerization degree N of aromatic acid and methoxy polyethylene glycol (CH ₃ (OCH ₂ CH ₂ ) nOH) in the range of 10-40 is 2-10% of the aqueous solution. Chloride-based zinc-iron to which an organic solvent additive consisting of 0.1-1.0% of aromatic acid is added at a concentration of 0.2-8.0 ml / L, based on the weight of the mixed solution of 8-22% of polyethylene glycol and methoxypolyethylene. alloy electroplating utilized in the temperature of 40-70 ℃, the current density of the plating solution of pH 1.0-6.0 20-200A / dm ² and a plating liquid and the cathode contact The method of the iron alloy electroplated steel sheet-adhesion, and surface roughness and surface good appearance of zinc, characterized in that electroplating in the hayeoseo the plating conditions of 0.5-2.5m / sec.