KR102350114B1 - Eco-friendly aluminum electrolytic chromate treatment method - Google Patents

Abstract

The present invention relates to an eco-friendly aluminum electrolytic chromate treatment method. In the eco-friendly aluminum electrolytic chromate treatment method according to the present invention, after removing oil and fat from a surface of aluminum or aluminum alloy by electrolytic degreasing, the aluminum or aluminum alloy is immersed into an electrolyte, is attached on an anode, and is chromate treated. The eco-friendly aluminum electrolytic chromate treatment method according to the present invention followed by the configuration performs electrolyte chromate treatment on the surface of an aluminum product, which requires conductivity, high corrosion resistance, and high paint adhesion, to produce the eco-friendly aluminum product that has improved corrosion resistance and is harmless to air and water environments.

Description

Eco-friendly aluminum electrolytic chromate treatment method {ECO-FRIENDLY ALUMINUM ELECTROLYTIC CHROMATE TREATMENT METHOD}

The present invention relates to an environmentally friendly aluminum electrolytic chromate treatment method, and more particularly, by performing electrolytic chromate treatment on the surface of an aluminum product that requires electricity and requires high corrosion resistance and paint adhesion, it is harmless to the air and water environment and has corrosion resistance. It relates to an eco-friendly aluminum electrolytic chromate treatment method capable of producing an improved eco-friendly aluminum product.

In general, metals such as aluminum alloys, titanium alloys, and magnesium alloys naturally form thin oxide films with high corrosion resistance due to their high reactivity with air in the atmosphere, but naturally formed oxide films have limitations in uniformity and corrosion resistance. Anodizing surface treatment method is widely used to artificially form an oxide film with uniformity and higher corrosion resistance.

Such anodizing is a compound word of anode and oxidation, and it is possible to prevent rusting by the anodizing process and improve appearance, abrasion resistance, heat resistance, and adhesion. In the anodizing surface treatment method, It protects the inside of the metal by artificially making an oxide film on the surface of a metal such as an aluminum alloy, a titanium alloy, a magnesium alloy, etc.

The device used for such anodizing surface treatment immerses the metal, which is the surface treatment object, in an electrolyte solution mainly containing sulfuric acid or sodium hydroxide, and the electrolyte becomes the cathode side and the surface treatment target metal becomes the anode side when direct current flows through the surface An oxide film is formed on the surface of the metal to be treated.

On the other hand, chromate on aluminum is a method of chemically treating the surface of an aluminum alloy to form a thin film on the surface. Contrary to the insulation of anodizing, it is a work method that requires electricity.

At the same time, the surface of aluminum (Al) products, which increases hardness and wear resistance, is ionized, and ^{Cr 3+ ions of Al 3+} and Cr 3+ ions made from chromates including Cr (chromium) are replaced with each other to form a film ^{of Cr 3+ on aluminum products.}

_{Aluminum chromate is generally composed of CrOHCrO 4} , Cr(OH) ₃ , MgCrO ₄ etc. formed on the surface by the following reactions.

① Na ₂ Cr ₂ O ₇ = 2Na ⁺ + Cr ₂ O ₇ ^2-

② Cr ₂ O ₇ ^2- + 14H ⁺ + 6e = 2Cr ³⁺ + 7H ₂ O

③ Cr ₂ O ₇ ^2- + 2Cr ³⁺ + 3H ₂ O = 2CrOHCrO ₄ + 4H ⁺

④ Al + 2H ₂ O = Al ³⁺ + 2OH ^- + H ₂

⑤ 2Cr ³⁺ + 6OH ^- = 2Cr(OH) ₃

⑥ Cr ₂ O ₇ ^2- + 2OH ^- = 2CrO ₄ ^2- + H ₂ O

⑦ Al ³⁺ + CrO ₄ ^2- = Al ₂ (CrO ₄ ) ₃

_{The hexavalent Cr 2} O ₇ ^2- ion formed by dissociation of Na ₂ Cr ₂ O ₇ in ① acts as an oxidizing agent and can be reduced to the ^{trivalent Cr 3+ ion as in the reaction formula ②.} When trivalent and hexavalent chromium ions are present in the solution, CrOHCrO ₄ , a chromic acid composite film, is formed on the aluminum surface as shown in Reaction Equation ④.

On the other hand, when aluminum is dissolved, OH ^- ions are formed as in Reaction Equation ④, and the pH of the surface increases. At this time, the generated OH ^- _{ions form Cr(OH) 3} according to Reaction Equation ⑤ _{or Al 2} (CrO ₄ ) ₃ according to Reaction Equations ⑥ and ⑦. The surface film formed as described above, such as CrOHCrO ₄ , Cr(OH) ₃ , Al ₂ (CrO ₄ ) _{3 ,} etc. not only improves corrosion resistance, but also provides various functionalities such as increase in coating adhesion and improvement of mechanical properties to the surface. .

However, unlike anodizing, chromate on aluminum has significantly lower corrosion resistance and lowering adhesion to paint.

The corrosion resistance of the anodizing and chromate is compared as follows.

Corrosion resistance comparison anodizing (1000hr ~ 7000hr) chromate (72hr)

In addition, chromate is a strong acid and strong alkali component, such as sulfuric acid, caustic soda, nitric acid, hydrofluoric acid, which are used in the pretreatment process, there is a problem of using substances that cause damage to the environment as well as the human body.

In addition, chromate is widely used in communication equipment systems or electronic products for the purpose of energization, and due to the nature of the product, there is a risk of corrosion when installed outdoors (seaside, etc.) to be.

Domestic Patent Publication No. 10-1998-065637 (published on October 15, 1998) Domestic Registered Patent No. 10-0627380 (Registered on September 15, 2006) Domestic Registered Patent No. 10-0838445 (registered on June 09, 2008)

The present invention is an eco-friendly aluminum electrolytic chromate treatment method that can produce eco-friendly aluminum products with improved corrosion resistance and harmless to the air and water environment by performing electrolytic chromate treatment on the surface of aluminum products that require electricity and high corrosion resistance and paint adhesion is to provide

In addition, the present invention can secure superior corrosion resistance compared to existing chromate products, exhibit the same electrical characteristics, and is harmless to the human body and the environment, and is an eco-friendly environment that can be applied in various ways such as repeaters, communication equipment, or electronic devices installed in poor outdoor environments To provide an aluminum electrolytic chromate treatment method.

Various problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

The environmentally friendly aluminum electrolytic chromate treatment method according to the present invention is an electrolytic chromate treatment method, after removing the oil and fat from the surface of aluminum or aluminum alloy by electrolytic degreasing, the aluminum or aluminum alloy is immersed in an electrolyte solution to attach it to the anode and chromate treatment proceed with

The chromate treatment is a step of dissolving 20% (w/w) of citric acid, an electrolyte, and 10% ( ^w / _w ) of oxalic acid, which is an electrolyte, in pure water, adding a ^{Cr 3+ agent to the electrolyte solution} , and attaching the object to be plated to the positive electrode (+ electrode) to apply a current.

For the chromate treatment, 1/2 of pure water is filled in a PVC or PP-based plating tank, and 20% (w/w) of citric acid (w/w) and 10% ( ^w / _w ) of oxalic acid, which are electrolytes, are 1: After mixing with water in a weight ratio of 1, stirring while heating to a temperature of 60 to 70 ° C. After complete dissolution, put in a plating bath filled with 1/2 pure water, and the rest is filled again with pure water, then Cr ³⁺ agent 5% (w/w) is added and stirred, the chromate treatment time is performed for 7 to 15 minutes, the electrolyte temperature is 20 to 25° C., and a voltage may be applied to 10V to proceed.

Specific details of other embodiments are included in the detailed description.

Eco-friendly aluminum electrolytic chromate treatment method according to the present invention requires electricity and electrolytic chromate treatment on the surface of an aluminum product that requires high corrosion resistance and paint adhesion to produce eco-friendly aluminum products with improved corrosion resistance and harmless to air and water environment can

In addition, the eco-friendly aluminum electrolytic chromate treatment method according to the present invention can secure superior corrosion resistance compared to existing chromate products, exhibit the same electrical properties, and is harmless to the human body and the environment, heavy machinery or communication equipment installed in poor outdoor environments or It can be applied to various electronic devices, etc.

It will be fully understood that embodiments of the technical idea of the present invention may provide various effects not specifically mentioned.

1 is a view schematically showing an apparatus for generating trivalent chromate in an environmentally friendly aluminum electrolytic chromate treatment method according to the present invention.

Advantages and features of the present invention, and methods for achieving them, will become apparent with reference to the embodiments described below in detail. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed subject matter may be thorough and complete, and that the spirit of the present invention may be sufficiently conveyed to those skilled in the art.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of the environmentally friendly aluminum electrolytic chromate treatment method according to the present invention will be described in detail.

1 is a view schematically showing an apparatus for generating trivalent chromate in an environmentally friendly aluminum electrolytic chromate treatment method according to the present invention.

In the eco-friendly aluminum electrolytic chromate treatment method according to the present invention, the overall process diagram may be composed of an acid degreasing process, a first water washing process, an electrolytic degreasing process, a second water washing process, an electrolytic chromate process, a third water washing process, a drying process, and a packaging process. have.

Since the overall process diagram including the aluminum electrolytic chromate process is a known technique, only the electrolytic chromate process according to the present invention will be specifically described for convenience of explanation and clarity of the technical idea of the present invention.

Referring to Figure 1, the configuration of the device for generating trivalent chromate in the environmentally friendly aluminum electrolytic chromate treatment method according to the present invention is as follows.

Material of each plating bath: PVC or PP material

Acid degreasing process - air blower

Washbasin - air blower, pure water supply

Electrolytic degreasing process - blower (air blower), cathode (substrate), anode (lead plate or aluminum plate) device, rectifier 15V/1000A

Electrolytic chromate process - blower (air blower), anode (substrate to be plated), cathode (lead plate or aluminum plate) device, rectifier 15V/2000A, cooling device 20Hp

chemical reaction

(+)pole ; Anode reaction in the treatment solution

Al → Al ³⁺ + 3e ^- , 2H ⁺ + 2e ^- → H ₂ ↑

(-)pole; Surface reaction in treatment solution (cathode reaction)

2Cr ³⁺ + 6OH ^- → 2Cr(OH) ₃ ↑

The dry bath and working method of electrolytic chromate in the environmentally friendly aluminum electrolytic chromate treatment method according to the present invention are as follows.

In the environmentally friendly aluminum electrolytic chromate treatment method according to the present invention, after removing oil and fat from the surface of aluminum or aluminum alloy by electrolytic degreasing, the aluminum or aluminum alloy is immersed in an electrolyte to attach to the anode, and chromate treatment can be performed.

The chromate treatment comprises the steps of dissolving 20% (w/w) of citric acid, an electrolyte, and 10% ( ^w / _w ) of oxalic acid, as an electrolyte, in pure water, and adding a ^{Cr 3+ agent to the electrolyte.} and applying a current by attaching the object to be plated to the positive electrode (+ electrode).

Specifically, in the environmentally friendly aluminum electrolytic chromate treatment method according to the present invention, 1/2 of pure water is filled in a PVC or PP-based plating tank, and 20% (w/w) of citric acid (w/w) and 10% of oxalic acid, which are electrolytes ( ^w / _w ) is mixed with water in a weight ratio of 1:1 and stirred while heating to a temperature of 60 to 70 ° C. After complete dissolution, put in a plating bath filled with 1/2 of pure water, and the rest is converted back to pure water fill up

Next, while working with an air blower, Cr ³⁺ 5% (w/w) is added and stirred so as to be uniformly mixed.

The chromate time is performed for 7 to 15 minutes, the electrolyte temperature is 20 to 25 °C, and the voltage may be applied to 10V.

Hereinafter, a preferred embodiment of the environmentally friendly aluminum electrolytic chromate treatment method according to the present invention will be described in more detail.

< Example 1 >

12 aluminum die-casting products (ALDC12) for repeater filter, a communication equipment, in an ^{aqueous solution of 20% (w/w) citric acid and 10% (w} / _w ) oxalic acid at a liquid temperature of 25℃, 10V AC current Electrolytic chromate treatment with a furnace for 7 minutes to form a film with a film thickness of 1㎛.

As a result, corrosion resistance of more than 240 hours in the salt spray test and excellent durability were exhibited even in natural conditions of more than 60 days, and there was no problem in electrical characteristics (energization).

< Example 2 >

In the same aluminum die-casting 12 products as in Example 1, in an aqueous solution of 20% (w/w) citric acid and 10% ( ^w / _w ) oxalic acid at a solution temperature of 25°C, 10V AC current for 15 minutes During the electrolytic chromate treatment, a film with a film thickness of 2 μm was formed.

As a result, the salt spray test showed corrosion resistance for more than 480 hours and excellent durability even when left in the natural state for more than 90 days, and there was no problem in electrical characteristics (electricity).

< Example 3 >

Electrolytic chromate treatment of aluminum 5052 plate for electric vehicle battery cell in citric acid 20%(w/w) and oxalic acid 10%( ^w / _w ) aqueous solution at 25℃, 10V AC current for 7 minutes Thus, a film was formed with a film thickness of 2 μm.

As a result, the salt spray test showed corrosion resistance for more than 480 hours and excellent durability even when left in the natural state for more than 90 days, and there was no problem in electrical characteristics (electricity).

< Example 4 >

The same aluminum 5052 material as in Example 3 was prepared in an aqueous solution of 20% citric acid (w/w) and 10% oxalic acid ( ^w / _w ) at a solution temperature of 25° C. and 10V alternating current for 15 minutes. Electrolytic chromate treatment was performed to form a film with a film thickness of 3 μm.

As a result, corrosion resistance of more than 1000 hours in salt spray test and excellent durability even in natural conditions of more than 120 days were shown, and there was no problem in electrical characteristics (energization).

In the above, a preferred embodiment of the present invention has been described, but those of ordinary skill in the art to which the present invention pertains will understand that the present invention may be embodied in other specific forms without changing the technical spirit or essential features thereof. will be able Therefore, it should be understood that the embodiment described above is illustrative in all respects and not restrictive.

Claims (3)

In the electrolytic chromate treatment method,
After removing the oil and fat from the surface of aluminum or aluminum alloy by electrolytic degreasing, the aluminum or aluminum alloy is immersed in an electrolyte to attach to the anode, and chromate treatment is performed,
The chromate treatment is a step of dissolving 20% (w/w) of citric acid (w/w) and 10% ( ^w / _w ) of oxalic acid as an electrolyte in pure water, adding a ^{Cr 3+ agent to the electrolyte solution} , and attaching the object to be plated to the positive electrode (+ electrode) to apply a current,
In the chromate treatment, 1/2 of pure water is filled in a PVC or PP-based plating tank, and 20% (w/w) of citric acid (w/w) and 10% ( ^w / _w ) of oxalic acid, which are electrolytes, are 1: After mixing with water in a weight ratio of 1, stirring while heating to a temperature of 60 to 70 ° C. After complete dissolution, put in a plating bath filled with 1/2 pure water, and the rest is filled again with pure water, and then Cr ³⁺ agent Eco-friendly aluminum electrolytic chromate, characterized in that 5% (w/w) is added and stirred, the chromate treatment time is 7 to 15 minutes, the electrolyte temperature is 20 to 25°C, and the voltage is applied at 10V processing method. delete delete

Images