Kelvin probe measurement potential and metal corrosion potential calibration device and method

Abstract

The present application belongs to the technical field of electrochemical testing, and particularly relates to a Kelvin probe measurement potential and metal corrosion potential calibration device and method. The main structure of the Kelvin probe measurement potential and metal corrosion potential calibration device comprises an insulating holder, a metal test box arranged on the holder, and a reference electrode arranged on the metal test box. The Kelvin probe measurement potential and metal corrosion potential calibration method comprises five steps of installation, preparation, SKP potential testing, corrosion potential testing, and calibration. The device has a simple structure, the method is easy to operate, there is no cross contamination in the measurement process, the influence of human factors and environmental factors on the SKP potential measurement value in the measurement process is solved, the accuracy of the test result and the correctness of the metal material corrosion resistance performance screening result are improved, and important references are provided for the development of new steel varieties, the selection of materials in engineering structure design, and the evaluation of the service life of steel.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical testing, and particularly relates to a Kelvin probe measurement potential and metal corrosion potential calibration device and method. BACKGROUND

[0002] The scanning Kelvin probe (SKP) can be used for metal surface potential measurement, is a rapid and sensitive non-destructive monitoring technology, can not contact the surface of the sample to be measured, and can detect the metal surface electron work function in air or vacuum conditions through a vibrating capacitor probe, and has been widely used in corrosion detection and corrosion monitoring. The micro-area electrochemical system SKP module is used in the simulated general atmosphere environment and the simulated marine atmosphere environment, the Volta potential of the metal or semiconductor surface is detected based on the non-destructive and non-contact conditions, the pitting probability or corrosion resistance of the metal material is evaluated, the human error can be effectively reduced; the SKP module can be used for measuring the potential of different samples, and the high-throughput in-situ non-destructive detection can be realized to realize the rapid screening of the corrosion resistance of different material samples; the SKP module can be used for evaluating the cathodic delamination degradation of the coating and the repair performance of the self-repairing coating; the SKP module can be used for measuring the hydrogen diffusion coefficient of high-strength steel. The main factors affecting the accuracy of the SKP probe potential measurement value include the probe size, the distance between the probe and the sample surface, and the surrounding environmental factors (temperature and humidity). Therefore, the potential correction is a necessary step before using the Kelvin probe, the SKP potential is usually linearly related to the metal corrosion potential, and the calibration of the SKP potential and the corrosion potential is a basic prerequisite for ensuring the accuracy of the measurement data.

[0003] Stratmann et al. expounds that there is a linear relationship between the metal corrosion potential (or open circuit potential) and the scanning Kelvin probe measurement potential: In the formula,

[0004] E corr represents the corrosion potential of the sample, represents the Volta potential difference between the probe and the sample obtained by the scanning Kelvin probe measurement, and the value of A can be determined by simultaneously measuring the values of E corr and . For a specific type of probe, the value of A is determined by setting the distance between the probe and the sample and the specific sensitivity range of the instrument. The calibrated Kelvin probe can be used for evaluating the corrosion tendency of the metal material.

[0005] The calibration method commonly used in the prior art is to connect the back parts of three metal plates (pure copper plate, pure iron plate, and pure zinc plate) of the same size by soldering, connect a wire for connecting the working electrode of the SKP sample and the open circuit potential measurement to the back part of the ternary metal sample, and then encapsulate and polish flat. During testing, saturated copper sulfate, saturated ferrous sulfate, and saturated zinc sulfate solutions are respectively dropped onto the surfaces of the pure copper plate, the pure iron plate, and the pure zinc plate, and after the dropping is completed, the SKP potential and the open circuit potential are measured respectively, and the SKP potentials and the open circuit potentials of different metals obtained are calibrated. However, the following disadvantages are obvious: first, the surfaces of the ternary metal sample need to be directional polished before measurement, and due to the close arrangement of the metal samples, cross contamination is easy to occur during the polishing process, which affects the potential distribution of the metal surface; second, during the dropping of the saturated metal salt solution, improper operation can easily cause mixing between different solutions or penetration through the boundary to different metal substrates; third, the height of the droplet formed by the saturated salt solution dropped on the surface of the metal sample is too low, and the reference electrode is placed in the solution, which is easy to cause liquid expansion and overflow to contaminate the adjacent metal substrate.

[0006] Therefore, a Kelvin probe measurement potential and metal corrosion potential calibration device and method are developed and designed to avoid the cross contamination phenomenon occurring in the measurement process. SUMMARY

[0007] The purpose of the present application is to overcome the shortcomings of the prior art, develop and design a Kelvin probe measurement potential and metal corrosion potential calibration device and method, and eliminate the differences in the SKP potential measurement value caused by human factors and environmental factors during the measurement process.

[0008] In order to achieve the above-mentioned purpose, the main structure of the Kelvin probe measurement potential and metal corrosion potential calibration device according to the present application comprises an insulating holder, a metal test box arranged on the insulating holder, and a reference electrode arranged on the metal test box; the insulating holder is composed of a plurality of U-shaped clamping grooves, a fixing plate is arranged in the clamping groove, the back surface of the metal test box is connected to the fixing plate through bolts and gaskets, the top surface is provided with a circular hole, and the front surface is provided with a reference electrode; the reference electrode is connected to the metal test box through PVC bolts and penetrates the metal test box.

[0009] The metal test box according to the present application has a size of 25mm×25mm×15mm and is made of pure copper (99.9%), pure iron (99.5%), and pure zinc (99.9%); the bolts and the gaskets are made of metal materials, and the gaskets have the functions of fixing the bolts and connecting the test wires; the reference electrode comprises a solid reference electrode.

[0010] The Kelvin probe measurement potential and metal corrosion potential calibration method according to the present application comprises the following steps:

[0011] Step 1, installation

[0012] First, polish the round hole;

[0013] Then, install the metal test box on the insulating seat and adjust the level;

[0014] Finally, set the reference electrode on the metal test box;

[0015] Step 2, preparation

[0016] First, configure the saturated sulfate solution;

[0017] Then, drop the saturated sulfate solution into the round hole;

[0018] Finally, connect the metal test box with the SKP potential measuring device and connect the reference electrode with the corrosion potential measuring device;

[0019] Step 3, test the SKP potential

[0020] First, start the SKP potential measuring device and move the probe to 100 μm above the center of the saturated sulfate solution surface;

[0021] Then, set the amplitude, frequency and sensitivity of the SKP potential measuring device;

[0022] Finally, measure the SKP potential of the Cu / CuSO4, Fe / FeSO4 or Zn / ZnSO4 electrode by the SKP potential measuring device;

[0023] Step 4, test the corrosion potential

[0024] Measure the corrosion potential of the Cu / CuSO4, Fe / FeSO4 or Zn / ZnSO4 electrode by the corrosion potential measuring device;

[0025] Step 5, calibration

[0026] Calibrate the measured SKP potential and corrosion potential.

[0027] The saturated sulfate solution involved in the present application includes saturated copper sulfate solution, saturated ferrous sulfate solution and saturated zinc sulfate solution.

[0028] Compared with the prior art, the Kelvin probe measurement potential and metal corrosion potential calibration device has the main body structure comprising an insulating card holder, a metal test box arranged on the insulating card holder, and a reference electrode arranged on the metal test box, and the Kelvin probe measurement potential and metal corrosion potential calibration method comprises five steps of installation, preparation, test of SKP potential, test of corrosion potential and calibration; the device structure is simple, the method operation is simple, there is no cross contamination phenomenon in the measurement process, the influence of human factors and environmental factors on the SKP potential measurement value in the measurement process is solved, the accuracy of the test result and the correctness of the metal material corrosion resistance performance screening result are improved, and important reference is provided for the development of new steel varieties, the material selection of engineering structure design and the evaluation of steel service life. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The Kelvin probe measurement potential and metal corrosion potential calibration device is related to a main body structure principle schematic diagram.

[0030] Figure 2 The Kelvin probe measurement potential and metal corrosion potential calibration device is related to a partial structure principle schematic diagram.

[0031] Figure 3 The Kelvin probe measurement potential and metal corrosion potential calibration device is related to a use state schematic diagram.

[0032] Figure 4 The Kelvin probe measurement potential and metal corrosion potential calibration device is related to a 250 mu m probe measurement SKP potential and corrosion potential calibration curve diagram.

[0033] Figure 5 The Kelvin probe measurement potential and metal corrosion potential calibration device is related to a 500 mu m probe measurement SKP potential and corrosion potential calibration curve diagram. Specific implementation method

[0034] The Kelvin probe measurement potential and metal corrosion potential calibration device is related to a use state schematic diagram.

[0035] Example 1

[0036] The main body structure of the Kelvin probe measurement potential and metal corrosion potential calibration device relates to the embodiment and comprises an insulating holder 1, a clamping groove 2, a metal test box 3, a fixed plate 4, a bolt 5, a gasket 6, a round hole 7, a reference electrode 8 and a PVC bolt 9; the insulating holder 1 is composed of three U-shaped clamping grooves 2, the clamping groove 2 is provided with the metal test box 3 and the fixed plate 4, the back of the metal test box 3 is connected with the fixed plate 4 through the bolt 5, the gasket 6 is further arranged between the metal test box 3 and the bolt 5, the top surface of the metal test box 3 is provided with the round hole 7, the front surface is provided with the reference electrode 8, one end of the reference electrode 8 is arranged in the metal test box 3, and the other end is arranged outside the metal test box 3, and the metal test box 3 is connected with the reference electrode 8 through the PVC bolt 9.

[0037] The back of the metal test box 3 is provided with a threaded hole with a diameter of 2.5 mm and a depth of 2.5 mm, so as to be connected with the fixed plate 4 through the bolt 5 and the gasket 6, the front surface is provided with a through-threaded slot with a notch diameter of 5 mm, so as to be connected with the reference electrode 8 through the PVC bolt 9; the round hole 7 has a diameter of 10 mm and a depth of 10 mm, and is formed by machining.

[0038] The specific process of the Kelvin probe measurement potential and metal corrosion potential calibration method relates to the embodiment and comprises the following steps.

[0039] Step 1, installation

[0040] Firstly, the round hole 7 is polished to 1200 mesh by using the silicon carbide sandpaper;

[0041] Then, the metal test box 3 made of pure copper is connected with the fixed plate 4 through the bolt 5 and the gasket 6, and is installed on the insulating holder 1 and leveled by using the level;

[0042] Finally, the reference electrode 8 is arranged on the metal test box 3 through the PVC bolt 9;

[0043] Step 2, preparation

[0044] Firstly, the blue saturated copper sulfate solution is prepared by using the copper sulfate pentahydrate;

[0045] Then, the saturated copper sulfate solution is added dropwise into the round hole 7 through the pipette, so that the round hole 7 is just filled with the saturated copper sulfate solution and no saturated copper sulfate solution overflows;

[0046] Finally, the gasket 6 is connected with the SKP potential measurement device through the test lead, and the reference electrode 8 is connected with the corrosion potential measurement device through the test lead;

[0047] Step 3, test SKP potential

[0048] First, start the SKP potential measuring device, move the 500 μm probe to the center position of the saturated copper sulfate solution, and gradually approach the liquid surface. When the bottom end of the probe is 100 μm away from the liquid surface, stop moving;

[0049] Then, set the amplitude of the SKP potential measuring device to 30 μm, the frequency to 80 Hz, and the sensitivity to 1 mV;

[0050] Finally, measure the SKP potential of the Cu / CuSO4 electrode by the SKP potential measuring device;

[0051] Step 4, test the corrosion potential

[0052] Measure the corrosion potential of the Cu / CuSO4 electrode by the corrosion potential measuring device;

[0053] Step 5, calibration

[0054] Make a calibration curve for the measured SKP potential and corrosion potential of the Cu / CuSO4 electrode.

[0055] Example 2:

[0056] The main structure of the Kelvin probe measurement potential and metal corrosion potential calibration device involved in this embodiment is the same as that of Example 1.

[0057] The specific process of the Kelvin probe measurement potential and metal corrosion potential calibration method involved in this embodiment is different from that of Example 1 in that:

[0058] The metal test box 3 of pure copper material involved in step 1 is replaced by a metal test box 3 of pure iron material;

[0059] Step 2 is to prepare a light green saturated ferrous sulfate solution by dissolving ferrous sulfate heptahydrate. The saturated copper sulfate solution involved in the following steps is replaced by a saturated ferrous sulfate solution, and the Cu / CuSO4 electrode is replaced by a Fe / FeSO4 electrode;

[0060] The 500 μm probe involved in step 3 is replaced by a 250 μm probe.

[0061] Example 3:

[0062] The main structure of the Kelvin probe measurement potential and metal corrosion potential calibration device involved in this embodiment is the same as that of Example 1.

[0063] The specific process of the Kelvin probe measurement potential and metal corrosion potential calibration method involved in this embodiment is different from that of Example 1 in that:

[0064] The metal test box 3 of pure copper material involved in step 1 is replaced by a metal test box 3 of pure zinc material;

[0065] Step 2 is to prepare a colorless clear saturated zinc sulfate solution by zinc sulfate heptahydrate, and the following steps involving saturated copper sulfate solution are replaced by saturated zinc sulfate solution, and Cu / CuSO4 electrode is replaced by Zn / ZnSO4 electrode.

Claims

1. A method for calibrating the potential measurement and metal corrosion potential using a Kelvin probe, characterized in that, The Kelvin probe measurement potential and metal corrosion potential calibration device is implemented based on the following process steps: Step 1, installation First, polish the round hole; Then, install the metal test box on the insulating holder and level it; Finally, set the reference electrode on the metal test box; Step 2, preparation First, prepare the saturated sulfate solution; Then, add the saturated sulfate solution to the round hole; Finally, connect the metal test box to the SKP potential measurement device and connect the reference electrode (8) to the corrosion potential measurement device; Step 3, test the SKP potential First, start the SKP potential measurement device and move the probe to 100 μm above the center of the saturated sulfate solution surface; Then, set the amplitude, frequency, and sensitivity of the SKP potential measurement device; Finally, measure the SKP potential of the Cu / CuSO4, Fe / FeSO4, or Zn / ZnSO4 electrode using the SKP potential measurement device; Step 4, test the corrosion potential Measure the corrosion potential of the Cu / CuSO4, Fe / FeSO4, or Zn / ZnSO4 electrode using the corrosion potential measurement device; Step 5, calibration Calibrate the measured SKP potential and corrosion potential to obtain a calibration curve; The main structure of the Kelvin probe measurement potential and metal corrosion potential calibration device includes an insulating holder, a metal test box arranged on the insulating holder, and a reference electrode arranged on the metal test box. The insulating holder is composed of several U-shaped clamping grooves, and a fixing plate is arranged in the clamping groove. The back of the metal test box is connected to the fixing plate through bolts and gaskets, the top surface is provided with a round hole, and the front surface is provided with a reference electrode. The reference electrode is connected to the metal test box through a PVC bolt and penetrates the metal test box.

2. The method of calibrating Kelvin probe measurements of potential versus metal corrosion potential of claim 1, wherein, The back of the metal test box is provided with a threaded hole with a diameter of 2.5 mm and a depth of 2.5 mm, so that it can be connected to the fixing plate through bolts and gaskets. The front surface is provided with a through-threaded slot with a slot diameter of 5 mm, so that it can be connected to the reference electrode through a PVC bolt. The size of the metal test box is 25 mm x 25 mm x 15 mm, and the material includes pure copper, pure iron, and pure zinc.

3. The method of calibrating Kelvin probe measurements of potential versus metal corrosion potential of claim 1, wherein, The bolts and gaskets are made of metal, and the gaskets have the functions of fixing the bolts and connecting the test leads.

4. The method of calibrating Kelvin probe measurements of potential versus metal corrosion potential of claim 1, wherein, The diameter of the round hole is 10 mm, and the depth is 10 mm, which is formed by machining.

5. The method of calibrating Kelvin probe measurements of potential versus metal corrosion potential of claim 1, wherein, The reference electrode includes a solid reference electrode.

6. The method of calibrating Kelvin probe measurements of potential versus metal corrosion potential according to any one of claims 1-5, wherein, The saturated sulfate solution includes saturated copper sulfate solution, saturated ferrous sulfate solution, and saturated zinc sulfate solution.

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