KR101136186B1 - Anti-corrosion composition for galvanized steel plateand - Google Patents

Abstract

The present invention relates to a corrosion preventing composition for galvanized steel sheet, 0.01 to 3% by weight of trivalent chromium ion; 1 to 50% by weight citric acid as a metal complexing agent for improving corrosion resistance; 0.01 to 1% by weight of at least one metal ion catalyst selected from the group consisting of nickel, celium, cobalt and molybdenum cations; 0.01 to 2.0 wt% polyethylene oxide; 0.1-10% by weight of silicate as corrosion-resistant reinforcing agent to further increase corrosion resistance; 1.6 to 3.4% by weight of a colorant so as to have excellent decoration and corrosion resistance of the plating layer surface; And to the total 100% by weight, the rest relates to a corrosion-resistant composition for galvanized steel sheet containing water.

Trivalent chromium, zinc plating, colorant.

Description

Anti-corrosion composition for galvanized steel plateand

The present invention relates to a corrosion preventing composition for galvanized steel sheet. More particularly, the present invention relates to a corrosion-resistant composition for galvanized steel sheet capable of producing a galvanized steel sheet having excellent appearance by replacing toxic hexavalent chromium with no physical property deterioration and nontoxic trivalent chromium.

Chromium has three valences: divalent, trivalent and hexavalent. Here, in general, the zinc sheet for home appliances or building materials uses a solution containing hexavalent chromium ions to improve the corrosion resistance of the surface, such hexavalent chromium has hardness, wear resistance, lubricity, release property, corrosion resistance, decorative properties It is excellent in its application to a wide range of industries, including molds, automotive parts and heavy equipment parts.

As such, hexavalent chromium forms compounds such as chromate (formula M2CrO4: M is a monovalent cation), dichromate M2Cr2O7, and the like. These compounds are yellow to red in color and generally have strong oxidation and are highly toxic.

For example, 30 mg of potassium dichromate causes mild poisoning, and the adult lethal dose is 6-8 g. Contact causes ulcers on the skin or mucous membranes, and enters the body causing disorders in the intestines, liver, and kidneys. In addition, the toxic intensity of hexavalent chromium is about 1/1000 of mercury.

Therefore, it has been pointed out that if a worker inhales chromium dust at a chromium manufacturing plant for a long time, it irritates the airways and causes nasal septum perforation, rhinitis, chest disease, etc., and causes lung cancer. In addition, the water quality standard of the water supply law is 0.05 ppm or less, and the Labor Safety and Sanitation Law is regulated to 0.1 mg or less in 1 K of air in the workplace.

That is, such hexavalent chromium has been identified as the above-mentioned hazards one after another, and regulations are being tightened, and the industrial site that emits a substance containing hexavalent chromium has begun to be recognized as an industry causing pollution. Accordingly, development of an environmentally friendly surface treatment agent that can replace hexavalent chromium, which has been used to improve the surface corrosion resistance of galvanized steel sheets applied to various industrial fields, is being started one after another.

Therefore, the present invention was created in order to solve the problems described above, by replacing the hexavalent chromium with trivalent chromium to remove the harmful to the human body, to improve the corrosion resistance, to show the appearance of excellent color and decoration It is an object to provide an excellent anti-corrosion composition for galvanized steel sheet.

In addition, the present invention can be produced at a rapid time at room temperature can be immediately applied to the galvanized steel sheet, does not require a separate heating device and cooling device, corrosion prevention composition for galvanized steel sheet can reduce the equipment and production cost There is another purpose to provide.

Corrosion preventing composition for galvanized steel sheet according to the present invention to achieve the above object is 0.01 to 3% by weight of trivalent chromium ion; 1 to 50% by weight citric acid as a metal complexing agent for improving corrosion resistance; 0.01 to 1% by weight of at least one metal ion catalyst selected from the group consisting of nickel, celium, cobalt and molybdenum cations; 0.01 to 2.0 wt% polyethylene oxide; 0.1-10% by weight of silicate as corrosion-resistant reinforcing agent to further increase corrosion resistance; 1.6 to 3.4% by weight of a colorant so as to have excellent decoration and corrosion resistance of the plating layer surface; And the remainder comprises water relative to the total 100% by weight.

Here, the pH in the composition is preferably 1.5 to 2.8. In addition, it is preferable to add 0.01 to 2.0% by weight of an organic acid as at least one pH buffer selected from the group consisting of gluconic acid, acetic acid and formic acid to adjust the pH in the composition, wherein the organic acid is trivalent in the total composition. It is characterized in that it comprises 0.5 to 2.5 moles per mole of chromium ion. On the other hand, the molecular weight of the polyethylene glycol is characterized in that 100000 to 1000000.

On the other hand, the anti-corrosion composition for galvanized steel sheet is preferably treated on the surface of the galvanized steel sheet for 0.5 minutes to 3.0 minutes at a temperature of room temperature to form a 0.5 ㎛ coating on the surface of the steel sheet.

Further, the colorant is characterized in that at least one compound selected from the group consisting of sodium hydroxide, nitric acid and sodium nitrate, sodium carbonate. Here, it is preferable that the surface of the plating layer by the colorant has any one color of brown, black, and iridescent color.

With such a colorant, any one of colorants consisting of sodium hydroxide and nitric acid is selected for the entire anti-corrosion composition for galvanized steel sheet such that the surface of the plating layer is black, and 1.6 wt% or more of sodium hydroxide and 1.9 wt% of nitric acid in the selected colorant. It is characterized by any one added above.

In addition, any one of colorants consisting of sodium hydroxide and nitric acid is selected for the entire anti-corrosion composition for galvanized steel sheet by the colorant so that the surface of the plating layer is brown, and sodium hydroxide is less than 1.6% by weight in the selected colorant, 1.9 nitric acid. Less than one percent by weight is added.

On the other hand, it is preferable to add 2.0% by weight of sodium carbonate selected from the colorants to the entire corrosion-protective composition for galvanized steel sheet so that the surface of the plating layer by the colorant has a rainbow color.

The present invention is to replace the hexavalent chromium with trivalent chromium to remove the harmful to the human body, to improve the corrosion resistance, to show the appearance of excellent color has excellent decorative effect, can be manufactured at room temperature fast zinc Immediately applicable to the coated steel sheet, there is no need for a separate heating device and cooling device, there is an advantage that can reduce the equipment and production costs.

An embodiment of the anti-corrosion composition for galvanized steel sheet according to the present invention as described above will be described in detail.

The anti-corrosion composition for galvanized steel sheet according to the present invention includes trivalent chromium ion, metal complexing agent, metal ion catalyst, polyethylene oxide, silicate, pH buffer, colorant and water.

The trivalent chromium ion is used as a salt form of chromium nitrate or chromium chloride. It is also possible to reduce hexavalent chromium and use it. Examples of the hexavalent chromium that can be used after reduction to trivalent chromium include conventional hexavalent chromium compounds such as chromic anhydride, sodium dichromate, potassium dichromate and ammonium dichromate. In this case, chromium nitrate, chromium chloride, or the like may be used alone or in combination of two or more thereof. Here, the trivalent chromium ion in the total composition is preferably included in the range of 0.1% to 3.0% by weight.

That is, when the trivalent chromium ion is less than 0.1% by weight, the chromium thickness is significantly thinner, and the corrosion resistance to external foreign matters is drastically reduced. In addition, when the trivalent chromium ion exceeds 3.0% by weight, the chromium thickness becomes considerably thick, which is excellent in corrosion resistance, but a large amount of expensive chromium ions are lost, thereby reducing economic efficiency. Preferably, trivalent chromium ion is preferably included in the total composition of 0.4 to 1.4% by weight.

The metal complexing agent is to extend the service life by increasing the durability and corrosion resistance, citric acid is preferably used. Here, the citric acid is less than 1.0% by weight of the total composition significantly lowers the corrosion resistance, while if it exceeds 50.0% by weight is economical and the stability of the solution is lowered to produce a precipitate. Therefore, the content of citric acid is included in 1.0% by weight to 50.0% by weight. Preferably from 10 to 30% by weight. In addition, the citric acid is contained 0.5 to 2.5 moles with respect to 1 mole of trivalent chromium ion in the total composition.

The metal ion catalyst is used to promote the reaction, and contains 0.01 wt% to 1.0 wt%. Here, as the metal ion catalyst, nickel, celium, cobalt, molybdenum, or the like is used, and is added as salts such as nitric acid, sulfuric acid, phosphoric acid, chlorine, and the like.

In order to infiltrate the anti-corrosion composition for zinc plating according to the present invention uniformly and smoothly to the surface of zinc or zinc alloy plating, 0.01 wt% to 2.0 wt% of polyethylene oxide is added. Here, the polyethylene oxide (PEO) is used that has a molecular weight of 100000 to 1000000. When the content of the polyethylene oxide is less than 0.01% by weight, it is not possible to form a uniform plating layer on the surface of the zinc alloy plating. When the content of the polyethylene oxide exceeds 2.0% by weight, the stability of the liquid is lowered. Therefore, preferably 0.05 to 1.5% by weight is included in the total composition.

The silicate (silicate) is an anticorrosion enhancer for enhancing corrosion resistance, and adds 0.1 wt% to 10.0 wt%. Here, the silicate is a compound of a neutral salt in which hydrogen of various silicic acids is substituted with a metal atom, and is a compound containing an anion in which one or more silicon center atoms are surrounded by a negatively charged ligand. Therefore, the silicate can further improve the corrosion resistance of the corrosion preventing composition for galvanized steel sheet.

Gluconic acid, acetic acid, formic acid are used as the pH buffer. The pH of the anti-corrosion composition for galvanized steel sheet is preferably maintained at 1.5 to 2.8. When the pH is less than 1.5, dissolution of the zinc and zinc alloy plating layers is accelerated, and it is difficult to form a smooth chromate layer. When the pH exceeds 2.8, corrosion resistance is poor. The pH is adjusted by lowering using inorganic acids such as nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, or by using caustic soda solution, ammonia water, sodium carbonate, sodium bicarbonate and the like.

The colorant is added to represent the color of the chromate layer formed on the surface of the galvanized steel sheet in brown, black, iridescent color, and the like. Here, the colorant is added 1.6 to 3.4% by weight. The coloring agent is used sodium hydroxide, nitric acid and sodium nitrate, sodium carbonate and the like.

Here, in order to make the surface of the plating layer black by using the coloring agent, one of sodium hydroxide or nitric acid is selected for the entire corrosion preventing composition for galvanized steel sheet. In order to make the plating layer surface black in each colorant, when the sodium hydroxide 1.6 weight or more is added, it shows black. On the other hand, when nitric acid is selected and added, 1.9% by weight or more of nitric acid is added to give black color.

When the surface of the plating layer is brown using the colorant, one of colorants including sodium hydroxide and nitric acid is selected, and sodium hydroxide in the selected colorant is less than 1.6 wt% and less than 1.9 wt% of nitric acid. When added, the surface of the brown plating layer is shown.

Furthermore, in order to make the surface of the plating layer appear rainbow color by using the colorant, when 2.0 wt% of sodium carbonate selected from the colorants is added, the surface of the plating layer of rainbow color can be obtained, and thus, the required color clip can be variously modified.

On the other hand, in order to ensure that the anti-corrosion composition for galvanized steel sheet containing trivalent chromium ion has the same quality as hexavalent chromium, the anti-corrosion composition for galvanized steel sheet is used at room temperature. Therefore, it is possible to obtain a chromate film at room temperature without special setting of the temperature range, and to reduce the process of the chromate film obtained only through the conventional heating process, which can shorten the production time, reduce the cost, and require a variety of colors. Production is possible according to

Here, when the anti-corrosion composition for galvanized steel sheet according to the present invention is used under the temperature condition of room temperature to obtain a chromate coating, it is difficult to obtain a chromate coating having excellent liquidity and excellent uniformity, durability and corrosion resistance while exceeding room temperature. When the heating is performed as in the prior art, the dissolution of the zinc layer is intensified, resulting in a defect of the chromate coating layer. Therefore, it is preferably used in a temperature range of room temperature to a maximum heating temperature of 40 ° C. In addition, the composition may vary depending on the temperature, concentration, etc. of the liquid, but is preferably treated for about 0.5 to 3.0 minutes to form a film of 0.5 ㎛.

Hereinafter, the present invention will be described in more detail with reference to the following examples. Here, the present invention is not limited by the embodiments.

Example 1

It was prepared by installing a stirrer in a 1 L flask. Then, 40.0 g of chromium nitrate was added to the 1 L flask. Subsequently, 10.0 g of citric acid, a metal complexing agent, was added, followed by 1.0 g of metal ion catalyst nickel, 1.0 g of polyethylene oxide (PEO; molecular weight 100000), 1.0 g of silicate, and 20.0 g of sodium hydroxide, 20.0 g of nitric acid, and sodium carbonate. 1.0 g was added and distilled water was added until the total solution became 1 L, and diluted for about 30 minutes to 1 hour to complete a corrosion preventing composition for galvanized steel sheet.

[Example 2]

It was prepared by installing a stirrer in a 1 L flask. Then, 30.0 g of chromium nitrate was added to the 1 L flask. Then, 1.0 g of nickel, a metal ion catalyst, 1.0 g of polyethylene oxide (PEO; molecular weight 100000), 1.0 g of silicate, and 40.0 g of sodium hydroxide, 30.0 g of nitric acid, and 1.0 g of sodium carbonate were added to distilled water. It was added until the dilution for about 30 minutes ~ 1 hour to complete the anti-corrosion composition for galvanized steel sheet.

Here, it can be seen that the corrosion preventive composition for galvanized steel sheet of Example 1 and Example 2 was black when applied to the steel sheet surface.

Example 3

It was prepared by installing a stirrer in a 1 L flask. Then, 20.0 g of chromium chloride was added to the 1 L flask. Subsequently, 10.0 g of citric acid, a metal complexing agent, was added, followed by 1.0 g of nickel as a metal ion catalyst, 1.0 g of polyethylene oxide (PEO; molecular weight 100000), 1.0 g of silicate, 0.5 g of acetic acid as a pH buffer and 10.0 of sodium hydroxide as a coloring agent. g, 20.0 g of nitric acid and 1.0 g of sodium carbonate were added, distilled water was added until the total liquid became 1 L, and diluted for about 30 minutes to 1 hour to complete a corrosion preventing composition for galvanized steel sheet.

Example 4

It was prepared by installing a stirrer in a 1 L flask. Then, 30.0 g of chromium chloride was added to the 1 L flask. Then, 1.0 g of nickel, a metal ion catalyst, 1.0 g of polyethylene oxide (PEO; molecular weight 100000), 1.0 g of silicate, and 10.0 g of sodium hydroxide, 30.0 g of nitric acid, and 1.0 g of sodium carbonate were added to distilled water. It was added until the dilution for about 30 minutes ~ 1 hour to complete the anti-corrosion composition for galvanized steel sheet.

Here, it can be seen that the corrosion preventive composition for galvanized steel sheets of Examples 3 and 4 is brown when applied to the steel sheet surface.

[Example 5]

It was prepared by installing a stirrer in a 1 L flask. Then, 40.0 g of chromium nitrate was added to the 1 L flask. Subsequently, 10.0 g of citric acid, a metal complexing agent, was added, followed by 1.0 g of nickel as a metal ion catalyst, 1.0 g of polyethylene oxide (PEO; molecular weight 100000), 1.0 g of silicate, and 10.0 g of sodium hydroxide, 10.0 g of nitric acid, and sodium carbonate. 1.0 g was added and distilled water was added until the total solution became 1 L, and diluted for about 30 minutes to 1 hour to complete a corrosion preventing composition for galvanized steel sheet.

Here, it can be seen that the anti-corrosion composition for galvanized steel sheet of Example 5, when applied to the surface of the steel sheet, shows a rainbow color.

Comparative Example 1

It was prepared by installing a stirrer in a 1 L flask. Then, 30.0 g of chromium nitrate was added to the 1 L flask. Then, 10.0 g of citric acid, which is a metal complexing agent, was added, 100 g of distilled water was added thereto, and gradually heated to 80 ° C., followed by stirring for 2 hours. Thereafter, after cooling to 60 ° C, 1.0 g of a metal ion catalyst was added thereto, distilled water was added until the total solution became 1 L, and diluted for about 2 hours to complete a corrosion preventing composition for galvanized steel sheet.

Comparative Example 2

It was prepared by installing a stirrer in a 1 L flask. Then, 30.0 g of chromium chloride was added to the 1 L flask. Then, 10.0 g of citric acid, which is a metal complexing agent, was added, 100 g of distilled water was added thereto, and gradually heated to 80 ° C., followed by stirring for 2 hours. Thereafter, after cooling to 60 ° C, 1.0 g of a metal ion catalyst was added thereto, distilled water was added until the total solution became 1 L, and diluted for about 2 hours to complete a corrosion preventing composition for galvanized steel sheet.

Here, it can be seen that the anti-corrosion composition for galvanized steel sheet of Comparative Example 1 and Comparative Example 2 was light brown when applied to the steel sheet surface.

[Experimental Example]

In order to evaluate the performance of the anti-corrosion composition for galvanized steel sheet prepared by Examples 1 to 5 and Comparative Examples 1 and 2, respectively, the polished iron plate polished on one surface was 40 at a working temperature of 1.0 A / dm 2 at room temperature. A cyan plated galvanized steel sheet plated with minutes was used. Here, the unit is g.

The cyan plated galvanized steel sheet was plated, washed with water, activated with a 0.5% -HNO3 solution, washed with water, and then chromated by using a corrosion-preventing composition for galvanized steel sheets according to Examples and Comparative Examples. Here, the pH of the anti-corrosion composition for galvanized steel sheet was adjusted in Example 3 and Comparative Example 2 by acetic acid, the remaining Examples 1, 2, 5 and Comparative Example 1 was adjusted through a metal complexing agent was not added separately. .

The chromate-treated galvanized steel sheets of Examples 1, 2, 3, 4, 5 and Comparative Examples 1 and 2 were subjected to appearance evaluation and corrosion resistance evaluation. Good condition without stains or cracks, the color of the colorant is somewhat poor, and a slight stain appears on the surface. Put it.

The corrosion resistance was evaluated through the Salt Spray Tester (SST) test method according to KS D 9502. At this time, the compressed air pressure for spraying brine by the SST test method was 1.0 kgf / cm 2 and the spray amount was 1.5 ml / 80. Cm 2 · hr. The specific evaluation was made by measuring the time when 5% of white blue occurred on the surface. The evaluation results are shown in Table 2 below.

As shown in the experimental example after the appearance evaluation and corrosion resistance evaluation through the above examples and comparative examples, the galvanized steel sheet corrosion prevention composition according to the present invention is environmentally friendly to replace the conventional hexavalent chromium ion It is possible to implement a variety of colors, such as black, brown, rainbow colors, excellent decorative appearance.

In particular, as described above, the anti-corrosion composition for galvanized steel sheet according to the present invention can be used at a minimum time by stirring dilution at room temperature, there is no need for heating and cooling process in the conventional anti-corrosion composition for galvanized steel sheet There is no need to provide a separate heating and cooling device, thereby reducing the cost of the production equipment. In addition, since it is possible to quickly produce and use at room temperature, it is easy to carry out, and through this, it is obvious that the manufacturing cost and the consumer price can be reduced.

On the other hand, in the detailed description of the present invention has been described with respect to specific embodiments, to those skilled in the art that various modifications are possible without departing from the scope of the invention, such modifications are claimed It is in the range of a base material.

Claims (11)

0.1 to 3 weight percent of trivalent chromium ion; 1 to 50% by weight citric acid as a metal complexing agent for improving corrosion resistance; 0.01 to 1% by weight of at least one metal ion catalyst selected from the group consisting of nickel, celium, cobalt and molybdenum cations; 0.01 to 2.0 wt% polyethylene oxide; 0.1-10% by weight of silicate as corrosion-resistant reinforcing agent to further increase corrosion resistance; 1.6 to 3.4% by weight of a colorant so as to have excellent decoration and corrosion resistance of the plating layer surface; And an anticorrosion composition for galvanized steel sheet containing water with respect to a total of 100% by weight, wherein the pH in the composition is 1.5 to 2.8 and is selected from the group consisting of gluconic acid, acetic acid and formic acid to adjust the pH in the composition. 0.01 to 2.0% by weight of an organic acid as at least one pH buffer is added, wherein the citric acid is contained 0.5 to 2.5 moles based on 1 mole of trivalent chromium ion in the total composition, and the molecular weight of the polyethylene oxide is 100000 to 1000000, The anti-corrosion composition for galvanized steel sheet is treated on the surface of the galvanized steel sheet at room temperature for 0.5 minutes to 3.0 minutes to form a 0.5 μm coating on the surface of the steel sheet. The colorant is at least one compound selected from the group consisting of sodium hydroxide, nitric acid, sodium nitrate and sodium carbonate, the surface of the plating layer by the colorant has a color of any one of brown, black, iridescent color, the colorant By selecting any one of the coloring agent consisting of sodium hydroxide and nitric acid to the entire anti-corrosion composition for galvanized steel sheet so that the surface of the plating layer is black, any one of 1.6% by weight or more of sodium hydroxide, 1.9% by weight or more of nitric acid in the selected colorant. Is added, and one of the colorants consisting of sodium hydroxide and nitric acid is selected for the entire anti-corrosion composition for galvanized steel sheet so that the surface of the plating layer is brown by the colorant, and the sodium hydroxide in the selected colorant is less than 1.6% by weight, Any one less than 1.9 wt% nitric acid It added and the galvanized steel sheet corrosion-resistant composition characterized in that the surface of the plating layer is added to the sodium carbonate 2.0% by weight of the selected colorant for the entire galvanized steel sheet corrosion inhibiting compositions to exhibit rainbow colors by the color agent. delete delete delete delete delete delete delete delete delete delete