JP3139938B2 - Cathodic protection current monitor and monitoring system using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion current monitor for monitoring the anticorrosion state of a metal structure subjected to cathodic protection stably and unattended for a long period of time, and to an anticorrosion monitoring system using the same.

[0002]

2. Description of the Related Art Hitherto, cathodic protection by a galvanic anode method or an external electrode method has been applied to metal structures mainly composed of steel structures exposed to seawater and freshwater.
It is necessary to make sure that these structures maintain their anticorrosion state at appropriate values for a long period of time. Conventionally, this has been confirmed by placing a reference electrode such as a silver / silver chloride electrode or a saturated calomel electrode in the vicinity of the site to be measured or holding it by a diver, and measuring the electrochemical potential of the metal structure in water. In recent years, a dedicated robot has been developed, and attempts have been made to automate the potential measurement. Since the chemical stability of the reference electrode used for potential measurement cannot be maintained for a long period of time, attempts to directly monitor the state of cathodic protection by directly attaching it to an actual structure have been applied to too many properties in terms of investment efficiency. Did not.

[0003]

On the other hand, large steel structures have recently been constructed in a seawater environment.
It has become paramount to reduce these maintenance costs and to establish a method for ascertaining the anticorrosion state at low labor costs from the viewpoint of structural safety. For this purpose, a cheap and highly stable reference electrode is directly attached to the structure, and the electrochemical information related to the anticorrosion state is monitored constantly or intermittently. In this way, it is possible to construct a structural safety assurance technology that does not require labor costs. Japanese Patent Application No. Hei 6-77701 discloses a structural design of an electrode aiming at such a technique. This is based on a potential measurement type of cathodic protection which focuses on zinc showing a relatively stable potential in seawater. This is a monitoring method. This method has a long life of the electrode due to the consumption of zinc, and there are some concerns in realizing the super long-term maintenance. Therefore, it has been demanded to consider a more stable monitoring method of the cathodic protection method.

[0004]

Therefore, in the present invention, stable measurement is carried out for an extremely long period of time by the development of a technology capable of grasping the state of cathodic protection by unmanned measurement by directly measuring the corrosion prevention current density per surface area instead of the potential. A technology has been established so that the sensing electrodes can be maintained and the state of cathodic protection can be ascertained under the same biofouling conditions as actual structures. Specifically, (1) a sensing electrode made of the same kind of metal as the underwater metal structure attached to the underwater metal structure which has been protected from corrosion, and the underwater metal structure are insulated by a lead wire coated with insulation. An anticorrosion current monitor characterized by being connected via a resistance current measuring device. (2) The cathodic protection described in (1) above, wherein the sensing electrode is fixed by welding or bolting a frame made of the same or similar metal as the underwater metal structure to be corroded to the underwater metal structure. Current monitor. (3) The cathodic protection current monitor according to (1), wherein the insulated lead wire connected to the sensing electrode is coated with a corrosion-resistant metal. (4) A plurality of the cathodic protection current monitors according to any one of (1) to (3) are arranged on the underwater metal structure,
An anticorrosion monitoring system for the entire underwater metal structure that aggregates and monitors the current data from each monitor. Solved the technical problem.

[0005]

The operation of the present invention will be described below. FIG. 1 shows a basic configuration of the present invention using an underwater steel structure as an example. The sacrificial anode 2 attached to the underwater steel structure 1 is generally made of a zinc alloy or an aluminum alloy, but since these metals are lower in potential than steel, they cause an anodic reaction and release current into seawater. I do. As a result, the current 3
Will flow in and will be cathodic protected. that time,
A sensing electrode 4 made of a metal plate of the same type or the same type as the cathodically protected structure and having its back and end surfaces insulated is attached to a part of the structure in such a manner that the sensing electrode 4 is attached to a part of the structure. Are electrically connected via the non-resistance ammeter 5, a current caused by the anti-corrosion current flows through the circuit, and by monitoring the output of the non-resistance ammeter, the anti-corrosion state at the site can be understood. For example, if a sufficient cathode current flows, the anticorrosion state is good, and conversely, if no current flows or if an anode current flows, it can be determined that the state is abnormal.

FIG. 2 shows an example of the sensing electrode 4. In the case of the example of this figure, a lead wire 6 for extracting a current is attached to a metal plate equivalent to or similar to the structure, and the back surface and the end surface are coated with an insulating and chemically stable resin or ceramic 7, If necessary, the lead wire is covered with a pipe 8 that is sufficiently durable in seawater, such as titanium or seawater-resistant stainless steel, so as to ensure long-term durability of the electrode. Note that the outer periphery of the lead wire 6 is also covered with the insulating coating 9.

FIG. 3 shows a device for attaching the sensing electrode to the underwater portion of the structure. FIG. 3A shows a frame 10 made of the same or similar metal as the structure, which is directly fillet-welded to the structure 1. The above-described sensing electrode 4 is inserted into the pocket formed by the frame 10. To prevent the electrodes from falling off under the influence of waves or the like, a stopper is welded to the shoulder of the frame, or the electrode insulating portion is tightened with screws from the entire surface of the frame. FIG. 3B is a conceptual diagram of a method of attaching the sensing electrode 4 to the structure using the bolts 12 attached to the structure 1 by stud welding, and is made of an arbitrary material having sufficient strength from the entire surface. The fixing tool 11 is fixed by tightening it with a nut. The diagram shown here is a schematic diagram for disclosing the image, and it goes without saying that various forms can be adopted as long as the basic concept is similar.

FIG. 4 is a system image for remotely monitoring the anticorrosion state of the pier 14 of the marine bridge 13 using the cathodic protection monitor including the anode 2 and the sensing electrode 4 of the present invention. The system collects data on the state of the anticorrosion current constantly or intermittently, and issues an alarm if there is any abnormality. Further, by using a telephone line or the like, it is possible to centrally manage the state of anticorrosion current in each place in an office of a corrosion prevention management company or the like.

[0009]

FIG. 5 shows the results of monitoring the state of cathodic protection in a steel pipe pile during an ocean exposure test using the cathodic protection current monitor of the present invention. Until 730 days from the start of cathodic protection, the cathodic protection current was sufficient, but then gradually decreased to 7
On the 50th day, the current value became zero. At this time, when the diver was checked the state of the anode, it was found that the anode had been completely consumed. As described above, it has been proved that the present invention can sufficiently monitor the state of cathodic protection, which is indispensable for maintaining structural strength in seawater for an extremely long time.

[0010]

According to the current monitor of the present invention described above, it is possible to efficiently and effectively improve the safety and long-term durability of the underwater metal structure in the cathodic protection state. Further, according to the monitoring system of the present invention, it is possible to monitor the anticorrosion status of the underwater metal structure remotely and unattended.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a specific example in which the present invention is applied to an underwater steel structure.

FIG. 2 is a perspective view showing an example of a sensing electrode used in the present invention.

FIG. 3 is a partial explanatory view showing a state in which a sensing electrode is attached to a submarine portion of a structure.

FIG. 4 is an explanatory diagram of a system for remotely monitoring the cathodic protection monitor provided on a pier according to the present invention.

FIG. 5 is a diagram showing the effect of the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal structure 2 Anode 3 Current wire 4 Sensing electrode 5 Non-resistance ammeter 6 Lead wire 7, 9 Insulation coating 8 Corrosion resistant metal pipe 10 Frame 11 Stopper 12 Bolt 13 Bridge 14 Bridge pier 15 Management building

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23F 13/00-13/22 G01N 17/02 G01N 27/26 351

Claims (4)

(57) [Claims] 1. A non-resistive current measurement using a sensing wire made of the same kind of metal as the underwater metal structure attached to the underwater metal structure which has been protected from corrosion, and a lead wire which is insulated and coated with the underwater metal structure. A cathodic protection current monitor characterized by being connected via a vessel. 2. The cathodic protection according to claim 1, wherein the sensing electrode is fixed by welding or bolting a frame made of the same or similar metal as the underwater metal structure to be corroded to the underwater metal structure. Current monitor. 3. An insulated lead wire connected to a sensing electrode is coated with a corrosion-resistant metal.
The cathodic protection current monitor described. 4. The underwater metal structure as claimed in claim 1, wherein a plurality of the anticorrosion current monitors according to claim 1 are arranged on the underwater metal structure, and the current data of each monitor is collected and monitored. Cathodic protection monitoring system.