JP2000329411A - Water touching part for corrosion resistant hot water supply apparatus, manufacture thereof and hot water supply apparatus employing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent corrosion of copper or copper alloy in a hot water supply apparatus by forming a water repellent silicon coating at least on the surface of the copper or copper alloy basic material of a water touching part for the hot water supply apparatus thereby forming a coating superior in adhesion and durability. SOLUTION: When the water touching surface of a water touching part 1 is treated with a silane based compound (RSiX: R is a hydrophobic group such as an alkyl group or a fluoroalkyl group, X is s substituent such as halogen or alkoxyl group), the silane based compound is bonded to a silanol group existing on the surface of the water touching part in a hot water supply apparatus composed of a copper or copper alloy basic material and condensed to form a polysiloxane layer. Consequently, the surface of the copper or copper alloy basic material 1 is covered with a hydrophobic group, e.g. an alkyl group or a fluoroalkyl group, and a water repellent layer 2 is formed. Since the water repellent layer 2 is integrated with metallic atoms composing the copper or copper alloy of the basic material 1 through covalent bond, a thin film extremely superior in adhesion and durability is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-repellent component for a corrosion-resistant water heater having a coating having excellent corrosion resistance formed on at least the inner surface of a water heater made of copper or copper alloy which comes into contact with water. And a water heater including as a part.

[0002]

2. Description of the Related Art Conventionally, as a base material of an instantaneous water heater and a water heater, copper phosphate deoxidized which has excellent heat resistance in addition to heat conductivity and conductivity is used. In order to prevent the corrosiveness, a method of applying a thin fluororesin on the surface of the phosphoric acid-deoxidized copper and then baking it is adopted. In addition, other methods of applying a resin include a method of applying a paint dissolved or suspended in a solvent and drying the solvent.

[0003]

However, in the above-mentioned method of applying a fluororesin, adhesion to a copper or copper alloy substrate of a water heater is poor, and there is a problem in durability. In addition, the method of applying other resins also has poor adhesion, and has a problem in durability. Therefore, an object of the present invention is to form a film having excellent adhesion and durability and prevent corrosion of copper or a copper alloy of a water heater.

[0004]

According to the present invention, a water-repellent silicone coating is formed on at least a surface of a copper or copper alloy substrate of a water-contacting part for a water heater, which is in contact with water. By doing so, free carbonic acid and the like that cause corrosion of the base material do not come into direct contact with the copper or copper alloy base material, so that Cu, Sn, Zn, etc. in the copper alloy material that causes corrosion Of water and improve the corrosion resistance of wetted parts of the water heater.

It is more preferable to use a silane compound for the water-repellent silicone coating. By doing so, a molecular coat film that is covalently integrated with the base material can be obtained, so that a very thin film can be fitted to provide high adhesion strength and provide a corrosion-resistant water heater with excellent corrosion resistance. It becomes possible.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

For the water-repellent coating, for example, a silicone resin or the like, which is a polymer of a silane compound having a hydrophobic group such as alkylsilane and fluoroalkylsilane, can be used. Silicone resin is excellent in adhesion of a copper or copper alloy substrate. Further, a silicone resin having a fluoro group which is a polymer of a fluoroalkylsilane, in addition to the properties of the above silicone resin, has an extremely low surface energy and also has an advantage of low reactivity with other substances, More preferred.

FIG. 1A shows a silane compound (RSix: R is a hydrophobic group such as an alkyl group or a fluoroalkyl group, and X is a substituent such as a halogen or alkoxyl group) shown in FIG. ), It binds to and condenses with silanol groups (-Si-OH) present on the above-mentioned surface of the wetted parts of the copper or copper alloy base material of the water heater to form a polysiloxane layer. As a result, the surface of the copper or copper alloy substrate 1 is covered with a hydrophobic group such as an alkyl group or a fluoroalkyl group as shown in FIG.
Is formed. The water-repellent layer 2 is covalently integrated with the metal atoms constituting the copper or copper alloy of the base material 1 and is a thin film having extremely excellent adhesion and durability.

The solid content of the silane compound such as alkylsilane and fluoroalkylsilane is preferably more than 0.5% by weight and 5% by weight or less, more preferably 1% by weight or more and 3% by weight or less based on the solvent. Is good. As the solvent, methanol, methyl ethyl ketone, toluene, or the like can be used in addition to isopropyl alcohol. Further, water for hydrolysis may be added in a necessary molar amount to the silane compound, and a small amount of nitric acid or hydrochloric acid may be further added as a catalyst if necessary.

[0010] As a method of coating the surface of the water-contacting part which comes into contact with water, for example, a spraying method, a printing method, a dipping method and the like can be suitably used. Among them, the dipping method is particularly excellent for coating the inner surface of the copper or copper alloy base material of the water heater.

[0011]

The present invention will be described more specifically with reference to the following examples. Prepare a phosphorus deoxidized copper sample used as a member of the heat exchanger of the water heater, wash with an organic solvent,
For example, a water repellent containing heptadecafluorodecyltrimethoxysilane to be a water repellent silicone coating was prepared and dipped. Formulation of water repellent g ・ Heptadecafluorodecyltrimethoxysilane 32 ・ Water 4.6 ・ Nitric acid 2.6 ・ Isopropyl alcohol 1600 When the sample is immersed in the water repellent for 30 minutes, the surface of the sample film contains many hydroxyl groups. Therefore, the methoxy group of heptadecafluorodecyltrimethoxysilane reacts with the hydroxyl group to cause a demethoxylation reaction. After that, the sample is taken out and, after natural drying, is baked at a temperature of about 200 ° C. A bond of heptadecafluorodecylsilane is formed on the sample surface, and a film thickness of about 1 nm can be formed in a bonded state as shown in FIG. 1B.

In order to evaluate the corrosion resistance in a short period of time, an evaluation acceleration test was performed. The free carbonic acid concentration was increased, the water temperature was set higher than room temperature, the water quality was set to be highly corrosive, and the highly corrosive water was continuously supplied to the sample for three months. Corrosion hardly occurred on the sample surface of the example, and patina was strongly generated on the sample surface of the comparative example, and the result that the sample surface was corroded was obtained.

[0013]

As described above, according to the present invention,
Since the water-repellent silicone thin film is formed on the surface of the copper or copper alloy of the water heater, the initial performance of the water heater is maintained for a long time without corrosion. Since the water-repellent silicone film does not chemically bond to the surface of the water-repellent silicone film even when scale is generated, the water-repellent silicone film has no scale deposition and also has an effect of preventing the performance of the water heater from deteriorating.

[Brief description of the drawings]

FIG. 1 is a view conceptually showing a step of forming a water-repellent layer on a surface of a water-contacting part according to the present invention which is in contact with water, and shows a case where a water-repellent layer is formed with a silane-based compound.

[Explanation of symbols]

 1. Base material 2. Water repellent layer

Claims (8)

[Claims] 1. A water-repellent component for a corrosion-resistant water heater, characterized in that a water-repellent silicone coating is formed on at least a surface of the copper or copper alloy substrate of the water-repellent component for water heater that is in contact with water. 2. The water-repellent component for a corrosion-resistant water heater according to claim 1, wherein an MO—Si bond exists at an interface between the substrate and the water-repellent silicone coating. Is a metal constituting copper alloy). 3. The water-repellent silicone coating is a coating of a hydrolyzable alkyl silane or a dehydration condensate of a hydrolyzable fluoroalkyl silane.
Or the wetted parts for a corrosion-resistant water heater according to 2. 4. A water heater comprising the wetted parts according to claim 1. 5. A method for producing a water-repellent component for a corrosion-resistant water heater, comprising a step of forming a water-repellent silicone coating on at least a surface of the substrate that is in contact with water. 6. The component is a heat exchanger made of a copper or copper alloy substrate, and after completing the heat exchanger, performing a step of forming a water-repellent silicone coating on at least a surface of the substrate that is in contact with water. A method for producing a wetted part for a corrosion-resistant water heater. 7. The step of forming a water-repellent silicone coating on at least the surface of the substrate which is in contact with water comprises applying a silicone-based coating agent having a hydrophobic group to at least the surface of the substrate which is in contact with water. The method according to claim 5 or 6, comprising a step of forming and a step of curing the coating. 8. The silicon-based coating agent is at least one selected from the group consisting of a hydrolyzable alkyl silane, a hydrolyzable fluoroalkyl silane, a hydrolyzate of the silane, and a dehydration condensate of the silane. The method for producing a wetted part for a corrosion-resistant water heater according to claim 7.