JPH11209885A - Method for preventing microcell corrosion of buried pipeline - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method for effectively preventing the macrocell corrosion of a buried pipeline running through a reinforced-concrete structure without need to dig the soil or concrete wall by which the difficulty that the soil around the external wall of the structure is dug up from the ground and a galvanic anode or an insoluble anode is embedded to apply cathodic protection or that the concrete wall is cut through from the inside of the structure to set the electrode in the soil outside the external wall is solved. SOLUTION: A galvanic anode or an external-energizer insoluble anode is mounted on the internal wall, floor and ceiling of a reinforced-concrete structure which a buried pipeline pierces or on all these concrete wall faces, and the anode is connected to the pipeline in the structure. A zinc galvanic anode 3 formed into sheet is preferably used as the anode, and a grounding resistance reducing agent 4 is preferably applied on the sheet-shaped anode on the concrete wall face side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing macrocell corrosion of a steel pipe in which an underground pipe is provided through a reinforced concrete structure such as a manhole, a common ditch or a bridge.

[0002]

2. Description of the Related Art Generally, when a pipe buried in the ground penetrates a reinforced concrete structure such as a manhole, a common ditch or a bridge provided in the underground soil, the pipe comes into contact with a reinforcing steel in the structure at the penetrating portion. It is known that by doing so, C / S-based macrocell corrosion occurs and is corroded. Conventionally, in order to prevent this, a method of excavating soil near the outer wall of the structure from the ground and embedding a galvanic anode or an insoluble anode and enforcing a cathodic protection method, or Japanese Patent Publication No. 6-53940.
As described in Japanese Unexamined Patent Application Publication No. Hei 7-26389 or JP-A-7-26389, an anticorrosion current flows directly into a buried pipe by excavating a concrete wall from the inside of a structure and protruding an electrode into soil on an outer wall. Was.

[0003]

Problems to be Solved by the Invention However, the former method among the above-mentioned conventional methods involves a large amount of excavation from the ground and the situation of obstacles and underground buried objects other than pipes is unknown. It was difficult. Moreover, the latter method among conventional methods has a problem that the excavation of the wall of the reinforced concrete structure has a risk of inflow of groundwater, and when the wall is thick, it is necessary to rely on mechanical excavation. . In any case, the transportation of heavy equipment accompanying the excavation work of soil and concrete, the disposal of surplus soil after excavation, and the disposal of waste such as concrete debris must be taken into consideration, and the measures for sudden inflow of groundwater, etc. must also be taken into account. It had to be.

An object of the present invention is to provide a method capable of effectively preventing macrocell corrosion of a buried pipe penetrating a reinforced concrete structure without having the conventional problems as described above.

[0005]

SUMMARY OF THE INVENTION In general, a potential for eliminating corrosion that occurs between a concrete structure and soil, a so-called C potential.
It is said that the / S macrocell elimination potential is desirably −600 mV or less (tube-to-ground potential measurement: saturated copper sulfate reference electrode).
The present inventors, without the need for soil or concrete wall excavation work, assuming that the reinforcing bar and the pipe of the reinforced concrete structure are in electrical contact, to polarize the reinforcing bar, reduce the potential difference with the pipe, As a result of various studies on the method of setting the tube-to-ground potential to be equal to or less than the macrocell dissolution potential,
The present invention has been accomplished. That is, the method according to the present invention comprises the steps of mounting a galvanic anode or an external power supply insoluble anode on the inner wall, floor, ceiling or all concrete walls of a reinforced concrete structure through which an underground pipe penetrates, and installing the anode and the inside of the reinforced concrete structure. A method for preventing macrocell corrosion of a buried pipe, characterized by connecting the pipe with the above pipe, which solves the above problem. In the present invention, the anode is preferably a sheet-shaped zinc galvanic anode, and more preferably, a grounding resistance reducing agent is applied to the reinforced concrete wall surface side of these sheet anodes.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reinforced concrete structure having an inner wall exposed to the atmosphere through which an underground pipe is penetrated.
By attaching a galvanic anode or an external power insoluble anode to the floor, ceiling or all these concrete walls, and connecting the anode to the piping exposed inside the reinforced concrete structure, the anticorrosion current is passed from the anode to the reinforcing steel and piping. A cathode circuit that returns to the anode is formed, thereby polarizing the reinforcing bars of the reinforced concrete structure, reducing the potential difference from the piping, and preventing macrocell corrosion of the buried piping.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the reinforced concrete structure is a manhole in the method of the present invention will be described. FIG.
FIG. 2 is a schematic side view of the embodiment, and FIG. In these figures, anchor bolts 8 are driven at regular intervals into a concrete wall 2 of a manhole 1 of a reinforced concrete structure by an electric drill so as not to come into contact with a reinforcing bar, and a zinc anode sheet plate 3 is attached to the wall. In this case, the anode in this case applies corrosion prevention by a so-called galvanic anode. As the anode material, not only zinc but also magnesium or the like having a lower potential than the pipe material can be used, and the shape may be a block shape or the like. Is preferably in the form of a sheet according to the dimensions of the wall. The anode may be an insoluble anode provided with an external power supply. In the figure, one side of the zinc anode sheet plate 3 which is in contact with the concrete wall surface has a putty-like ground by adding water to a mixture of magnesium chloride and bentonite as disclosed in, for example, Japanese Patent No. 271455. It is preferable to apply the resistance reducing agent 4. Next, the zinc anode sheet plate 3 coated with the grounding resistance reducing agent 4 is attached to the anchor bolt 8 with the grounding side of the grounding resistance reducing agent 4 facing the concrete wall surface, and then firmly attached to the concrete wall 2 with the nut 9. Tighten and tighten. The anchor bolt 8 has a lead wire 5
Is mounted so that the anode sheet plate 3 can be energized. Also, energizing terminal leads 7 are attached to the piping, each energizing lead 5 and energizing terminal lead 7 are tied together, rise up to near the manhole entrance 16, and their ends are protected with vinyl tape 15. It was fixed to the wall near the entrance 16 of the manhole. Bolt fixing part 10 to which lead wire 5 for electric current is attached and lap part of zinc anode sheet plate 3
11 was coated with epoxy resin 12. Further, the terminal lead wire 7 for electric current was attached to the pipe by thermite welding, and the welded portion was covered and repaired with the asphalt pitch 14. In the illustrated embodiment, the energizing lead wire 5 and the energizing terminal lead wire 7 are shown as being respectively provided at one place. However, the number of anchor bolts 8 and nuts 9 is such that the zinc anode sheet plate 3 is a concrete wall surface. It is natural that a plurality of power supply leads 5 may be installed in order to securely attach the power supply leads. In this case, each of the power supply lead wires 5 is connected, and the power supply lead wires 5 are connected to the power supply terminal lead wires 7. Further, in the present invention, the anode is the inner wall of the concrete structure, the floor,
Attach to the ceiling or any of these concrete walls.

In the embodiment described above, the zinc anode sheet plate 3 and the pipe 6 are connected by a lead wire,
A cathode circuit is formed in which the anticorrosion current returns from the anode to the anode through a reinforcing bar and piping. As a result, the rebar of the concrete structure is polarized to reduce the potential difference from the pipe,
Macrocell corrosion of buried piping can be prevented.

Since the energizing lead wire 5 connected to the anode and the energizing terminal lead wire 7 connected to the pipe are fixed to the concrete wall near the manhole entrance 16, respectively, it is possible to prevent the pipe from being corroded by the anode. Not only that, it is easy to measure the tube-to-ground potential at any time, and the maintenance and management of anticorrosion becomes easy. The tube-to-ground potential (saturated copper sulfate reference electrode) was -420 mV at 0 m at the upstream side (position shown in Fig. 1) outside the manhole wall before construction, and -5 at 1 m.
60mV, downstream of the manhole wall before construction (Fig. 1
At the 0 m point, and -630 mV at the 1 m point. However, 4 months after construction, -5 at 0m upstream
60mV, -650mV at 1m point, -620 at 0m downstream
mV, it was -740mV at 1m point. As a result, except for the point 0 m upstream from the macrocell corrosion elimination potential -600 mV,
In each case, it was found that the electric potential was polarized in the base direction, and the anticorrosion effect appeared. In the measurement 6 months after the installation, the 0 m point on the upstream side is -605 mV, and the other points are all lower than the measured values of 4 months, and the anticorrosion elimination potential -600 mV is cleared to prevent macrocell corrosion of the buried piping. Sufficient anticorrosion potential.

[0010]

According to the present invention as described above, it is possible to prevent macrocell corrosion of a buried pipe without excavating a wall of a reinforced concrete structure.

[Brief description of the drawings]

FIG. 1 is a schematic side view of an anode mounting in which a method of the present invention is applied to a manhole.

FIG. 2 is a sectional view of FIG.

FIG. 3 shows tube-to-ground potentials before and after implementation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Manhole 2 Wall 3 Zinc anode sheet plate 4 Grounding resistance reducing agent 5 Lead wire for energization 6 Piping 7 Terminal lead wire for energization 8 Anchor bolt 9 Nut 10 Bolt tightening part 11 Lapping part 12 Epoxy resin 13 Thermit welding 14 Asphalt 15 Vinyl tape 16 Manhole entrance 17 Reinforcing bar

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16L 1/024 F16L 58/00 58/00 1/02 R

Claims (3)

[Claims] 1. A current-flow anode or an external power-insoluble anode is attached to the inner wall, floor, ceiling or all concrete walls of a reinforced concrete structure through which a buried underground pipe penetrates, and the anode is connected to a pipe inside the reinforced concrete structure. A method for preventing macrocell corrosion of buried piping, characterized by connecting. 2. The method according to claim 1, wherein the anode is a zinc galvanic anode formed in a sheet shape. 3. A sheet-like anode coated with a grounding resistance reducing agent on a reinforced concrete wall side.
The method for preventing macrocell corrosion of buried piping as described.