Determination method for studying influence of carbon element on electrochemical corrosion behavior of steel grounding body

Abstract

The invention relates to a determination method for researching the influence of carbon on the electrochemical corrosion behavior of a steel grounding body, and particularly aims at the corrosion influence of a common flexible graphite grounding material on a carbon steel grounding material at present. With wide application of carbon-based grounding materials in the grounding industry, solving of the problem of accelerated corrosion of the carbon-based grounding materials to other metal materials (especially steel materials) is very important. The invention provides an electrochemical corrosion behavior testing method based on an electrochemical workstation, which is characterized in that a flexible graphite grounding material and a traditional carbon steel grounding material are prepared into a graphite-carbon steel couple pair, and the influence of carbon elements contained in a carbon-based grounding material on the corrosivity of the steel grounding material is researched. The application range and grounding safety and stability of the carbon-based grounding material in the technical field of grounding engineering can be improved by carrying out objective test research on the applicability of the carbon-based grounding material.

Description

Technical Field

[0001] The invention belongs to the technical field of grounding engineering, and in particular relates to a determination method for studying the effect of carbon element on the electrochemical corrosion behavior of a steel grounding body. Background Art

[0002] Carbon-based grounding materials, mainly graphite grounding materials, are currently the most widely used type of non-metallic conductive materials in the field of electrical grounding. Graphite's metallic conductivity, chemical inertness, and good corrosion resistance make it have great development potential in electrical grounding materials.

[0003] However, in some operation and maintenance excavations, it was found that carbon-based grounding materials have accelerated corrosion on other metal materials (especially steel materials). The main reason is that carbon-based grounding materials are materials with carbon as the main element, and carbon elements may form a primary battery (galvanic corrosion) with other metal grounding materials, aggravating the corrosion of other metal materials.

[0004] Therefore, the use of carbon-based grounding materials may also increase the failure risk of the grounding grid, making the application of carbon-based grounding materials controversial in the industry. The above also led to some regions explicitly prohibiting the use of carbon-based materials such as resistance reducing agents and graphite-based flexible graphite grounding bodies. The reason is that existing scientific research on carbon-based grounding materials is insufficient in objective experimental research and cannot form a solid explanatory theory. Summary of the invention

[0005] The present invention provides a determination method for studying the effect of carbon element on the electrochemical corrosion behavior of steel grounding bodies, which can obtain the influence mechanism of carbon-based grounding materials on the corrosion of steel and provide theoretical support for the wide application of carbon-based grounding materials in the field of grounding engineering.

[0006] The present invention is achieved through the following technical solutions:

[0007] 1. A method for determining the effect of carbon on the electrochemical corrosion behavior of steel grounding bodies, using an electrochemical workstation to conduct a galvanic corrosion experiment on a "graphite-carbon steel" galvanic couple. Graphite is used as the cathode sample and carbon steel is used as the anode sample. There is a large driving potential difference (~400mV) greater than 0.25V between the two at the initial stage of coupling, which meets the necessary conditions for galvanic corrosion.

[0008] 2. Preparation of cathode graphite sample in galvanic couple;

[0009] 3. Preparation of anode carbon steel specimen for galvanic couple;

[0010] 4. Preparation of soil electrolyte;

[0011] 5. Construction of "graphite-carbon steel" galvanic corrosion experimental device;

[0012] 6. Determination of galvanic corrosion behavior of "graphite-carbon steel";

[0013] 7. Export test data for data processing and analysis.

[0014] Compared with the prior art, the present invention has the following excellent technical effects:

[0015] Efficient evaluation of corrosion behavior: The electrochemical corrosion behavior of grounding materials is studied through electrochemical work. The operation is simple, the measurement takes a short time, and the measurement results are accurate, which can achieve a rapid evaluation of corrosion performance.

[0016] Economical: Compared with the traditional weight loss method, the use of an electrochemical workstation to test electrochemical corrosion behavior can save a lot of time and labor costs spent on sample burial.

[0017] The beneficial effects of the present invention are:

[0018] Enhance grounding safety: Carbon-based grounding materials are widely used. By studying the corrosiveness of carbon-based grounding materials themselves and their corrosive effects on other grounding materials, we can timely predict the safety hazards caused by the application of carbon-based grounding materials, reduce blind consumption, and ensure the reliable operation of the power system.

[0019] Increase service life: Traditional metal grounding materials will be affected by various factors during long-term use, such as carbon-based grounding materials (graphite grounding modules and carbon-based resistance reducers), resulting in performance degradation. By studying the influence of carbon elements on the corrosion behavior of carbon steel, improvement measures can be made in advance to extend the service life of traditional metal grounding materials.

[0020] Prevent corrosion: The carbon element in carbon-based materials may form a macroscopic galvanic cell with traditional metal grounding materials, resulting in electrochemical corrosion. By studying the effect of carbon elements on the electrochemical corrosion behavior of carbon steel, effective measures are proposed to prevent the metal grounding materials from being aggravated by corrosion.

[0021] Provide theoretical support: Through objective experimental research on the applicability of carbon-based grounding materials, a theoretical basis is provided for the widespread application of carbon-based grounding materials in the field of grounding engineering.

[0022] Therefore, the proposed "a determination method for studying the influence of carbon elements on the electrochemical corrosion behavior of steel grounding bodies" has obvious beneficial effects, which can increase the application scope of carbon-based grounding materials in the field of grounding engineering technology and enhance the safety and stability of grounding. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the overall flow chart of the method of the present invention;

[0024] Figure 2 is a diagram of a galvanic corrosion experimental device in the method of the present invention;

[0025] Figure 3 The relationship curve between the galvanic corrosion current and galvanic corrosion potential of the anode carbon steel obtained by the method of the present invention and the coupling time;

[0026] Figure 4 It is a schematic diagram of "graphite-carbon steel" galvanic corrosion in the method of the present invention. DETAILED DESCRIPTION

[0027] In order to clearly and completely understand the technical solution, the present invention is further described in conjunction with the embodiments and drawings. In some specific embodiments of the present invention, the test method for studying the corrosion of carbon element to steel grounding material comprises the following steps:

[0028] S1: Preparation of cathode graphite sample in galvanic couple

[0029] like Figure 1 (a), comprising the following sub-steps:

[0030] S11 disassembles a single graphite wire from the finished linear graphite grounding material;

[0031] S12 unfolds the graphite wire into sheets, and cuts the graphite sheets with a length and width of 1 cm;

[0032] S13 uses epoxy resin glue to encapsulate the other five sides of the flake graphite, leaving only one side with an area of ​​1 cm×1 cm, and leaves it for a day to allow the epoxy resin to air-dry and take shape.

[0033] S2: Preparation of anode carbon steel specimen for galvanic couple

[0034] like Figure 1 (b), comprising the following sub-steps:

[0035] S21 uses a cutting machine to cut carbon steel material into small cubes with a cross-sectional area of ​​1 cm × 1 cm;

[0036] S22 uses sandpaper of different mesh sizes to polish the surface of small square carbon steel to clean the surface oxide layer;

[0037] S23 Soak the carbon steel sample in acetone solution for 5 minutes, then rinse it repeatedly with alcohol to remove residual grease on the surface;

[0038] S24 uses epoxy resin glue to encapsulate the other five sides of the block, leaving only one side with an area of ​​1cm×1cm, and leaves it for a day to allow the epoxy resin to air-dry and take shape.

[0039] S3: Preparation of soil electrolyte

[0040] like Figure 1 (c), comprising the following sub-steps:

[0041] S31 Weigh 50 g of air-dried soil sample that has passed through a 2 mm pore size sieve and put it into a 1000 ml wide-mouth plastic extraction bottle, add 250 ml of decarbonated water, add a stopper, and shake on a shaker for 5 min;

[0042] S32 Use the suction filtration equipment (suction funnel) to filter in time, and discard the first 10ml of filtrate. If the filtrate is turbid, it should be filtered again until a clear leachate is obtained, that is, a soil leachate with a water-soil ratio of 5:1.

[0043] S4: Construction of the “graphite-carbon steel” galvanic corrosion experimental device

[0044] like Figure 1 (d) and Figure 2 As shown, the galvanic corrosion experimental device includes an electrochemical electrolytic cell, a soil electrolyte, a carbon steel sample, a graphite sample, two platinum sheet working electrode clips, and a reference electrode (saturated calomel, Hg / HgO electrode), and also includes the following sub-steps:

[0045] S41 adds the soil leachate into a three-electrode electrolytic cell;

[0046] S42 fixes the anode carbon steel and cathode graphite samples on working electrode 1 and working electrode 2 respectively, and then immerses the two working electrodes and the reference electrode in the electrolytic cell;

[0047] The two working electrodes of S43 are arranged in parallel and their heights are kept consistent.

[0048] S5: Determination of galvanic corrosion behavior of “graphite-carbon steel”

[0049] like Figure 1 (e), comprising the following sub-steps:

[0050] S51 opens the Versa Studio electrochemical test software, selects the "Galvanic corrosion" module, and the test scan rate is one test point every 5 minutes;

[0051] S52 starts from the test and after 4 hours of test time, 48 test points are obtained, of which the data corresponding to the time 0h is the data measured at 5s;

[0052] S53 derives galvanic corrosion potential and galvanic corrosion current data.

[0053] Example 1

[0054] A test method for studying the effect of carbon elements in a "graphite-carbon steel" galvanic couple on the corrosion of steel grounding materials, such as Figure 1 As shown, the following steps are included:

[0055] S1: Preparation of a cathode graphite sample with a single exposed side of 1 cm in length and width in a “graphite-carbon steel” couple, the steps include:

[0056] S11 disassembles a single graphite wire from the finished linear graphite grounding material;

[0057] S12 unfolds the graphite wire into a sheet, and cuts the graphite sheet into a size of 1 cm in length and width and 1 cm in width;

[0058] S13 uses epoxy resin glue to encapsulate the other five sides of the flake graphite, leaving only one side with an area of ​​1 cm×1 cm, and leaves it for a day to allow the epoxy resin to air-dry and take shape.

[0059] S2: Preparation of anode carbon steel specimen with one side exposed in length and width of 1 cm in a “graphite-carbon steel” thermocouple pair, the steps include:

[0060] S21 uses a cutting machine to cut carbon steel material into small cubes with a cross-sectional area of ​​1 cm × 1 cm;

[0061] S22 uses sandpaper of different mesh sizes to polish the surface of small square carbon steel to clean the surface oxide layer;

[0062] S23 Soak the carbon steel sample in acetone solution for 5 minutes, then rinse it repeatedly with alcohol to remove residual grease on the surface;

[0063] S24 uses epoxy resin glue to encapsulate the other five sides of the block, leaving only one side with an area of ​​1cm×1cm, and leaves it for a day to allow the epoxy resin to air-dry and take shape.

[0064] S3: Preparation of soil electrolyte in Southwest China (Yunnan), the steps include:

[0065] S31 Weigh 50 g of air-dried soil sample that has passed through a 2 mm pore size sieve and put it into a 1000 ml wide-mouth plastic extraction bottle, add 250 ml of decarbonated water, add a stopper, and shake on a shaker for 5 min;

[0066] S32 Filter using a suction filtration device (suction funnel), and discard the first 10 ml of filtrate. If the filtrate is turbid, re-filter until a clear leachate is obtained, i.e., a soil leachate with a water-soil ratio of 5:1.

[0067] S4: Build a "graphite-carbon steel" galvanic corrosion experimental device, which includes an electrochemical electrolytic cell, soil electrolyte, carbon steel sample, graphite sample, two platinum working electrode clips, and a reference electrode (saturated calomel, Hg / HgO electrode), and also includes the following sub-steps:

[0068] S41 adds the Yunnan soil leachate to a three-electrode electrolytic cell;

[0069] S42 fixes the anode carbon steel and cathode graphite samples on working electrode 1 and working electrode 2 respectively, and then immerses the two working electrodes and the reference electrode in the electrolytic cell;

[0070] The two working electrodes of S43 are arranged in parallel and their heights are kept consistent;

[0071] S5: The determination of the galvanic corrosion rate and galvanic corrosion potential of "graphite-carbon steel" includes the following steps:

[0072] S51 Check the instrument status, make sure the host power supply is connected reliably, the USB communication cable and the electrode cable are normal, and no sample is connected;

[0073] S52: clamp two working electrodes with two working electrode wire clamps (WE) on the device respectively, and clamp the reference electrode with another reference electrode wire clamp (RE);

[0074] S53 opens the Versa Studio electrochemical test software, selects the "Galvanic corrosion" module, and the test scan rate is one test point every 5 minutes;

[0075] S54 starts from the test and after 4 hours of test time, 48 test points are obtained, of which the data corresponding to the time 0h is the data measured at 5s;

[0076] S55 exports the galvanic corrosion potential and galvanic corrosion current data, and uses origin software to draw the corresponding curves, such as Figure 3 (a) shown.

[0077] In addition, other embodiments were also carried out. The implementation steps in Embodiment 2, Embodiment 3 and Embodiment 4 are basically the same as those in Embodiment 1, except that the soil in S3 described in Embodiment 1 was replaced with soil from North China (Inner Mongolia), Central China (Henan) and South China (Dongguan), and finally the galvanic corrosion potential and galvanic corrosion current curves in the four soil electrolytes were obtained, as shown in FIG. Figure 3 shown.

[0078] refer to Figure 3, the galvanic potential drops sharply in the first 0.5 hours, and then as time goes by, the rate of decline decreases and finally tends to a stable value. This is because at the beginning of the coupling, the driving potential difference between the galvanic pairs is large, and the galvanic corrosion tendency is also large. As time goes on, electrochemical polarization causes a passivation film to form on the anode carbon steel surface of the galvanic pair, and the corrosion reaction gradually reaches a dynamic equilibrium, and the potential difference gradually stabilizes, resulting in a decrease in the corrosion rate. The reason for the formation of the galvanic current curve is similar to that of the galvanic potential curve. At the moment when the linear graphite and carbon steel are coupled, the galvanic current rises sharply to a maximum value, then continuously decays, and finally reaches stability. The reason is that in the early stage of coupling, the anode in the "carbon steel-linear graphite" galvanic pair is completely exposed to the soil solution, and the large potential difference drives the anode to dissolve quickly. As the galvanic pair electrodes are polarized, the force driving the anode to dissolve decreases, and a layer of corrosion products is generated on the electrode surface, causing resistance polarization, so the galvanic current gradually decreases and tends to stabilize.

[0079] In the "carbon steel-graphite" galvanic couple, carbon steel acts as a more active metal anode, losing electrons to undergo an oxidation reaction, while graphite acts as a cathode, receiving electrons to undergo a reduction reaction. The C in the cathode graphite and the Fe in the anode carbon steel form a primary cell; Figure 4 A large amount of electron transfer increases the corrosion rate of the anode metal and reduces the corrosion rate of the cathode. The anode carbon steel is corroded more seriously, and the cathode graphite is protected, that is, graphite aggravates the corrosion of carbon steel.

Claims

1. A method for studying the effect of carbon on the electrochemical corrosion behavior of steel grounding electrodes. It is characterized in that The steps include: S1: Preparation of cathode graphite sample in galvanic couple; S2: Preparation of anode carbon steel specimen for galvanic couple; S3: Preparation of soil electrolyte; S4: Construction of "graphite-carbon steel" galvanic corrosion experimental device; S5: Determination of the galvanic corrosion behavior of "graphite-carbon steel" couples.

2. The method for determining the effect of carbon on the electrochemical corrosion behavior of a steel grounding body according to claim 1, It is characterized in that Step S1 includes the following sub-steps: S11 disassembles a single graphite wire from the finished linear graphite grounding material; S12 unfolds the graphite wire into sheets, and cuts the graphite sheets with a length and width of 1 cm; S13 uses epoxy resin glue to encapsulate the other five sides of the flake graphite, leaving only one side with an area of ​​1 cm×1 cm, and leaves it for a day to allow the epoxy resin to air-dry and take shape.

3. The method for determining the effect of carbon on the electrochemical corrosion behavior of a steel grounding body according to claim 1, It is characterized in that Step S2 includes the following sub-steps: S21 uses a cutting machine to cut the carbon steel material into small carbon steel cubes with a cross-sectional area of ​​1 cm×1 cm; S22 uses a variety of sandpapers with different mesh sizes to polish the surface of the small square carbon steel and clean the oxide layer on the surface; S23 Soak the carbon steel sample in acetone solution for 5 minutes, then rinse it repeatedly with alcohol to remove residual grease on the surface; S24 used epoxy resin glue to encapsulate the other five sides of the small square carbon steel, leaving only one side with an area of ​​1cm×1cm, and let it stand for a day to allow the epoxy resin to air-dry and take shape.

4. The method for determining the effect of carbon on the electrochemical corrosion behavior of a steel grounding body according to claim 1, It is characterized in that Step S3 includes the following sub-steps: S31 Weigh 50 g of air-dried soil sample that has passed through a 2 mm pore size sieve and put it into a 1000 ml wide-mouth plastic extraction bottle, add 250 ml of decarbonated water, add a stopper, and shake on a shaker for 5 min; S32 was immediately filtered using a suction filtration device (suction funnel), and the initial 10 ml of filtrate was discarded. If the filtrate is turbid, it should be filtered again until a clear extract is obtained, that is, a soil extract with a water-to-soil ratio of 5:

1.

5. The method for determining the effect of carbon on the electrochemical corrosion behavior of a steel grounding body according to claim 1, It is characterized in that The construction of the "graphite-carbon steel" galvanic corrosion experimental device described in S4, the galvanic corrosion experimental device includes an electrochemical electrolytic cell, a soil electrolyte, a carbon steel sample, a graphite sample, two platinum sheet working electrode clips, and a reference electrode (saturated calomel, Hg / HgO electrode), step S4 includes the following sub-steps: S41 adds the soil leachate into a three-electrode electrolytic cell; S42 fixes the anode carbon steel and cathode graphite samples on working electrode 1 and working electrode 2 respectively, and then immerses the two working electrodes and the reference electrode in the electrolytic cell; The two working electrodes of S43 are arranged in parallel and their heights are kept consistent.

6. The method for determining the effect of carbon on the electrochemical corrosion behavior of a steel grounding body according to claim 1, It is characterized in that Determination of the galvanic corrosion behavior of the "graphite-carbon steel" described in S5, step S5 comprises the following sub-steps: S51 opens Versa Studio software, selects the "Galvanic corrosion" module, and tests at a scan rate of one test point every 5 minutes; S52 starts from the test and after 4 hours of test time, 48 test points are obtained, of which the data corresponding to the time 0h is the data measured at 5s; S53 derives galvanic corrosion potential and galvanic corrosion current data.

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