JP3340684B2 - Cathodic protection linear electrode body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-diameter metal pipe such as tap water or cooling water having a pipe inner diameter of 50 mm or less and a length of 10 m or more and having a curved pipe section including a plurality of elbow pipes and / or vent pipes. The present invention relates to an electrode body for electrolytically protecting the inner surface of an electrode.

[0002]

2. Description of the Related Art In general, cathodic protection is widely used as a countermeasure against metal corrosion, and effectively functions, for example, as a countermeasure against corrosion of steel structures on the shore and reinforcing steel in concrete. Cathodic protection requires a cathode (a metal structure to be protected against corrosion), an anode (an electrode body for supplying an anticorrosion current), and an electrolyte (seawater, tap water, soil, or the like). In the case of steel or a reinforcing bar, the installation of the electrode body is relatively easy, and the limitation as the electrode body is small. However, in a pipe for flowing tap water, cooling water, or the like, in order to prevent the inner surface of the metal pipe from being corroded, an anticorrosive body must be disposed so as to pass through the inside of the pipe, which limits the workability.

Conventionally, as a method for preventing the inner surface of a metal tube from being electrically corroded as described above, Japanese Patent Publication No. 5-24235 discloses a method for stopping red water. That is, a method is described in which a branch joint having an opening is provided in a pipe passage, and a corrosion-resistant linear electrode surrounded by a porous electrically insulating resin tube is inserted from the opening to perform electrolytic protection. . Japanese Utility Model Application Laid-Open No. 5-72967 discloses that a plurality of strands of synthetic fiber are spirally wound on a surface of a platinum-plated titanium wire electrode so as to have a winding angle of 15 to 45 ° as an electrical insulating coating material. A wound dressing is described. However, in the former publication, there is only a description of a platinum-coated titanium wire for the material of the electrode body as a red water stopping method, and the diameter is preferably 1.5 mm or less, and in the example, the description is made with 1.0 mm. . Also,
The latter publication also uses a platinum-coated titanium wire and discusses various means for coating the wire.

[0004]

[Problems to be Solved by the Invention] However, in the case of tap water piping to general homes or condominiums and various cooling water pipings, the pipe inner diameter is, for example, 50 mm or less, preferably 30 m
m or less, and more than 10 m in length, or more than 30 m in length, and has a curved pipe portion including a plurality of elbow pipes and / or vent pipes. In the case where the inner surface of a small-diameter metal pipe such as tap water or cooling water is to be subjected to anticorrosion, there is a problem that the conventional electrode body has insufficient flexibility and is difficult to pass through a curved pipe portion. However, if the diameter of the electrode body is reduced to increase the flexibility, the electrical resistance value deviates from a desired range. Further, when the diameter is 1.0 mm or less, the resistance value increases and the current distribution increases. However, there is also a problem that non-uniformity is caused. For example, in the case of the platinum-coated titanium wire described in the above-mentioned conventional gazette, a wire having a diameter of 1.5 mm is not sufficiently flexible, so that it is difficult to pass through a curved tube portion.
Then, there is a problem that the electric resistance value becomes high and the current distribution becomes non-uniform.

[0005] The present inventor has proposed that the present situation is a metal pipe having a pipe inner diameter of, for example, 50 mm or less and a length of 10 m or more, such as a tap water pipe to general households or condominiums and various cooling water pipes. Alternatively, the present invention provides an anticorrosion linear metal body which can easily and sufficiently supply a sufficient current to the inner surface of a metal pipe having a curved pipe section having a length of 30 m or more and including a plurality of elbow pipes and / or vent pipes. The purpose is to do so.

[0006]

According to the present invention, there is provided a cathodic protection linear electrode body having a tube inner diameter of not more than 50 mm and a length of not less than 10 m, and having a curved pipe portion including a plurality of elbow pipes and / or vent pipes. In an electrode body for electrolytic protection of the inner surface of a small-diameter metal pipe such as tap water or cooling water, the elastic modulus is 0.8 × 10 ^5.
１．２1.2 × 10 ⁵ N / m ² and electric resistance value is 0.03３
A metal body having a characteristic value in the range of 0.2 Ω / m and a non-conductive PFA (ethylene tetrafluoride / perfluoroalkoxyethylene copolymer resin) fiber coated around the metal body. Specifically, the metal body is preferably a Cu-Nb-Pt line or an Al-Nb-Pt line.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The cathodic protection linear electrode body according to the present invention has a tube inner diameter of 50 mm or less, preferably 30 mm or less, and a length of 10 m.
As described above, since this is an electrode body for electrolytically protecting the inner surface of a small-diameter metal pipe such as tap water or cooling water having a curved pipe section including a plurality of elbow pipes and / or vent pipes, it is inserted and disposed in the metal pipe. It is necessary to have an electric resistance value within an appropriate range in order to provide a suitable current distribution with ease.
The present inventors have made intensive studies on various metal bodies satisfying the above requirements, and as a result, have achieved the present invention.

[0008] Now, the length of the metal body of the various metal bodies increases with the length of the small-diameter metal pipe into which the metal body is inserted and arranged, and the electrical resistance increases as the length increases. Here, a φ 0.75 mm Ti-Pt wire and a φ 0.75 mm Cu-
FIG. 1 shows the length and current loss (IR) of the electrode metal body when an Nb-Pt wire is disposed in a tap water pipe and a voltage of 10 V is loaded. In addition, the current loss (IR) was calculated by Equation 1. By the way, when the outflow current (corrosion prevention current) from the electrode in this case is compared with the current ratio between the 10 m and 30 m points on the side close to the power supply, the Ti-Pt wire of φ0.75 mm has 1
At 1m at 0m, the value at 0.8 at 30m is 20% short of the anticorrosion current at this point. In order to satisfy this, the 10m point is in an over-corrosion-protected state, resulting in uneven corrosion protection as a whole. Cu-Nb-φ0.75mm
There is almost no difference in the current ratio between the 10m and 30m points on the Pt line.

[0009]

(Equation 1) Here, Ra: electrode contact resistance, h: pipe (tap water pipe) radius, a: electrode radius, L: electrode length, ρ: water resistivity (1
0,000Ωcm).

Thus, as is apparent from FIG.
The longer the pipe length exceeds 10 m, the greater the current loss IR. The current loss IR is determined by the electrode material characteristics (material, diameter) and its length.

In the present invention, an electrode is placed in a small-diameter metal pipe such as tap water or cooling water having a pipe inner diameter of 50 mm or less and a length of 10 m or more and having a curved pipe section including a plurality of elbow pipes and / or vent pipes. , The electrode must have a moderate elastic modulus. In other words, if the elastic modulus is too small, it is too rigid to follow the curved pipe part, so it cannot pass through the curved pipe part. Conversely, if the elastic modulus is too large, it is too soft to bend at the curved pipe part. I can't get it up and pass it through the curved tube. According to the study of the present inventors, the elastic modulus of the electrode is 0.8 × 10 ⁵ N / m ² or more and 1.2 × 1
It should be within the range of 0 ⁵ N / m ² or less. As described above, in the linear electrode for cathodic protection used for anticorrosion of the inner surface of a small-diameter metal tube to be subjected to anticorrosion in the present invention, a) the electrode body has appropriate flexibility, and b) the electric resistance of the electrode conductor. It is necessary that the value be within a predetermined range. FIG. 2 illustrates this relationship, and those having flexibility (elastic modulus) and electric resistance within the range of the hatched portion in FIG. 2 are applicable. Further, c) the coated insulating synthetic fiber does not affect the porosity in its knitting method, and the coating material does not deteriorate due to oxygen or chlorine generated by the electrolytic reaction on the electrode surface. In the case of anticorrosion, a coating material that does not cause a problem of dissolution is required. In response to this requirement, that is, a requirement that the material be porous, durable, have strong acid resistance and chlorine resistance, and be flexible, the present invention uses PFA (tetrafluoroethylene) among fluororesins. Ethylene perfluoroalkoxyethylene copolymer resin) as the coating material. It is preferable that the PFA is formed by bag knitting using several single fibers in order to secure porosity and prevent deterioration and fraying.

[0012]

EXAMPLE A 3A 15A pipe was assembled at 6 right angles using a fitting elbow as shown in FIG. 3, and a sponge ball previously attached to a Tengs thread was blown from one end of the pipe with compressed air by a compressor. After the ball is pulled out from the other end of the tube end, the end of the Tengx thread on this side is connected to a spherical body of 7.0 mm in diameter with a hole of 2.0 mm in the center, and the same direction And fixed a linear electrode. In such a state, with respect to various electrode bodies woven in a bag with fluorine fiber (PFA), a passing test was performed on the right angles of the pipe 6 while pulling the Tengs thread from the other and simultaneously pushing the linear electrode. As a result, the annealed copper wire having a diameter of 0.75 mm was not able to pass though having sufficient flexibility. This is presumably because the copper wire is too flexible and the elastic restoring force is weak, so that the friction increases when the copper wire follows the pipe. In contrast, Cu-N with a diameter of 0.75 mm
Although the b-Pt electrode was twice as elastic as the copper wire, it could pass through six right angles. As another electrode body, a wire electrode body having a diameter of 1.0 mm, in which Nb and Pt were clad in order on an Al core wire, also showed similar transmissivity. In addition, the conventional Pt-Ti linear electrode with a diameter of 1.5 mm has too high elasticity to pass through only two right angles, and a 0.75 mm Pt-Ti electrode and a 0.75 mm Cu-Nb-Pt electrode depending on the diameter may be used. Similarly, some can be passed, but as shown below, the Pt-Ti electrode has a diameter
In the case of 1.5 mm or less, the resistance value becomes high, and in any case, it is not suitable as an electrode body for small-diameter piping.

Next, the voltage drop at the end of the pipe when various electrode bodies were applied to the inner surface of the pipe was measured. Piping is 20A and length 30
When a linear electrode with a diameter of 0.75 mm is inserted into the tap water pipe inner surface of m, the current from the electrode end at the position of 30 m is:
The IR drop is caused by the specific resistance of the electrode.
ρ = 8000Ω · cm (tap water)
= 3.48Ω, and the generated current at 10V voltage is 10V / 3.48Ω
= 2.87A, and the IR drop is 0.931Ω / m from Table 1 in the case of a Pt-Ti linear electrode.
31Ω / m × 2.87A = 2.67V. In the case of a Cu—Nb—Pt linear electrode (cross-sectional diameter: 0.75 × 0.18, Pt 0.635 μm clad), the specific resistance of the electrode is 0.0334Ω / m from Table 1. Therefore, IR = 0.0334Ω / m × 2.87A = 0.958V. Therefore, in the case of corrosion protection of small-diameter metal pipes such as tap water and cooling water, which include an actual pipe inner diameter of 50 mm or less, a length of 10 m or more, and a curved pipe portion having a plurality of elbow pipes and / or vent pipes, the inner diameter of the pipe is If it is determined that, for example, an output voltage of about 5 V is applied, a preferable range of the resistance value of the electrode body is determined in order to obtain a preferable anticorrosion current, and at the same time, the electrode body is disposed in the pipe. It must be understood that the material must have an elastic modulus in a suitable range. In response to the demand, a Cu-Nb-Pt linear electrode (cross-sectional diameter: 0.75 x 0.18, Pt 0.635
μm clad) is suitable. Similarly, according to the study of the present inventors, the Al-Nb-PT wire of φ1.0 mm is also shown in FIG.
It has been found that the elastic modulus and the electric resistance value are within a predetermined range, and are suitable for use in the present invention. In addition, various alloy wires, plated wires provided with one or more plating layers, or clad drawn wires clad with one or more kinds of materials, etc., have an elastic modulus and an electric resistance value falling within the shaded range of FIG. Any of them can be applied to the present invention.

[0014]

[Table 1]

[0015]

According to the present invention as described above, the linear electrode body according to the present invention has a tube inner diameter of 50 mm or less, a length of 10 m or more and a plurality of elbow tubes and / or Tap water having a curved pipe portion having a vent pipe,
Ideal for corrosion prevention of small diameter metal piping such as cooling water.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a pipe length and a current loss by changing a linear electrode body.

FIG. 2 is a graph showing the relationship between the electric resistance value and the elastic modulus of the range of the present invention indicated by oblique lines.

FIG. 3 is a schematic explanatory view showing a pipe shape used in an example of the present invention.

Claims (3)

(57) [Claims] 1. An inner surface of a small-diameter metal pipe such as tap water or cooling water having a pipe inner diameter of 50 mm or less and a length of 10 m or more and having a curved pipe section including a plurality of elbow pipes and / or vent pipes. The electrode body has an elastic modulus of 0.8 × 10
^{5 to} 1.2 × 10 ⁵ N / m ² and an electric resistance of 0.03
A cathodic protection linear electrode body comprising a metal body having a characteristic value in the range of ~ 0.2 Ω / m and a non-conductive PFA (ethylene tetrafluoride / perfluoroalkoxyethylene copolymer resin) fiber coated around the metal body. 2. The electrode according to claim 1, wherein the metal body is a Cu—Nb—Pt wire. 3. An electrode according to claim 1, wherein said metal body is an Al—Nb—Pt wire.