Multi-angle scouring and in-situ electrochemical testing device

Abstract

The present application belongs to the technical field of pipeline erosion corrosion and electrochemical corrosion measurement, and particularly relates to a multi-angle erosion corrosion and in-situ electrochemical testing device, which maintains the basic characteristics of the pipeline as a whole, the flow state in the pipeline is close to the actual pipeline flow state, and the main structure comprises an outer sleeve, an inner sleeve arranged in the outer sleeve, a reference electrode arranged on the outer sleeve, a working electrode and an auxiliary electrode arranged on the inner sleeve, and an electrochemical workstation connected with the reference electrode, the working electrode and the auxiliary electrode, can effectively simulate the actual working condition of the pipeline, realize the fixed erosion angle erosion corrosion test of the metal sample and the coating sample, can perform the weight loss and electrochemical measurement, and can realize the erosion corrosion test of the metal sample and the coating sample under the cathodic protection state, obtain the corrosion data of the sample under the cathodic protection, and in addition, the positions of the working electrode, the auxiliary electrode and the reference electrode are fixed, do not have a significant impact on the flow state, and are beneficial to the stability of the electrochemical test process.

Description

Technical fields:

[0001] This invention belongs to the field of pipeline erosion corrosion and electrochemical corrosion measurement technology, specifically involving a multi-angle erosion corrosion and in-situ electrochemical testing device, which provides basic data for analyzing the erosion corrosion mechanism of the sample to be tested. Background technology:

[0002] Pipelines are an important component of industries such as petroleum, chemical, power, and shipbuilding. Currently, pipelines used in industrial fields are mainly made of metal. However, corrosion failures of metal pipelines occur frequently during service, with erosion corrosion being the most common type of corrosion.

[0003] Erosion corrosion is damage that occurs when the relative movement between a metal surface and a corrosive medium exceeds a certain range. In existing technologies, there are three types of test apparatus for studying erosion corrosion: rotary, jet, and pipe-flow, each simulating the erosion process in different ways. Rotary test apparatuses fix the test sample on a cylinder or disk, and the rotation of a motor drives the sample to move within the corrosive medium to achieve the erosion effect. This is mainly used to evaluate the erosion corrosion resistance of materials. Jet test apparatuses directly spray fluid onto the sample surface through an ejector to simulate the erosion corrosion process. This is mainly used to determine the limiting flow velocity of materials and to study the erosion corrosion mechanism. Pipe-flow test apparatuses use a circulating pump to drive the fluid medium to flow within a pipe, eroding the metal sample. Generally, tubular or annular samples are used directly, or the metal sample is embedded in a groove on the inner wall of the pipe to simulate actual fluid flow within the pipe. This is mainly used for sample-level performance evaluation.

[0004] The scouring angle, also known as the angle of attack, refers to the angle formed between the fluid inside the pipe and the inner wall surface of the pipe. Changes in the scouring angle affect the scouring corrosion behavior of the metal by influencing the normal stress and shear stress on the metal surface. Generally, jet-type test devices or rotary test devices are used to study the influence of the scouring angle on the scouring corrosion of metals. For example, the English literature X. Tang, LY Xu, YFCheng. Electrochemical corrosion behavior of X-65 steel in the simulated oil–sand slurry. II: Synergism of erosion and corrosion, Corrosion Science, 2008, 50(5):1469-1474. discloses a method for evaluating the influence of the scouring angle on the scouring corrosion behavior of materials using a jet-type scouring test device. Chinese Patent 200810249618.6 discloses a multifunctional underwater jet cavitation test device that simulates the process of scouring corrosion and cavitation corrosion on the surface of metal samples by jetting high-pressure liquid streams. Chinese Patent 202410246317.7 discloses a rotating erosion in-situ electrochemical testing device, which simulates the erosion process of liquid on a metal surface by high-speed rotation of a rotating disk, and can perform in-situ electrochemical tests. (Xing Jiandong, Gao Yimin, Zhang Guoshang. Research on Erosion Corrosion Wear of Stainless Steel and High Carbon Steel. Journal of Xi'an Jiaotong University, 2004.)

[0005] (05):469-473. A method for evaluating the influence of scouring angle on the scouring corrosion behavior of materials using a rotating scouring test device is disclosed. The fluid scouring process simulated by the jet test device and the rotating test device differs significantly from the actual flow state inside the pipeline, and the obtained test data is not very instructive for the practical application and design of pipelines.

[0006] The internal flow pattern of a pipe-flow test device is closest to that of an actual pipeline, and it can most directly simulate the erosion corrosion behavior of the pipeline. However, due to structural limitations, it can only test the erosion corrosion performance of actual samples inside pipes such as straight pipes, bends, valves, reducers, and tees. It cannot use sheet-like samples to study the erosion corrosion performance of materials under different erosion angles. For example, Chinese Patent 201310248151.4 discloses a pipe-flow internal wall erosion corrosion test device, which includes: a power pump, a discharge pipe I, a stirring pump, a cooler, an electromagnetic flowmeter, an auxiliary electrode, a test sample, a reference electrode, a discharge pipe II, and a slurry tank. The specific structure is as follows: the input end of the stirring pump is directly connected to the slurry tank, and a cooler is installed on the pipe connecting the output end of the stirring pump to the slurry tank. The cooler, as a cooling system, is independent of the slurry tank. A bypass is provided on the pipe connecting the output end of the stirring pump to the slurry tank. Material pipe I; the slurry tank is connected to the power pump and the agitator pump via pipelines. The input end of the power pump is directly connected to the slurry tank via a pipeline. The pipeline connecting the output end of the power pump to the slurry tank is equipped with an electromagnetic flowmeter and the test sample. The electromagnetic flowmeter is installed on the test pipe section from the power pump to the test sample. A bypass, discharge pipe II, is provided on the pipeline connecting the output end of the power pump to the slurry tank. An auxiliary electrode and a reference electrode are provided on the pipeline connecting the output end of the power pump to the slurry tank. The reference electrode and the auxiliary electrode are installed on the pipeline near the test sample. Chinese Patent 202411505121.1 discloses a test device for online electrochemical testing and plate-based testing of pipeline erosion corrosion, comprising: a high-pressure gas cylinder, a storage tank, a venting pipeline, a pump body, a media pipeline, a test pipeline, an online electrochemical testing unit, and a plate-based testing unit; the high-pressure gas cylinder is used to store test gas; the storage tank is used to store test media; the venting pipeline extends directly to the bottom of the storage tank; the high-pressure gas cylinder supplies test gas to the storage tank through the venting pipeline; the inlet end of the pump body is connected to the storage tank, and the outlet end of the pump body is connected to the media pipeline; the media pipeline is connected to the test pipeline; the pump body extracts the test media, which passes through a section of the media pipeline, and then enters the test pipeline; the test pipeline includes: an elbow section and a straight section, the elbow section being connected to the media pipeline, and the straight section... The system is connected to a storage tank. The online electrochemical testing unit includes: a three-electrode system in a bend section, a three-electrode system in a straight section, and an electrochemical workstation. The three-electrode system in the bend section is located in the bend section of the test pipeline. It includes: a first working electrode, a first reference electrode, and a first auxiliary electrode. The three-electrode system in the straight section is located in the straight section of the test pipeline. It includes: a second working electrode, a second reference electrode, and a second auxiliary electrode. The electrochemical workstation is connected to the corresponding electrodes of the three-electrode systems in the bend section and the straight section, respectively, for testing different electrochemical detection techniques. The sample-mounted test unit is located in either the bend section or the straight section of the test pipeline. The sample-mounted test unit includes: a sample holder and a sample. The sample is embedded in the sample holder.The method involves fixing sheet-like samples onto the surface of tubular samples for erosion corrosion testing. The erosion angle of the installed sheet-like samples can only be controlled by changing the shape of the tubular samples, which limits the control range. Furthermore, changes in the shape of the tubular samples can cause changes in the flow regime, making it difficult to conduct research on variable erosion angles.

[0007] Therefore, we developed and designed a multi-angle erosion corrosion and in-situ electrochemical testing device that can be used in conjunction with existing pipe flow testing devices to evaluate the corrosion behavior of materials at different erosion angles through methods such as corrosion morphology changes, corrosion weight loss, and in-situ electrochemical testing. Summary of the Invention:

[0008] The purpose of this invention is to overcome the shortcomings of the existing technology and to develop and design a multi-angle scouring corrosion and in-situ electrochemical testing device, so as to realize the scouring corrosion test of metal samples, coating samples, etc. in pipeline systems or pipe flow scouring corrosion test devices according to the preset scouring angle, and to perform in-situ electrochemical testing on the test samples.

[0009] To achieve the above objectives, the main structure of the multi-angle erosion corrosion and in-situ electrochemical testing device of the present invention includes an outer sleeve and an inner sleeve disposed therein, a reference electrode disposed on the outer sleeve, a working electrode and an auxiliary electrode disposed on the inner sleeve, and an electrochemical workstation connected to the reference electrode, the working electrode and the auxiliary electrode respectively.

[0010] Specifically, the outer sleeve is connected to the inner sleeve through reducing joints at both ends, the middle part of the inner sleeve is located inside the outer sleeve, and the two ends extend out of the outer sleeve;

[0011] The reference electrode is mounted on the outer sleeve;

[0012] The working electrode is located in the middle of the inner sleeve;

[0013] The auxiliary electrodes are coated on both ends of the inner sleeve;

[0014] The reference electrode, working electrode, and auxiliary electrode are connected to the electrochemical workstation via wires.

[0015] The main structure of the outer sleeve includes a four-way connector and large sleeves arranged before and after it, as well as a reference electrode and a gland set on the four-way connector;

[0016] The main structure of the inner sleeve includes small sleeves set at the front and rear, a support frame, and threaded holes set on it.

[0017] The inner sleeves involved in this invention are classified into large-angle inner sleeves (30° < scouring angle ≤ 90°) and small-angle inner sleeves (0° ≤ scouring angle ≤ 30°) according to the applicable range of the scouring angle:

[0018] The large-angle inner sleeve is equipped with four metal support frames, each with an internal threaded hole. The angle α between the center line of two internal threaded holes on the same horizontal plane and the support frame is the scouring angle of the sample to be tested.

[0019] The small-angle inner sleeve is equipped with two metal support frames, each of which has two internal threaded holes. The angle α between the center line of the two internal threaded holes on the same support frame and the support frame is the scouring angle of the sample to be tested.

[0020] The reference electrode is placed in the four-way connector, with its bottom flush with the inner wall of the four-way connector to avoid affecting the flow of water. The reference electrode is equipped with a wire for connection to the electrochemical workstation.

[0021] The working electrode is the sample to be tested, and it has a blind hole with internal threads, the same size as the threaded hole, and the position corresponding to the threaded hole; a wire is led out from the working electrode and passes through the gland for connection to the electrochemical workstation. The gland is installed in a four-way connector to seal the wire.

[0022] The auxiliary electrode is a titanium-based noble metal oxide coating, which is applied to the inner wall of the small sleeve;

[0023] The large sleeve is made of PVC plastic;

[0024] Both the small sleeve and the support frame are made of titanium alloy.

[0025] The multi-angle scouring corrosion and in-situ electrochemical testing device involved in this invention is installed as a whole in a pipeline. When the fluid flows inside it, it continuously scours the sample to be tested at a preset scouring angle. The corrosion development process is monitored by performing in-situ electrochemical tests on the sample to be tested.

[0026] Compared with existing technologies, this invention maintains the basic characteristics of a pipeline, and the flow state inside the pipe is close to that of an actual pipeline. It can effectively simulate the actual working conditions of a pipeline, realize erosion corrosion tests on metal and coating samples at a fixed erosion angle, perform weight loss and electrochemical measurements, and realize erosion corrosion tests on metal and coating samples under cathodic protection to obtain corrosion data of samples under cathodic protection. In addition, the positions of the working electrode, auxiliary electrode, and reference electrode are fixed, which will not significantly affect the flow state and is conducive to the stability of the electrochemical testing process. Among them, the auxiliary electrode is tubular and symmetrically distributed on both sides of the working electrode, ensuring that the area of ​​the auxiliary electrode is more than five times larger than that of the working electrode, improving the ability of the auxiliary electrode to receive electrochemical signals and the accuracy of electrochemical testing. Its structure is simple, its principle is scientific and reliable, and it can be directly connected to the pipeline system or the pipe flow erosion corrosion test system. The device size can be selected according to the pipeline requirements, and it has a wide range of applications and strong adaptability. Attached image description:

[0027] Figure 1 This is a schematic diagram of the main structure principle of Embodiment 1 of the present invention.

[0028] Figure 2 This is a schematic diagram of the main structure of the outer sleeve according to Embodiment 1 of the present invention.

[0029] Figure 3 This is a schematic diagram of the main structure of the inner sleeve according to Embodiment 1 of the present invention.

[0030] Figure 4 This is a top view of the main structure of the inner sleeve according to Embodiment 1 of the present invention.

[0031] Figure 5 This is an assembly diagram of the main structure of the inner sleeve according to Embodiment 1 of the present invention.

[0032] Figure 6 This is a schematic diagram of the main structure principle of Embodiment 2 of the present invention.

[0033] Figure 7 This is a schematic diagram of the main structure of the inner sleeve involved in Embodiment 2 of the present invention.

[0034] Figure 8 This is a top view of the main structure of the inner sleeve according to Embodiment 2 of the present invention. Detailed implementation method:

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1:

[0037] The multi-angle erosion corrosion and in-situ electrochemical testing device involved in this embodiment is a large-angle multi-angle erosion corrosion and in-situ electrochemical testing device, used to conduct erosion corrosion tests and electrochemical tests on the sample under test with a erosion angle of 60°. The main structure is as follows. Figure 1 As shown, it includes an outer sleeve 1, a reducing connector 2, an inner sleeve 3, a reference electrode 4, a working electrode 5, an auxiliary electrode 6, a wire 7, and an electrochemical workstation 8;

[0038] The outer sleeve 1 is connected to the inner sleeve 3 through the reducing joints 2 at both ends. The middle part of the inner sleeve 3 is located inside the outer sleeve 1, and the two ends extend out of the outer sleeve 1.

[0039] The outer sleeve 1 is equipped with a reference electrode 4;

[0040] The inner sleeve 3 has a working electrode 5 in the middle and auxiliary electrodes 6 at both ends. The area of ​​the auxiliary electrodes 6 is more than five times the area of ​​the working electrode 5.

[0041] Reference electrode 4, working electrode 5 and auxiliary electrode 6 are connected to electrochemical workstation 8 via wires 7;

[0042] The main structure of the outer sleeve 1 is as follows: Figure 2 As shown, it includes a four-way connector 11, a large sleeve 12, and a gland 13; the front and rear ports of the four-way connector 11 are connected to the large sleeve 12, and the upper and lower ports are connected to the reference electrode 4 and the gland 13, respectively.

[0043] The main structure of the inner sleeve 3 is as follows Figure 3-4 As shown, it includes a small sleeve 31, a support frame 32, and a threaded hole 33; two small sleeves 31 are connected by four support frames 32, and each support frame 32 is provided with a threaded hole 33. The angle α between the center line of the two threaded holes 33 located on the same horizontal plane and the support frame 32 is 60°, which is the scouring angle of the sample to be tested.

[0044] When assembling the working electrode 5 involved in this embodiment, as follows: Figure 5 As shown:

[0045] First, it is fixed to the support frame 32 by plastic bolts 100;

[0046] Then, insulating pads 200 are provided on both the upper and lower surfaces of the support frame 32;

[0047] Finally, a wire 7 is placed between the insulating pads 200 of the working electrode 5, and the wire 7 extends out of the outer sleeve through the gland 13 so that the working electrode 5 can be connected to the electrochemical workstation 8.

[0048] Example 2:

[0049] The multi-angle erosion corrosion and in-situ electrochemical testing device involved in this embodiment is a small-angle multi-angle erosion corrosion and in-situ electrochemical testing device, used to conduct erosion corrosion tests and electrochemical tests on the sample under test with a erosion angle of 30°. The main structure is the same as in Embodiment 1. Figure 6 As shown, the difference lies in the main structure of the inner sleeve 3, such as Figure 7-8 As shown, the two small sleeves 31 are connected by two support frames 32. Each support frame 32 is provided with two threaded holes 33. The angle α between the center line of the two threaded holes 33 on the same support frame 32 and the support frame 32 is 30°, which is the scouring angle of the sample to be tested.

Claims

1. A multi-angle erosion corrosion and in-situ electrochemical testing device, characterized in that, The main structure includes an outer sleeve and an inner sleeve inside it, a reference electrode on the outer sleeve, a working electrode and an auxiliary electrode on the inner sleeve, and an electrochemical workstation connected to the reference electrode, working electrode, and auxiliary electrode respectively. The outer sleeve is connected to the inner sleeve through reducing joints at both ends. The middle part of the inner sleeve is located inside the outer sleeve, and the two ends extend out of the outer sleeve. The main structure of the outer sleeve includes a four-way connector and large sleeves and glands at the front and rear. The main structure of the inner sleeve includes small sleeves at the front and rear, support frames, and threaded holes on them. The inner sleeve is divided into large-angle inner sleeves and small-angle inner sleeves according to the applicable range of the scouring angle. The large-angle inner sleeve is provided with four metal support frames, each with an internal threaded hole located on the same horizontal plane. The angle α between the centerline of the two internally threaded holes and the support frame is the scouring angle of the sample to be tested. The small-angle inner sleeve is equipped with two metal support frames, each with two internally threaded holes. The angle α between the centerline of the two internally threaded holes on the same support frame and the support frame is the scouring angle of the sample to be tested. The reference electrode is set in the four-way connector, with its bottom flush with the inner wall of the four-way connector, and is connected to the electrochemical workstation via a wire. The working electrode is the sample to be tested, with a blind hole with internal threads, the same size as the threaded hole, and the position corresponding to the threaded hole. A wire is led out from the working electrode, passes through the gland, and is connected to the electrochemical workstation. The gland is installed in the four-way connector to seal the wire. The auxiliary electrode is a titanium-based noble metal oxide coating, which is applied to the inner wall of the small sleeve.

2. The multi-angle erosion corrosion and in-situ electrochemical testing device according to claim 1, characterized in that... The large sleeve is made of PVC plastic; the small sleeve and the support frame are both made of titanium alloy.

3. The multi-angle erosion corrosion and in-situ electrochemical testing device according to claim 1 or 2, characterized in that, During operation, the entire unit is installed in a pipeline. As the fluid flows inside, it continuously scours the sample under test at a preset scour angle. The corrosion development process is monitored by performing in-situ electrochemical tests on the sample under test.

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