JPS60200973A - Surface-treated corrosion resistant copper pipe - Google Patents

Abstract

PURPOSE:To provide a surface-treated corrosion resistant copper pipe which decreases dissolution copper and is easy to handle by forming the film of the copper oxide stable in water on at least the inside surface of the copper pipe. CONSTITUTION:The film of a copper oxide having 0.1-10mum thickness is forcibly formed on at least the inside surface of a copper pipe, i.e., a copper pipe consisting of copper and an alloy consisting essentially of copper. The formation of the copper oxide is executed by the oxidation treatment of, for example, the following formulation: The oxidation treatment is executed under the conditions of 95 deg.C and 1-5min in an aq. soln. consisting of 100g/l NaOH and 15g/l KClO3. As a result, the dissolution of the base metal of the copper pipe is considerably decreased and the need for a water treatment for the purpose of inhibiting corrosion is eliminated; in addition, the need for termination for the purpose of connection is eliminated and joining by brazing is possible. The effect of preventing dissolution of the copper is obtd. even if the copper pipe is connected by the operation similar to the operation in the prior art.

Description

BACKGROUND AND OBJECTS OF THE INVENTION The present invention relates to steel pipes used in tap water and hot water supply environments.

Various materials are used for piping materials for tap water and hot water supply, including copper, steel, stainless steel, synthetic resin, plated steel pipes, and resin-coated pipes. Steel pipes are widely used because of their good corrosion resistance against hot water. In particular, steel pipes are widely used for drought piping in buildings because of their stability and workability.

However, in special water quality environments, the surface of the steel pipes dissolves, and the copper concentration in the water exceeds the Ministry of Health and Welfare's water quality standards.
/I) or more. Furthermore, even if the copper concentration is less than 1 ppm, if sanitary equipment or the like is used for a long period of time, this copper may precipitate as a copper salt and cause the problem of blue coloring. Measures to reduce copper dissolution have conventionally been taken by reducing water quality, ie, corrosive environment, and changing materials, but these have caused the following problems.

Measures to reduce water quality and corrosive environments have mainly been taken by adding chemicals to the water supply. For example, in acidic water supplies, such as alkaline caustic soda and sodium bicarbonate, where the water quality is such that scale as a protective film is difficult to form, a small amount of 1-lium silicate, 1-lium phosphate, etc. is injected. However, this method requires the replenishment of used chemicals and the installation and maintenance of new chemical injection equipment. In addition, these tasks are generally outsourced to specialized bacteria collectors, and are not suitable for private residences.

As countermeasures by changing the material, there have been examples of adopting highly corrosion-resistant alloys, such as stainless steel, and resin-coated pipes that are stable for water supply and hot water supply. However, with these materials, it is impossible to perform simple solder joints as with steel pipes, and it is difficult to leave the ends of the joints untreated, especially in cladding pipes, resulting in problems with corrosion resistance.

Other measures to prevent copper dissolution include metal plating, but similar to the previous example, there were problems such as poor terminal treatment and the effects of contact corrosion of different types.

In view of the above points, the present invention has been made with the object of providing a steel pipe that contains less copper Wf and Vf and is easy to handle.

[Summary of the Invention 1 In the present invention, in order to reduce copper dissolution, a copper oxide film that is stable in water is formed at least on the inner surface of the steel pipe.

Copper pipes used for water supply and heating piping initially react very easily with water and dissolve a large amount of copper, but as they are used for a long time and a protective oxide film is formed, the copper dissolves. decreases. For example, regular water supply during new pipe construction (Tokyo Metropolitan Water)
The concentration of copper contained in water when stagnant for 24 hours is 1-21) m, whereas the concentration of copper in water stagnant for 24 hours after one year of use is 0.2-0. .5p
It is pm. In areas where dissolution of copper actually causes problems such as coloring of water and precipitation of copper salts,
Generally, it decreases with the period of use.

This is because a copper oxide film is formed on the surface of the steel pipe in water to protect the copper. The present invention forcibly forms a protective film on this copper oxide.

As for the thickness of the copper oxide film, if the film is formed almost uniformly and no defective parts (base metal) are exposed, a few molecular layers is sufficient, but considering the safety factor. o,oi
It is desirable that the value is less than μm. However, if this film is made too thick, it will easily fall off when subjected to bending or impact, so the limit is 10 μm.

In addition, in the present invention, the quality of steel mainly refers to copper and copper.

It refers to a tube material made of an alloy that adheres to the body.

[Embodiment 1 of the invention Examples of the present invention are shown below.

1. Oxidation treatment After degreasing a steel pipe with an outer diameter of 15.88 mm and a wall thickness of 770.71 mm, oxidation treatment was performed using the following recipe (all aqueous solution). Recipe ■ Caustic soda 100o r/l, potassium chlorite 15q/l Processing temperature: 95°C1 Processing time: 1 to 5 minutes Prescription■ Caustic soda 50gr/l, over-Iil! Potassium I acid 10g/l Processing temperature 95-100"C1 Processing time 1-10 minutes Prescription ■ Copper sulfate 120q/l, Potassium permanganate 15g/l, Processing eddy current 80-95°C1 Processing time 1-10 minutes, 2. Dissolution test Copper pipes treated with the above four types of formulations and untreated copper pipes,
Fill each with distilled water, running water (weakly corrosive), and artificial tap water (strongly corrosive, with adjusted Pl-1), and seal tightly.
After holding at 0'C for 24 hours, the copper concentration in each water was measured.

The measurement results of copper concentration are shown in Table 1, and the tap water quality is shown in Table 2.

As is clear from Tables 1 and 2, when the formulation and the thickness of the oxide film differ, the molten state of copper also changes. However, if the thickness of the oxide film is 0.01μ01 or more, the effect of preventing copper dissolution becomes significant.

[Effects of the Invention] As is clear from the above, the present invention reduces the dissolution of base metal by forcibly forming a copper oxide film on the surface of the copper plane, so corrosion can be suppressed. There is no need for water treatment for connection, no terminal treatment for connection, and soldering is possible. Furthermore, there are advantages such as the ability to prevent copper melting even when the work is similar to that of conventional steel pipe connection work.

1 Indication of 1982 Patent Application No. 57152 2 Name of the invention Corrosion-resistant surface treated steel pipe 3 Shin making the amendment 4 Agent 〒100 1 Detailed description of the invention in the specification to be amended.

Contents of correction The first line of page 6 of the detailed description is corrected as follows.

[Chloric acid) Jium 50y/f! Processing temperature: 60-80℃ Processing time: 1-10 minutes Prescription■ t[t'M　120qr/f Potassium permanganate 157/, fl’j or more

Claims (3)

[Claims] (1) A corrosion-resistant surface-treated steel pipe characterized by forming a film of an oxide hardly soluble in water on at least the inner surface of the steel pipe. (2) The steel pipe according to item 1 above, wherein the oxide film is formed by a chemical conversion reaction. (3) The steel pipe according to item 1 or 2 above, wherein the coating has a thickness of 0.01 to 10 μm.