JP2012154783A - Small electrode system for electrochemical measurement with optical microscopic observation function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small electrode system for electrochemical measurement with an optical microscopic observation function with a simple structure, capable of performing electrochemical measurement of any small targeted area of a material surface and performing simultaneous observation of the small targeted area during the electrochemical measurement of an electrode surface.SOLUTION: In a measurement method that performs electrochemical measurement and optical microscopic observation at the same time, a small electrode system has a liquid reservoir that has an electrode area of 0.0008 cmor smaller and in which a water-dipped objective lens is arranged, a coating on the periphery of an electrode surface is composed of a combination of two or more kinds of insulators, and the maximum thickness of the coating is 100 μm or less. As for the coating, pieces of a coating adhesive tape, composed of an adhesive tape and a hardening resin, are placed opposite to each other 200 μm or less apart. It is preferable that the space between the pieces is filled with the hardening resin or that the brightness L* with the adhesive tape placed on the electrode material surface is 60 or less.

Description

  The present invention provides an electrochemical measurement function capable of observing an electrode surface in situ while electrochemically measuring a minute corrosion starting point of a corrosion resistant material, a starting point of a plating reaction, a formation process of a minute defect portion, and the like. The present invention relates to a measurement microelectrode system.

  The surface of a practical material is uneven, and in order to control electrochemical reactions such as corrosion and plating reactions, it is necessary to extract a minute region of the material surface and analyze the individual electrochemical reactions. For example, local corrosion of metallic materials is an electrochemical reaction starting from non-metallic inclusions with a size of several μm. In-situ observation of the corrosion process with a microscope can be performed simultaneously with electrochemical measurement of only that part. It is important for phenomenon elucidation.

JP 2004-239781 A

T. Suter, T. Peter, and H. Bohni, Mater. Sci. Forum, 192-194, 25, 1995

  As a system that can analyze the electrochemical reaction that occurs in any specific minute region of the material surface, it is equipped with a counter electrode and a reference electrode inside, and the tip of a glass capillary with an inner diameter of 10-100 μm filled with electrolyte is interposed A method of performing electrochemical measurement by pressing against an area including an object has been devised, and a specific method thereof has been disclosed (for example, see Non-Patent Document 1). According to this, the glass capillary is attached to the objective lens revolver of the optical microscope. After identifying the part to be subjected to electrochemical measurement with an optical microscope, it is possible to press the microcapillary against the center of the field of view at the time of microscopic observation by rotating the revolver. It is the same principle as the total. However, since an elongated glass capillary is used, it is practically impossible to observe the electrode surface simultaneously with electrochemical measurement.

  On the other hand, Patent Document 1 discloses a technique for performing electrochemical measurement on a microchip having a microchannel while simultaneously observing a microregion where a chemical reaction occurs with a thermal lens microscope. However, in this case, not the arbitrary position on the surface of the material but the position of the minute region where the chemical reaction occurs is fixed (specified) when the microchip is manufactured.

  That is, by observing the surface of a metal material with an optical microscope or the like, the position of a minute region to be subjected to electrochemical measurement is determined from the result, and the surface of the electrode can be observed in-situ with the microscope while performing electrochemical measurement of that portion. There is no known method for providing a microelectrode system.

  The present invention has been made in view of the above circumstances, and the purpose of the present invention is to have a simple structure and to perform electrochemical measurement of a desired minute area on the surface of the material and in situ observation of the electrode surface during electrochemical measurement. The present invention is to provide a microelectrode system for electrochemical measurement having an optical microscope observation function.

  The present inventor completed various aspects of the present invention by making various test studies to compensate for the disadvantages of the prior art and to solve unsolved problems. The gist of the present invention is as follows.

(1) In a measurement method in which electrochemical measurement and optical microscope observation are performed at the same time, the electrode area is 0.0008 cm ² or less, the liquid reservoir has a water immersion type objective lens, and the outer periphery of the electrode surface is covered. A microelectrode system for electrochemical measurement having an optical microscope observation function, characterized by being composed of a combination of two or more kinds of insulators and having a maximum thickness of 100 μm or less.

  (2) In the electrode system of (1) above, a microelectrode system for electrochemical measurement having an optical microscope observation function, characterized in that the coating on the outer peripheral portion of the electrode surface is composed of an adhesive tape and a curable resin.

  (3) In the electrode system of (1) or (2) above, the covering adhesive tape on the outer periphery of the electrode surface is opposed to each other with a width of 200 μm or less, and the gap is filled with a curable resin. A microelectrode system for electrochemical measurements with an optical microscope observation feature.

  (4) In the electrode system according to any one of (1) to (3), the lightness L * after adhering the adhesive tape to the electrode material surface is 60 or less. Microelectrode system for chemical measurement.

  The present invention provides an electrochemical measurement microelectrode system having a simple structure and having an electrochemical measurement of an arbitrary targeted micro area on a material surface and an optical microscope observation function capable of observing the electrode surface in situ during electrochemical measurement. Is in the provision of. According to the present invention, it is possible to easily produce an electrode surface in which only a minute part is exposed by specifying an observation position within a visual field using a stereomicroscope or a normal optical microscope. Furthermore, by using a water immersion type objective lens, it is possible to measure the relationship between the potential and current in the observation region while recording an image with an observation magnification of about 1000 times.

1 is a cross-sectional view of an electrochemical measurement microelectrode system having an optical microscope observation function according to the present invention, and a schematic diagram of a water immersion objective lens, a reference electrode and a counter electrode, and an electrochemical measurement circuit. The figure which looked at the electrode surface and insulation coating of the microelectrode system for electrochemical measurements provided with the optical microscope observation function concerning this invention from the upper direction. The figure seen from the upper part of the microelectrode system for electrochemical measurements provided with the optical microscope observation function concerning this invention. A photograph of the electrode surface coated with a small area containing MnS inclusions on a SUS304 steel surface with polyimide tape and epoxy resin. An anodic polarization curve measured in 0.1M NaCl for a small region containing MnS inclusions on a SUS304 steel surface using an electrode surface coated with polyimide tape and epoxy resin. An enlarged photograph of the central part of the electrode surface containing MnS inclusions taken in the electrolyte during the anodic polarization process. Photo of electrode surface and insulator after electrochemical measurement. An enlarged photograph of the center of the electrode surface during electrochemical measurement when the electrode surface is to be covered only with polyimide tape. An enlarged photograph of the central part of the electrode surface during electrochemical measurement when the electrode surface is to be coated only with 300 μm thick silicone.

  The best mode for carrying out the present invention will be described below.

1-3 shows a schematic configuration diagram of a microelectrode system for electrochemical measurement according to an embodiment of the present invention. In the measurement method in which electrochemical measurement and optical microscope observation are performed at the same time, the present invention has an electrode area of 0.0008 cm ² or less, a liquid reservoir portion 3 in which a water immersion type objective lens is disposed, and an electrode surface outer peripheral portion. For electrochemical measurement with optical microscope observation function, characterized in that the insulation coating is composed of two or more types of insulators (1, 2) with different surface tensions, and their maximum thickness is 100 μm or less Microelectrode system. In these drawings, an example in which the adhesive tape 1 and the cured resin 2 are used as two or more kinds of insulators having different surface tensions on the outer periphery of the electrode surface is shown.

When performing electrochemical measurement of a minute region and microscopic observation of the electrode surface at the same time, it is necessary that the field of view that can be observed with a microscope and the size of the electrode surface are substantially the same. If the observation magnification with a microscope is reduced, the observation area increases, but the resolution of the image decreases. In order to observe the situation where the form of the surface of the metal material changes with the electrochemical reaction, the magnification of the objective lens needs to be 50 times or more, preferably 100 times. For this purpose, the electrode area needs to be 0.0008 cm ² or less. If the area is larger than this, there will be a significant discrepancy between the observation area in the microscope and the size of the electrode surface, making it difficult to compare the electrochemical parameters with the microscope observation results on a one-to-one basis.

Next, the insulating coating around the electrode surface, but in general electrochemical measurement, the insulating coating on the electrode surface is implemented with one type of insulator such as an adhesive tape or a cured resin. However, if the electrode surface becomes small and the electrode area becomes 0.0008 cm ² or less, if only one type of insulator is used, fine bubbles (air) remain in the boundary area between the electrode surface and the insulator. This causes problems in electrochemical measurement and microscopic observation. For example, when four sheets of adhesive tape are used and a square electrode surface is formed at the center by sticking in the shape of a well, air remains in the overlapping portions of the adhesive tapes formed at the four corners. Furthermore, even if a single adhesive tape with a portion corresponding to the electrode surface cut is used, it is difficult to reduce or eliminate the remaining bubbles. If the bubbles remain excessively, light from the light source of the microscope is irregularly reflected and scattered, making observation with a microscope difficult.

On the other hand, when the coating on the outer periphery of the electrode surface is composed of a combination of two or more types of insulators, fine bubbles gather around one type of insulator due to the difference in surface tension between the individual insulators. Coarsening occurs and bubbles can be easily removed. For this reason, in the measurement method in which the electrochemical measurement and the optical microscope observation are performed simultaneously, when the electrode area is 0.0008 cm ² or less, the insulating coating on the outer periphery of the electrode surface needs to be composed of two or more types of insulators. is there.

  By the way, as the two or more kinds of insulators, a combination of an adhesive tape and a curable resin is preferable from the viewpoint of easy covering operation. Furthermore, in terms of easily forming a minute electrode surface at the target position of the test piece, the adhesive coating adhesive tape faces each other with a width of less than 200 μm, and the gap is filled with a curable resin. It is desirable that That is, by observing a microscope, a measurement position is determined, an adhesive tape is attached to the position, and a cured resin is poured into the electrode surface, so that an electrode surface can be produced easily and easily in a short time. Furthermore, by making the adhesive tapes face each other at an interval of less than 200 μm in width, the resin can be poured very easily, and as a result, formation of a minute electrode surface is facilitated. In the present invention, the composition of the pressure-sensitive adhesive tape and the cured resin to be used is not limited. However, the pressure-sensitive adhesive tape is a substance having a large contact angle with water droplets or bubbles, such as polyimide, and the cured resin is a water droplet or an epoxy resin. A combination of substances having a small contact angle with the bubbles is desirable. Further, in the present invention, the viscosity of the cured resin is not particularly limited, but 4 to 10 Pa · s is preferable, and 7.5 to 8.5 Pa · s is most desirable from the viewpoint of workability. Further, as the cured resin, a room temperature curing type has an advantage of good workability.

  In order to observe the electrode surface, an objective lens is required. However, in electrochemical measurements, the electrode surface is present in the electrolyte, so a water immersion type objective lens is used to obtain a high-resolution image. There is a need to. For this reason, in the present invention, it is necessary to have a liquid reservoir in which a water immersion type objective lens is arranged. The material of the liquid reservoir is not particularly defined, but it needs to be a material that does not react with an electrolyte such as acrylic or glass. Moreover, it is preferable to install the lid | cover which prevents volatilization of a liquid as needed at the upper part of a liquid reservoir part.

  By the way, in order to obtain a clear image in microscopic observation, it is necessary to make the thickness of the insulating coating formed on the outer peripheral portion of the electrode surface 100 μm or less. If the thickness of the insulating coating is increased beyond this, the image becomes unclear. This is considered to be caused by light refraction, diffraction, scattering, diffuse reflection, etc. of the material constituting the insulating coating, but the details are unknown.

  Furthermore, in order to obtain a clear image in microscopic observation, it is desirable that reflected light and stray light from other than the electrode surface be as small as possible. For this reason, when performing clear image observation, it is necessary that the lightness L * after applying the adhesive tape to the electrode material surface is 60 or less. When the lightness L * exceeds 60, stray light and reflected light increase, and the contrast of the observation image decreases. The lightness L * in this case is a value when the light source C is used.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to description of an Example.

As shown in FIG. 4, polyimide tape (thickness 69 μm, adhesive: silicone) and epoxy resin (room temperature curing, curing agent: polyamide) aiming at MnS inclusions exposed on the surface of SUS304 stainless steel whose surface was polished Amine) was used to form the electrode surface. The maximum thickness of the insulator was 75 μm, the interval between the polyimide tapes was 160 μm, and the electrode area was 0.00056 cm ² . The lightness L * of the tape surface after the polyimide tape was applied to the electrode material surface was 55. In FIG. 4, the upper and lower sides of the figure are polyimide tapes, and the left and right sides are epoxy resins. FIG. 5 shows an anodic polarization curve measured with a 0.1 M NaCl aqueous solution (non-deaerated) using a water immersion objective lens with a magnification of 100 times by preparing an acrylic liquid reservoir using this as the electrode surface. The potential was scanned with a dynamic potential at 23 mV / min from −0.3 V (Ag / AgCl electrode standard with 0.1 M NaCl as the internal solution) in the anodic polarization direction. Cathode current and anode current, current increase due to anodic dissolution current of MnS inclusions, and current oscillation accompanying micropit formation starting from inclusions can be measured. Thus, it can be seen that the electrode system of the present invention enables electrochemical measurement even on a microelectrode surface. FIG. 6 is an enlarged photograph of the central portion of the electrode surface taken in the electrolytic solution in the process of anodic polarization. From the enlarged photograph of the MnS inclusions in the center of the electrode, it can be seen that the morphological change accompanying the dissolution of the sulfide can be clearly observed. FIG. 7 is a photograph of the electrode surface and insulator after electrochemical measurement. From this, it can be seen that in the present invention, there is no crevice corrosion generated between the insulating coating on the outer periphery of the electrode and the metal test piece, which is often a problem in the conventional microelectrode system.

  FIG. 8 is an enlarged photograph of the center portion of the electrode surface at the time of electrochemical measurement when it is desired to cover the electrode surface only with a polyimide tape (thickness: 69 μm, adhesive: silicone) as a comparative example of the present invention. The thickness of the insulator was 69 μm. It can be seen that the image is unclear compared to FIG. 7 which is an example of the present invention. This is due to light scattering and irregular reflection caused by fine bubbles remaining at the boundary between the polyimide tape and the electrode surface. Similarly, FIG. 9 is an example of an image at the time of electrochemical measurement in the case where only a silicone resin is used and the thickness is 300 μm as a comparative example of the present invention. It can be seen that the image is very blurred. This is because the thickness of the insulator exceeds 100 μm, in addition to light scattering and irregular reflection by fine bubbles.

  As an application example of the present invention, it is possible to observe the electrode surface in-situ at the same time as electrochemical measurement of minute corrosion starting points such as non-metallic inclusions of stainless steel, starting point of plating reaction and formation process of minute defects It can be used as a microelectrode system for electrochemical measurement having an optical microscope observation function.

DESCRIPTION OF SYMBOLS 1 ... Adhesive tape 2 ... Cured resin 3 ... Liquid reservoir part

Claims (4)

In the measurement method that performs electrochemical measurement and optical microscope observation at the same time, the electrode area is 0.0008 cm ² or less, it has a liquid reservoir where a water immersion type objective lens is placed, and there are two or more types of coating on the outer periphery of the electrode surface A microelectrode system for electrochemical measurement having an optical microscope observation function, characterized in that the maximum thickness is 100 μm or less. The electrode system according to claim 1, wherein the coating on the outer peripheral portion of the electrode surface is made of an adhesive tape and a curable resin, and is equipped with an optical microscope observation function. 3. The electrode system according to claim 1, wherein the covering adhesive tape on the outer peripheral portion of the electrode faces each other with a width of 200 μm or less, and a curable resin is filled in the gap. Microelectrode system for electrochemical measurement with microscope observation function. The electrode system according to any one of claims 1 to 3, wherein the lightness L * after adhering the adhesive tape to the surface of the electrode material is 60 or less, the microelectrode for electrochemical measurement having an optical microscope observation function system.