JPH0251989B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cathodic protection of piping in cases where cathodic protection of the entire system is difficult.

It may be difficult to perform cathodic protection for the entire system of gas or water pipes buried in the ground or water. This occurs, for example, when pipes come into contact with other structures. However, as shown in FIG. 1, cathodic protection has conventionally been applied to parts of bare metal pipes where there is a high risk of corrosion.

In Fig. 1, a flexible sheet 2 surrounds the pipe 1, including the soil, at a predetermined distance from the pipe 1 buried in the soil, and a galvanic anode 3 is installed between the pipe 1 and the flexible sheet 2. The galvanic anode 3 and the piping 1 are electrically connected by a lead wire 4 to prevent corrosion and prevent the anti-corrosion current from dispersing to other structures or other parts of the piping.

However, when using the conventional corrosion prevention method as described above, the corrosion prevention work is large-scale and requires a large excavation volume around the circumference of the pipe. This also resulted in the disadvantage that the cost required for anti-corrosion work was not high.

The present invention has been made in view of the above, and it is an object of the present invention to provide a method for electrolytic corrosion protection of piping, which eliminates the above-mentioned drawbacks and can provide corrosion protection in a simple manner.

According to the present invention, this purpose is achieved by attaching a plate-shaped galvanic anode whose outer surface is coated with an insulating coating to the outer periphery of the pipe to be protected against corrosion. There is underground water that has dissolved salts such as sodium chloride, but electrolytic molecules such as sodium chloride dissociate into positive and negative ions in the water, and when an electric field is applied, the ions move and carry electricity. (Thus, sand and soil containing groundwater are essentially considered to be electrolytes.) This is achieved by winding the corrosion protection target pipe through the medium.

The method of the present invention will be explained below using examples.

FIGS. 2a and 2b are a sectional view and a side view of an embodiment to which the method of the present invention is applied.

Reference numeral 11 indicates a bare steel pipe as a pipe to be protected against corrosion, which is buried, for example, in the ground. Reference numeral 12 denotes a galvanic anode made of, for example, plate-shaped zinc and whose outer surface is coated with insulation. The insulating coating 13 is made of, for example, synthetic resin or insulating paint by baking or painting.

The galvanic anode 12 is wound around a bare steel pipe 11 via an electrolyte 14 whose inner surface is made of sand and soil containing groundwater, and both ends of the galvanic anode 12 are tightened with bolts and nuts 15 made of synthetic resin. Then, it is wound and fixed around the bare steel pipe 11.

Since the galvanic anode 12 and the object to be prevented 11 are not electrically connected, a bond wire 16 is used to connect them.
is necessary. This bond wire may lead from individual galvanic anodes, or may bond galvanic anodes together.
It is also possible to bond to the object to be protected against corrosion in only one place.

By configuring as described above, the part of the bare steel pipe 11 to be protected against corrosion is surrounded by the galvanic anode 12,
The target portion of the bare steel pipe 11 is protected from corrosion by the galvanic anode 12 . In addition, the bare steel pipe 11 is
Since the area to be protected is surrounded and the outer surface of the galvanic anode is coated with insulation, dispersion of the anti-corrosion current to the area to be protected is also prevented.

Since the space between the corrosion protection target 11 and the galvanic anode 12 is uniformly filled with electrolyte such as conductive sand or soil containing groundwater, the supply of anticorrosion current is uniform and the corrosion prevention effect is high. The insulation coating 13 on the outside of the insulation coating 12 does not need to be in close contact with the galvanic anode, and air, water, soil, etc. may exist between them.

In addition, in the embodiment shown in FIG. 2, the galvanic anode 12 at the end of the galvanic anode 12 or the end of the insulating coating is fixed with bolts and nuts 15, and the galvanic anode 12 is wound around the bare steel pipe 11. The explanation was given using the case where it was fixed twice, but
As shown in FIG. 3, the ends of the galvanic anode 12 or the ends of the insulating coating are partially overlapped, and the overlapping parts are fixed with adhesive or the like, so that the galvanic anode 12
may be wound and fixed around the outer periphery of the bare steel pipe 11.

It can also be applied to steel pipe piles instead of the bare steel pipe 11.

As explained above, according to the method of the present invention, a galvanic anode whose outer surface is coated with insulation is wound and fixed around the outer periphery of the pipe to be protected against corrosion, and a large flexible sheet is inserted into the excavated groove as in the conventional method. It is no longer necessary to surround the pipe to be protected against corrosion at a predetermined distance from the pipe to be protected against corrosion, and there is no need to increase the cross-sectional area of the excavated trench for cathodic protection. Electrolytic corrosion protection work can be easily performed.

In addition, only the inner surface of the galvanic anode acts for corrosion prevention, and the amount of wear of the galvanic anode can be reduced. Furthermore, the anticorrosion current does not diffuse to the outside.

Further, there is almost no need to prepare the base of the pipe to be protected against corrosion.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining a conventional cathodic protection method for piping. FIGS. 2a and 2b are a sectional view and a side view of an embodiment to which the method of the present invention is applied. FIG. 3 is a sectional view showing a modification of one embodiment to which the method of the present invention is applied. 11... Bare steel pipe, 12... Galvanic anode, 13...
Insulating coating, 15... Bolt/Nut, 14... Electrolyte, 16... Bond wire.

Claims (1)

[Claims] 1. A plate-shaped galvanic anode whose outer surface is coated with insulation is placed on the outer periphery of the pipe to be protected from corrosion, through an electrolyte such as ground water containing salts, so that the inner surface of the galvanic anode faces the pipe to be protected from corrosion. A method for electrolytic corrosion protection of piping, characterized in that the pipe to be protected against corrosion is electrolytically protected by winding and fixing the pipe.