Model test device and test method for electrified accelerated corrosion of large-diameter water delivery pipeline

Abstract

The invention discloses a power-on accelerated corrosion large-diameter water delivery pipeline model test device and test method, and belongs to the technical field of water conservancy projects. The device comprises a large-diameter water conveying pipeline test piece (3), a connecting pipeline (4), power equipment, an electrochemical system, a plurality of measuring instruments and a plurality of valves, two ends of the large-diameter water conveying pipeline test piece are respectively connected with two ends of the connecting pipeline to form a circulating channel; the power equipment is arranged on the connecting pipeline; the electrochemical system comprises an electrolyte (9), a working electrode (5), a stainless steel electrode (13), a direct-current power supply (6) and a wire (7); the electrolyte is filled in the circulating channel; the working electrode is welded at one end of the large-diameter water conveying pipeline test piece, and the stainless steel electrode is arranged in the other end of the large-diameter water conveying pipeline test piece and is connected with the positive electrode and the negative electrode of the direct-current power supply through wires respectively. According to the invention, the condition of pipe collocation natural corrosion can be well simulated, and an accurate and effective test result can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of water conservancy engineering, and in particular relates to a large-diameter water pipeline model test device and a test method for accelerated corrosion by electrification. Background Art

[0002] Based on the structural characteristics and service environment of steel or ductile iron water pipelines, the scouring effect of flowing water combined with electrochemical corrosion will accelerate the corrosion damage of the pipeline, affecting the service life of the water pipeline and the safe and stable operation of related projects. Therefore, studying the corrosion behavior of large-diameter water pipelines is of great significance for the health assessment and service life prediction of in-service water pipelines. However, the test cycle of obtaining water pipelines for research through natural exposure corrosion is too long, which is not conducive to conducting research.

[0003] In order to obtain the corrosion components of water pipelines in the laboratory for research as soon as possible, some rapid corrosion test methods have been developed, including artificial climate simulation accelerated corrosion, power-on accelerated corrosion and other methods, among which the power-on accelerated corrosion method has been widely used. In the traditional power-on accelerated corrosion process, steel sheets are used as test materials, and the immersion method, semi-immersion method or veneer method with strong corrosive media as electrolytes are selected. It has the characteristics of saving time and controlling the corrosion rate, but there are still some shortcomings, including: using steel sheets as test materials cannot fully simulate the corrosion behavior of large-diameter water pipelines, and the immersion method with strong corrosive media as electrolytes is inconsistent with the flowing fresh water in the actual service environment of water pipelines, and the results may be biased. Therefore, the traditional method of accelerating the corrosion of large-diameter water pipelines by direct current cannot well simulate the natural corrosion of pipes. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the above-mentioned related art at least to a certain extent.

[0005] To this end, the purpose of the present invention is to provide a large-diameter water pipeline model test device and test method for accelerated corrosion by electricity, which can well simulate the natural corrosion of pipes and obtain accurate and effective test results.

[0006] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0007] The embodiment of the present invention provides a large-diameter water pipeline model test device for accelerated corrosion by electricity, the device comprising: a large-diameter water pipeline test piece 3, a connecting pipeline 4, a power device, an electrochemical system, a plurality of measuring instruments and a plurality of valves;

[0008] The two ends of the large-diameter water delivery pipeline specimen 3 are respectively connected to the two ends of the connecting pipeline 4 to form a circulation channel; the power equipment is arranged on the connecting pipeline 4;

[0009] The electrochemical system includes an electrolyte 9, a working electrode 5, a stainless steel electrode 13, a DC power supply 6 and a conductor 7;

[0010] The electrolyte 9 is filled in the circulation channel; the working electrode 5 is welded to one end of the large-diameter water pipeline specimen 3, and the stainless steel electrode is placed inside the other end of the large-diameter water pipeline specimen 3, and is connected to the positive and negative poles of the DC power supply 6 through wires 7 respectively.

[0011] In addition, the large-diameter water pipeline model test device for accelerated corrosion by electricity according to the present invention may also have the following additional technical features:

[0012] In some embodiments, the device further comprises an electrolyte container for containing sufficient electrolyte, and the electrolyte container is in communication with the circulation channel.

[0013] In some embodiments, the electrolyte 9 is water, and the electrolyte container is a water tower.

[0014] In some of the embodiments, the power device is a booster pump.

[0015] In some embodiments, the measuring instrument includes a pressure gauge 10 and a flow meter 11 ; the pressure gauge 10 and the flow meter 11 are both arranged on the connecting pipe 4 .

[0016] In some of the embodiments, the valve includes a first valve 8 and a second valve 12; the first valve 8 and the second valve 12 are respectively arranged on the connecting pipe 4 at both ends of the large-diameter water pipeline specimen 3.

[0017] The embodiment of the present invention further provides a method for testing a large-diameter water pipeline model by applying electricity to accelerate corrosion, which is implemented by using any of the above-mentioned large-diameter water pipeline model testing devices by applying electricity to accelerate corrosion; the method comprises the following steps:

[0018] S1. Prepare large-diameter water pipeline specimens and record the initial mass of the large-diameter water pipeline specimens;

[0019] S2. Assemble a large-diameter water pipeline model test device for accelerated corrosion by electricity;

[0020] S3, start the electrochemical system and power equipment, and conduct an electric accelerated corrosion test;

[0021] S4. After the test, clean the corrosion residue on the large-diameter water pipeline specimen and record the post-test quality of the large-diameter water pipeline specimen;

[0022] S5. Calculate the actual corrosion rate based on the initial mass and post-test mass of the large-diameter water pipeline specimen.

[0023] In addition, the method for testing the large-diameter water pipeline model by energizing to accelerate corrosion according to the present invention may also have the following additional technical features:

[0024] In some embodiments, the method further comprises:

[0025] S6. Calculate the theoretical corrosion rate based on the current applied in the power-on accelerated corrosion test; obtain the power-on corrosion efficiency based on the ratio of the actual corrosion rate to the theoretical corrosion rate;

[0026] The feasibility of the electric accelerated corrosion test was evaluated based on the electric corrosion efficiency.

[0027] In some of the embodiments, the variable frequency booster pump is adjusted during the power-on accelerated corrosion test to ensure that the water flow rate and internal water pressure in the circulation pipeline remain consistent throughout the test; the DC power supply is adjusted to ensure that the current passing through the large-diameter water pipeline specimen remains consistent during the entire power-on process.

[0028] In some embodiments, the theoretical corrosion rate is calculated according to Faraday's theorem;

[0029] The calculation formula of the actual corrosion rate is:

[0030] ω=(m 0 -m 1 ) / m 0 ×100%

[0031] In the formula, m 0 is the initial mass, m 1 For the quality after the test.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] In the embodiment of the present invention, the model test method for large-diameter water pipeline with electrical accelerated corrosion is provided, and actual flowing fresh water is selected instead of strong corrosive medium as the electrolyte for electrical accelerated corrosion. Compared with strong corrosive medium, flowing fresh water is more suitable for the service environment of large-diameter water pipeline, and is conducive to reflecting the actual corrosion behavior of water pipeline.

[0034] In an embodiment of the present invention, a model test method for a large-diameter water pipeline with electrical accelerated corrosion is provided, in which a large-diameter water pipeline specimen is selected instead of a steel sheet as a test material. Compared with a steel sheet, a large-diameter water pipeline specimen is closer to the structural form of a large-diameter water pipeline, which is beneficial for completely simulating the corrosion behavior of a large-diameter water pipeline.

[0035] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention is a schematic structural diagram of an experimental device for accelerating corrosion of a large-diameter water pipeline by applying electricity according to an embodiment of the present invention.

[0037] Description of reference numerals:

[0038] 1- water tower; 2- booster pump; 3- large-diameter water pipeline specimen; 4- connecting pipeline; 5- working electrode; 6- DC power supply; 7- wire; 8- first valve; 9- electrolyte; 10- pressure gauge; 11- flow meter; 12- second valve; 13- stainless steel electrode. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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. 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.

[0040] The embodiments of the present invention are described in detail below through specific embodiments and application scenarios in conjunction with the accompanying drawings.

[0041] See also Figure 1As shown, in some embodiments of the present invention, an experimental device for accelerating the corrosion of a large-diameter water pipeline by electricity is provided, comprising a water tower 1, a booster pump 2, a large-diameter water pipeline specimen 3, a connecting pipe 4, a working electrode 5, a stainless steel electrode 13, a DC power supply 6, a wire 7, a first valve 8, an electrolyte 9, a pressure gauge 10, a flow meter 11, a second valve 12 and a plurality of sampling joints, wherein the sampling joints are used to disassemble the large-diameter water pipeline specimen so as to sample different positions inside the pipeline specimen, including taking pictures of the appearance morphology after the pipeline is corroded, and collecting corrosion products for component analysis and microscopic scanning, etc., so as to further study the corrosion behavior characteristics of the water pipeline. The two ends of the large-diameter water pipeline specimen 3 are connected through an external connecting pipe 4, the booster pump 2 is arranged on the connecting pipe 4, and the water tower 1 is also arranged on the connecting pipe 4. The booster pump 2 provides power, so that the electrolyte 9 can form a loop in the pipeline composed of the large-diameter water pipeline specimen 3, the connecting pipe 4 and the water tower to achieve circulation. The booster pump 2 is also used to adjust the water flow velocity and water pressure in the pipeline. The first valve 8 and the second valve 12 are both arranged in the connecting pipe 4, and are respectively arranged at the two ends close to the large-diameter water pipeline specimen 3, for opening or closing the water flow of the connecting pipe 4. The pressure gauge 10 and the flow meter 11 are both arranged on the connecting pipe 4, for measuring the water pressure and flow in the connecting pipe 4 respectively. A plurality of sampling joints 13 arranged at different positions are arranged in the large-diameter water pipeline specimen 3, and each sampling joint 13 is used for sampling at a respective position for analysis. The working electrode 5 is welded at one end of the large-diameter water pipeline specimen 3; the stainless steel electrode 13 is arranged inside the other end of the large-diameter water pipeline specimen 3, and is respectively connected to the DC power supply 6. The working electrode 5 and the stainless steel electrode 13 are used to provide two key electrode functions in the electrochemical system.

[0042] In some embodiments of the present invention, the electrolyte 9 is flowing fresh water for testing, which is consistent with the specific engineering service environment.

[0043] In some embodiments of the present invention, the water tower 1 is a stainless steel water tower; the booster pump 2 is a variable frequency booster pump.

[0044] In some embodiments of the present invention, the connecting pipe 4 is a PVC pipe, which is connected to the end of the large-diameter water pipe test piece 3 through a flange. The connecting test device forms a water circulation system.

[0045] In some embodiments of the present invention, the large-diameter water pipeline specimen 3 is made of a steel pipe or a ductile iron pipe.

[0046] In some embodiments of the present invention, the size of the stainless steel electrode 13 is: 24 mm in diameter, 800 mm in length. The range of the DC power supply 6 is: output voltage 0-500 V, output current 0-30 A.

[0047] In some embodiments of the present invention, a method for conducting an electric accelerated corrosion test on a large-diameter water pipeline model is provided, the steps of which include:

[0048] (1) Preparing a large-diameter water pipeline test piece; the specific steps include:

[0049] a. Cut the required length of water pipeline, remove dust, rust and other impurities on the inner wall of the pipeline, ensure that the inner wall of the water pipeline is dry, clean and free of foreign matter (anti-corrosion paint can be sprayed on the inner wall of the water pipeline), weigh the actual weight of the water pipeline, and record it as the initial mass of the water pipeline m. 0 ;

[0050] b. Install electrodes at both ends of the water pipeline, connect the electrodes to a DC power supply through a wire, and spray five common water pipeline anti-corrosion materials (epoxy powder, zinc plus coating galvanizing, high chlorinated polyethylene, phenolic resin, rubber coating) inside the water pipeline to study the anti-corrosion effect and corrosion behavior characteristics of different anti-corrosion coatings. In addition, epoxy resin is applied to the inner wall surface for packaging to ensure insulation of the outer surface and ensure test safety, so that a large-diameter water pipeline specimen with accelerated corrosion can be obtained;

[0051] (2) Conducting an electric accelerated corrosion test; the specific steps include:

[0052] a. The two ends of the prepared large-diameter water pipeline specimen are tightly connected to the connecting pipeline through flanges;

[0053] b. Press Figure 1 As shown, various test equipments are assembled, including a water tower 1, a booster pump 2, a first valve 8, a pressure gauge 10, a flow meter 11, a second valve 12 and a plurality of sampling joints 13. The booster pump and two valves are turned on and adjusted to a preset flow rate and water pressure;

[0054] c. Set the current intensity value to determine the preset theoretical corrosion degree of large-diameter water pipelines;

[0055] d. Calculate the power-on time based on the current intensity, theoretical corrosion degree and Faraday's law of formula (1);

[0056] t=Δm·Z·F / M Fe ·I (1)

[0057] Where, t is the power-on time s, Δm is the theoretical mass loss of the pipeline g, Z is the chemical valence of the reaction electrode +2, F is the Faraday constant 96500C / mol, M Fe is the atomic weight of iron 56g / mol, I is the current intensity A;

[0058] e. Turn on the power supply and start the power-on accelerated corrosion test;

[0059] f. By observing the data changes of the pressure gauge and flow meter, adjust the variable frequency booster pump during the power-on process to ensure that the water flow rate and internal water pressure in the circulation pipeline remain consistent throughout the process;

[0060] g. By observing the changes in the data displayed by the DC power supply, adjust the DC power supply to ensure that the current passing through the large-diameter water pipeline test piece remains consistent during the entire power-on process;

[0061] h. The test ends when the power-on time meets the setting.

[0062] (3) Calculation of the efficiency of accelerated corrosion by power-on; the specific steps include:

[0063] a. After the power-on accelerated corrosion test, drain the water in the large-diameter water pipeline, disassemble the flanges at both ends (by disassembling the sampling joints, the appearance characteristics and corrosion products of each part of the water pipeline can be sampled and analyzed), and then weigh the actual mass of the large-diameter water pipeline after cleaning, which is recorded as m. 1 ;

[0064] b. Calculate the actual corrosion rate according to formula (2):

[0065] ω=(m 0 -m 1 ) / m 0 ×100% (2)

[0066] c. Calculate the galvanic corrosion efficiency by the ratio of the actual corrosion rate to the theoretical corrosion rate, and evaluate the feasibility of the galvanic accelerated corrosion test device and test method for large-diameter water pipelines based on the galvanic corrosion efficiency.

[0067] Embodiment 1:

[0068] Cut a Q235 steel water pipe with a length of 6m, an inner diameter of 720mm, and a wall thickness of 10mm. Remove dust, rust and other impurities on the inner wall of the pipe to ensure that the inner wall of the water pipe is dry, clean and free of foreign matter. Weigh the actual weight of the water pipe and record it as the initial mass of the water pipe m. 0 .

[0069] Weld a wire to one end of the water pipe and apply epoxy resin to the surface except for the inner wall.

[0070] Connect flanges at both ends of the water delivery pipeline and connect them to the PVC connecting pipes.

[0071] After assembling the test device, turn on the booster pump, adjust to the preset flow rate and water pressure, set the current intensity to 20A, and calculate the current density to 0.015mA / cm 2 , design the theoretical mass loss rate of the water pipeline, and calculate the corresponding power-on time according to Faraday's theorem (1). The results are shown in Table 1.

[0072] During the power-on process, observe the data changes on the pressure gauge and flow meter and adjust the variable frequency booster pump to ensure that the water flow velocity and internal water pressure in the circulation pipeline remain consistent during the entire process; adjust the DC power supply by observing the data changes displayed on the DC power supply to ensure that the current passing through the large-diameter water pipeline test piece is consistent during the entire power-on process.

[0073] After the power-on accelerated corrosion test, drain the water in the large-diameter water pipeline, disassemble the connecting flanges at both ends, and sample and analyze the appearance characteristics and corrosion products of each part of the water pipeline by disassembling the sampling joint. According to the requirements of the national standard GB / T 16545-2015 "Removal of corrosion products on corrosion specimens of metals and alloys", prepare a chemical cleaning solution, using 50L hydrochloric acid (HCl, ρ = 1.19g / ml), 350g hexamethylenetetramine, and distilled water to prepare a 100L solution. First, use tap water to fully clean the large-diameter water pipeline. During the cleaning process, use a soft brush to lightly brush the surface of the large-diameter water pipeline specimen; then use a spray pot to evenly spray the prepared chemical cleaning solution. The solution will produce a violent chemical reaction on the corrosion products, and the corrosion products remaining on the large-diameter water pipeline will quickly disappear or flow down with the solution. Repeat the above steps several times to thoroughly clean the corrosion products. After washing with water again, weigh the actual mass m of the large-diameter water pipeline 1 .

[0074] The actual corrosion rate of this embodiment is calculated by the aforementioned formula (2).

[0075] The energized corrosion efficiency was calculated by the ratio of the actual corrosion rate to the theoretical corrosion rate. The results are shown in Table 1.

[0076] Table 1 Accelerated corrosion test efficiency

[0077]

[0078] From the results in Table 1, it can be seen that the inner wall of a large-diameter water pipeline is accelerated to corrode in a flowing water environment. The actual corrosion rate of the pipeline is less than the theoretical corrosion rate, but its corrosion efficiency can be as high as about 67.6% to 69.6% calculated by Faraday's law.

[0079] According to the above analysis, the test device and method can effectively carry out accelerated corrosion tests on large-diameter water pipelines, better simulate and reflect the corrosion conditions of large-diameter water pipelines, and accurately evaluate the corrosion effects, which is of great significance to the durability design and life prediction of large-diameter water pipelines.

[0080] The parts of the present invention that are not described in detail may refer to the prior art in the art or are known to those skilled in the art.

[0081] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A large-diameter water pipeline model test device for accelerated corrosion by electricity, characterized in that: The device comprises: a large-diameter water pipeline test piece (3), a connecting pipeline (4), a power device, an electrochemical system, a plurality of measuring instruments and a plurality of valves; The two ends of the large-diameter water delivery pipeline specimen (3) are respectively connected to the two ends of the connecting pipeline (4) to form a circulation channel; the power equipment is arranged on the connecting pipeline (4); The electrochemical system comprises an electrolyte (9), a working electrode (5), a stainless steel electrode (13), a direct current power source (6) and a conductor (7); The electrolyte (9) is filled in the circulation channel; the working electrode (5) is welded to one end of the large-diameter water pipeline specimen (3); the stainless steel electrode is placed inside the other end of the large-diameter water pipeline specimen (3) and is connected to the positive and negative electrodes of the DC power supply (6) via wires (7), respectively.

2. The large-diameter water pipeline model test device for accelerated corrosion by electricity according to claim 1 is characterized in that: The device further comprises an electrolyte container for containing sufficient electrolyte, wherein the electrolyte container is communicated with the circulation channel.

3. The large-diameter water pipeline model test device for accelerated corrosion by electricity according to claim 2 is characterized in that: The electrolyte (9) is water, and the electrolyte container is a water tower.

4. The large-diameter water pipeline model test device for accelerated corrosion by electricity according to claim 1 is characterized in that: The power equipment is a booster pump.

5. The large-diameter water pipeline model test device for accelerated corrosion by electricity according to claim 1 is characterized in that: The measuring instrument comprises a pressure gauge (10) and a flow meter (11); the pressure gauge (10) and the flow meter (11) are both arranged on the connecting pipeline (4).

6. The large-diameter water pipeline model test device for accelerated corrosion by electricity according to claim 1 is characterized in that: The valve comprises a first valve (8) and a second valve (12); the first valve (8) and the second valve (12) are respectively arranged on the connecting pipe (4) at both ends of the large-diameter water pipeline test piece (3).

7. A method for testing a large-diameter water pipeline model by accelerating corrosion through electricity, characterized in that: The method is implemented by using the large-diameter water pipeline model test device for accelerated corrosion by electricity as described in any one of claims 1 to 6; the steps of the method include: S1. Prepare large-diameter water pipeline specimens and record the initial mass of the large-diameter water pipeline specimens; S2. Assemble a large-diameter water pipeline model test device for accelerated corrosion by electricity; S3, start the electrochemical system and power equipment, and conduct an electric accelerated corrosion test; S4. After the test, clean the corrosion residue on the large-diameter water pipeline specimen and record the post-test quality of the large-diameter water pipeline specimen; S5. Calculate the actual corrosion rate based on the initial mass and post-test mass of the large-diameter water pipeline specimen.

8. The method for testing a large-diameter water pipeline model by electrical accelerated corrosion according to claim 7, characterized in that: The method further comprises the steps of: S6. Calculate the theoretical corrosion rate based on the current applied in the power-on accelerated corrosion test; obtain the power-on corrosion efficiency based on the ratio of the actual corrosion rate to the theoretical corrosion rate; The feasibility of the electric accelerated corrosion test was evaluated based on the electric corrosion efficiency.

9. The method for testing a large-diameter water pipeline model by electrical accelerated corrosion according to claim 7, characterized in that: During the power-on accelerated corrosion test, the variable frequency booster pump is adjusted to ensure that the water flow velocity and internal water pressure in the circulation pipeline remain consistent during the entire test process; the DC power supply is adjusted to ensure that the current passing through the large-diameter water pipeline specimen remains consistent during the entire power-on process.

10. The method for testing a large-diameter water pipeline model by electrical accelerated corrosion according to claim 7, characterized in that: The theoretical corrosion rate is calculated according to Faraday's theorem; The calculation formula of the actual corrosion rate is: ； In the formula, is the initial mass, For the quality after the test.

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