JPS60134198A - Surface treatment of aluminium heat exchanger - Google Patents

Abstract

PURPOSE:To perform surface treatment excellent in corrosion resistance and hydrophilicity by a method in which aluminium heat exchanger is subjected to an anodic oxidation treatment and then to a pore sealing treatment. CONSTITUTION:The defective portions of a porous anodized layer are repaired by a pores sealing treatment to raise the corrosion resistance of the porous anodized layer and also provide a hydrophilicity originating from the structure of the anodized film for it. The anodic oxidation treatment is made using a sulfuric acid anodizing liquid, a chromic acid bath, etc., under conditions selected from several to several tens V of voltage, several to several tens deg.C of temperature, and several to several tens of minutes of time. The pores sealing treatment to be made after the anodic oxidation treatment is those like a chromate treatment or a boemite treatment using sodium dichromate.

Description

Detailed Description of the Invention The present invention relates to a surface treatment method for an aluminum heat exchanger (especially an evaporator) for air conditioning, which has excellent corrosion resistance and hydrophilicity, and has high practical value. All-aluminum heat exchangers have come to be used due to the need for

Heat exchangers include a condenser and an evaporator, and the evaporator is required to have a long corrosion-resistant life and high water wettability.

As shown in Fig. 1, the evaporator consists of a pipe section 1 that serves as a flow path for the refrigerant and a fin section 2 that exchanges heat with the air. fin 2
The water droplets 3 accumulate in a part of the container and obstruct the air flow, or the accumulated water droplets are pushed by the air flow and cause a dew drop phenomenon.

Therefore, in order to make the surface of the fin 1 hydrophilic, the following surface treatments are performed, but all of them have the following drawbacks.

Surface treatment Disadvantages ■ Boehmite treatment □ Insufficient corrosion resistance ■ Water glass treatment □ Hydrophilicity deteriorates over time ■ Anodized soil Pure water sealing - Insufficient corrosion resistance The present invention This paper proposes a surface treatment method that is superior in both corrosion resistance and hydrophilicity compared to other materials, and does not pose any problems in use.

That is, the present invention relates to a surface treatment method for an aluminum heat exchanger for air conditioning, which is characterized by performing a sealing treatment after anodizing treatment, which is excellent in both corrosion resistance and hydrophilicity.

According to the method of the present invention, it is possible to obtain an evaporator that has superior corrosion resistance and hydrophilicity compared to conventional evaporators, and does not cause any problems in use.

The principle of the method of the present invention is to repair defects in the porous layer of the anodic oxide film through a sealing treatment, thereby improving corrosion resistance and maintaining the hydrophilicity due to the structure of the anodic oxide film. can be done.

The anodizing treatment in the present invention includes a sulfuric acid anodizing solution, a chromic acid bath (e.g., 4 thichromic acid), an oxalic acid bath (e.g., 3% oxalic acid), and an anodizing bath (e.g., sulfuric acid 14 parts, oxalic acid 1.5 qb). ) etc., and the voltage is several to several tens of volts.
1 The temperature is selected from several to several tens of degrees Celsius, and the time is appropriately selected from several to several tens of minutes. Note that voltage and temperature affect the formation rate and structure of the oxide film, and time affects the thickness of the oxide film.

The sealing treatment after the above anodizing treatment is chromate treatment using Alodine (part name manufactured by Nippon Paint C Co., Ltd.), Bonderite (part name manufactured by Nippon Paint C Co., Ltd.), or boehmite treatment using sodium dichromate. Processing similar to processing can be adopted.

The above alodine and bonderite include chromate-based products (containing chromate ions, fluoride ions, and cyanate ions) and phosphochromate-based products (containing phosphate ions, fluoride ions, and chromate ions). ), and examples of chromate-based compounds include Allodinna 600.100.
．． 1200° Bonderite 713 and the like, and examples of phosphoric acid pmate salts include Allozinna 101,407 and Bonderite 701,705.

Treatment using alodine and bonderite is at room temperature, 1 to 1
0 minutes, and treatment using sodium dichromate is 90~
Example 1 The all-aluminum evaporator shown in Figure 1 was immersed in a sulfuric acid anodizing solution (sulfuric acid 1yor/z) at a voltage of 18 V and a liquid temperature of 20°C. Anodize for 30 minutes. After the treatment, the evaporator is washed with water and neutralized according to the usual method. After that, it is immersed in Allozinna 1200 for 5 minutes at room temperature to seal the hole.

- G) Treat and wash with water.

The water droplet contact angle of the evaporator fin portion surface-treated as described above is an initial value of 5 degrees or less, and even after 250 hours of water immersion, the water droplet contact angle remains in the range of 5 degrees to 17 degrees, with little change over time.

Furthermore, when a 500-hour salt water spray test was conducted, no white rust was observed, confirming corrosion resistance equal to or higher than that of conventional surface treatments.

Example 2 The all-aluminum evaporator shown in FIG. 1 was manufactured in the same manner as in Example 1, except that instead of the chromate treatment, it was immersed in a sodium dichromate solution (a 5-chloride aqueous solution) for 15 minutes at 95°C for sealing. When the surface of the vessel was treated, the same effect as in Example 1 could be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an evaporator of a heat exchanger, and FIG. 2 is a diagram showing a state in which water droplets accumulate in a conventional evaporator.

Claims (1)

[Claims] A surface treatment method with excellent corrosion resistance and hydrophilicity, which is characterized by applying sealing treatment to an aluminum heat exchanger for air conditioning after anodizing treatment.