JPS6367134B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal reference electrode and a corrosion tank for measuring the corrosion rate of metal materials by electrochemical means in a high temperature and high pressure environment.

When using a reference electrode in a test under high temperature and high pressure, it is preferable to use an internal reference electrode, since using a so-called external reference electrode lacks accuracy because the actual environment of the sample metal differs from the measurement environment. However, in conventional internal reference electrodes for high-temperature, high-pressure water, due to the difference in thermal expansion coefficients between the electrode container and the electrode liquid, when the electrode is heated to a high temperature (approximately 300°C), the volume of the electrode liquid in the electrode container is equal to the volume of the container. The container expands by about 20 to 30 percent more than the container itself, which puts a lot of pressure on the container, which can cause the seal to deteriorate or break. In addition, since the electrode container is sealed, the test liquid may flow in from the liquid junction.On the other hand, if the electrode liquid thermally expands at high temperatures and a large pressure is generated, the electrode liquid flows out from the liquid junction into the test liquid. The biggest problem in practical use is that the test solution becomes contaminated and the concentration of the electrode solution changes due to repeated exposure to high and room temperatures, causing electrode deterioration in a short period of time and loss of reproducibility.

The present invention solves the drawbacks of the above-mentioned conventional examples, that is, even if the electrode solution in the electrode container expands or contracts, the electrode solution may flow out of the electrode container, or conversely, the test solution may flow into the electrode container. The purpose of this work was to provide an internal reference electrode for a corrosion test tank in a high temperature and high pressure environment, which was devised and improved to avoid this.

In order to achieve the above object, in the present invention, an internal reference electrode used in a test tank for corrosion testing in a high temperature and high pressure environment is arranged in a fixed position, and its tip is housed in the test tank. In a reference electrode having a tubular electrode container inserted into a liquid, the electrode liquid, the electrode, and the electrode wire extending from this are placed in the electrode container, and the tip is connected to the test liquid to conduct electricity. and) a means for applying a predetermined pressure to the internal space of the electrode container is provided at the distal end, and) a piston member is movably fitted into the distal end of the electrode container, and the hollow portion is provided with a means for applying a predetermined pressure to the internal space of the electrode container. The wire was made to run through it.

When the electrode liquid in the electrode container undergoes a pressure change such as expansion or compression, the piston member is moved to the distal end side, and the pressure in the internal space on the distal end side of the electrode container is adjusted to the pressure setting means. The pressure was set equal to the pressure in the test tank (equal to the pressure inside the test tank). In this way, the pressure in the internal space at the tip of the electrode container becomes equal to the pressure in the test tank, so it is possible to prevent the electrode solution and the test solution from mixing.

Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 shows sample metal 2a in an environment of high temperature and high pressure water.
(test electrode) to measure the relationship between current density and potential, that is, the polarization curve, and estimate the amount of corrosion from this curve. As is well known, the circuit shown in Figure 1 is called the constant potential method, and when a deviation △E is shown in the potential E set in advance between the test electrode 2a and the reference electrode 1, this is amplified and the deviation becomes zero. This is an example using a constant potential device 7 that automatically adjusts the current from the counter electrode 3a. pressure vessel 4
It has a heating device 6 on the outside, and a test liquid 8, a test electrode 2a made of a metal material, a reference electrode 1, and a counter electrode 3 inside.
Three electrodes (a) are set, and the portions 1c, 2c, and 3c of the electrode lead wires that pass through the pressure vessel lid plate 5 are electrically insulated and high-pressure sealed.

FIG. 2 shows in detail the internal reference electrode of the present invention. At the liquid junction with the test liquid, a porous zirconia plug 15 is installed at the tip of the electrode protection tube.
It is also possible to completely connect the liquid while preventing the Kcl solution from flowing out. Furthermore, in consideration of the Kcl solution oozing out from the plug during long-term use, a liquid buffer 14 is provided and a zirconia powder 16 impregnated with the test liquid is placed in it to prevent the Kcl solution from directly flowing into the test liquid. It may be buffered like this. In this case, a test liquid passage hole 14a of approximately 0.5 mmφ is provided at the tip of the liquid buffer 14.
is provided.

The electrode container 13 is screwed together with the liquid buffer 14,
The zirconia plug 15 is fixed by tightening.

The upper part 13a of the electrode container is screwed together with a seal plug 9 that seals from the atmosphere.Since the seal plug 9 is tapered and is made of a registered trademark of Teflon, by tightening the nut 11, the seal plug and the Ag wire 18b are connected via the ring 10. Seal plug part 9a,
9b is sealed.

Since the internal reference electrode of the present invention has a high voltage design, the electrode holder screw portion 21e is required for attachment to the container lid plate 5.
It is an internal reference electrode that is electrically and mechanically stable in high temperature and high pressure environments.

The electrodes and the electrode solution are not limited to those used in the examples, but may be used as long as they fulfill their predetermined functions under high temperature and high pressure. The internal reference electrode of this embodiment is provided with a piston 12 made of an insulating material such as resin in an electrode container 13 made of an insulating material such as zirconium oxide, and an Ag/Agcl electrode rod 18 is inserted into the piston 12. 12 and liquid junction plug 15
Fill the electrode solution 17 between the electrodes 18 and 18.
This is an Ag/Agcl electrode having an Ag/Agcl electrode portion 18a. Test solution 8a and electrode solution 17 such as Kcl solution
The seal 12 on the outer surface of the piston 12 is between
a and a packing 12b on the inner surface, and the piston 12 is sealed between the inner surface of the electrode container and the packing 12b on the inner surface.
It is slidably attached to the surface of an insulating tube 18c that electrically insulates the electrode rod 18b. Although resin is used as the material for the piston 12 in this embodiment, any material may be used as long as it has insulation properties.

Between the piston 12 and the seal plug 9, the pressure PKg/cm ² in the pressure vessel is applied to the piston 12 through the hole 13c of the electrode vessel located above the piston, so the pressure is the same on both the outer and inner surfaces of the electrode vessel 13. equilibrium is maintained. Therefore, the electrode liquid 17
Even if the volume expands due to high temperature, the piston 12 moves by that amount and flows out from the liquid junction plug 15.The electrode liquid in the electrode container is always maintained, and even when the temperature is repeated at high temperature and room temperature, the movement of the piston 12 prevents the electrode liquid from flowing out from the liquid junction plug 15. The outflow of the liquid 17 and the inflow of the test liquid 8 due to expansion and contraction of the electrode liquid 17 are prevented, and an accurate potential can be measured as a constant concentration of the electrode liquid without being affected by temperature and pressure.

Further, in this embodiment, since rubber is used for the gaskets 12a and 12b, the electrode holder 21 is cooled, and the cooling water 21c is introduced into the cooling jacket 21a to cool the sliding part of the piston 12, so that it can withstand high-temperature use. It is made to be obtained.

As described above, according to the present invention, the piston member is moved according to the volume change of the electrode liquid,
The pressure in the internal space from the tip of the electrode container containing the electrode solution was always equal to the pressure in the test tank. This prevents the electrode solution in the electrode container from flowing out into the test tank due to a change in the volume of the electrode solution, or conversely, preventing the test solution from flowing into the electrode container. In addition, while the tip of the electrode container is positioned in the test chamber under high temperature and high pressure environment, the piston member is fitted to the electrode container that is axially distant from the tip. It is the terminal part,
Not affected by high temperature and high pressure. As a result, it is possible to accurately measure potential even under high temperature and high pressure environments.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a corrosion tank to which an internal reference electrode according to the present invention is applied, and FIG. 2 is a sectional view showing the structure of the internal reference electrode used in the corrosion tank of FIG. Explanation of symbols of main parts, 2a... Sample metal (test electrode), 1... Reference electrode, 3a... Counter electrode, 7... Constant potential device, 4... Pressure vessel, 6... Heating device, 8... Test liquid, 5... Electrode container Lid plate, 12...Piston, 18...
Electrode rod, 15... Liquid junction plug, 17... Electrode liquid, 12
a, 12b...Packing, 18c...Insulating tube,
9... Seal plug, 13c... Hole of electrode container, 21
...Electrode holder, 21a...Cooling jacket, 21
c... Cooling water, 14... Liquid buffer, 16... Zirconia powder, 14a... Test liquid conduction hole, 13... Electrode container,
21e... Electrode holder screw part.

Claims (1)

[Claims] 1. An internal reference electrode used in a test tank for corrosion testing in a high temperature and high pressure environment, which is arranged in a fixed position and whose tip is immersed in a test liquid contained in the test tank. It has an inserted tubular electrode container, an electrolytic solution, an electrode, and an electrode wire extending from the electrode are arranged near the tip of the internal space of the electrode container, and the test liquid is placed in the tip of the electrode container. A means is provided to maintain electrical conductivity by establishing a liquid connection with the
A means for applying a pressure equal to the pressure in the test chamber to the internal space of the electrode container is provided at the distal end, and a piston member is movably fitted to the distal end of the electrode container, and a piston member is movably fitted to the distal end of the electrode container. passes through the center of the piston member, and when the electrode liquid in the electrode container undergoes a volume change such as expansion or compression, the piston member is moved to the distal end side of the electrode container, and the An internal reference electrode for a corrosion test tank in a high temperature and high pressure environment, characterized in that the pressure at the tip of the electrode container is equal to the pressure set by the pressure setting means. 2. The internal reference electrode according to claim 1, wherein a buffer is provided at the tip of the electrode container to prevent the test liquid from flowing in and to prevent the electrode liquid from flowing out. . 3. The internal reference electrode according to claim 2, wherein an annular seal member is interposed between the piston member and the electrode wire and between the electrode container.