JPH07286986A - Corrosion potential measurement electrode structure for marine steel structures - Google Patents

Abstract

PURPOSE:To provide a corrosion potential measurement electrode structure stable in a long time and excellent in durability, which is formed out of a corrosion protected body such as a marine steel structure and the like, to which cathodic protection is applied by flow anodic method using aluminum alloys, zinc alloys and the like or by an external power supply method. CONSTITUTION:Insulating material 2 is applied around a steel core 1, the surface of which is covered by a stainless pipe 3 including Cr and Mo, which satisfies that (1%Cr by weight+3%muo by weight) is equal to or more than 22, or by a titanium pipe, cables 4 made of metals identical to the aforesaid metals in constitutent are installed at the ends of the pipe, and a remaining metallic surface made of zinc 5 is cased into a circular cylinder shape so as to be formed into a cover, so that the corrosion potential measurement electrode structure is formed up, which is welded to the corrosion protected body in such a way that the core is in a level. Therefore, corrosion potential can be stably measured over a long period of time, the structure is extremely less damaged except the loss in weight of zinc, and is provided with (high durability. Corrosion potential can thereby be monitored at all times for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a galvanic anode method using an aluminum alloy, a zinc alloy or the like as a long-term anticorrosion method for marine steel structures, and an object to be anticorrosion subjected to cathodic protection by an external power source method. The present invention relates to an electrode structure for long-term stable and long-term durability for measuring anticorrosion potential.

[0002]

2. Description of the Related Art The cathodic potential is the most important factor for confirming that the body to be protected is in the anticorrosive state, and it is necessary to measure this periodically to confirm that the anticorrosive potential is reached. To measure the anticorrosion potential of a marine steel structure, the terminal of the reference electrode is brought into electrical contact with the structure, the electrode body is suspended in seawater, and a diver presses the tip of the electrode to the measurement position on the structure surface. A method of measuring with a voltmeter having a high resistance (1 MΩ or more) is used. As a reference electrode, a saturated Amano electrode or a seawater silver chloride electrode is used.

When the depth of water is deep in an offshore structure, or when the flow velocity is very high, there are cases where a predetermined position cannot be measured by the method of suspending the reference electrode from the venue for measurement.
In such a case, the saturated sweet syrup electrode or the seawater silver chloride electrode cannot withstand continuous use for a long time. A method is used in which zinc is insulated and attached to a predetermined position of a structure using zinc as a reference electrode, and the potential of a corrosion-prevented body is measured. It is known that high-purity zinc or anticorrosion zinc anode can measure the cathode potential at a predetermined position within a potential change range of about ± 30 mV.

Therefore, the zinc electrode can be designed with the size of zinc to design the life of the electrode. The problem is that the zinc shows a stable potential for a long period of time, so it is possible to make the electrode structure with long-term durability in severe marine environment such as erosion due to sand or high flow velocity, collision of trees etc. or fatigue due to waves. . For example, a sacrificial anticorrosion electrode structure that can ensure a stable anticorrosion function for a long period of time has been patented 14
No. 95866 is disclosed. However, in the electrode structure for measuring the anticorrosion potential, the metal body forming the electrode must be insulated from the structure body. In addition, the zinc reference electrode that is often used at present is covered with resin so that it is insulated from the structure body. However, simply attaching the electrode to the structure has low durability, and frequent maintenance is required.

[0005]

From the current state of the art, the present invention aims to provide an electrode structure in which a stable potential of zinc is exhibited for a long time and which has long-term durability in a severe marine environment. To do.

[0006]

In order to achieve the above object, the present invention has the following constitution. According to claim 1, first, an insulator is coated around the steel core. The insulator is made of an organic material such as epoxy resin or Teflon resin, or a material such as ceramics having a volume resistivity of 10 ⁸ Ωcm or more. The surface of the insulator is coated with a stainless steel tube containing Cr and Mo in which [wt% Cr + 3 × wt% Mo] is 22 or more. The composition of stainless steel is [wt% Cr + 3 x wt%
The reason for setting Mo] to be 22 or more is as follows.
[Weight% Cr + 3 × weight% Mo] is an index showing the resistance to occurrence of local corrosion such as pitting corrosion and crevice corrosion of stainless steel in seawater. If cathodic protection with a saturated anti-corrosion electrode of -770 mV or less is applied, Cr + 3Mo
Of 22 or more, the stainless steel has excellent durability in the marine environment without long-term local corrosion.

At the end of the pipe, there is a stainless steel cable attachment part of the same component, and the attachment of the cable to the pipe is
Use rivets, pins, or bolts and nuts so that they can be removed when the electrodes are replaced. Zinc is cast into a cylindrical shape on the surface of the stainless steel pipe other than the mounting portion, and a steel core is welded to the potential measurement position of the body to be protected so that the axis of the cylinder is horizontal. The reason why the axis of the cylinder is horizontal is that when noble stainless steel with natural potential in seawater is brought into contact with base zinc, zinc elutes fastest from the interface of the contact part, and after a long time, This is because even if corrosion progresses abnormally rapidly at the interface between stainless steel and zinc and the stainless steel and zinc separate, the contact state with the stainless steel can be maintained due to the gravity acting on the zinc.

In the second aspect, the stainless steel pipe, the cable, and the fasteners such as bolts, nuts and rivets of the first aspect are made of titanium. Titanium does not cause local corrosion in natural seawater and is as durable as or better than stainless steel.

[0009]

The present invention will be described below based on the embodiments shown in the drawings. As shown in FIG. 1, a steel core 1 is covered with an insulator (Teflon resin) 2 and a stainless steel pipe 3 (Cr: 20%, Ni: 18%, Mo: 6%) is coated on the surface thereof. Then, attach a stainless steel cable 4 of the same composition to the end, cast zinc 5 (99% or more) into a stainless steel pipe in a cylindrical shape with an outer diameter of 100 mm and a length of 200 mm, and coat it with an electrode for measuring anticorrosion potential. A was produced. Similarly, a steel core 1 is covered with an insulator 2, the surface thereof is covered with a titanium pipe 3, a titanium cable 4 is attached to the end thereof, and zinc 5 (99% or more) is attached to the titanium pipe. Outer diameter 10
0 mm, 200 mm long, cast into a cylindrical shape,
An electrode B for measuring anticorrosion potential was produced.

Further, as shown in FIG. 2, the concrete portion 8
Steel pipe pile with an outer diameter of 600 mm used as a pillar for
In the lower part of the titanium clad steel plate 10 which is covered with the splash zone and the tidal zone, the aluminum alloy galvanic anode 11 for corrosion protection of steel pipe piles is used.
The electrode A or B for measuring anticorrosion potential was welded at a position furthest away from so that the axis was horizontal. Each electrode cable is protected by an insulating coating tube 7 so as not to come into contact with the corrosion-protected body. In the electrode A, the insulator (epoxy resin) 6 is filled inside the covering tube 7. In the electrode B, the covering tube 7
Insulator 6 is not filled inside. A voltmeter 12 was used to measure the anticorrosion potential between the cable 4 and the potential measuring terminal 13 protruding on the concrete portion 8. The results are shown in Table 1.

It has been shown that the electrodes A and B of the present invention can stably measure the anticorrosive potential for a long period of time, have no damage other than the reduction of zinc, and have high durability. Also,
Even when compared with a highly accurate method in which a diver directly brings a saturated sweet syrup electrode suspended from the sea close to the measurement position to measure the potential, the reliability of the measured value remains almost unchanged. In addition, it became possible to constantly monitor the anticorrosion potential, which dramatically increased the safety of the anticorrosion zone.

[0012]

[Table 1]

[0013]

INDUSTRIAL APPLICABILITY As described above, the electrode of the present invention can stably measure the anticorrosive potential for a long period of time, and has extremely small damage and high durability in addition to the reduction of zinc. In addition, long-term and constant monitoring of the protective potential became possible.

[Brief description of drawings]

FIG. 1 shows an electrode structure of the present invention, (a) is a side view,
(B) is a front view.

FIG. 2 shows an example in which the electrode of the present invention is installed on a concrete support steel pipe pile having cathodic protection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Core 2 ... Insulator 3 ... Stainless steel pipe or titanium pipe 4 ... Stainless steel cable or titanium cable 5 ... Zinc 6 ... Insulating filler 7 ... Insulating covering pipe 8 ... Concrete 9 ... Support steel pipe pile 10 ... Steel pipe pile Coated titanium clad steel plate 11 ... Galvanic anode 12 ... Voltmeter 13 ... Potential measuring terminal

Claims (2)

[Claims] 1. A steel core is coated with an insulating material, and the surface thereof is coated with a stainless steel pipe containing Cr and Mo in which [wt% Cr + 3 × wt% Mo] is 22 or more, and the end thereof is coated. Attach the cable of the same component to the part,
And, the remaining stainless steel pipe surface is cast-coated in a cylindrical shape with zinc, so that the axis of the cylinder is horizontal, the corrosion resistance is characterized by welding the steel core to the potential measurement position of the corrosion-protected body. Measurement electrode structure. 2. A steel core is coated with an insulating material, a titanium tube is coated on the surface thereof, a titanium cable is attached to the end thereof, and a zinc column is formed on the remaining titanium tube surface with zinc. An electrode structure for measuring anticorrosion potential, characterized in that the core is made of cast steel and is welded to the anticorrosion target at a potential measurement position so that the cylinder axis is horizontal.