A fast corrosion measuring pen and testing method thereof

Abstract

The present invention provides a rapid corrosion measuring pen and a testing method thereof, wherein the rapid corrosion measuring pen comprises: a pen barrel with an opening at one end; a liquid absorbing pad, which is arranged at the open end of the pen barrel, and electrolyte is absorbed in the liquid absorbing pad; a conductive pen tip, which is retractably arranged on the liquid absorbing pad and has a contracted state and an extended state, in which the conductive pen tip is located inside the liquid absorbing pad and is electrically connected to the liquid absorbing pad, and in which the conductive pen tip is located outside the liquid absorbing pad; an electrode head, which is arranged in the pen barrel and one end of which contacts the liquid absorbing pad, and the electrode head comprises a reference electrode, a first insulating layer and an auxiliary electrode arranged in sequence from inside to outside; and a circuit board, which is arranged in the pen barrel and is electrically connected to the conductive pen tip, the reference electrode and the auxiliary electrode respectively. The present invention can realize rapid and accurate measurement of the corrosion condition of the target area.

Description

Technical Field

[0001] The invention belongs to the technical field of metal corrosion and protection, and in particular relates to a rapid corrosion measuring pen and a testing method thereof. Background Art

[0002] At present, the research on metal corrosion monitoring technology is in a stage of rapid development, and there are related research reports and application results both at home and abroad. The electrochemical techniques for metal corrosion testing mainly include: potentiometry, linear polarization method, AC impedance method, and electrochemical noise method.

[0003] Due to the randomness and non-stationarity of electrochemical noise technology signals, it is greatly affected by external interference. In addition, the accumulated electrochemical noise data is not rich, and its data analysis method is not perfect, so there are still few practical applications. The AC impedance method can effectively analyze the electrochemical corrosion process of metals, but it has high requirements for equipment and is easily affected by external interference. Therefore, this method is usually used in laboratory tests. The potential method and linear polarization method are widely used in engineering sites because of their simple operation and low equipment requirements. However, the linear polarization method can only calculate the polarization resistance R P value, take the B value through experience, and then according to the formula I=B / R P The corrosion rate is obtained. This method lacks accuracy in the measurement results because it cannot effectively estimate the B value. The potential method can only measure the potential of the metal being measured and qualitatively judge the corrosion of the metal, but cannot effectively evaluate the corrosion rate.

[0004] At the same time, electrochemical corrosion testing technology usually requires a three-electrode system: auxiliary electrode, reference electrode and working electrode. The reference electrode and auxiliary electrode can be realized through external connection of the instrument. The working electrode of the corrosion test on metal is the metal structure itself. Therefore, the connection between the instrument and the metal structure and the charge transfer channel between the three electrodes are the difficulties in the implementation of electrochemical testing.

[0005] Therefore, in actual engineering, the traditional electrochemical test method cannot effectively perform corrosion tests on steel structures in atmospheric and splash zones and in the absence of conductive media, such as oil and gas pipelines, metal storage tanks, steel structures, etc., due to the lack of electrolyte between the reference electrode and the metal being tested. At the same time, the traditional electrochemical test method can only test the surface potential of the metal structure, and cannot achieve in-situ measurement and analysis of the metal corrosion rate. Summary of the invention

[0006] The object of the present invention is to provide a rapid corrosion measuring pen and a testing method thereof, which can realize rapid and accurate measurement of the corrosion condition of a target area.

[0007] The present invention is achieved through the following technical solutions:

[0008] A rapid corrosion measuring pen, comprising:

[0009] A pen holder with an open end;

[0010] The liquid absorbing pad is arranged at the open end of the pen barrel, and electrolyte is absorbed in the liquid absorbing pad;

[0011] The conductive pen tip is retractably arranged on the liquid absorbing pad and has a retracted state and an extended state. In the retracted state, the conductive pen tip is located inside the liquid absorbing pad and is electrically connected to the liquid absorbing pad. In the extended state, the conductive pen tip is located outside the liquid absorbing pad.

[0012] The electrode head is arranged in the pen barrel and one end of which is in contact with the liquid absorbing pad. The electrode head comprises a reference electrode, a first insulating layer and an auxiliary electrode which are arranged in sequence from the inside to the outside;

[0013] The circuit board is arranged in the pen barrel and is electrically connected to the conductive pen tip, the reference electrode and the auxiliary electrode respectively.

[0014] Furthermore, the conductive pen tip includes a conductive contact head, a second insulating layer and an elastic member connected in sequence. An installation groove for accommodating the conductive contact head is provided at one end of the liquid-absorbing gasket facing the outside of the pen barrel. An end of the elastic member away from the second insulating layer is connected to the bottom of the installation groove. When the elastic member contracts, the conductive contact head is located in the installation groove and is electrically connected to the liquid-absorbing gasket.

[0015] Furthermore, the liquid-absorbing gasket is a water-absorbing sponge, and the electrolyte is a KCl solution.

[0016] Furthermore, a rechargeable battery is included, which is connected to the circuit board and is used to supply power to the circuit board.

[0017] Furthermore, the circuit board is connected to a display screen, and the display screen is arranged throughout the pen holder.

[0018] Further, the circuit board includes a current amplifier, an A / D converter and a microprocessor which are connected in sequence.

[0019] Furthermore, the cross-sections of the reference electrode and the auxiliary electrode are both ring-shaped, the reference electrode is an Ag / AgCl gel electrolyte reference electrode, and the outer surface of the reference electrode is covered with a dense AgCl film layer.

[0020] Furthermore, two buttons are arranged on the circuit board, and the two buttons are arranged through the pen holder.

[0021] Furthermore, a hanging frame is provided on one end of the pen barrel away from the opening, and / or a pen cap is sleeved on the opening end of the pen barrel.

[0022] A testing method using the above-mentioned rapid corrosion measuring pen comprises the following steps:

[0023] The conductive pen tip is brought into contact with the metal to be tested, so that the conductive pen tip is in a contracted state and the metal to be tested is brought into contact with the liquid absorbing pad;

[0024] Measure the initial corrosion potential E0 and initial corrosion current I0 of the metal to be tested;

[0025] Applying a plurality of polarization potentials to the metal to be tested in sequence to obtain a polarization current generated by the metal to be tested at each polarization potential, wherein the plurality of polarization potentials include E1, E2, E3, E4 and E5;

[0026] According to the formula The polarization resistance is calculated, where R P is the polarization resistance, I1 is the polarization current generated by the metal to be tested under the polarization potential E1;

[0027] According to the formula The corrosion current is calculated, where I corr is the corrosion current, I2 is the polarization current generated by the metal to be tested at the polarization potential E2, I3 is the polarization current generated by the metal to be tested at the polarization potential E3, I4 is the polarization current generated by the metal to be tested at the polarization potential E4, and I5 is the polarization current generated by the metal to be tested at the polarization potential E5;

[0028] According to the formula The corrosion rate is calculated, where V is the corrosion rate, A is the atomic mass of the metal, n is the ion valence of the metal, and F is the Faraday constant.

[0029] Compared with the prior art, the beneficial effects of the present invention are: small and portable, no need for external circuits and electrolytes, only the conductive pen tip needs to be aimed at the part to be tested for measurement, and it can be used for small area corrosion testing of steel structures and various metal surfaces, especially for parts that are difficult to access with large instruments; the liquid-absorbing gasket contains electrolyte, has excellent water retention and conductivity, and ensures the normal operation of the rapid corrosion measuring pen. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the structure of the rapid corrosion measuring pen of the present invention;

[0031] Figure 2 This is a diagram showing the arrangement of the electrode tips of the rapid corrosion measuring pen of the present invention;

[0032] Figure 3 It is a schematic diagram of the conductive pen tip of the rapid corrosion measuring pen of the present invention being extended;

[0033] Figure 4 It is a schematic diagram of the retracted state of the conductive pen tip in the rapid corrosion measuring pen of the present invention;

[0034] Figure 5The figure is a schematic diagram of the structure of the pen cover in the rapid corrosion measuring pen of the present invention.

[0035] In the figure, 1-pen holder, 11-hanging frame, 2-liquid absorption pad, 21-mounting slot, 3-conductive pen tip, 31-conductive contact head, 32-second insulating layer, 33-elastic member, 4-electrode head, 41-reference electrode, 42-first insulating layer, 43-auxiliary electrode, 5-circuit board, 6-rechargeable battery, 7-display screen, 8-button, 9-pen cover. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0039] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0040] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0041] See also Figures 1 to 4 , Figure 1 This is a schematic diagram of the structure of the rapid corrosion measuring pen of the present invention. Figure 2 This is the electrode head arrangement diagram of the rapid corrosion measurement pen of the present invention. Figure 3 This is a schematic diagram of the conductive pen tip of the rapid corrosion measuring pen of the present invention being extended. Figure 4 The schematic diagram of the retracted state of the conductive pen tip in the rapid corrosion measuring pen of the present invention. A rapid corrosion measuring pen comprises a pen barrel 1, a liquid absorbing pad 2, a conductive pen tip 3, an electrode tip 4 and a circuit board 5. The pen barrel 1 is open at one end; the liquid absorbing pad 2 is arranged at the open end of the pen barrel 1, and electrolyte is absorbed in the liquid absorbing pad 2; the conductive pen tip 3 is retractably arranged on the liquid absorbing pad 2 and has a retracted state and an extended state. In the retracted state, the conductive pen tip 3 is located inside the liquid absorbing pad 2 and is electrically connected to the liquid absorbing pad 2. In the extended state, the conductive pen tip 3 is located outside the liquid absorbing pad 2; the electrode tip 4 is arranged in the pen barrel 1 and one end thereof contacts the liquid absorbing pad 2. The electrode tip 4 comprises a reference electrode 41, a first insulating layer 42 and an auxiliary electrode 43 arranged in sequence from inside to outside; the circuit board 5 is arranged in the pen barrel 1 and is electrically connected to the conductive pen tip 3, the reference electrode 41 and the auxiliary electrode 43 respectively.

[0042] In practical use, the fast corrosion measuring pen of the present invention uses the conductive pen tip 3 as a conductor, and by contacting the conductive pen tip 3 with the external metal to be measured, the conductive pen tip 3 is contracted to a contracted state, the conductive pen tip 3 is fully in contact with the metal to be measured, and is electrically connected to the liquid absorbing pad 2, and the liquid absorbing pad 2 is in contact with the metal to be measured, so that the metal to be measured acts as a working electrode, and the liquid absorbing pad 2 contains an electrolyte, which can act as a conductive medium, so that the auxiliary electrode 43, the reference electrode 41, and the working electrode are connected. The circuit board 5 receives the electrical signals from each electrode, and the corrosion potential, corrosion current and corrosion rate of the metal to be measured can be obtained through internal signal processing and analysis. After the measurement is completed, the conductive pen tip 3 is disconnected from the metal to be measured, and the conductive pen tip 3 is extended to an extended state.

[0043] The pen holder 1 is designed to be in the shape of a gel pen, and the size can be designed to be less than or equal to Φ30mm*120mm for easy carrying.

[0044] In one embodiment, the conductive pen tip 3 includes a conductive contact head 31, a second insulating layer 32 and an elastic member 33 connected in sequence. The end of the liquid absorbing pad 2 facing the outside of the pen barrel 1 is provided with a mounting groove 21 for accommodating the conductive contact head 31. The end of the elastic member 33 away from the second insulating layer 32 is connected to the bottom of the mounting groove 21. When the elastic member 33 contracts, the conductive contact head 31 is located in the mounting groove 21 and is electrically connected to the liquid absorbing pad 2. By pressing the conductive contact head 31 externally, the elastic force of the elastic member 33 is overcome so that the conductive contact head 31 is inserted into the mounting groove 21, and the conductive contact head 31 contacts the groove wall of the mounting groove 21, so that the conductive contact head 31 is electrically connected to the liquid absorbing pad 2. When the external pressure is eliminated, the conductive contact head 31 is pushed out of the outside of the mounting groove 21 under the elastic force of the elastic member 33, and the conductive contact head 31 is separated from the contact with the liquid absorbing pad 2. Preferably, the elastic member 33 is a spring. The conductive contact head 31 may be made of a material with good conductive properties, such as the conductive contact head 31 may be made of copper.

[0045] In one embodiment, the liquid absorbing pad 2 is a water-absorbing sponge, and the electrolyte is a KCl solution. The water-absorbing sponge has high water absorption, and contains KCl solution, so that the reference electrode 41 and the auxiliary electrode 43 are connected to the metal to be tested, reducing the resistance of the test system and ensuring the accuracy of the test data.

[0046] In one embodiment, the rapid corrosion measuring pen of the present invention further includes a rechargeable battery 6, which is connected to the circuit board 5 and is used to supply power to the circuit board 5. During the measurement process, the rapid corrosion measuring pen needs to supply power to the circuit board 5, so that the circuit board 5 can apply a polarization potential to the metal to be measured through the conductive pen tip 3. Considering that some engineering sites cannot be powered, a rechargeable battery 6 is provided in the pen barrel 1. The rechargeable battery 6 can be charged and can supply power to the circuit board 5 for a long time. Therefore, the rapid corrosion measuring pen of the present invention does not require an external power supply and can be used in engineering sites that cannot be powered. In one embodiment, in order to facilitate charging of the rechargeable battery 6, a pen cap is detachably installed at one end of the pen barrel 1 away from the opening.

[0047] In one embodiment, the circuit board 5 is connected to a display screen 7, which is arranged throughout the pen holder 1. The circuit board 5 sends the obtained measurement data to the display screen 7 for display, so that the measurement personnel can observe the measurement data, such as the corrosion potential, corrosion current and corrosion rate of the metal to be measured.

[0048] In one embodiment, the circuit board 5 includes a current amplifier, an A / D converter and a microprocessor connected in sequence. The current amplifier can receive a small current from the electrode, and amplify the received small current and transmit it to the A / D converter. The A / D converter is used to convert the current into a digital signal and send the digital signal to the microprocessor. The microprocessor analyzes and processes the digital signal to obtain the corrosion potential, corrosion current and corrosion rate of the metal to be tested.

[0049] In one embodiment, the cross-sections of the reference electrode 41 and the auxiliary electrode 43 are both annular, and the reference electrode 41 is an Ag / AgCl gel electrolyte reference electrode 41, and the outer surface of the reference electrode 41 is covered with a dense AgCl film layer. This setting can achieve the fluidity and water retention of the electrolyte inside the reference electrode 41, and ensure the accuracy of the reference electrode 41. At the same time, the reference electrode 41 and the auxiliary electrode 43 are both designed to be annular, ensuring that the reference electrode 41 and the auxiliary electrode 43 are in full contact with the liquid absorbing pad 2, thereby ensuring that the internal circuit is conductive during the test. Further, the reference electrode 41 has a jacket made of polytetrafluoroethylene, and the inner gel electrolyte uses polyacrylamide and a saturated KCl solution, and one end of the jacket is provided with a microporous ceramic.

[0050] In one embodiment, two buttons 8 are provided on the circuit board 5, and the two buttons 8 are arranged throughout the pen holder 1. The measurement mode of the circuit board 5 can be changed by the buttons 8, such as potential test or corrosion rate test, and the two buttons 8 correspond to the potential test and the corrosion rate test respectively.

[0051] Please refer to Figure 5 , Figure 5 The structure of the pen cap in the rapid corrosion measuring pen of the present invention is schematically shown. In one embodiment, a hanging frame 11 is provided on the end of the pen barrel 1 away from the opening, and / or a pen cap 9 is sleeved on the open end of the pen barrel 1. The pen barrel 1 can be hung and carried by the hanging frame 11, so that it is convenient for the measurement personnel to carry the rapid corrosion measuring pen of the present invention. The pen cap 9 is sleeved on the pen barrel 1 to protect the conductive pen tip 3.

[0052] A testing method using the above-mentioned rapid corrosion measuring pen comprises the following steps:

[0053] S1, bringing the conductive pen tip 3 into contact with the metal to be tested, so that the conductive pen tip 3 is in a contracted state, and the metal to be tested is in contact with the liquid absorbing pad 2;

[0054] S2, measuring the initial corrosion potential E0 and initial corrosion current I0 of the metal to be tested;

[0055] S3, applying a plurality of polarization potentials to the metal to be tested in sequence to obtain a polarization current generated by the metal to be tested at each polarization potential, wherein the plurality of polarization potentials include E1, E2, E3, E4 and E5;

[0056] S4. According to the formula The polarization resistance is calculated, where R P is the polarization resistance, I1 is the polarization current generated by the metal to be tested under the polarization potential E1;

[0057] S5. According to the formula The corrosion current is calculated, where I corr is the corrosion current, I2 is the polarization current generated by the metal to be tested at the polarization potential E2, I3 is the polarization current generated by the metal to be tested at the polarization potential E3, I4 is the polarization current generated by the metal to be tested at the polarization potential E4, and I5 is the polarization current generated by the metal to be tested at the polarization potential E5;

[0058] S6. According to the formula The corrosion rate is calculated, where V is the corrosion rate, A is the atomic mass of the metal, n is the ion valence of the metal, and F is the Faraday constant.

[0059] In the above step S1, when the rapid corrosion measuring pen of the present invention is actually used, the conductive pen tip 3 is used as a conductor. By contacting the conductive pen tip 3 with the external metal to be measured, the conductive pen tip 3 is contracted to a contracted state, the conductive pen tip 3 is fully in contact with the metal to be measured, and is electrically connected to the liquid absorbent pad 2. At the same time, the liquid absorbent pad 2 is in contact with the metal to be measured, so that the metal to be measured acts as a working electrode. The liquid absorbent pad 2 contains an electrolyte, which can act as a conductive medium, so that the auxiliary electrode 43, the reference electrode 41, and the working electrode are conductive.

[0060] In the above step S2, before measuring the corrosion rate, it is necessary to perform a potential measurement, that is, to measure the corrosion potential E0 and corrosion current I0 of the metal to be measured. When performing the potential measurement, the circuit board 5 receives the electrical signal from the electrode, and converts the electrical signal into a digital signal output through internal signal processing and analysis, so as to obtain the corrosion potential E0 and corrosion current I0 of the metal to be measured.

[0061] In the above step S3, 5 feedback current data need to be obtained when measuring the corrosion rate. Therefore, the circuit board 5 actively applies 5 polarization potentials to the metal to be tested based on the corrosion potential E0. The 5 polarization potentials are E1, E2, E3, E4 and E5, respectively. Among them, E1=E0+10mV, E2=E0+120mV, E3=E0+130mV, E4=E0-120mV, E5=E0-130mV, thereby obtaining 5 polarization currents generated by the metal to be tested under the 5 polarization potentials, and the 5 polarization currents are I1, I2, I3, I4 and I5, respectively.

[0062] In the above step S4, the polarization resistance R in the corrosion rate calculation PIt is estimated by using the linear slope of the applied potential and the feedback current data relative to the corrosion potential +10mV. Therefore, the formula Calculate the polarization resistance R P .

[0063] In the above step S5, the slope calculation method of the Tafel zone anodic polarization curve in the corrosion rate calculation is calculated by using the linear slope of the applied potential relative to the corrosion potential +120mV, +130mV and the feedback current data, so the slope of the anodic polarization curve β a By formula The calculation method of the slope of the cathode polarization curve in the Tafel zone in the corrosion rate calculation is to use the linear slope of the applied potential relative to the corrosion potential -120mV, -130mV and the feedback current data to calculate, so the slope of the cathode polarization curve β b By formula Calculate and then use the corrosion rate calculation formula The polarization resistor R P , slope of the anodic polarization curve β a and the slope of the cathodic polarization curve β b Substituting into the corrosion rate calculation formula, we can get The corrosion current I can be calculated corr .

[0064] In the above step S6, based on the corrosion current I corr , and then according to the corrosion rate formula The corrosion rate V can be calculated. This test method uses a two-point method to obtain the slope of the straight line to obtain the polarization resistance R P . And then the slope of the Tafel zone polarization curve β a , β b All of them are obtained by simplified two-point linear fitting. The corrosion rate of the metal to be tested can be calculated by simply recording the current feedback when a certain potential is applied to the metal to be tested. The calculation is convenient and fast, time-saving and efficient, and has good applicability.

[0065] Compared with the prior art, the beneficial effects of the present invention are: small and portable, no external circuits and electrolytes are required, and only the conductive pen tip 3 needs to be aligned with the part to be tested for measurement. It can be used for small area corrosion testing of steel structures and various metal surfaces, especially for areas that are difficult for large instruments to enter; the liquid absorbent pad 2 contains electrolyte, has excellent water retention and conductivity, and ensures the normal operation of the rapid corrosion measuring pen.

[0066] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A testing method using a rapid corrosion measuring pen, characterized in that: A rapid corrosion measuring pen is included, and the rapid corrosion measuring pen includes: A pen holder with an open end; A liquid absorbing pad is arranged at the open end of the pen barrel, and electrolyte is absorbed in the liquid absorbing pad; A conductive pen tip is retractably arranged on the liquid absorbing pad and has a retracted state and an extended state. In the retracted state, the conductive pen tip is located inside the liquid absorbing pad and is electrically connected to the liquid absorbing pad. In the extended state, the conductive pen tip is located outside the liquid absorbing pad. An electrode head is arranged in the pen barrel and one end of which is in contact with the liquid absorbing pad, and the electrode head comprises a reference electrode, a first insulating layer and an auxiliary electrode arranged in sequence from inside to outside; A circuit board is arranged in the pen barrel and is electrically connected to the conductive pen tip, the reference electrode and the auxiliary electrode respectively; The method comprises the following steps: The conductive pen tip is brought into contact with the metal to be tested, so that the conductive pen tip is in a contracted state and the metal to be tested is brought into contact with the liquid absorbing pad; Measure the initial corrosion potential E0 and initial corrosion current I0 of the metal to be tested; Applying a plurality of polarization potentials to the metal to be tested in sequence to obtain a polarization current generated by the metal to be tested at each polarization potential, wherein the plurality of polarization potentials include E1, E2, E3, E4 and E5; According to the formula The polarization resistance is calculated, where R P is the polarization resistance, I1 is the polarization current generated by the metal to be tested under the polarization potential E1; According to the formula The corrosion current is calculated, where I corr is the corrosion current, I2 is the polarization current generated by the metal to be tested at the polarization potential E2, I3 is the polarization current generated by the metal to be tested at the polarization potential E3, I4 is the polarization current generated by the metal to be tested at the polarization potential E4, and I5 is the polarization current generated by the metal to be tested at the polarization potential E5; According to the formula The corrosion rate is calculated, where V is the corrosion rate, A is the atomic mass of the metal, n is the ion valence of the metal, and F is the Faraday constant.

2. The testing method according to claim 1, characterized in that: The conductive pen tip includes a conductive contact head, a second insulating layer and an elastic member connected in sequence; the end of the liquid-absorbing gasket facing the outside of the pen barrel is provided with a mounting groove for accommodating the conductive contact head; the end of the elastic member away from the second insulating layer is connected to the bottom of the mounting groove; when the elastic member contracts, the conductive contact head is located in the mounting groove and is electrically connected to the liquid-absorbing gasket.

3. The testing method according to claim 1, characterized in that: The liquid-absorbing pad is a water-absorbing sponge, and the electrolyte is a KCl solution.

4. The testing method according to claim 1, characterized in that: A rechargeable battery is also included, and the rechargeable battery is connected to the circuit board and is used to supply power to the circuit board.

5. The testing method according to claim 1, characterized in that: The circuit board is connected with a display screen, and the display screen is arranged through the pen holder.

6. The testing method according to claim 1, characterized in that: The circuit board includes a current amplifier, an A / D converter and a microprocessor which are connected in sequence.

7. The testing method according to claim 1, characterized in that: The cross sections of the reference electrode and the auxiliary electrode are both ring-shaped. The reference electrode is an Ag / AgCl gel electrolyte reference electrode, and the outer surface of the reference electrode is covered with a dense AgCl film layer.

8. The testing method according to claim 1, characterized in that: Two buttons are arranged on the circuit board, and the two buttons are arranged through the pen holder.

9. The testing method according to claim 1, characterized in that: A hanging frame is arranged on the end of the pen barrel away from the opening, and / or a pen cap is sleeved on the opening end of the pen barrel.

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