JPS636800B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a surface treatment method for aluminum heat exchangers, and its main purpose is to improve the corrosion-preventing effect of heat exchangers against salt damage caused by road antifreeze agents in coastal areas with severe corrosive environments or in winter. be. Corrosion prevention methods for aluminum heat exchangers include:
Conventionally, the fins assembled on the surface of the tube were made of an aluminum alloy material containing Zn or Mg, which has a base potential, and the sacrificial effect of the fin material caused the tube to It is common practice to prevent corrosion (see, for example, Japanese Patent Application Laid-open No. 110149/1983). In the conventional method described above, the materials used for the tube and fins are limited to specific materials, making them more expensive than standard materials, and contaminating the furnace due to evaporation of Zn, Mg, etc. during brazing in the furnace. Not only does this cause the inconvenience of accelerated corrosion, but especially when used in a severely corrosive environment, the fins will corrode (pitting) in a relatively short period of time due to their sacrificial effect, which will reduce heat exchange efficiency. In addition, there are problems such as the perforations of the fins becoming clogged with foreign matter and increasing ventilation resistance. In addition, conventionally, the surface of the fin material of aluminum heat exchangers has been surface-treated with an organic polymer resin solution containing porous silica particles, and furthermore, after surface treatment with the organic polymer resin solution, tannin or tannin liquid has been applied on top of the surface treatment. A method has been developed to prevent corrosion by applying a treatment solution containing
However, such conventional methods require degreasing and cleaning of the aluminum surface as pretreatment, and forced drying at a temperature of approximately 120°C after applying the resin solution. Furthermore, if the thickness of the organic polymer resin film exceeds 10 μm, the heat conductivity deteriorates significantly, so it must be made into an extremely thin film of about 2 μm, which requires very advanced coating technology, and the treatment process is difficult. Not only is it extremely troublesome and requires fairly large-scale processing equipment, but if resin-based coatings are exposed to low temperatures below 0℃ or high temperatures above 100℃ for long periods of time, the coating surface will crack and the rust prevention effect will deteriorate. Therefore, there are problems such as a limited usage temperature range. The present invention provides a surface treatment method for aluminum heat exchangers that can solve the problems of the conventional methods as described above. That is, in the present invention, tubes and fins made of aluminum or aluminum alloy are combined, and after these are fixed by furnace brazing or welding to form a heat exchanger, a solvent is applied to the carrier without pretreatment such as washing of these surfaces. A coating made from a corrosion-resistant compound containing electromagnetic inorganic substances such as calcium sulfonate and petrolatum oxide is applied to the surface of the tube and fin by means such as spraying or dipping, based on microcrystalline wax. Forms a strong microscopic plate-like fish scale film (a dense overlapping particle layer in which countless highly ionized microscopic particles adhere tightly like fish scales to the surface of heat exchanger components such as tubes and fins). It is characterized by this. The fish scale film formed on the surface of the heat exchanger components as described above is an inorganic substance, so the film thickness is 50 μm.
There is no effect on heat conductivity at all if the coating is applied, and since it adheres densely to the coating surface like fish scales, it does not sag or run off during coating, and it adheres evenly to sharp edges, allowing the coating to be applied evenly. Not only does it significantly simplify the coating work, as it can be moved immediately after use, but the coating film will not crack in the practical temperature range of -40℃ to 260℃.
No peeling, sagging, etc. occur at all, and even in severe corrosive environments, it can provide accurate corrosion effects over a long period of time. Further, the coating method for applying the anticorrosive compound paint according to the present invention may be any method such as spraying using a general spray gun, brushing, or dipping. Example: A 6.5% thixotropic paste paraffin was applied to the surfaces of the tubes and fins of a heat exchanger, which had an integral structure by combining aluminum tubes and fins and brazing them in a furnace. Based on microcrystalline wax with a solution carrier, calcium sulfonate, calcium carbonate, and petrolatum oxide at 2.6% each.
Paints containing 1.7% and 39% were applied using a dip coating method to obtain a heat exchanger with a microplate-shaped fish scale coating formed on the tube and fin surfaces. Specimen 1 and Specimen 2 are specimens in which the thickness of the fish scale film is in the range of 13 to 25 μm and 13 μm or less, respectively, and an organic polymer containing porous silica particles is coated on the surface of an aluminum heat exchanger. As a control example, a resin film was formed to a thickness of 10μ and a tannin treatment liquid was applied on it.
Corrosion resistance times were compared using the JIS-Z-2371 test method. The results are shown in the table below.

[Table] From the above results, it was found that the corrosion resistance time of the product of the present invention was significantly longer than that of the conventional product, and that it was able to maintain a sufficient corrosion protection effect even under severe corrosive environment conditions.

Claims (1)

[Claims] 1. Electrochemical inorganic substances such as calcium sulfonate and petrolatum oxide and microcrystals are applied to the surface of an aluminum heat exchanger, which has an integral structure of tubes and fins made of aluminum or aluminum alloy materials, brazed in a furnace, welded, etc. A coating made of a corrosion-resistant compound containing wax is applied to form a fish scale-like protective film on the surface of the heat exchanger, which is made up of a layer of dense overlapping particles in the form of highly ionized microplates with strong polarity. Surface treatment method for aluminum heat exchangers.