JPS58142198A - Heat exchanger for bath boiler - Google Patents

Abstract

PURPOSE:To improve the anticorrosive property and the durability of the title heat exchanger by a method wherein a baking paint is coated on the surface of the heat exchanger for a bath boiler attached with aluminum fins to a predetermined thickness by a dipping method. CONSTITUTION:The heat exchanger 1 is dipped in an epoxy denatured silicon resin material and subjected to a baking process so that coating layers of less than 15mum in thickness are formed on the inner and the outer surface of the heat exchanger 1. Thus, it is possible to improve the durability and the anticorrosive property of the heat exchanger by the formation of the complete coatings on the surfaces of the heat exchanger to a properly selected thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates particularly to a heat exchanger for a bathtub made of aluminum, and provides a heat exchanger that is corrosion resistant and durable.

Conventionally, heat exchangers for bathtubs have generally been made of, for example, aluminum treated with boehmite, and aluminum castings have also been put into practical use in some cases.

Bath pots are used in harsh environments, and even though they are treated with boehmite, they lack corrosion resistance.

In particular, on the inner surface (water side) of the heat exchanger, corrosion progresses from the pinholes, and scale sticks to the heat exchanger, which becomes a nucleus and causes the hole axis.On the outer surface (combustion side), exhaust gas, etc. This is because they are subject to severe attacks due to influences, dew condensation, etc.

Although aluminum is suitable as a material for heat exchangers from the viewpoints of thermal conductivity and workability, there are problems with such corrosion resistance, so improvements have been strongly desired. The present invention has been devised and improved in view of these problems, and uses a baking type paint on the surface of an aluminum-based bathtub heat exchanger, and heats it by a dipping method. Inside the exchanger.

A coating layer of 15 μm or less is formed on both outer surfaces. Baking can form an extremely dense and hard film on J: type paints, and even if pinholes occur on the coating surface for some reason, the baking will remain stable and dense on the aluminum surface at the pinhole area due to the heating during the process. oxide layer can be formed.

Therefore, corrosion from the pinhole portion can be eliminated.

Using the dipping method, it is possible to treat every corner of the heat exchanger, both inside and outside, at the same time, making it highly suitable for mass production. Furthermore, by reducing the film thickness to 15 μm or less, it is corrosion resistant and prevents cracking during baking and cooling, dramatically increasing the corrosion resistance and durability of aluminum-based heat exchangers for bathtubs. be. In the following, one embodiment of the present invention will be described based on the drawings. In the figure, 1 is a heat exchanger for a bathtub made of aluminum as a base metal, and is connected to a bathtub 7 through an inlet pipe 3 and a hot water outlet pipe 4. Water inlet pipe 3. The tapping pipe 4 is provided with fins 2 at a constant pitch.

The heat exchanger 1 includes a can body 6 together with a bar 5 located below.
This is what makes up the bath kettle.

First, the heat exchanger 1 is made of epoxy modified silicone resin.
The inner and outer surfaces were immersed in Elicor lining.

Baking was carried out at 250'C for 30 minutes, and the film thickness after baking was 8 to 12 μm.

Corrosion resistance (salt water spray test: continuous 200
)1r, cast test: continuous 4sHr), boiling water test, steam test (method of spraying pressurized steam), etc., no rusting, softening of the paint film, blistering, peeling, etc. were observed. It was in good condition.

Next, a type of coating 1 in which colloidal silica is added to silicone resin; 1. (” Vestar (product name):
When a similar test was carried out using "DOWC Rning" at 200 DEG C. for 10 minutes to form a coated surface with a thickness of 6 to 8 .mu.m, very good results were obtained in this case as well.

Regarding corrosion resistance, artificial corrosion accelerating liquid (AL), which is an accelerated test, was used.
TOONA water (using TOONA water) was used, and this was placed in bath 41j7, and it was found to be la in repeated tests under normal usage conditions.Although the untreated product had extremely severe pore axes, it was treated with the above-mentioned paint, and the coating layer was removed. The formed material was not found to have any pitting and had sufficient corrosion resistance. Regarding the thickness of the coating layer, corrosion resistance and baking are closely related to the effects on the coating film during curing and cooling, and to cost, so it is an extremely important consideration. If the film thickness is extremely thin, the reliability and durability of the coating film will be impaired;
If it gets close to the surface, it becomes too thick, and this is thought to be due to distortion during curing, but the firing material gets cranked at times, making it impossible to obtain a complete coating. According to Ia approval, in terms of reliability as a comprehensive surface treatment, the thickness is preferably 15 μm or less, and preferably 5 μm or less.
About 12 μm is good. At this time, if the object to be coated is dried while being rotated, a relatively uniform coating film can be obtained. As mentioned above, bath kettle heat exchangers are used in extremely harsh environments.

In other words, its inner surface contains salt that dissolves in the hot water, as well as various additives that are added to the bath (including bath clean, some of which contain sulfur, etc.). Impact, water or scale build-up. In addition, since the outside surface is naturally heated by gas, etc., the heat, combustion exhaust gas, water vapor, and even the formation of acids (HNO3, etc.) due to the mixing of NOx in the exhaust gas into dew condensation water. , subject to oxidation and wet corrosion due to puncture, etc. Corrosion is fully expected in aluminum heat exchangers under such conditions, and there are concerns about durability. However, according to the present invention, corrosion can be prevented by baking and hardening using a type of paint. By processing and forming a coating layer with a predetermined thickness, heat resistance, hot water resistance, and corrosion resistance are significantly improved.
This is an extremely practical device that can extend the durability of the heat exchanger by as much as 100%.

[Brief explanation of drawings]

The figure is a configuration diagram of a heat exchanger for a bathtub, showing an embodiment of the present invention. 1...Heat exchanger, 2...Fin, 3.
... Water inlet pipe, 4... Hot water outlet pipe.

Claims (1)

[Claims] It has heat-absorbing fins, and a baking-type paint is used on the aluminum-based surface, and the film thickness is 15 μm by dipping.
A heat exchanger for bathtubs with a coating layer of less than m.