JPS61291979A - Corrosion-proof copper or copper alloy tube - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a Cu or Cu alloy tube without deteriorating the heat transfer characteristics by forming an amorphous metallic film on the inner surface of the tube contacting with a corrosive medium. CONSTITUTION:An amorphous metallic film is formed on the inner surface of a heat exchanger tube of Cu or a Cu alloy to prevent the corrosion of the inner surface contacting with a corrosive medium such as seawater or hot water. The amorphous metallic film is a film of Ni-P, Ni-B or Ni-P-B formed by electroless nickel plating or a film of Fe-Cr-P, Fe-Cr-B or other alloy formed by electroplating. The amorphous metallic film maintains stably the amorphous state up to about 200-300 deg.C with slight deterioration in the heat transfer characteristics of the tube. When the tube is used in piping for supplying hot water, the bluing of water or other trouble can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a corrosion-resistant copper or copper alloy tube with improved corrosion resistance.

BACKGROUND OF THE INVENTION Copper or copper alloy tubes are generally used for water conduits and heat exchanger tubes in heat exchangers.

Problems to be Solved by the Invention It is known that in steel pipes for hot water supply, the problem of "blue water" occurs due to eluted copper ions, and in some cases, hot water leaks due to pitting corrosion. In addition, various copper alloy tubes are used as heat exchanger tubes in heat exchangers that use seawater for cooling, but they cause corrosion problems to a greater or lesser extent.1-1 In particular, penetration leakage accidents due to corrosion can lead to temporary plant shutdowns.

Therefore, various measures are being taken for heat exchanger tubes in order to prevent penetration leakage accidents due to corrosion from both safety and economical points of view. For example, titanium tubes are used which have excellent corrosion resistance against seawater, but they not only have inferior heat transfer properties but also have the disadvantage of being expensive. Attempts have also been made to increase corrosion resistance by coating the inner surface of the tube, but coatings made primarily of organic resins significantly degrade heat transfer characteristics and cannot be applied to heat exchanger tubes.

Means for Solving the Problems In view of this, the present invention has been developed as a result of various studies and has developed a corrosion-resistant copper or copper alloy tube that does not reduce heat transfer characteristics, is inexpensive, and has improved corrosion resistance. This is characterized in that an amorphous metal coating is formed on the surface of the tube made of copper or copper alloy on the side that comes into contact with the corrosive medium.

Function The present invention is intended to form an amorphous metal coating on the surface of a tube made of copper or copper alloy on the side that comes into contact with corrosive media such as hot water or seawater. Since it does not exist, it exhibits extremely excellent corrosion resistance and prevents corrosion of pipe bodies made of copper or copper alloys. Amorphous metals with various metal element compositions are made by quenching molten metal, but this method involves forming an amorphous metal coating on the inner surface of a tube made of copper or copper alloy. It is difficult. However, by selecting a combination of metal element compositions and a coating method, an amorphous metal coating can be easily formed. For example, according to electroless plating, especially electroless nickel plating, N1-P,
Amorphous metal coatings such as Ni-B and Ni-P-B are obtained.

A commercially available electroless nickel plating bath can be used, or it can be prepared as the basic composition has been clarified. That is, the above-mentioned NIPs NI P B-NI B is a product whose main components are Ni salt such as NiSO4, NaHPO- or/and NaBH4, and a reducing agent such as dimethylamine borane, and a pH adjuster and a stabilizer. By coexisting salts such as MO and W, N1-P
An amorphous metal coating such as -KN i -P-Mo can also be formed. Further, an amorphous metal coating such as Co--P can be entirely formed on top of NiO.

Although electroless plating has been described above, a similar amorphous metal coating can also be formed by electroplating. That is, by applying a high current using a pulse wave current only at instants on the order of microseconds, normal nucleation can be effectively suppressed to a large extent, so that high-quality amorphous metal plating can be obtained. In addition to the plating method, methods such as heating and melting the surface layer with a laser and rapid cooling are also possible, and in particular, this method allows the formation of Fe-Cr-P, Fe-C.
Amorphous metal coatings such as r-B, Fe-Cr-Mo-P can be obtained.

Unlike coatings made mainly of organic resin, the amorphous metal coating described above hardly deteriorates the heat transfer properties of the pipe, and moreover, it stably maintains its amorphous state up to 200 to 300 degrees Celsius. Or, it is effective for ordinary uses of copper alloy tubes, for example, as heat exchanger tubes for heat exchangers.

Example 1 Aluminum J [tubes (JISH3300, C687
A steel alloy tube of the present invention was obtained by electroless nickel plating on the inner surface.

As an aluminum brass tube, the outer diameter is 25.4 nm and the wall thickness is 1.
．． Using a tube with a length of 24 m and a length of 2 m, the inner surface of the tube was pickled with dilute hydrochloric acid, then washed with water, and then coated with a commercially available electroless nickel plating bath (trade name: Nyclad 719. JJ Noh Pharmaceutical Co., Ltd.) for about 90 m.
Plating was carried out for about 1 hour at a temperature of .degree. C. to coat the Ni-11%P amorphous metal to a thickness of about 20.mu.

The copper alloy tube of the present invention and the conventional aluminum brass tube that does not form an amorphous metal coating are installed in a transient type seawater corrosion test equipment.
Seawater at a temperature of approximately 25°C was flowed into the pipe at a rate of 100 tons per second.
A corrosion test was conducted for several months. The corrosion weight loss was determined from the weight before and after the corrosion test, and the corrosion rate of both pipes was calculated. As a result, the conventional aluminum brass tube has a diameter of 0.03mm/yea.
r, whereas in the copper alloy of the present invention it is 0.01/yea
r, and the corrosion rate is about A
It can be seen that the reduction is as follows.

Example 2 Electroless nickel plating was applied to the inner surface of a steel pipe for hot water supply in the same manner as in Example 1 to coat approximately 20% of the Ni-11%P amorphous metal.
The steel pipe of the present invention was obtained by coating to a thickness of 0 μm. This steel pipe of the present invention and a conventional steel pipe that does not form an amorphous metal coating are used for the piping of a hot water heater, and hot water of about 60°C is heated at about 1 t/sec.
The amount of Cu2+ eluted into the hot water was investigated.

As a result, it was 0.03W/l for the steel pipe of the present invention, compared to 1■/l for the conventional steel pipe, reducing the elution of Cu2+ to about 1/30, making it extremely effective in preventing troubles caused by "blue water." It turns out that there is something.

Effects of the Invention As described above, the present invention can effectively prevent corrosion of copper or copper alloy pipes, can be used especially for hot water supply piping, can prevent problems caused by "blue water," and can use seawater for cooling. When used in the heat exchanger tubes of heat exchangers, it has significant industrial effects, such as preventing penetration leakage due to corrosion.

Claims (1)

[Claims] A corrosion-resistant copper or copper alloy tube characterized in that an amorphous metal coating is formed on the surface of the tube body made of copper or copper alloy on the side that comes into contact with a corrosive medium.