KR100711767B1 - ELECTROLYTE FOR Zn-Ni ALLOY ELECTRODEPOSITION, PREPARING METHOD OF Zn-Ni ALLOY ELECTRODEPOSITED STEEL SHEET USING SAME AND STEEL SHEET PREPARED THEREBY - Google Patents

Abstract

The present invention relates to a zinc-nickel alloy electroplating composition, a method for producing an electroplated steel sheet using the same, and a zinc-nickel alloy electroplated steel sheet prepared according to the present invention. , Nickel ions, chlorine ions, and additives, and the nickel ions are included in a concentration ratio (Ni ²⁺ / (Zn ²⁺ + Ni ²⁺ )) of 0.11 to 0.15. The additive also includes saccharin, citrate, uric acid and sulfonate.

The zinc-nickel alloy electroplating composition according to the present invention can form a uniform electrodeposition layer, exhibit excellent plating adhesion, and minimize side reaction hydrogen generation. In addition, the electroplated steel sheet formed from the electroplating composition has excellent surface appearance and surface roughness.

Zinc, nickel, plating composition, additives, chloride bath

Description

ELECTROLYTE FOR Zn-Ni ALLOY ELECTRODEPOSITION, PREPARING METHOD OF Zn-Ni ALLOY ELECTRODEPOSITED STEEL SHEET USING SAME AND STEEL SHEET PREPARED THEREBY}

[Technical Field]

The present invention provides a zinc-nickel alloy electroplating composition capable of forming a uniform electrodeposition layer, exhibiting excellent plating adhesion, and minimizing side reaction hydrogen generation, and a method of manufacturing an electroplated steel sheet using the same. A zinc-nickel alloy electroplated steel sheet produced according to the present invention.

[Private Technology]

In general, a technique of forming a metal plating layer on iron is widely used for rust prevention, decoration and the like. In particular, since the development of zinc electroplating, which is excellent in securing corrosion resistance of steel sheets, zinc electroplating has been widely used in the fields of home appliances, automobiles, construction, and the like. However, since zinc electroplating is performed in a harsh atmosphere, it is necessary to increase the thickness of the galvanizing layer in order to secure corrosion resistance. Due to this, there are various problems such as an increase in cost, a decrease in adhesion, and a decrease in processability.

In order to solve this problem of zinc electroplating, zinc-nickel alloy electroplating has been developed. Zinc-nickel alloy electroplating is classified according to the components of the bath, of which the production method of plating products based on acidic baths is generally widely used. Acid baths also include sulfide baths as bases and chloride baths as bases.

Chloride baths have better electrical conductivity than sulfide baths, enabling high current density plating, and because they use soluble anodes, they are more convenient and less expensive to control than sulfide baths that use insoluble anodes. Such soluble anodes mainly use zinc and nickel, and zinc generally accounts for about 85% or more. Therefore, the uniform solubility of the zinc anode, that is, no sludge or foreign matter remains on the anode can produce a good plated product.

However, since zinc and nickel have a large potential difference in the chloride plating bath, sludge in the zinc hydroxide system due to electroless substitution of nickel at the zinc anode is likely to occur. The produced sludge adheres to the surface of the anode and dissolves unevenly when zinc is melted by continuous operation, which rapidly changes the concentration of the plating solution, and also impedes the plating voltage to increase the plating voltage and causes uneven electrodeposition, resulting in adhesion of the plating layer. Deterioration and surface quality of the plated product (surface appearance and surface roughness).

As a method for solving such a problem, there is a method of reducing the acidity (pH) of the plating liquid to suppress sludge generation. However, the above method has a problem in that the plating material is cured because hydrogen is generated when the pH is 1.5 or less during zinc-nickel plating.

In addition, British Patent No. 189258 discloses a method for increasing Ni content, increasing current efficiency, and improving plating uniformity by using additives such as acetylene alcohol and aromatic sulfonic acid. However, the problem of the operation defect by the sludge generation at the time of plating for 4 hours or more in the chloride bath did not improve.

Japanese Patent No. 59-211589 discloses mixed precipitation of yellowish brown or blue violet oxide accompanying incidental to precipitates by adding a part of ammonium chloride to the plating solution containing zinc chloride and nickel chloride as a main component of a chloride bath and sulfate and changing plating conditions. A method of effectively suppressing is disclosed. However, the above method only suppresses the generation of sludge only at the beginning of operation, and generates sludge over time.

In addition, Japanese Patent No. Hei 2-57695 discloses gloss and ductility by adding RS (R`O) <sub>n</sub> H or S-((R`O) _n H) ₂ (where R is an alkylene group having 1 to 24 carbon atoms). Although a method of improving is disclosed, the generation of sludge is not suppressed, and also the pH is greatly changed during prolonged plating.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to form a uniform electrodeposition layer due to good reactivity and electrodeposition reaction of the anode, showing excellent plating adhesion, and generating hydrogen as a side reaction. An object of the present invention is to provide a zinc-nickel alloy electroplating composition which can be minimized, a method of manufacturing an electroplated steel sheet using the same, and a zinc-nickel alloy electroplated steel sheet produced accordingly.

In order to achieve the above object, a first exemplary embodiment of the present invention includes zinc ions, nickel ions, chlorine ions, and additives, wherein the nickel ions have a concentration ratio of 0.11 to 0.15 (Ni ²⁺ / (Zn ^2+). + Ni ²⁺ )) to provide a zinc-nickel alloy electroplating composition.

At this time, the additives include saccharin, citrate, uric acid and sulfonate, and more preferably 1.5 to 4 parts by weight of saccharin, 0.01 to 0.1 part by weight of uric acid and 0.5 to 2 parts by weight of sulfonate, based on 1 part by weight of citrate. .

In addition, the zinc-nickel alloy electroplating composition is preferably adjusted by the concentration of chlorine ions in the plating composition by a chlorine ion concentration regulator comprising one or more selected from the group consisting of potassium chloride, calcium chloride and sodium chloride and ammonium chloride. Do.

In a second exemplary embodiment of the present invention, the zinc-nickel alloy electroplating composition may have a pH of 3.5 to 5, a temperature of 50 to 70 ° C, a current density of 40 to 200 A / dm ^2, and a relative flow rate of 0.5 to 2.5 of the plating composition with respect to the steel sheet. Provided is a method for producing a zinc-nickel alloy electroplated steel sheet which is plated on a steel sheet under m / sec.

A third exemplary embodiment of the present invention also provides a zinc-nickel alloy electroplated steel sheet manufactured by the above manufacturing method.

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

The present invention uses a zinc-nickel alloy electroplating composition containing a specific combination of additives, so that the reactivity and electrodeposition reaction of the positive electrode is good to form a uniform electrodeposition layer, showing excellent plating adhesion In addition, it was possible to minimize the generation of hydrogen which is a side reaction.

Specifically, the zinc-nickel alloy electroplating composition according to the first exemplary embodiment of the present invention is

Zinc ions;

Nickel ions;

Chlorine ions; And

Includes additives including saccharin, citrate, uric acid and sulfonates,

The nickel ions are included in a concentration ratio (Ni ²⁺ / (Zn ²⁺ + Ni ²⁺ )) of 0.11 to 0.15.

More preferably, the concentration ratio (Ni ²⁺ / (Zn ²⁺ + Ni ²⁺ )) of nickel ions in the zinc-nickel alloy electroplating composition is 0.12 to 0.14. If the Ni content in the plating layer is 10% or more, it shows excellent corrosion resistance. If the concentration ratio of nickel ions in the zinc-nickel electroplating composition is less than 0.11, the nickel content in the plating layer is low, and the corrosion resistance is lowered. It is not preferable because the content is increased to 14% or more, and there is a risk of moldability deterioration and peeling during processing due to the increase in hardness.

In addition, the metal ions (Zn ²⁺ + Ni ²⁺ ) of zinc and nickel in the zinc-nickel alloy electroplating composition are preferably included at a concentration of 70 to 140 g / L, more preferably 90 to 110 g / L. . If the total metal ion concentration is less than 70 g / L, the current efficiency may decrease, and the surface may become black due to hydrogen generation during high current operation due to the lack of metal ions. If it exceeds 140 g / L, the adhesion of the plating layer is bad and the electrodeposition cost is high. It is not preferable to become high.

Accordingly, the concentration of nickel ions in the zinc-nickel alloy electroplating composition is preferably 7.7 to 21.9 g / L. If the concentration of nickel ions is less than 7.7 g / L, burning may be blackened due to the lack of total metal ions in the plating layer. If the concentration of nickel ions exceeds 21.9 g / L, the plating may be performed in the form of powder, resulting in poor adhesion.

The concentration of the zinc ion is preferably 49 to 133 g / L in the zinc-nickel alloy electroplating composition. If the concentration of zinc ions is less than 49 g / L, the corrosion resistance of the plating layer may be reduced. If the concentration of zinc ions is more than 133 g / L, the workability may be lowered, which is not preferable.

In addition, the concentration of chlorine ions in the zinc-nickel alloy electroplating composition is preferably 220 to 340 g / L, more preferably 240 to 300 g / L. If the concentration of chlorine ions is less than 220 g / L, the conductivity is poor, the adhesion of the plating layer is poor, the surface burns black, and the surface solubility of the anode is also poor. In addition, when the concentration of the chlorine ion exceeds 340g / L, the chloride solubility is poor, there is a possibility that the surface scratches may occur due to precipitation is not preferable.

 Zinc ions included in the zinc-nickel alloy electroplating composition are ionized from zinc containing salts, such as zinc chloride, and nickel ions are ionized from salts containing nickel, such as nickel chloride. Chlorine ions are also ionized from salts containing chlorine, for example ammonium chloride.

Therefore, the concentration of zinc ions, nickel ions, and chlorine ions included in the zinc-nickel alloy electroplating composition may be adjusted according to the salt content thereof.

For example, in the case of chlorine ions, the zinc-nickel alloy electroplating composition preferably contains ammonium chloride in an amount of 20 to 60 g / L, more preferably 20 to 40 g / L. If the amount of ammonium chloride is less than 20 g / L, uniform dissolution of the positive electrode decreases, and if it exceeds 60 g / L, the plating layer may change to dark brown, which is not preferable.

In addition, in the case of the chlorine ions, the concentration of chlorine ions in the zinc-nickel alloy electroplating composition is further added by using a chlorine ion concentration regulator including at least one selected from the group consisting of potassium chloride, calcium chloride, sodium chloride and ammonium chloride. I can regulate it.

The additives include saccharin, citrate, uric acid and sulfonate and are added in the zinc-nickel alloy electroplating composition in an amount of 0.1 to 4 ml / L, more preferably 0.5 to 3.5 ml / L. If the amount of the additive is less than 0.1ml / L, the sludge of the plating composition is not suppressed, uniform electrodeposition property is not secured, and the white appearance of the surface appearance is not reduced, which is undesirable. It is unpreferable because adhesiveness becomes poor by the adsorption | suction of ions carrying metals.

As the citrate, sodium citrate and the like can be used.

The saccharin is preferably included in an amount of 1.5 to 4 parts by weight, more preferably 2 to 3 by weight based on 1 part by weight of citrate. If the weight ratio of saccharine to citrate is less than 1.5, the gloss is not polished due to the surface unevenness of the plated layer, and if it exceeds 4, the ion adsorption interference is severe and the plated layer adhesion is poor.

The uric acid is preferably included in 0.01 to 0.1 parts by weight with respect to 1 part by weight of citrate, more preferably in the weight ratio of 0.02 to 0.05. If the weight ratio of uric acid to sodium citrate is less than 0.01, there is no improvement in the whiteness of the plated layer, and if it exceeds 0.1, a black pattern occurs on the surface.

The sulfonate is preferably included in an amount of 0.5 to 2 parts by weight, more preferably 1 to 1.5 by weight, based on 1 part by weight of citrate. If the weight ratio of citrate to sulfonate is less than 0.5, the plating structure shape is not controlled and there is no improvement in whiteness. Examples of such sulfonates include sodium sulfonate and the like.

The additive is used as a solution dissolved in water, wherein water is mixed at 1.5 to 3 parts by weight, more preferably 1.5 to 2 parts by weight, based on 1 part by weight of the additive. If the weight ratio is less than 1.5, the effect of suppressing hydrogen generation is small and the plating efficiency is lowered. When it exceeds 3, the mutual reaction between additives becomes difficult and the surface whiteness, glossiness, and adhesiveness of a plating layer fall.

The zinc-nickel alloy electroplating composition according to the first exemplary embodiment of the present invention includes an additive including saccharin, citrate, uric acid, and sulfonate, so that the reactivity and electrodeposition of the positive electrode are good and uniform. The electrodeposition layer can be formed, also exhibits excellent plating adhesion, and can minimize the generation of hydrogen as a side reaction.

According to a second exemplary embodiment of the present invention, a method of manufacturing a zinc-nickel alloy electroplated steel sheet using the zinc-nickel alloy electroplating composition is provided.

More specifically, the manufacturing method of the zinc-nickel alloy electroplating steel sheet according to the second exemplary embodiment of the present invention is a zinc-nickel alloy electroplating composition pH 3.5 to 5.0, temperature 50 to 70 ℃, current density 40 To 200 A / dm ² and the plated steel sheet under conditions of a relative flow rate of 0.5 to 2.5 m / sec of the plating composition for the steel sheet.

The zinc-nickel alloy electroplating composition is the same as described above.

It is preferable that pH at the time of plating is 3.5-5, More preferably, it is 3.5-4.5. If the pH is less than 3.5, the plating efficiency is lowered due to hydrogen generation at the cathode, and black comb fringes are generated on the surface of the plating layer. If the pH is higher than 5.0, the formation of hydroxides and the contamination of the plating solution are severely generated.

Moreover, it is preferable that temperature is 50-70 degreeC, More preferably, it is 50-60 degreeC. If the temperature is less than 50 ℃, solubility of various salts is lowered, the content of nickel, which is an alloy metal in the plating layer is lowered, and if it exceeds 70 ℃ steam generation is severe due to the evaporation of the plating composition and the equipment corrosion occurs badly.

The current density is preferably 40 to 200 A / dm ² , more preferably 60 to 120 A / dm ² . If the current density is less than 40A / dm ^2, the glossiness of the plating layer is lowered, and a defect of excessive precipitation of nickel appears in the plating layer. However, if the current density is increased, the plating speed is increased, and the productivity is improved. However, if the current density exceeds 200 A / dm ² , burning phenomenon occurs in the plated layer and the contact between the steel sheet and the current collector is not preferable.

It is preferable that the relative flow velocity of the plating composition with respect to the steel plate which is a to-be-plated body of a zinc- nickel alloy is 0.5-2.5 m / sec, More preferably, it is 1-2 m / sec. If the relative flow rate is less than 0.5 m / sec, the plating property may deteriorate due to coarsening of the plating crystals and burning of the plating layer, and it is not preferable because the relative flow rate exceeds 2.5 m / sec because it exceeds the practical range.

According to a third exemplary embodiment of the present invention, there is provided a zinc-nickel alloy electroplated steel sheet manufactured by the above manufacturing method.

The zinc-nickel alloy electroplated steel sheet according to the third exemplary embodiment of the present invention is excellent in whiteness, glossiness, adhesion and surface roughness.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention and the present invention is not limited to the following examples.

EXAMPLE

Example  1 to 11

Cold rolled steel plate with a base metal, the sum of the concentrations of zinc ions and nickel ions in the plating composition = 100 g / L, the concentration ratio of Ni ions in the plating composition [Ni / (Ni + Zn)] = 0.12 (zinc ion 88 g / L, nickel ions 12 g / L, 270 g / L of chlorine ions) were added to the plating composition in which the additives as shown in Table 1 were added in the amounts shown in Table 1, respectively, at a temperature of 60 ° C., pH 4.5, and a relative flow rate of 1.5 m / sec, a current density of 80A / dm ² under the plating conditions were applied to the coating amount of 30g / m ² to prepare a specimen of Comparative Examples and Examples.

The physical properties of each specimen were evaluated and shown in Table 1 below.

The whiteness of the plating layer was measured by a color and color difference meter, and evaluated as 68 or more and less than 68 as poor.

Glossiness was measured by Erichsen's Glossmeter (Glossmeter), evaluated as 70 or more good, less than 70 as poor.

The adhesion of the plated layer was evaluated to be good and the case where the plated layer was not adhered to the tape after the specimen was bent at 120 ° and adhered to the tape to be compressed.

In addition, the surface roughness of the plating layer was good if the roughness difference between the roughness of the steel sheet after plating and the steel sheet before plating was 0.5 µm or less on the basis of Rmax.

division Additive Composition (Weight Ratio) Additive amount (ml / L) Plating quality Sodium Citrate: Saccharin Sodium Citrate: Sodium Sulfonate Sodium Citrate: Uric Acid Water: total additive Plating layer whiteness Plated Glossiness Adhesion Surface roughness Example One 1: 1.5 1: 1 1: 0.2 1: 2 0.5 Good Good Good Good 2 1: 4.0 1: 1 1: 0.2 1: 2 0.5 Good Good Good Good 3 1: 2 1: 0.5 1: 0.02 1: 2 0.5 Good Good Good Good 4 1: 2 1: 2 1: 0.02 1: 2 0.5 Good Good Good Good 5 1: 2 1: 1 1: 0.01 1: 2 0.5 Good Good Good Good 6 1: 2 1: 1 1: 0.1 1: 2 0.5 Good Good Good Good 7 1: 2 1: 1 1: 0.02 1: 1.5 0.5 Good Good Good Good 8 1: 2 1: 1 1: 0.02 1: 3 0.5 Good Good Good Good 9 1: 2 1: 1 1: 0.02 1: 2 0.1 Good Good Good Good 10 1: 2 1: 1 1: 0.02 1: 2 0.5 Good Good Good Good 11 1: 2 1: 1 1: 0.02 1: 2 4.0 Good Good Good Good

As shown in Table 1, it can be confirmed that the plating quality in the steel plate plated from the nickel-zinc alloy electroplating composition of Examples 1 to 11 including the additive within the content ratio range of the additive components of the present invention are all excellent. there was.

Example  12-19 and Comparative example  1-8

The plating amount is 30g / on a cold rolled steel sheet having a metal as shown in Table 2 below at a temperature of 60 ° C., pH 3.5, and a relative flow rate of 1.5 m / sec of the plating composition for the steel sheet and a current density of 80 A / dm ^2. Samples of Comparative Examples and Examples were prepared by applying m ² . In this case, 0.5 ml / L of the additive in Example 1 was used as the additive added in the plating composition.

The physical properties of each specimen were evaluated in the same manner as before, and the results are shown in Table 2 below.

division Composition of Plating Composition Plating quality Concentration of (Zn ^{2 +} + Ni ^{2 +} ) (g / L) Concentration ratio of Ni ^{2 +} / (Zn ^{2 +} + Ni ^{2 +} ) NH ₄ Cl (g / L) Cl ^- concentration (g / L) Whiteness Glossiness Adhesion Roughness Example 12 70 0.13 30 270 Good Good Good Good 13 140 0.13 30 270 Good Good Good Good 14 90 0.11 30 270 Good Good Good Good 15 90 0.15 30 270 Good Good Good Good 16 90 0.13 20 270 Good Good Good Good 17 90 0.13 60 270 Good Good Good Good 18 90 0.13 30 220 Good Good Good Good 19 90 0.13 30 340 Good Good Good Good Comparative example One 65 0.13 30 270 Bad Bad Bad Bad 2 145 0.13 30 270 Bad Bad Bad Bad 3 90 0.105 30 270 Bad Bad Bad Bad 4 90 0.155 30 270 Bad Bad Bad Bad 5 90 0.13 19 270 Bad Bad Bad Bad 6 90 0.13 61 270 Bad Bad Bad Bad 7 90 13 30 210 Bad Bad Bad Bad 8 90 13 30 350 Bad Bad Bad Bad

As shown in Table 2, all of the plating layers formed in Examples 12 to 19 included in the content range of the plating composition of the present invention exhibited good surface quality, adhesion, roughness, and the like, but the content range of the plating composition of the present invention Deviations of Comparative Examples 1 to 8 were all poor in surface quality, adhesion and roughness.

The zinc-nickel alloy electroplating composition according to the present invention can form a uniform electrodeposition layer, exhibit excellent plating adhesion, and minimize side reaction hydrogen generation. In addition, the electroplated steel sheet formed from the electroplating composition has excellent surface appearance and surface roughness.

Claims (9)

Zinc ions; Nickel ions; Chlorine ions; And Includes additives including saccharin, citrate, uric acid and sulfonates, The nickel ions are contained in a concentration ratio of 0.11 to 0.15 (Ni ²⁺ / (Zn ²⁺ + Ni ²⁺ )), The additive is based on 1 part by weight of citrate, saccharin 1.5 to 4 parts by weight; 0.01 to 0.1 parts by weight of uric acid; And sulfonate 0.5 to 2 parts by weight of zinc-nickel alloy electroplating composition. The method of claim 1, The zinc-nickel alloy electroplating composition is a zinc-nickel alloy electroplating composition comprising a metal ion (Zn ²⁺ + Ni ²⁺ ) of zinc and nickel in a concentration of 70 to 140g / L. The method of claim 1, The zinc-nickel alloy electroplating composition is a zinc-nickel alloy electroplating composition comprising chlorine ions at a concentration of 220 to 340g / L. The method of claim 1, The zinc-nickel alloy electroplating composition is a zinc-nickel alloy electroplating in which the chlorine ion concentration is controlled by a chlorine ion concentration regulator including at least one selected from the group consisting of potassium chloride, calcium chloride, sodium chloride and ammonium chloride. Composition. The method of claim 1, And the additive is included in the zinc-nickel alloy electroplating composition in an amount of 0.1 to 4 ml / L. delete The method of claim 1, The zinc-nickel alloy electroplating composition is a zinc-nickel alloy electroplating composition further comprises water in an amount of 1.5 to 3 parts by weight based on 1 part by weight of the additive. The zinc-nickel alloy electroplating composition according to any one of claims 1 to 5 and 7 may be prepared at a pH of 3.5 to 5, a temperature of 50 to 70 ° C, a current density of 40 to 200 A / dm ² and a plating composition for a steel sheet. A method for producing a zinc-nickel alloy electroplated steel sheet, which is plated on a steel sheet under conditions of a relative flow rate of 0.5 to 2.5 m / sec. Zinc-nickel alloy electroplated steel sheet manufactured by the manufacturing method according to claim 8.