JPS5829868B2 - Silver-silver oxide reference electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a silver-silver oxide electrode used as a reference electrode when measuring the potential of a test electrode in an alkaline solution or when performing constant potential electrolysis, and in particular to measuring the hydrogen content in metals. The present invention relates to improvements in reference electrodes for hydrogen detectors used in hydrogen detectors.

When hydrogen is dissolved in a metal, the metal becomes brittle due to the interaction with mechanical tensile stress, which is generally known as hydrogen embrittlement.The degree of hydrogen embrittlement is
This can be determined by measuring the amount of hydrogen contained in the metal.

If an electrochemical method is used to measure the hydrogen content in this metal, it is possible to measure the target location while the structure is in its installed state.

Attach a hydrogen detector filled with electrolyte to the surface of the metal material under test, use a reference electrode and a constant potential electrolysis device, use the metal material under test as the positive electrode, and use the detector side electrode as the counter electrode to conduct constant potential electrolysis at the hydrogen withdrawal potential. , an ionization reaction of hydrogen dissolved in the metal material occurs, and a current flows.

When the permeation rate of hydrogen in the metal due to hydrogen extraction reaches a steady state, the magnitude of the current flowing between the metal material and the counter electrode is proportional to the hydrogen content at the location where the detector is installed. By measuring the current, the hydrogen content in the metal can be determined.

The hydrogen detection device used for this measurement is shown in FIG.

In Figure 1, 1 is an electrolytic cell, usually made of plastic material, 2 is a counter electrode, a nickel rod is used, and 3
is the reference electrode, and a calomel electrode is usually used.

4 consists of a constant potential electrolyzer and a current measuring section, 5 is a current or hydrogen amount indicator, 6 is a metal material to be tested, 7 is an electrolytic solution, usually INNaoH (1N caustic soda) solution, 10 is a nickel layer plated on the hydrogen drawing surface of the metal material under test.

In the hydrogen detector shown in FIG. 1, the reference electrode 3 must have a stable potential for a long period of at least one year.

Calomel electrodes (Hg Hg2C'2) made of mercury and mercury compounds are generally used as reference electrodes, but many commercially available products use glass for their sleeves, which makes them easy to break. If both are damaged, environmental pollution due to mercury becomes a problem.

Therefore, the potential is -0.1 to 0.3 volts vs. SCE
(vs. saturation calomel electrode potential) (Yoshizawa, Tsuruta, Yamakawa, Anticorrosion Technology, 24°514. (1975)
)), and as a result of considering electrodes that do not use mercury compounds, it was determined that a silver-silver oxide (Ag-Ag20) electrode would be appropriate.

However, when a silver wire whose surface was covered with silver oxide was immersed in 1N NaOH solution and its potential relative to a saturated calomel electrode was measured, it showed a stable potential for only one day, as shown in column //61 of the table. Ta.

This is due to the fact that silver oxide dissolves in an alkaline solution.

In view of the above-mentioned circumstances, the present invention aims to provide a silver-silver oxide electrode that can provide a stable potential over a long period of time in an alkaline solution as a reference electrode in a hydrogen detector. This invention will be explained.

FIG. 2 shows a silver-silver oxide comparison electrode according to an embodiment of the present invention. Reference numeral 14 is an electrode with a silver surface and a portion of silver oxide, and the core material is silver, platinum, Ni, or the like.

15 is a 1N NaOH solution saturated with silver oxide;
5' is a 1N NaOH solution saturated with silver oxide containing a water-soluble or swellable polymeric substance.

It is.

Reference numeral 16 denotes a container for containing the electrode and the solution, which is made of a tube made of glass or synthetic resin, and the tip thereof is provided with an extremely narrow opening, or, as shown in 17, is a container made of porous glass, porous synthetic resin, or felt. , a solution that accommodates but allows ions to pass through.

is designed to prevent it from leaking easily.

18 is a fixing member for fixing the electrode 14 to the container 16, and 19 is an external alkaline solution, i.e., an IN NaOH electrolyte that is the electrolyte of the hydrogen detector, or an alkali in which the silver-silver oxide of this invention is immersed as a reference electrode. Melt.

It is a liquid.

A silver rod whose surface was oxidized with sodium hypochlorite was used as the electrode 14 in FIG.
Calomel electrode saturated in solution.

When the potential was measured, the results shown in column /162 of the table were obtained.

As is clear from the results, it is clear that it has sufficient stability to be used as a reference electrode in an alkaline solution, and is suitable as a reference electrode for hydrogen detectors.

A platinum wire plated with silver was used as the electrode 14 in FIG.
When the potential with respect to a saturated calomel electrode was measured in 19 lN NaOH solution using a NaOH solution, /%3 in the table
As shown in the column, the values were almost the same as the results of the above example.

Although the electrode 14 in this example did not have silver oxide formed on its surface in advance, when it was immersed in the solution 15', a silver oxide layer was formed on a part of the surface, and like the electrode 14 used in the previous example, Ag-Ag2O forming an electrode.

As shown by the potential measurement results for the above two examples, the silver-silver oxide reference electrode of the present invention exhibits a stable potential in an alkaline solution for more than one year, and is a comparative electrode for hydrogen detectors. It is an effective electrode.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a hydrogen detection device, in which the hydrogen detector is shown in a longitudinal section, and FIG. 2 is a longitudinal sectional view of a silver-silver oxide comparison electrode of the present invention. In the figure, 1 is an electrolytic cell, 2 is a counter electrode, 3 is a reference electrode, 4 is a constant potential electrolyzer, 5 is an indicator, 6 is a metal material to be tested, 7 is an electrolytic solution, 10 is a nickel plating layer, and 14 is a surface Electrode 15 is silver with a part of it being silver oxide, 1- is saturated with silver oxide.
NaOH solution, 15' is a lNaOH solution saturated with silver oxide containing a water-soluble or swellable polymer substance, 16 is a container, 17 is a filter, 18 is a fixing member, 19 is lNNa
It is an OH solution.

Claims (1)

[Scope of Claims] 1. An electrode whose surface is silver and a portion of which is made of silver oxide, an alkaline solution saturated with silver oxide, and which accommodates the electrode and the solution and allows ions to pass through at least a portion of the electrode but not through the solution. 1. A silver-silver oxide reference electrode for use in an alkaline solution, characterized by comprising a means that is impermeable. 2. The silver-silver oxide comparison electrode according to claim 1, wherein a water-soluble or swellable polymeric substance is contained in an alkaline solution saturated with silver oxide.