JPS6383659A - Monitor for atmospheric corrosion - Google Patents

Abstract

PURPOSE:To enable obtaining of a corrosion rate with a sample metallic material by laminating working electrodes, counter electrodes and reference electrodes via thin insulating films interposed between the respective electrodes. CONSTITUTION:This monitor is formed by laminating the working electrodes 1 made of the sample metallic material; for example, mild iron, the counter electrodes 2 and the reference electrodes 3, interposing the thin film spacers 4 consisting of an insulating material between the electrodes and integrally fastening the electrodes by means of fastening bolts 5 having an insulating characteristic to constitute an electrode laminate 6. Such monitor is rested in the air atmosphere above the limit humidity and temp. for the generation of corrosion. Condensation is then generated and accelerated with alumina powder 8 as a medium and as a result, the surfaces of the respective electrodes are held wet. This power 8 is chemically equiv. to the dust in the actual environment of the atmosphere and does not impair the atmospheric corrosion mechanism of the sample metallic material. The rate of the atmospheric corrosion is, therefore, determined by an electrochemical measurement method by measuring the potential change of the electrodes 1 with respect to the electrodes 3 while slight current is passed in this state between the electrodes 1 and the electrodes 2 from a power source 9.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to an atmospheric corrosion monitor for determining the atmospheric corrosion rate of a test metal material in an atmospheric environment using an electrochemical measurement method.

[Prior art and its problems]

When designing various equipment and equipment where corrosion in the atmospheric environment is a problem, it is necessary to monitor and estimate the corrosion resistance of the test metal materials in the atmospheric environment in order to obtain important information for material selection and anticorrosion measures. There is a need for this, and as a means of achieving this, atmospheric corrosion tests are generally conducted. Various methods are known for testing the corrosion of such metal materials, but one method that allows the corrosion rate to be determined in a short period of time is to immerse an electrode made of the metal under test in a corrosive solution. A method in which the polarization reaction rate, that is, the corrosion rate is determined by electrochemical measurement in this state, is known as the polarization resistance method. By the way, atmospheric corrosion is basically due to the action of oxygen and water contained in the air, and atmospheric corrosion progresses when the metal surface is wet with almost no water. Therefore, in the conventional electrochemical measurement method described above, in which the test is performed by immersing the test metal piece in a liquid, it is greatly affected by disturbances due to the difference in the corrosion mechanism, and the corrosion rate for atmospheric corrosion cannot be accurately measured. It is impossible to apply the above-mentioned electrochemical measurement method because water cannot be measured and water is not present when the test metal material is exposed to the atmosphere as it is.

[Purpose of the invention]

This invention was made in consideration of the above points, and it is possible to determine the corrosion rate of a test metal material by an electrochemical measurement method without damaging the corrosion mechanism of the metal material in the atmosphere. The purpose is to provide an atmospheric corrosion monitor with

[Key points of the invention]

In order to achieve the above object, this invention monitors atmospheric corrosion using a t-electrode stacked structure in which a working electrode, a counter electrode, and a reference electrode made of a metal material under test are laminated with an insulating thin film interposed between them. At the same time, a chemically inert insulating powder is coated and deposited to cover the laminated surface of the electrode laminate exposed to the atmosphere, and the powder is removed by leaving the electrode laminate in an air atmosphere. Condensation, which is a factor in atmospheric corrosion, is applied, and in this state a minute current is passed between the working electrode and the counter electrode, and the corrosion rate of the metal material under test is determined from the potential change between the counter electrode and the reference electrode. This is what I did.

[Embodiments of the invention]

FIGS. 1 and 2 show an atmospheric corrosion monitor according to an embodiment of the present invention, and the corrosion monitor includes a working electrode 1 made of a metal material 2, for example, soft iron. Counter electrode 2. The reference electrodes 3 are stacked side by side as shown in the figure, and a thin film spacer 4 made of an insulating material is interposed between each electrode, and then an insulating fastening bolt 5 is inserted.
are tightened together to form an electrode laminate 6, and further embedded in a resin package 7 so that the side surface of the electrode laminate 6 is exposed to the outside. Note that the spacer 4 is preferably a thin film of 200 μm or less as thin as possible. Furthermore, when the monitor is used, an insulating powder 9, for example, alumina powder 8, is deposited to cover the exposed laminated surface of the electrode laminate 6, as shown in FIG. On the other hand, the effect 'r!' on the electrode stack 6!
1 pole 1. Lead wires are drawn out from the opposing electrodes 2 to which a DC power source 9 and an ammeter 10 are connected, and the reference electrode 3
An electrometer 11 is connected between the counter electrode 8iil and the counter electrode 8iil. Such atmospheric corrosion monitors the critical humidity for corrosion occurrence. By leaving it in an air atmosphere at a temperature higher than that, dew condensation occurs here using the powder 8 described above as a medium. As a result, the surface of each electrode becomes wet. Moreover, this powder 8 is chemically equivalent to dust in the actual atmospheric environment and does not impair the atmospheric corrosion mechanism of the metal material under test. Therefore, in this state, while flowing a minute current that becomes a polarizing current between the working electrode 1 and the counter electrode 2 from the power supply 9, the change in the potential of the working electrode 1 with respect to the reference electrode 3 is measured with the electrometer 11. Atmospheric corrosion rates can now be determined using electrochemical measurement methods similar to the conventional polarization resistance method. Figure 3 shows that alumina powder is deposited on the laminated surface of the atmospheric corrosion monitor shown in Figure 1, which is constructed by selecting soft iron as the test metal material, and is placed in an air atmosphere at a temperature of 40 ± 1°C and a relative humidity of 79 ± 2%. An example of measuring the atmospheric corrosion rate obtained when the specimen was left inside is shown below. That is, the minute current value applied between the working electrode and the counter electrode and the potential change value of the working electrode with respect to the reference electrode are measured by the method described above, and here, a formula known as the polarization resistance method is used. I corr-K (I app /ΔB) -...
-------(L) However, Icorr: Corrosion current density Iapp: Applied current (polarization current) ΔE: Potential change: Constant K in constant -0,03, applied current and potential change obtained by measurement By substituting into the formula fil, the atmospheric corrosion rate was calculated by replacing it with the corrosion current density. In addition, in order to evaluate the measurement results of the atmospheric corrosion rate obtained in this way, a comparison was made with the corrosion rate determined from the change in the weight of the test metal piece measured before and after the test using the atmospheric exposure method. As a result, the measurement accuracy error was 10%.
It was demonstrated that by using the atmospheric corrosion monitor of the present invention, the atmospheric corrosion rate can be measured with high accuracy by electrochemical measurement method.

【Effect of the invention】

As described above, according to the present invention, the working electrode, the opposing electrode, and the reference electrode made of the metal material under test are interposed with an insulating thin film interposed between them! ! A chemically inert insulating powder is coated and deposited on the laminated surface of the i-layered electrode laminate exposed to the atmosphere, and the electrode laminate is left in the air atmosphere. By passing a minute current between the working electrode and the counter electrode with dew condensation on the powder, and determining the corrosion rate of the metal under test from the potential change of the working electrode with respect to the reference electrode, This method has high practical value because it allows the surface of the test metal to become moist by forming dew condensation without damaging the corrosion mechanism of the test metal, and in this state, the atmospheric corrosion rate can be determined accurately using electrochemical measurement method. Atmospheric corrosion monitors can be provided.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the configuration of an atmospheric corrosion monitor according to an embodiment of the present invention, FIG. 2 is a diagram showing how the monitor is used, and FIG. 3 is a diagram illustrating measurement of atmospheric corrosion rate. In each figure, 1: Working electrode, 2: Counter electrode, 3: Reference electrode, 4: Insulating thin film spacer, 6: Electrode stack, 8: Insulating powder, 9
: power supply, to:' current meter, 11: electrometer. Figure 1 Do-' Solo Figure 2 Figure 3

Claims (1)

[Claims] For an electrode stack in which a working electrode, a counter electrode, and a reference electrode made of a metal material under test are stacked with an insulating thin film interposed between them, a layered surface of the electrode stack exposed to the atmosphere is covered. a chemically inert insulating powder is coated and deposited, and the electrode stack is left in an air atmosphere to cause dew condensation on the powder, and a minute current is passed between the working electrode and the counter electrode, An atmospheric corrosion monitor characterized by determining the corrosion rate of a test metal material from the potential change of a working electrode with respect to a reference electrode.