KR100793987B1 - Electroplating solution for zinc-tungsten alloy electroplated steel sheet having an excellent corrosion resistance, the alloy electroplated steel sheet prepared by using the same, and producing method thereof - Google Patents

Abstract

The present invention relates to a plating solution for producing zinc-tungsten alloy electroplating steel sheet having excellent corrosion resistance, an alloy electroplating steel sheet prepared by using the same, and a method for manufacturing the same. Zinc chloride 100-200 g / l, sodium tungstate 0.2-5 g / l Plating solution for producing zinc-tungsten alloy electroplating steel sheet, including potassium chloride 150 ~ 400g / l, polyethylene glycol 0.1 ~ 2ml / l and citric acid 1.0 ~ 5g / l, in the alloy plating layer prepared using the plating solution The tungsten content of the metal is 0.1-5% by weight, and the zinc-tungsten alloy electroplated steel sheet, the remainder of which is composed of zinc, and using the plating solution, pH 2 ~ 5, temperature 30 ~ 70 ℃, current density 40 ~ 120A / dm ² and plating under the conditions of 0.1-5% by weight of the tungsten metal content in the alloy plating layer and the weight ratio of the excellent corrosion resistance, characterized in that to ensure that the rest is formed by a zinc zinc-tungsten alloy electroplating The production method of the steel sheet is provided.

According to the present invention, zinc-tungsten alloy plating can be deposited on the surface of a cold rolled steel sheet by electroplating, and zinc-tungsten alloy electroplating steel sheet excellent in corrosion resistance can be stably manufactured.

Electroplating, Current Density, Salt Spraying, Coating Weight, Current Efficiency

Description

Electroplating solution for zinc-tungsten alloy electroplated steel sheet having excellent corrosion resistance, alloy electroplated steel sheet manufactured by the same and a method for manufacturing the same (Electroplating solution for zinc-tungsten alloy electroplated steel sheet having an excellent corrosion resistance, the alloy electroplated steel sheet prepared by using the same, and producing method

The present invention relates to a plating solution for producing a zinc-tungsten alloy electroplating steel sheet, an alloy electroplating steel sheet prepared using the same, and a method for manufacturing the same, and more particularly, to a zinc-tungsten alloy which can be stably manufactured with excellent corrosion resistance. Electroplating solution, an alloy electrical steel sheet prepared using the same and a method for manufacturing the same.

Galvanized steel sheet has been used for a long time for home appliances and building materials as well as automotive because of its low cost and beautiful surface appearance. In addition, the standard electrode potential of zinc is -0.76V, which is electrochemically lower than that of -0.44V of iron. Therefore, when the zinc plating layer is formed on the steel sheet, it has excellent ability to protect the steel sheet due to the sacrificial method. However, when the corrosion of zinc progresses to a certain degree, the ability of the sacrificial method for the steel sheet is lost, and from this time, the steel sheet is corroded (red blue). To compensate for this, alloy electroplated steel sheets such as zinc-nickel, zinc-iron and zinc-cobalt have been developed and commercialized. Since these iron group metals are more precious metals than zinc, when the alloy is formed in the form of an intermetallic compound with zinc, the electrode potential moves in a more precious direction than zinc, thereby improving corrosion resistance. However, iron in zinc-iron alloy electroplated steel sheet is unstable in solution, so divalent iron is easily oxidized to trivalent iron, and this trivalent iron forms oxides or hydroxides in the form of sludge in the solution. And a large load on wastewater treatment. On the other hand, zinc-nickel alloy electroplated steel sheet avoids the use of nickel due to allergic reaction to human body and excellent corrosion resistance but poor plating adhesion. Zinc-cobalt alloy electroplated steel sheet has high cobalt price compared to its quality characteristics. It was not commercialized.

In addition, there are various post-treated steel sheets such as chromate, phosphate treatment or resin coating on the surface of galvanized steel sheet. However, chromate treatment is extremely harmful substance to human body. Is excellent, but the weldability is inferior and the corrosion resistance is not good because the film is electrically insulator. In addition, since the resin film is composed of organic materials, the weldability is poor, and in some circumstances, the film is destroyed by heat, and thus the original property is lost. All these processes are performed after plating, which is not preferable in terms of workability.

As a result, the development of alloy electroplated steel sheet having excellent corrosion resistance and not harmful to human body has been required.

Therefore, the present invention has been proposed to solve the above problems, the present invention by zinc and tungsten alloy electroplating in the metal state of the plating layer, zinc and tungsten are present in the plating layer to provide excellent corrosion resistance and can be stably manufactured To provide a plating solution for the production of zinc-tungsten alloy electroplated steel sheet.

In addition, an object of the present invention is to provide a zinc-tungsten alloy electroplating steel sheet prepared using the plating solution.

In addition, an object of the present invention is to provide a method for producing the zinc-tungsten alloy electroplated steel sheet.

According to the first aspect of the present invention, zinc chloride includes 100 to 200 g / l, sodium tungstate 0.2 to 5 g / l, potassium chloride 150 to 400 g / l, polyethylene glycol 0.1 to 2 ml / l and citric acid 1.0 to 5 g / l A plating solution for producing a zinc-tungsten alloy electroplated steel sheet is provided.

According to a second aspect of the present invention, a zinc-tungsten alloy electroplating steel sheet in which the metal tungsten content in the alloy plating layer manufactured using the plating solution is 0.1-5% by weight in weight ratio and the remainder is composed of zinc Is provided.

According to a third aspect of the present invention, the plating solution is used under the conditions of pH 2-5, temperature 30-70 ° C., current density 40-120 A / dm ² , and the metal tungsten content in the alloy plating layer is 0.1 by weight. Provided is a method for producing a zinc-tungsten alloy electroplated steel sheet excellent in corrosion resistance, characterized in that -5% by weight and the rest is formed of zinc.

Hereinafter, the present invention will be described in detail.

In the present invention, the cold-rolled steel sheet is used as a base metal for plating to perform plating, and plating is necessary to secure corrosion resistance. In addition, the plating formed should not be harmful to the human body.

According to the present invention, zinc-tungsten alloy plating can be deposited on the surface of the cold rolled steel sheet by electroplating, and when these alloys are present in an appropriate ratio, zinc-tungsten alloy electroplating steel sheets excellent in corrosion resistance can be stably manufactured. To this end, a zinc-tungsten alloy plated layer is required to be formed on the surface of the zinc-tungsten alloy plated steel sheet so that the metal tungsten content is 0.1-5% by weight in weight ratio and the remainder is composed of zinc.

In the present invention, the metal tungsten content of the zinc-tungsten alloy plated layer is limited to 0.1-5 wt% by weight and the rest is made of zinc. The reason why the metal tungsten content of the plating layer is limited to 0.1 to 5% by weight is that when the tungsten content is less than 0.1% by weight, there is no effect of improving the corrosion resistance.

In addition, when manufacturing a zinc-tungsten alloy plated steel sheet according to the present invention, the zinc chloride content in the plating solution is 100-200 g / l, the sodium tungstate content is 0.2-5g / l, and the potassium chloride content is 150-400g /. l, the content of polyethylene glycol is limited to 0.1 ~ 2ml / l, and the content of citric acid to 1.0 ~ 5g / l, wherein water is generally used as a solvent.

Thus, the reason for limiting the content of each component in the plating solution is as follows.

If the zinc chloride in the plating solution is less than 100g / l metal ion concentration is low, the limit current density is low, high-speed plating is impossible, if the concentration exceeds 200g / l, zinc is precipitated in the form of salt.

The reason why the concentration of sodium tungstate in the plating solution is limited to 0.2-4 g / l is because the concentration of metal tungsten in the plating layer can be secured from the lower limit of 0.1% by weight to the upper limit of 5% by weight. That is, if sodium tungstate is present in the solution at less than 0.2 g / l, the metal tungsten cannot be precipitated in the plating layer by more than 0.1% by weight. If sodium tungstate is more than 4 g / l in the plating solution, the metal tungsten content of the plating layer is 5% by weight. It is because it precipitates more than% and a plating layer becomes black and adhesiveness worsens.

In addition, the reason for limiting the supporting salt of potassium chloride to 150 ~ 400g / l is that if the potassium chloride in the plating solution is less than 150g / l, the conductivity of the solution is lowered, thereby increasing the plating voltage and thereby increasing the power ratio, thereby increasing tungsten in the plating solution. This is because the ions form complex ions to facilitate precipitation. When potassium chloride in the plating solution is more than 400 g / l, the concentration of the supporting salt increases and precipitates as a crystal, so the preferable concentration of potassium chloride is 150 to 400 g / l.

Polyethyleneglycol-based additives in the plating solution are added to make the plating layer finer and smoother. If the polyethyleneglycol-based additive is added below 0.1 ml / l, the grains of the plating layer are coarsened to form a coarse plating layer and 2.0ml / l. Since it is ineffective even if it adds exceeding, the polyethyleneglycol type additive is preferably 0.1-2.0 ml / l shown by this invention.

Citric acid in the plating solution is added to precipitate tungsten in the metal state. If the concentration of citric acid is less than 1.0g / l, tungsten cannot precipitate in the metal state. 1.0-5.0 g / l is preferable.

According to the present invention using the plating solution is carried out plating under the conditions of pH 2 ~ 5, temperature 30 ~ 70 ℃, current density 40 ~ 120A / dm ² .

The pH of the plating solution is limited to 2 to 5 because the pH of the solution is less than 2, the concentration of hydrogen ions in the solution is high, and the cathode current efficiency is lowered.

The reason for limiting the temperature of the plating solution to 30 ~ 70 ℃ is that the salt is easy to precipitate and the current efficiency is lower when the temperature of the solution is less than 30 ℃, and the solution is difficult to manage due to the large amount of evaporation of the solution above 70 ℃. Because.

Zinc from chloride bath - if reason tungsten electroplating when limiting the current density to 40 ~ 120A / dm ² is, if the current density of 40A / dm less than ^two is because the coating layer is black and rough plating layer is formed exceeds 120A / dm ^2, the limiting current This is because the current efficiency drops rapidly when the density is reached.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example  One

The cold rolled steel sheet having a thickness of 0.7mm was cut into 120x150mm, subjected to degreasing and pickling, and then plated under the following solution and plating conditions using a large electroplating apparatus in which the solution was circulated. First, sodium tungstate and citric acid were dissolved in water, and the remaining reagents were directly added to a 50-liter electroplating apparatus. After confirming that all of these reagents were dissolved, sodium tungstate and citric acid solution dissolved in advance were added. Potassium chloride as a supporting salt in the plating solution was 300 g / l, pH was 4.5, temperature 60 ° C., and the coating amount was 20 g / m ² .

The tungsten content and current efficiency of the plated layer were quantitatively analyzed using Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES), and the corrosion resistance was checked by using a salt spray tester. It measured using the system.

The solution and plating conditions were changed as follows during electroplating.

1) Zinc Chloride: 90 ~ 200g / l

2) Sodium Tungstate: 0.1 ~ 6g / l

3) citric acid: 0.8 ~ 5g / l

4) Additive: 0.08 ~ 2.0ml / l

5) Current Density: 30 ~ 130A / dm ²

Table 1 below shows the evaluation results.

division turn Plating solution Current density (A / dm ² ) Tungsten content (wt%) in film Corrosion Resistance (Red Blue Development Time) Whiteness (L *) Current efficiency (%) Zinc Chloride (g / l) Tungsten (g / l) Citric acid (g / l) Additive (ml / l) Comparative example One 120 - - - 60 - 12 85 98 2 90 0.2 One 0.07 60 0.2 42 82 69 3 120 0.1 1.2 0.15 40 0.06 17 81 94 4 120 0.5 0.8 0.15 60 2.5 20 76 95 5 120 6 4 2 60 6.6 51 58 78 6 120 4 3 1.5 130 4.5 44 75 75 7 200 3 4 0.08 120 3.8 58 55 96 8 120 3 4 2 30 2.7 55 61 97 Inventive Example One 100 0.2 One 0.1 40 0.1 48 72 92 2 100 0.2 5 2 50 0.4 51 69 92 3 120 3 2 One 100 3.9 54 70 87 4 120 0.2 One 0.1 120 0.3 50 71 85 5 150 0.5 One 0.7 60 1.6 52 76 90 6 150 1.2 4 0.2 100 2.3 56 75 88 7 150 2 One 1.5 80 4.1 55 71 90 8 200 5 5 One 40 5 60 68 95 9 200 5 5 2 120 4.8 58 70 85

As shown in Table 1, in the case of pure zinc plated steel sheet "1" of the comparative example, when the adhesion amount was 20 g / m ² , the red blue blue color began to be generated after 12 hours, and the amount of zinc chloride added was 90 g / l. In case of "2", the metal ion concentration is low, and the precipitation overvoltage increases, so the current efficiency decreases to 69%. In case of "3", the concentration of sodium tungstate in the plating solution is 0.1g / l. It can be seen that the content is low in corrosion resistance. In the case of "4" having an amount of citric acid added in the plating solution of 0.8 g / l, since the concentration of citric acid was low, tungsten ions did not form sufficient complex ions, indicating poor corrosion resistance. And when the concentration of sodium tungstate in the solution of "5" higher than 5g / l presented in the present invention is excellent in corrosion resistance, but the surface is black, it can be seen that the whiteness drops sharply. When the current density exceeds 120A / dm ² , the current efficiency decreases, and when the additive amount is less than 0.1ml / l or the current density is lower than 40A / dm ² , the surface of the plating layer also becomes black.

However, when plating under the solution and plating conditions presented in the present invention, the metal tungsten content in the film was precipitated to 0.1 to 5% by weight, which showed excellent corrosion resistance, whiteness of 68 or more, and current efficiency of 85% or more.

According to the present invention, zinc-tungsten alloy plating can be deposited on the surface of the cold rolled steel sheet by electroplating, and when these alloys are present in an appropriate ratio, zinc-tungsten alloy electroplating steel sheets excellent in corrosion resistance can be stably manufactured.

Claims (3)

Zinc-tungsten alloy electroplating steel sheet including zinc chloride 100 ~ 200g / l, sodium tungstate 0.2 ~ 5g / l, potassium chloride 150 ~ 400g / l, polyethylene glycol 0.1 ~ 2ml / l and citric acid 1.0 ~ 5g / l Plating solution for manufacture. A zinc-tungsten alloy electroplating steel sheet comprising a metal tungsten content in the alloy plating layer prepared by using the plating solution of claim 1 in a weight ratio of 0.1-5% by weight and the remainder being made of zinc. Plating is carried out under the conditions of pH 2 ~ 5, temperature 30 ~ 70 ℃, current density 40 ~ 120A / dm ² using the plating solution of claim ¹ , the metal tungsten content in the alloy plating layer is 0.1-5% by weight in weight ratio and the rest is Method for producing a zinc-tungsten alloy electroplating steel sheet excellent corrosion resistance characterized in that it is formed of zinc.