JPH0524234B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fin member for a heat exchanger used in automobiles, air conditioners, etc.

[Conventional technology]

Copper or copper alloy with a thickness of 30 to 50 μm is used for the fin members of automobile cooling water heat exchangers,
Those with improved strength, heat resistance, etc. are used by adding small amounts of tin, silver, cadmium, etc. within a range that does not reduce thermal conductivity.

In cold regions, the influence of antifreeze sprayed on roads and sea salt in areas near the coast causes significant corrosion not only on the car body but also on the radiator fin material. In order to prevent corrosion of the radiator fins, a coating of a rust preventive agent such as benzotriazole is sometimes formed on the fins. However, with conventional rust preventive agents, the coating was destroyed by the heat generated when the fin material was soldered to the tube material, so that it was not possible to obtain a sufficient effect as a rust preventive coating. It has also been proposed to form a rust-preventing film by applying salts of 2-undecylimidazole and its derivatives at a temperature of 0 to 100°C, but this has not resulted in a sufficient rust-preventing effect.

[Problem to be solved by the invention]

The present invention has developed a member for heat exchanger fins that has a rust-preventing coating that has better corrosion resistance than conventional products and will not be destroyed even by heat at 300-350°C for 1-5 minutes during soldering. This is an attempt to solve the above problems.

[Means to solve the problem]

Means for solving the problems according to the present invention is to apply a mixed solution of alkylimidazole, inorganic acid, water, and organic solvent to the surface of a fin member of a heat exchanger made of copper or copper alloy, and to apply this solution. The purpose of this method is to form a rust-preventive coating by heat-treating the applied copper or copper alloy at a temperature of 200 to 280°C for 20 seconds to 5 minutes.

As the alkylimidazole, it is preferable to use an alkyl group having a long chain alkyl group such as a decyl group, an undecyl group, or a dodecyl group. or,
As the inorganic acid used, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc. can be used. As the solvent, an organic solvent and water are used, and the ratio thereof is preferably around 1:1 by weight. Organic solvents include methanol, ethanol, propanol, acetone, benzene,
Toluene, trichloroethylene, carbon tetrachloride, etc. can be used. The application method is immersion at room temperature,
This can be done by spraying, brushing, etc.

[Effect]

Alkylimidazoles are soluble in organic solvents at room temperature, but almost insoluble in water. However, it ionizes and dissolves in acid solutions. Ionized alkylimidazole exhibits strong chemical reactivity with copper, forming a complex with copper and creating a monomolecular film on the copper surface. The inorganic acid and water activate the surface of the copper or copper alloy, and at the same time, the alkylimidazole participates in forming a complex with the copper as described above. Alkylimidazole dissolved in an organic solvent is bonded to this monomolecular film one after another by physical adsorption by long-chain alkyl groups, and the film grows due to hydrogen bonding between imidazoles. However, as it stands, it does not have sufficient strength as a corrosion-resistant coating. This is made into a durable film by subjecting it to a heat treatment held at 200 to 280°C for 20 seconds to 5 minutes. If it is less than 200°C, it is insufficient, and if it exceeds 280°C, the corrosion resistance will decrease due to deterioration of the film itself. If the holding time at this temperature is less than 20 seconds, it is insufficient; if it exceeds 5 minutes, the corrosion resistance will deteriorate due to the deterioration of the film. This heat treatment allows it to withstand soldering at 300 to 350°C for 1 to 5 minutes.

〔Example〕

Example 1 A copper alloy softening material with a thickness of 0.3 mm containing 0.15% by weight of tin and 0.002% by weight of phosphorus was produced, and then 2% by weight of 2-undecyl imidazole was prepared.
The sample was immersed for 10 seconds in a solution containing 2% hydrochloric acid (by weight) in an equal weight mixture of water and methanol, then pulled out, washed with water, and dried. Next, heat treatment was performed in the air at 220°C for 4 minutes. When this was subjected to a corrosion resistance test, a corrosion weight loss of 2.7 mg/cm ² was obtained. In addition, the corrosion resistance test was conducted using a plate thickness of 0.3 mm and a width of 0.3 mm.
One cycle consists of spraying a 5% by weight saline solution on a specimen measuring 25 mm and 90 mm in length for 1 hour, and then keeping it in a constant temperature and humidity atmosphere at a temperature of 50°C and a relative humidity of 70% for 23 hours. After placing the specimen in a corrosive environment for 45 cycles (45 days), the corrosion products that had formed were removed and the weight loss of the specimen was measured.

Example 2 0.010% by weight of tellurium and 0.003% by weight of phosphorus in copper
The thickness of the contained copper alloy was the same as in Example 1.
Create a specimen of 0.3 mm, width 25 mm, and length 90 mm, and
It was immersed for 10 seconds in a solution containing 2% by weight of undecylimidazole and 2% by weight of hydrochloric acid in an equal weight mixture of water and methanol, pulled up, washed with water, and dried. Then, it was heat-treated at 220°C for 4 minutes in the air. When this was subjected to a corrosion resistance test using salt water spray in the same manner as in Example 1, a corrosion loss of 2.3 mg/cm ² was obtained.

Comparative Example 1 A copper alloy specimen having the same composition as in Example 1 was heated at 350°C for 30 seconds without forming any film, and then subjected to the same salt spray test as in Example 1. The result was 4.8.
The corrosion weight loss was mg/cm ² , which was 1.8 times that of Example 1 of the present invention.

Comparative Example 2 A specimen with the same composition as in Example 1 was immersed in the same solution as in Example 1 for 10 seconds, washed with water, dried, and then heat-treated at 350°C for 8 minutes. When a similar salt spray test was conducted, 5.2
It showed a corrosion loss of mg/cm ² , which was 1.9 times that of Example 1 of the present invention.

Comparative Example 3 A specimen with the same composition as in Example 1 was immersed in the same solution as in Example 1 for 10 seconds, washed with water, dried, and then heat-treated at 150°C for 4 minutes. When a similar salt spray test was conducted, the result was 3.1mg/
cm ² corrosion loss compared to Example 1 of the present invention.
It showed a corrosion weight loss of 1.2 times.

Comparative Example 4 Using a sample having the same composition as in Example 1, a coating was formed on the surface by benzotriazole treatment. When this was subjected to the same salt spray test as in Example 1, the corrosion loss was 3.5 mg/cm ² , which was 1.3 times as much as in Example 1 of the present invention.

〔Effect of the invention〕

According to the present invention, it is possible to provide a member for a heat exchanger fin that is heat resistant and has better corrosion resistance than before.

Claims (1)

[Claims] 1. A mixed solution of alkylimidazole, inorganic acid, water, and organic solvent is applied to the surface of copper or copper alloy, and the copper or copper alloy coated with this solvent is heated to 200 to 280
1. A method for producing a heat exchanger fin member, which comprises performing a heat treatment at a temperature of 20 seconds to 5 minutes at a temperature of .degree.