CN106525710B - An electrochemical test device for acoustic emission detection of corrosion performance of materials and its application method - Google Patents

Abstract

The invention discloses an electrochemical testing device for detecting the corrosion performance of materials by acoustic emission and a method for using the device. The device includes an electrolytic cell, an electrochemical testing device, a heating device and a heat preservation device. The electrolytic cell includes a reaction cell, a reaction cell cover, a sealing gasket, a fastening device, and a sample installation device. The platinum mesh electrode and the reference electrode are installed in the Lujin capillary, the heating device is set outside the reaction pool, and the heat preservation device is set outside the heating device. The invention integrates the acoustic emission dynamic non-destructive detection technology and the electrochemical testing technology, and realizes the online, dynamic and real-time detection of the electrochemical corrosion process of materials.

Description

An electrochemical testing device for acoustic emission detection of corrosion performance of materials and its use method

technical field

The invention relates to the field of material corrosion performance testing devices, in particular to an electrochemical testing device for acoustic emission detection of material corrosion performance and a method for using the same.

Background technique

Corrosion is a slow damage process of materials in harsh service environments, which has the characteristics of strong concealment, accidental, sudden and serious destructiveness. Electrochemistry is a commonly used test method for quickly evaluating the corrosion resistance of materials, such as potentiodynamic polarization, constant potential polarization, cyclic potentiodynamic polarization, and electrochemical impedance testing. Electrochemical technology is mainly aimed at the destructive detection of small samples, with the purpose of predicting or evaluating the corrosion resistance of materials in advance, but it cannot conduct online detection of the corrosion status of large-scale components in service. Acoustic emission technology is a highly sensitive online non-destructive testing technology. Corrosion-related passivation film cracking, bubble rupture, stress corrosion cracking, etc. are typical AE sources. At present, acoustic emission technology has been successfully applied in fields such as long-distance oil pipeline leak detection and online assessment of storage tank corrosion. However, the application research of acoustic emission mechanism and quantitative evaluation of corrosion degree in the process of corrosion damage is still in its infancy. The main disadvantages of existing test devices that use both acoustic emission technology and electrochemical technology to detect material corrosion properties are: (1) The size of the sample to be tested required by the traditional test device is too large to test tiny samples. While the tested sample is in contact with the corrosive medium, it also requires a sufficient area to be connected to the waveguide rod or directly to the acoustic emission sensor, which requires that the size of the tested sample must be designed to be large enough. Welded joints are usually the weakest link in structural parts. If you want to perform acoustic emission and electrochemical detection on different areas of welded joints (weld root, cover surface, weld center, high temperature and low temperature thermal influence, etc.), based on the limitation of sampling, the existing test equipment cannot be realized; (2) In order to facilitate the installation of acoustic emission sensors, the tested sample is usually installed at the bottom of the electrolytic cell as a working electrode, so the existing test equipment limits the heating and insulation of corrosive media; (3) the acoustic emission of material corrosion performance in a variety of mixed gas environments cannot be simulated Detection and electrochemical detection; (4) The operation of sample installation and removal is complicated.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a sample holder for electrochemical corrosion testing and a method of use thereof;

The object of the present invention is also to provide a fixture for acoustic emission detection of material corrosion performance and its use method;

Another object of the present invention is to provide a corrosion electrochemical test device and its use method;

Another object of the present invention is to provide an electrochemical testing device for detecting the corrosion performance of materials by acoustic emission and a method for using the same.

The sample fixture for electrochemical corrosion test is composed of a stepped thread waveguide, a first-level sleeve, a second-level sleeve, a third-level sleeve and a sealing ring. The stepped-thread waveguide, the first-level sleeve, the second-level sleeve, the third-level sleeve and the sealing ring are coaxially arranged, wherein: the stepped-thread waveguide is provided with a first external thread and a second external thread, and the first external thread is connected with the internal thread of the first-level sleeve, so that the front end of the stepped-thread waveguide is placed in the first cavity and the second cavity of the first-level sleeve, and the second external thread is placed in the first cavity of the first-level sleeve. Outside the second cavity; a fixed end is provided at the rear end of the stepped thread waveguide; the external thread of the first-stage sleeve is connected with the internal thread of the third-stage sleeve, so that the first-stage sleeve is placed in the third cavity and the fourth cavity of the third-stage sleeve; the second-stage sleeve is set on the outside of the third-stage sleeve, and a sealing ring is arranged between the second-stage sleeve and the third-stage sleeve.

In the above technical solution, the sealing ring is a rubber sealing ring.

In the above technical solution, the diameter of the test surface of the sample is 5±0.01 mm, and the length is 7-8 mm.

In the above technical solution, the stepped threaded waveguide is made of metal material, such as ferritic stainless steel.

In the above technical solution, the primary sleeve, the secondary sleeve and the tertiary sleeve are all insulating materials, such as polytetrafluoroethylene.

When in use, the second external thread of the stepped thread waveguide rod is connected to the internal thread of the sample, and a couplant layer is set on the circumferential surface of the sample, and the fixed end of the stepped thread waveguide rod is rotated so that the test surface of the sample connected to the second external thread of the stepped thread waveguide rod is flush with the first alignment surface of the first-stage sleeve and the second alignment surface of the third-stage sleeve; the internal thread of the second sleeve is fixedly connected to the test device, and the electrochemical corrosion test is performed on the sample. The sample is used as the working electrode, and the wire is connected to the stepped thread waveguide outside the test device. The rod is connected to collect the electrochemical corrosion signal on the sample.

The fixture for acoustic emission detection of material corrosion performance is composed of a stepped thread waveguide, a first-level sleeve, a second-level sleeve, a third-level sleeve, a sealing ring and an acoustic emission sensor. The stepped thread waveguide, the first-level sleeve, the second-level sleeve, the third-level sleeve, the sealing ring and the acoustic emission sensor are arranged coaxially. The second external thread is placed outside the second cavity of the first-stage sleeve; a fixed end is provided at the rear end of the stepped thread waveguide rod, and an acoustic emission sensor in contact with it is arranged on the fixed end; the external thread of the first-stage sleeve is connected with the internal thread of the third-stage sleeve, so that the first-stage sleeve is placed in the third cavity and the fourth cavity of the third-stage sleeve; the second-stage sleeve is set on the outside of the third-stage sleeve, and a sealing ring is arranged between the second-stage sleeve and the third-stage sleeve.

In the above technical solution, the sealing ring is a rubber sealing ring.

In the above technical solution, the diameter of the test surface of the sample is 5±0.01 mm, and the length is 7-8 mm.

In the above technical solution, both the stepped threaded waveguide rod and the fixed end are metal materials, such as ferritic stainless steel.

In the above technical solution, the primary sleeve, the secondary sleeve and the tertiary sleeve are all insulating materials, such as polytetrafluoroethylene.

In the above technical solution, an adhesive layer is provided between the fixed end and the acoustic emission sensor.

In the above technical solution, the acoustic emission sensor is fixed on the fixed end by using a magnetic clamp.

When in use, the second external thread of the stepped thread waveguide rod is connected to the internal thread of the sample, and a couplant layer is set on the circumferential surface of the sample, and the fixed end of the stepped thread waveguide rod is rotated so that the test surface of the sample connected to the second external thread of the stepped thread waveguide rod is flush with the first alignment surface of the first-level sleeve and the second alignment surface of the third-level sleeve; the internal thread of the second sleeve is fixedly connected to the test device, and the sample is used for electrochemical corrosion testing. The rods are connected to collect the electrochemical corrosion signal on the sample; the acoustic emission elastic wave emitted by the sample during the corrosion process is transmitted to the acoustic emission sensor through the stepped thread waveguide rod, and the displacement signal is converted into an electrical signal and transmitted outward.

A corrosion electrochemical test device, including an electrolytic cell, an electrochemical test device, a heating device and a heat preservation device;

The electrolytic cell includes a reaction cell, a reaction cell cover, a sealing gasket, a fastening device, and a sample installation device. The reaction cell is cylindrical, and the upper edge of the reaction cell is provided with a flange. The hole is connected with the auxiliary electrode, and the threaded hole of the digital display thermometer probe is connected with the digital display thermometer; the threaded hole of the Lujin capillary is connected with the external thread of the Lujin capillary liquid injection port, so that the curved part of the Lujin capillary is located in the reaction pool, and its opening is facing the sample as the working electrode, and the internal thread of the Lujin capillary liquid injection port is connected with the external thread of the reference electrode, so that the reference solution in the reference electrode can flow to the opening for the sample; On the horizontal plane; the sample installation device is composed of a stepped thread waveguide, a first-level sleeve, a second-level sleeve, a third-level sleeve, and a sealing ring. The stepped thread waveguide, the first-level sleeve, the second-level sleeve, the third-level sleeve and the sealing ring are arranged coaxially, wherein: the stepped thread waveguide is provided with a first external thread and a second external thread, and a fixed end is set at the rear end of the stepped thread waveguide; Inside, the second external thread is placed outside the second cavity of the first-level sleeve; the outer thread of the first-level sleeve is connected to the inner thread of the third-level sleeve, so that the first-level sleeve is placed in the third cavity and the fourth cavity of the third-level sleeve; the second-level sleeve is set on the outside of the third-level sleeve, and a sealing ring is arranged between the second-level sleeve and the third-level sleeve;

The electrochemical test device includes an auxiliary electrode chuck, a reference electrode chuck, a working electrode chuck, and an electrochemical data processing system; the auxiliary electrode chuck, the reference electrode chuck, and the working electrode chuck are respectively connected to the auxiliary electrode on the electrolytic cell, the reference electrode, and the fixed end of the stepped thread waveguide, and then connected to the electrochemical data processing system through a signal transmission line;

The heating device is arranged on the outside of the reaction tank, the heat preservation device is arranged on the outside of the heating device, and the inner wall of the heating device is provided with a temperature sensor for detecting the temperature change of the electrolyte in the reaction tank.

In the above technical solution, the number of fastening devices is 6-8 groups, and the fastening device is composed of "bow"-shaped fastening device chucks, fastening screws and fastening gaskets, and the material of the fastening device chucks is 316 austenitic stainless steel; the fastening device chucks include a first horizontal section, a vertical section and a second horizontal section, and the upper surface of the second horizontal section is provided with a fastening gasket with a thickness of 2-3 mm.

In the above technical solution, the reaction tank cover is provided with a stainless steel positioning ring, and 6 to 8 fastening screw positioning grooves are evenly distributed on the stainless steel positioning ring. The fastening screw positioning grooves have a diameter of 4 to 5 mm and a depth of 0.5 to 0.6 mm. The fastening screw positioning grooves are used to position the fastening screws. Another function of the stainless steel positioning ring is to bear the fastening force exerted by the fastening screws, so as to prevent the fastening screws from damaging the reaction tank cover.

In the above technical solution, the number of threaded holes in the intake pipe is 3-4, the number of threaded holes in the exhaust pipe is 1-2, the number of threaded holes in the Lujin capillary is 1, the number of threaded holes in the auxiliary electrode is 1, and the number of threaded holes in the digital display thermometer probe is 1-2; The gold capillary, auxiliary electrode and digital display thermometer probe are respectively provided with sealing rings after being connected with the threaded hole of the intake pipe, the threaded hole of the exhaust pipe, the threaded hole of the Lujin capillary, the threaded hole of the auxiliary electrode, and the threaded hole of the digital display thermometer probe.

In the above technical solution, the inlet pipe and the exhaust pipe are glass tubes with external threads; one end of the inlet pipe is equipped with porous foam for bubble dispersion, the purpose is to disperse the input gas and accelerate its dissolution in the corrosive medium; the inlet pipe is fed with one of high-purity nitrogen or carbon dioxide or hydrogen sulfide, and the high-purity nitrogen deoxidizes the corrosive medium.

In the above technical scheme, the auxiliary electrode is a platinum mesh electrode; the reference electrode is installed in the gold capillary, the liquid injection port of the gold capillary has a structure with internal and external double threads, the external thread of the gold capillary is connected with the threaded hole of the gold capillary on the glass pool, the internal thread of the gold capillary is connected with the external thread of the reference electrode through a thread structure, and is sealed with a rubber sealing ring; Keep a distance of 0.5 ~ 1mm.

In the above technical solution, the number of temperature sensors is 1 to 8; the heating device uses a resistance heating water bath or oil bath to heat the electrolytic cell, and the temperature sensor automatically controls the heating rate and the temperature of the water or oil through a closed-loop method. After the target temperature, the heating device stops heating, and ensure that the water or oil in the heating device is always maintained at the target temperature ±0.1°C.

In the above technical solution, the diameter of the test surface of the sample is 5±0.01 mm, and the length is 7-8 mm.

In the above technical solution, the stepped threaded waveguide rod is made of metal material, such as ferritic stainless steel; the primary sleeve, secondary sleeve, and tertiary sleeve are all insulating materials, such as polytetrafluoroethylene.

In the above technical solution, the sealing ring is a rubber sealing ring.

When using a corrosion electrochemical test device, the second external thread of the stepped thread waveguide is connected to the internal thread of the sample, a couplant layer is arranged on the circumferential surface of the sample, and the fixed end of the stepped thread waveguide is rotated so that the test surface of the sample connected to the second external thread of the stepped thread waveguide is flush with the first alignment surface of the first-stage sleeve and the second alignment surface of the third-stage sleeve; the internal thread of the second sleeve is fixedly connected to the test device, and the electrochemical corrosion test is performed on the sample. The stepped thread waveguide is connected to collect the electrochemical corrosion signal on the sample; the digital display thermometer probe and temperature sensor detect the real temperature of the corrosion medium in the electrolytic cell, and the test can be started after reaching the test required temperature and keeping it stable.

An electrochemical testing device for detecting the corrosion performance of materials by acoustic emission, comprising an electrolytic cell, an electrochemical testing device, a heating device and a heat preservation device;

The electrolytic cell includes a reaction cell, a reaction cell cover, a sealing gasket, a fastening device, and a sample installation device. The reaction cell is cylindrical, and the upper edge of the reaction cell is provided with a flange. The hole is connected with the auxiliary electrode, and the threaded hole of the digital display thermometer probe is connected with the digital display thermometer; the threaded hole of the Lujin capillary is connected with the external thread of the Lujin capillary liquid injection port, so that the curved part of the Lujin capillary is located in the reaction pool, and its opening is facing the sample as the working electrode, and the internal thread of the Lujin capillary liquid injection port is connected with the external thread of the reference electrode, so that the reference solution in the reference electrode can flow to the opening for the sample; On the horizontal plane; the sample installation device is composed of a stepped thread waveguide, a first-level sleeve, a second-level sleeve, a third-level sleeve, a sealing ring, and an acoustic emission sensor. The stepped thread waveguide, the first-level sleeve, the second-level sleeve, the third-level sleeve, the sealing ring, and the acoustic emission sensor are arranged coaxially, wherein: the stepped thread waveguide is provided with a first external thread and a second external thread, and the first external thread is connected to the internal thread of the first-level sleeve, so that the front end of the stepped thread waveguide is placed in the first cavity and the second cavity of the first-level sleeve, and the second external thread is placed in the thread cavity. Outside the second cavity of the first-level sleeve; a fixed end is provided at the rear end of the stepped thread waveguide rod, and an acoustic emission sensor in contact with it is arranged on the fixed end; the external thread of the first-level sleeve is connected with the internal thread of the third-level sleeve, so that the first-level sleeve is placed in the third cavity and the fourth cavity of the third-level sleeve; the second-level sleeve is set on the outside of the third-level sleeve, and a sealing ring is arranged between the second-level sleeve and the third-level sleeve;

The electrochemical test device includes an auxiliary electrode chuck, a reference electrode chuck, a working electrode chuck, and an electrochemical data processing system; the auxiliary electrode chuck, the reference electrode chuck, and the working electrode chuck are respectively connected to the auxiliary electrode, the reference electrode, and the stepped thread waveguide on the electrolytic cell, and then connected to the electrochemical data processing system through a signal transmission line;

The heating device is arranged on the outside of the reaction tank, the heat preservation device is arranged on the outside of the heating device, and the inner wall of the heating device is provided with a temperature sensor for detecting the temperature change of the electrolyte in the reaction tank.

In the above technical solution, the number of fastening devices is 6-8 groups, and the fastening device is composed of "bow"-shaped fastening device chucks, fastening screws and fastening gaskets, and the material of the fastening device chucks is 316 austenitic stainless steel; the fastening device chucks include a first horizontal section, a vertical section and a second horizontal section, and the upper surface of the second horizontal section is provided with a fastening gasket with a thickness of 2-3 mm.

In the above technical solution, the reaction tank cover is provided with a stainless steel positioning ring, and 6 to 8 fastening screw positioning grooves are evenly distributed on the stainless steel positioning ring. The fastening screw positioning grooves have a diameter of 4 to 5 mm and a depth of 0.5 to 0.6 mm. The fastening screw positioning grooves are used to position the fastening screws. Another function of the stainless steel positioning ring is to bear the fastening force exerted by the fastening screws, so as to prevent the fastening screws from damaging the reaction tank cover.

In the above technical solution, the number of threaded holes in the intake pipe is 3-4, the number of threaded holes in the exhaust pipe is 1-2, the number of threaded holes in the Lujin capillary is 1, the number of threaded holes in the auxiliary electrode is 1, and the number of threaded holes in the digital display thermometer probe is 1-2; The gold capillary, auxiliary electrode and digital display thermometer probe are respectively provided with sealing rings after being connected with the threaded hole of the intake pipe, the threaded hole of the exhaust pipe, the threaded hole of the Lujin capillary, the threaded hole of the auxiliary electrode, and the threaded hole of the digital display thermometer probe.

In the above technical solution, the inlet pipe and the exhaust pipe are glass tubes with external threads; one end of the inlet pipe is equipped with porous foam for bubble dispersion, the purpose is to disperse the input gas and accelerate its dissolution in the corrosive medium; the inlet pipe is fed with one of high-purity nitrogen or carbon dioxide or hydrogen sulfide, and the high-purity nitrogen deoxidizes the corrosive medium.

In the above technical scheme, the auxiliary electrode is a platinum mesh electrode; the reference electrode is installed in the gold capillary, the liquid injection port of the gold capillary has a structure with internal and external double threads, the external thread of the gold capillary is connected with the threaded hole of the gold capillary on the glass pool, the internal thread of the gold capillary is connected with the external thread of the reference electrode through a thread structure, and is sealed with a rubber sealing ring; Keep a distance of 0.5 ~ 1mm.

In the above technical solution, the number of temperature sensors is 1 to 8; the heating device uses a resistance heating water bath or oil bath to heat the electrolytic cell, and the temperature sensor automatically controls the heating rate and the temperature of the water or oil through a closed-loop method. After the target temperature, the heating device stops heating, and ensure that the water or oil in the heating device is always maintained at the target temperature ±0.1°C.

In the above technical solution, the diameter of the test surface of the sample is 5±0.01 mm, and the length is 7-8 mm.

In the above technical solution, the stepped threaded waveguide rod is made of metal material, such as ferritic stainless steel; the primary sleeve, secondary sleeve, and tertiary sleeve are all insulating materials, such as polytetrafluoroethylene.

In the above technical solution, the sealing ring is a rubber sealing ring.

In the above technical solution, an adhesive layer is provided between the fixed end and the acoustic emission sensor.

In the above technical solution, the acoustic emission sensor is fixed on the fixed end by using a magnetic clamp.

When an electrochemical test device for acoustic emission detection of material corrosion performance is used, the second external thread of the stepped thread waveguide rod is connected to the internal thread of the sample, a coupling agent layer is arranged on the circumferential surface of the sample, and the fixed end of the stepped thread waveguide rod is rotated so that the test surface of the sample connected to the second external thread of the stepped thread waveguide rod is flush with the first alignment surface of the first-level sleeve and the second alignment surface of the third-level sleeve; the internal thread of the second sleeve is fixedly connected to the test device, and the electrochemical corrosion test is performed on the sample, using the sample as the working electrode. It is connected to the stepped threaded waveguide rod located outside the test device to collect the electrochemical corrosion signal on the sample; the acoustic emission elastic wave emitted by the sample during the corrosion process is transmitted to the acoustic emission sensor through the stepped threaded waveguide rod and the displacement signal is converted into an electrical signal, which is transmitted outward; the digital display thermometer probe and the temperature sensor cooperate to detect the actual temperature of the corrosive medium in the electrolytic cell, and the test can be started after the required temperature is reached and kept stable.

The present invention has the following beneficial effects:

1. The present invention integrates acoustic emission dynamic nondestructive testing technology and electrochemical testing technology, and realizes online, dynamic and real-time detection of the electrochemical corrosion process of materials; the sample installation device of the present invention is arranged on the side of the glass pool, and the heating and heat preservation device can heat or heat the corrosive medium through a water bath or an oil bath.

2. The test sample of the present invention is a small cylindrical sample, the area of the test surface is 19-20mm ² , and the length is only 7mm, which can reduce the damage to the actual component during the sampling process as close as possible. In addition, the present invention can realize the sampling of tiny parts of actual components, such as different areas of welded joints (weld root, cover surface, weld center, high temperature and low temperature heat effects, etc.).

3. The sample installation of the present invention adopts the method of threaded connection, and the corrosion acoustic emission signal and electrochemical signal are transmitted through the stepped thread waveguide rod. Compared with the traditional epoxy resin sealing and wire conduction method, the installation, disassembly and cleaning of the tested sample of the present invention are more portable and efficient.

4. The present invention includes a plurality of intake pipes, which can simulate the material corrosion process in a variety of complex corrosive gas environments; the present invention fixes the distance between the tip of the Lujin capillary and the tested sample, and unifies the influence of the distance between the tip of the Lujin capillary and the tested sample on the test results.

5. It is not limited by the material of the object to be inspected, as long as it is conductive.

6. It can be used in harsh and complex working conditions. The operator only needs to operate it remotely in a safe and suitable environment. It has a high degree of automatic detection, simple operation, high testing efficiency, can greatly reduce labor intensity, and has low energy consumption.

Description of drawings

Fig. 1 is the working flow chart of the electrochemical testing device of acoustic emission detection material corrosion performance of the present invention;

Fig. 2 is the front view of electrolytic cell of the present invention;

Fig. 3 is a side view of the electrolytic cell of the present invention;

Fig. 4 is the top view of electrolytic cell of the present invention;

Fig. 5 is a schematic diagram of the reaction tank of the present invention;

Fig. 6 is a schematic diagram of the fastening device of the present invention;

Fig. 7 is a schematic diagram of the reaction tank cover of the present invention;

Fig. 8 is a schematic diagram a of the sample installation device of the present invention;

Fig. 9 is a sectional view of Fig. 8;

Fig. 10 is a schematic diagram of the stepped thread waveguide of the present invention;

Fig. 11 is a schematic diagram of a primary sleeve of the present invention;

Fig. 12 is a schematic diagram of a secondary sleeve of the present invention;

Fig. 13 is a schematic diagram of a three-stage sleeve of the present invention;

Fig. 14 is a sample schematic diagram and a sectional view of the present invention;

Fig. 15 is a schematic diagram of the installation of the Lujin capillary of the present invention;

Fig. 16 is a schematic diagram b of the sample installation device of the present invention;

Among them: 1 Fastening device; 2 Reaction tank sealing gasket; 3 Temperature sensor; 4 Heating device; 5 Heat preservation device; 6 Reaction tank cover; 7 Reaction tank; 8 Sample installation device; 9 Flange;

1-1 fastening screw, 1-2 first horizontal section, 1-3 vertical section, 1-4 fastening gasket, 1-5 second horizontal section; 6-1 fastening screw positioning groove, 6-2 stainless steel positioning ring, 6-3 intake pipe threaded hole, 6-4 digital display thermometer probe threaded hole, 6-5 auxiliary electrode threaded hole, 6-6 Lujin capillary threaded hole, 6-7 exhaust pipe threaded hole; 6-6-1 reference electrode, 6-6-2 Lujin capillary, 6-6-3 bending 8-1 stepped thread waveguide, 8-2 fixed end, 8-3 primary sleeve, 8-4 secondary sleeve, 8-5 tertiary sleeve, 8-6 sealing ring, 8-7 sample, 8-8 acoustic emission sensor; 8-1-1 first external thread, 8-1-2 second external thread; 8-3-1 first alignment surface, 8-3-2 first cavity, 8-3-3 second cavity, 8-3-4 sealing surface, 8-3- 5 first-level sleeve external thread, 8-3-6 first-level sleeve internal thread; 8-4-1 second-level sleeve internal thread; 8-5-1 second alignment surface, 8-5-2 third cavity, 8-5-3 fourth cavity, 8-5-4 third-level sleeve internal thread; 8-7-1 test surface, 8-7-2 sample circumferential surface, 8-7-3 sample internal thread.

Figure 17 is the electrochemical corrosion polarization curve of duplex stainless steel in 1mol/L NaCl aqueous solution;

Fig. 18 is the relationship curve of electrochemical potential, current density and test time of duplex stainless steel in 1mol/L NaCl aqueous solution;

Figure 19 is the acoustic emission amplitude of duplex stainless steel during electrochemical corrosion;

Figure 20 is the acoustic emission count of duplex stainless steel during electrochemical corrosion;

Figure 21 is the acoustic emission energy of duplex stainless steel during electrochemical corrosion;

Figure 22 is the acoustic emission waveform of duplex stainless steel during cathodic polarization (point 1 in Figure 18);

Figure 23 is the acoustic emission waveform of duplex stainless steel during anodic polarization (2 points in Figure 18);

Figure 24 is the acoustic emission waveform of duplex stainless steel during anodic polarization (3 points in Figure 18);

Figure 25 is the acoustic emission waveform of duplex stainless steel during anodic polarization (point 4 in Figure 18);

Figure 26 is the acoustic emission waveform of duplex stainless steel during anodic polarization (5 points in Figure 18);

Figure 27 is the acoustic emission waveform of duplex stainless steel during anodic polarization (point 6 in Figure 18).

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but it should not be construed as a limitation of the present invention.

The sample fixture used for the electrochemical corrosion test, that is, the sample installation device in the above-mentioned accompanying drawing 8, consists of a stepped thread waveguide, a first-level sleeve, a second-level sleeve, a third-level sleeve and a sealing ring. The stepped thread waveguide, the first-level sleeve, the second-level sleeve, the third-level sleeve and the sealing ring are coaxially arranged, wherein: the stepped thread waveguide is provided with a first external thread and a second external thread, and the first external thread is connected with the internal thread of the first-level sleeve, so that the front end of the stepped thread waveguide is placed in the first cavity and the second cavity of the first-level sleeve Inside, the second external thread is placed outside the second cavity of the first-stage sleeve; a fixed end is provided at the rear end of the stepped thread waveguide; the external thread of the first-stage sleeve is connected with the internal thread of the third-stage sleeve, so that the first-stage sleeve is placed in the third and fourth cavities of the third-stage sleeve; the second-stage sleeve is set on the outside of the third-stage sleeve, and a sealing ring is arranged between the second-stage sleeve and the third-stage sleeve.

In the above technical solution, the sealing ring is a rubber sealing ring.

In the above technical solution, the diameter of the test surface of the sample is 5±0.01 mm, and the length is 7-8 mm.

In the above technical solution, the stepped threaded waveguide is made of metal material, such as ferritic stainless steel.

In the above technical solution, the primary sleeve, the secondary sleeve, and the tertiary sleeve are all insulating materials, such as polytetrafluoroethylene.

When in use, the second external thread of the stepped thread waveguide is connected to the internal thread of the sample, a couplant layer is provided on the circumferential surface of the sample, and the fixed end of the stepped thread waveguide is rotated so that the test surface of the sample connected to the second external thread of the stepped thread waveguide is flush with the first alignment surface of the first-level sleeve and the second alignment surface of the third-level sleeve. The internal thread of the second sleeve is fixedly connected with the test device, and the electrochemical corrosion test is carried out on the sample. The sample is used as the working electrode, and the wire is connected to the stepped thread waveguide rod located outside the test device to collect the electrochemical corrosion signal on the sample.

The fixture for acoustic emission detection of material corrosion performance, that is, the sample installation device in the above-mentioned attached drawing 16, is composed of a stepped thread waveguide, a first-level sleeve, a second-level sleeve, a third-level sleeve, a sealing ring and an acoustic emission sensor. In the first cavity and the second cavity of the sleeve, the second external thread is placed outside the second cavity of the first-level sleeve; a fixed end is provided at the rear end of the stepped thread waveguide rod, and an acoustic emission sensor in contact with it is arranged on the fixed end; the external thread of the first-level sleeve is connected with the inner thread of the third-level sleeve, so that the first-level sleeve is placed in the third and fourth cavities of the third-level sleeve; the second-level sleeve is set on the outside of the third-level sleeve, and a sealing ring is provided between the second-level sleeve and the third-level sleeve.

In the above technical solution, the sealing ring is a rubber sealing ring.

In the above technical solution, the diameter of the test surface of the sample is 5±0.01 mm, and the length is 7-8 mm.

In the above technical solution, both the stepped threaded waveguide rod and the fixed end are metal materials, such as ferritic stainless steel.

In the above technical solution, the primary sleeve, the secondary sleeve and the tertiary sleeve are all insulating materials, such as polytetrafluoroethylene.

In the above technical solution, an adhesive layer is provided between the fixed end and the acoustic emission sensor.

In the above technical solution, the acoustic emission sensor is fixed on the fixed end by using a magnetic clamp.

When in use, the second external thread of the stepped thread waveguide is connected to the internal thread of the sample, a couplant layer is provided on the circumferential surface of the sample, and the fixed end of the stepped thread waveguide is rotated so that the test surface of the sample connected to the second external thread of the stepped thread waveguide is flush with the first alignment surface of the first-level sleeve and the second alignment surface of the third-level sleeve. The internal thread of the second sleeve is fixedly connected with the test device, and the electrochemical corrosion test is carried out on the sample. The sample is used as the working electrode, and the wire is connected to the stepped thread waveguide rod located outside the test device to collect the electrochemical corrosion signal on the sample; the acoustic emission elastic wave emitted by the sample during the corrosion process is transmitted to the acoustic emission sensor through the stepped thread waveguide rod, and the displacement signal is converted into an electrical signal and transmitted outward.

A corrosion electrochemical testing device, comprising an electrolytic cell, an electrochemical testing device, a heating device, and a heat preservation device; the electrolytic cell includes a reaction cell, a reaction cell cover, a sealing gasket, a fastening device, and a sample installation device; the reaction cell is cylindrical, and the upper edge of the reaction cell is provided with a flange; The threaded hole of the intake pipe is connected with the air intake pipe, the threaded hole of the exhaust pipe is connected with the exhaust pipe, the threaded hole of the auxiliary electrode is connected with the auxiliary electrode, and the threaded hole of the digital display thermometer probe is connected with the digital display thermometer; the threaded hole of the Lujin capillary is connected with the external thread of the liquid injection port of the Lujin capillary, so that the bending part of the Lujin capillary is located in the reaction pool, and its opening is facing the sample as the working electrode. The opening of the Lujin capillary, the sample as the working electrode and the auxiliary electrode are located on the same horizontal plane; the sample installation device is composed of a stepped thread waveguide, a first-level sleeve, a second-level sleeve, a third-level sleeve, and a sealing ring. connected so that the front end of the stepped threaded waveguide rod is placed in the first cavity and the second cavity of the first-level sleeve, and the second external thread is placed outside the second cavity of the first-level sleeve; the outer thread of the first-level sleeve is connected with the inner thread of the third-level sleeve, so that the first-level sleeve is placed in the third and fourth cavities of the third-level sleeve; the second-level sleeve is set outside the third-level sleeve, and a sealing ring is set between the second-level sleeve and the third-level sleeve; The electrochemical test device includes an auxiliary electrode chuck, a reference electrode chuck, a working electrode chuck, and an electrochemical data processing system The auxiliary electrode chuck, the reference electrode chuck and the working electrode chuck are respectively connected to the auxiliary electrode on the electrolytic cell, the reference electrode and the fixed end of the stepped threaded waveguide rod, and then connected to the electrochemical data processing system through a signal transmission line; the heating device is arranged on the outside of the reaction tank, the heat preservation device is arranged on the outside of the heating device, and the inner wall of the heating device is provided with a temperature sensor for detecting the temperature change of the electrolyte in the reaction tank.

In the above technical solution, the number of fastening devices is 6-8 groups, and the fastening device is composed of "bow"-shaped fastening device chucks, fastening screws and fastening gaskets, and the material of the fastening device chucks is 316 austenitic stainless steel; the fastening device chucks include a first horizontal section, a vertical section and a second horizontal section, and the upper surface of the second horizontal section is provided with a fastening gasket with a thickness of 2-3 mm.

In the above technical solution, the reaction tank cover is provided with a stainless steel positioning ring, and 6 to 8 fastening screw positioning grooves are evenly distributed on the stainless steel positioning ring. The fastening screw positioning grooves have a diameter of 4 to 5 mm and a depth of 0.5 to 0.6 mm. The fastening screw positioning grooves are used to position the fastening screws. Another function of the stainless steel positioning ring is to bear the fastening force exerted by the fastening screws, so as to prevent the fastening screws from damaging the reaction tank cover.

In the above technical solution, the number of threaded holes in the intake pipe is 3-4, the number of threaded holes in the exhaust pipe is 1-2, the number of threaded holes in the Lujin capillary is 1, the number of threaded holes in the auxiliary electrode is 1, and the number of threaded holes in the digital display thermometer probe is 1-2; The gold capillary, auxiliary electrode and digital display thermometer probe are respectively provided with sealing rings after being connected with the threaded hole of the intake pipe, the threaded hole of the exhaust pipe, the threaded hole of the Lujin capillary, the threaded hole of the auxiliary electrode, and the threaded hole of the digital display thermometer probe.

In the above technical solution, the inlet pipe and the exhaust pipe are glass tubes with external threads; one end of the inlet pipe is equipped with porous foam for bubble dispersion, the purpose is to disperse the input gas and accelerate its dissolution in the corrosive medium; the inlet pipe is fed with one of high-purity nitrogen or carbon dioxide or hydrogen sulfide, and the high-purity nitrogen deoxidizes the corrosive medium.

In the above technical scheme, the auxiliary electrode is a platinum mesh electrode; the reference electrode is installed in the gold capillary, the liquid injection port of the gold capillary has a structure with internal and external double threads, the external thread of the gold capillary is connected with the threaded hole of the gold capillary on the glass pool, the internal thread of the gold capillary is connected with the external thread of the reference electrode through a thread structure, and is sealed with a rubber sealing ring; Keep a distance of 0.5 ~ 1mm.

In the above technical solution, the number of temperature sensors is 1 to 8; the heating device uses a resistance heating water bath or oil bath to heat the electrolytic cell, and the temperature sensor automatically controls the heating rate and the temperature of the water or oil through a closed-loop method. After the target temperature, the heating device stops heating and ensures that the water or oil in the heating device is always maintained at the target temperature ±0.1°C.

In the above technical solution, the diameter of the test surface of the sample is 5±0.01 mm, and the length is 7-8 mm.

In the above technical solution, the stepped threaded waveguide rod is made of metal material, such as ferritic stainless steel; the primary sleeve, secondary sleeve, and tertiary sleeve are all insulating materials, such as polytetrafluoroethylene.

In the above technical solution, the sealing ring is a rubber sealing ring.

When using a corrosion electrochemical test device, the second external thread of the stepped thread waveguide is connected to the internal thread of the sample, a couplant layer is arranged on the circumferential surface of the sample, and the fixed end of the stepped thread waveguide is rotated so that the test surface of the sample connected to the second external thread of the stepped thread waveguide is flush with the first alignment surface of the first-stage sleeve and the second alignment surface of the third-stage sleeve; the internal thread of the second sleeve is fixedly connected to the test device, and the electrochemical corrosion test is performed on the sample. The stepped thread waveguide is connected to collect the electrochemical corrosion signal on the sample; the digital display thermometer probe and temperature sensor detect the real temperature of the corrosion medium in the electrolytic cell, and the test can be started after reaching the test required temperature and keeping it stable.

An electrochemical testing device for acoustic emission detection of material corrosion performance, comprising an electrolytic cell, an electrochemical testing device, a heating device, and a heat preservation device; the electrolytic cell includes a reaction cell, a reaction cell cover, a sealing gasket, a fastening device, and a sample installation device; the reaction cell is cylindrical, and the upper edge of the reaction cell is provided with a flange; Lujin capillary threaded hole; the intake pipe threaded hole is connected with the air intake pipe, the exhaust pipe threaded hole is connected with the exhaust pipe, the auxiliary electrode threaded hole is connected with the auxiliary electrode, and the digital display thermometer probe threaded hole is connected with the digital display thermometer; the Lujin capillary threaded hole is connected with the external thread of the Lujin capillary liquid injection port, so that the bending part of the Lujin capillary is located in the reaction pool, and its opening is facing the sample as the working electrode. The liquid can flow to the opening of the sample; the opening of the Lujin capillary, the sample as the working electrode and the auxiliary electrode are located on the same horizontal plane; the sample installation device is composed of a stepped thread waveguide rod, a first-level sleeve, a second-level sleeve, a third-level sleeve, a sealing ring and an acoustic emission sensor. connected so that the front end of the stepped thread waveguide rod is placed in the first cavity and the second cavity of the first-stage sleeve, and the second external thread is placed outside the second cavity of the first-stage sleeve; a fixed end is provided at the rear end of the stepped thread waveguide rod, and an acoustic emission sensor in contact with it is arranged on the fixed end; the external thread of the first-stage sleeve is connected with the internal thread of the third-stage sleeve, so that the first-stage sleeve is placed in the third and fourth cavities of the third-stage sleeve; The electrochemical testing device includes an auxiliary electrode chuck, a reference electrode chuck, a working electrode chuck, and an electrochemical data processing system; the auxiliary electrode chuck, the reference electrode chuck, and the working electrode chuck are respectively connected to the auxiliary electrode, the reference electrode, and the stepped thread waveguide on the electrolytic cell, and then connected to the electrochemical data processing system through a signal transmission line; the heating device is arranged on the outside of the reaction cell, the heat preservation device is arranged on the outside of the heating device, and a temperature sensor is arranged on the inner wall of the heating device to detect the temperature change of the electrolyte in the reaction cell.

In the above technical solution, the number of fastening devices is 6-8 groups, and the fastening device is composed of "bow"-shaped fastening device chucks, fastening screws and fastening gaskets, and the material of the fastening device chucks is 316 austenitic stainless steel; the fastening device chucks include a first horizontal section, a vertical section and a second horizontal section, and the upper surface of the second horizontal section is provided with a fastening gasket with a thickness of 2-3 mm.

In the above technical solution, the reaction tank cover is provided with a stainless steel positioning ring, and 6 to 8 fastening screw positioning grooves are evenly distributed on the stainless steel positioning ring. The fastening screw positioning grooves have a diameter of 4 to 5 mm and a depth of 0.5 to 0.6 mm. The fastening screw positioning grooves are used to position the fastening screws. Another function of the stainless steel positioning ring is to bear the fastening force exerted by the fastening screws, so as to prevent the fastening screws from damaging the reaction tank cover.

In the above technical solution, the number of threaded holes in the intake pipe is 3-4, the number of threaded holes in the exhaust pipe is 1-2, the number of threaded holes in the Lujin capillary is 1, the number of threaded holes in the auxiliary electrode is 1, and the number of threaded holes in the digital display thermometer probe is 1-2; The gold capillary, the auxiliary electrode and the digital display thermometer probe are respectively provided with sealing rings after being connected with the threaded hole of the intake pipe, the threaded hole of the exhaust pipe, the threaded hole of the Lujin capillary, the threaded hole of the auxiliary electrode, and the threaded hole of the digital display thermometer probe.

In the above technical solution, the inlet pipe and the exhaust pipe are glass tubes with external threads; one end of the inlet pipe is equipped with porous foam for bubble dispersion, the purpose is to disperse the input gas and accelerate its dissolution in the corrosive medium; the inlet pipe is fed with one of high-purity nitrogen or carbon dioxide or hydrogen sulfide, and the high-purity nitrogen deoxidizes the corrosive medium.

In the above technical scheme, the auxiliary electrode is a platinum mesh electrode; the reference electrode is installed in the gold capillary, the liquid injection port of the gold capillary has a structure with internal and external double threads, the external thread of the gold capillary is connected with the threaded hole of the gold capillary on the glass pool, the internal thread of the gold capillary is connected with the external thread of the reference electrode through a thread structure, and is sealed with a rubber sealing ring; Keep a distance of 0.5 ~ 1mm.

In the above technical solution, the number of temperature sensors is 1 to 8; the heating device uses a resistance heating water bath or oil bath to heat the electrolytic cell, and the temperature sensor automatically controls the heating rate and the temperature of the water or oil through a closed-loop method. After the target temperature, the heating device stops heating and ensures that the water or oil in the heating device is always maintained at the target temperature ±0.1°C.

In the above technical solution, the diameter of the test surface of the sample is 5±0.01 mm, and the length is 7-8 mm.

In the above technical solution, the stepped threaded waveguide rod is made of metal material, such as ferritic stainless steel; the primary sleeve, secondary sleeve, and tertiary sleeve are all insulating materials, such as polytetrafluoroethylene.

In the above technical solution, the sealing ring is a rubber sealing ring.

In the above technical solution, an adhesive layer is provided between the fixed end and the acoustic emission sensor.

In the above technical solution, the acoustic emission sensor is fixed on the fixed end by using a magnetic clamp.

When an electrochemical test device for acoustic emission detection of material corrosion performance is used, the second external thread of the stepped thread waveguide rod is connected to the internal thread of the sample, a coupling agent layer is arranged on the circumferential surface of the sample, and the fixed end of the stepped thread waveguide rod is rotated so that the test surface of the sample connected to the second external thread of the stepped thread waveguide rod is flush with the first alignment surface of the first-level sleeve and the second alignment surface of the third-level sleeve; the internal thread of the second sleeve is fixedly connected to the test device, and the electrochemical corrosion test is performed on the sample, using the sample as the working electrode. It is connected to the stepped threaded waveguide rod located outside the test device to collect the electrochemical corrosion signal on the sample; the acoustic emission elastic wave emitted by the sample during the corrosion process is transmitted to the acoustic emission sensor through the stepped threaded waveguide rod and the displacement signal is converted into an electrical signal, which is transmitted outward; the digital display thermometer probe and the temperature sensor cooperate to detect the actual temperature of the corrosive medium in the electrolytic cell, and the test can be started after the required temperature is reached and kept stable.

Using the above four technical solutions to form a test device for electrochemical and acoustic emission detection, the details are as follows:

The specific structure of the reaction tank cover is shown in Fig. 7. The three inlet pipes and one exhaust pipe (not shown in the figure) are respectively connected to the corresponding inlet pipe threaded holes and exhaust pipe threaded holes on the reaction tank cover, and are sealed with a rubber sealing ring. One end of the air inlet pipe is encapsulated with porous foam for bubble dispersion and inserted into the bottom of the reaction tank. The other end is connected to the corresponding gas cylinder for input gas through a rubber tube. The other end of the tube is connected with a 5L sealed volumetric flask containing lye through a rubber tube, and enough sodium hydroxide lye (3L) is housed in the volumetric flask to absorb the acid gas discharged. The interface between all glass tubes and rubber tubes is sealed with silicone. A syringe is used to fill the Lukin capillary with a saturated potassium chloride aqueous solution to ensure that there are no air bubbles in the Lukin capillary, and then the reference electrode is connected with the internal thread of the Lukin capillary through a thread structure through an external thread, the reference electrode is a calomel electrode, and the reference solution is a saturated aqueous potassium chloride solution. For the specific structure of the sample installation device, please refer to Figures 8 and 9. Apply an appropriate amount of vacuum grease to the second external thread of the stepped thread waveguide to reduce the attenuation of the corrosive acoustic emission signal, and put a rubber seal ring on the second external thread of the stepped thread waveguide, and then evenly apply a small amount of silica gel on the circumferential surface of the sample after mechanical polishing, and then counter-rotate the second external thread of the stepped thread waveguide. Until the test surface of the sample is completely parallel to the first alignment surface and the second alignment surface, then wipe off the extruded excess silica gel with dust-free paper, and wipe the test surface of the sample several times with alcohol, and then put the sample installation device in the drying box for 24 hours. After the silica gel is completely cured, put the rubber sealing ring on the secondary sleeve, and then connect the entire sample installation device to the lateral external thread interface of the reaction pool through the internal thread of the secondary sleeve.

Slowly introduce the prepared corrosion solution into the reaction pool. In order to ensure that the test surface of the sample is completely immersed in the corrosion solution without overflowing, the volume of the corrosion solution injected into the reaction pool is required to be 1-1.4L.

Put the sealing gasket of the reaction cell on the cover of the reaction cell, and then gently put it on the reaction cell, adjust the direction of the reaction cell cover so that the tip of the Lukin capillary is facing the center of the test surface of the sample.

To install the 6 fastening devices, first attach the fastening gasket to the lower edge of the flange of the reaction tank, and at the same time align the fastening screws with the fastening screw positioning grooves on the stainless steel positioning ring, and then tighten the 6 fastening devices in a diagonal order.

Open the data acquisition and analysis software, and set the electrochemical test parameters and acoustic emission acquisition parameters. The setting of electrochemical test parameters includes electrochemical test methods and corresponding test parameters, such as open circuit potential stabilization time, scanning potential range, potential scanning speed, etc. need to be set for potentiodynamic polarization. The acoustic emission acquisition parameter setting includes the amplification factor of the signal amplifier, threshold value, sampling frequency, filtering range, real-time display parameters and the like. It should be noted that the electrochemical test parameters and acoustic emission acquisition parameters need to be adjusted according to the specific sample material, corrosion environment, and electrochemical test method; then a standard lead breaking experiment is performed to evaluate the coupling between the acoustic emission sensor and the stepped threaded waveguide rod. Carry out the lead breaking experiment near the acoustic emission sensor installation end on the said stepped threaded waveguide rod, when the collected lead breaking acoustic emission signal amplitude is higher than 90dB, it is considered that the acoustic emission sensor is well coupled with the said stepped threaded waveguide rod; then, open the cylinder valve of the input gas, and control the amount of input gas through a flow meter.

Finally, the experiment officially started. During the experiment, try to ensure a quiet environment and avoid touching the electrolytic cell and related connection lines. When the test is complete, the experiment will automatically stop.

Use this device to test the polarization curve and acoustic emission signal of UNS S31803 duplex stainless steel during potentiodynamic polarization (electrochemical test device: Gamry, Interface 1000, acoustic emission test device: PAC, PCI-2; acoustic emission sensor model: R15A; signal amplifier model: 2/4/6-AST), and the test solution is 1mol/L NaCl aqueous solution. After installing the device according to the above steps, open the data collection and analysis software to set the experimental parameters. The heating target temperature was set to 60°C. Electrochemical test parameter setting: The electrochemical test method is potentiodynamic polarization, the potential scanning range is -0.75 VSCE-0.6 VSCE, the scanning speed is 0.5mVSCE/s, the open circuit potential temperature time is 30min, and the test will automatically stop when the set current density exceeds 100μA/cm2 ^continuously . Acoustic emission acquisition parameter setting: the amplification factor of the signal amplifier is 40dB, the threshold value is 30dB, the sampling frequency is 2MSPS, the filtering range is 20kHz-1MHz, and the real-time acquisition parameters are amplitude, energy, count and waveform.

Open the valve of the high-purity nitrogen cylinder before the test, and control the high-purity nitrogen through the flow meter to deoxygenate the test solution at a flow rate of 0.1mL/min, and the deoxygenation time is 1h. At the same time, click to start heating until the solution temperature in the electrolytic cell is stable at 60±0.1°C. After that, click the Start Test button, and the test officially begins. The test results are shown in Figure 17-27.

Figure 17 is the electrochemical corrosion polarization curve of duplex stainless steel in 1mol/L NaCl aqueous solution (60°C). The polarization curve in Figure 17 is divided into two branches: cathodic polarization (shown in 1) and anodic polarization (shown in 2, 3, 4, 5, 6). During the cathodic polarization process, the hydrogen evolution reaction mainly occurs, and hydrogen bubbles are generated on the surface of the sample. The anodic polarization process mainly occurs in the dissolution of metal, the formation of passive film, and the dissolution of passive film. Starting from the corrosion potential, as the potential increases, a passivation film is gradually formed on the metal surface, and the passivation film will dissolve in a local area to produce sub-pitting pits, and the formed sub-pitting pits may also be repaired due to re-passivation, as shown in 2, 3, 4, and 5 in Figure 17. When the potential exceeds the pitting potential, the current density increases sharply due to the formation of stable pits, as shown by 6 in Fig. 17.

Fig. 18 is the relationship curve of electrochemical potential, current density and test time of duplex stainless steel in 1mol/L NaCl aqueous solution (60°C).

Figure 19 is the acoustic emission amplitude of duplex stainless steel during electrochemical corrosion. The acoustic emission amplitudes of 1, 2, 3, 4, 5, and 6 in Figure 19 correspond to the polarization potentials and current densities of 1, 2, 3, 4, 5, and 6 in Figure 16, respectively.

Figure 20 and Figure 21 are the acoustic emission counts and energy of duplex stainless steel during electrochemical corrosion, respectively. There is no significant difference in the amplitude, count and energy of acoustic emission signal amplitude, count and energy produced by hydrogen bubble rupture and the acoustic emission signal amplitude, count and energy produced by passive film rupture to form metastable pits. Compared with the AE signal generated by metastable pits, stable pits generated higher amplitude and energy AE signals, but the count value did not increase significantly.

Figures 22-27 are the acoustic emission waveforms of duplex stainless steel during potentiodynamic polarization, corresponding to 1, 2, 3, 4, 5, and 6 in Figure 17 or Figure 19, respectively. The rupture of hydrogen bubbles produces a typical burst acoustic emission signal, while the partial passive film rupture and the formation of stable pitting pits produce a mixed type of acoustic emission signal. The device can fully realize the purpose of testing the corrosion performance of materials by using acoustic emission technology and electrochemical technology at the same time.

Claims (3)

1. An electrochemical testing device for acoustic emission detection material corrosion performance, characterized in that: comprise electrolytic cell, electrochemical testing device, heating device and heat preservation device; described electrolytic cell includes reaction cell, reaction cell cover, sealing gasket, fastening device, sample installation device, described reaction cell is cylindrical, reaction cell upper end edge is provided with flange, described reaction cell cover and reaction cell top are cushioned with sealing gasket, reaction cell cover and reaction cell are connected to fastening device sealing; Thermometer probe threaded hole, Lujin capillary threaded hole; intake pipe threaded hole is connected with air intake pipe, exhaust pipe threaded hole is connected with exhaust pipe, auxiliary electrode threaded hole is connected with the auxiliary electrode, digital display thermometer probe threaded hole is connected with digital display thermometer; Lujin capillary threaded hole is connected with the external thread of Lujin capillary liquid injection port, so that the bending part of Lujin capillary is located in the reaction pool, and its opening is facing the sample as the working electrode. The reference liquid in the reference electrode can flow to the opening for the sample; the opening of the Lujin capillary, the sample as the working electrode and the auxiliary electrode are located on the same horizontal plane; the sample installation device is composed of a stepped thread waveguide rod, a primary sleeve, a secondary sleeve, a tertiary sleeve, a sealing ring and an acoustic emission sensor. The internal thread of the first-stage sleeve is connected so that the front end of the stepped thread waveguide rod is placed in the first cavity and the second cavity of the first-stage sleeve, and the second external thread is placed outside the second cavity of the first-stage sleeve; a fixed end is provided at the rear end of the stepped thread waveguide rod, and an acoustic emission sensor in contact with it is arranged on the fixed end; the external thread of the first-stage sleeve is connected with the internal thread of the third-stage sleeve, so that the first-stage sleeve is placed in the third and fourth cavities of the third-stage sleeve; A sealing ring is arranged between them; the electrochemical testing device includes an auxiliary electrode chuck, a reference electrode chuck, a working electrode chuck, and an electrochemical data processing system. The auxiliary electrode chuck, the reference electrode chuck, and the working electrode chuck are respectively connected to the auxiliary electrode, the reference electrode, and the stepped thread waveguide on the electrolytic cell, and then connected to the electrochemical data processing system through a signal transmission line; change; The number of fastening devices is 6-8 groups, and the fastening device is composed of "bow"-shaped fastening device chucks, fastening screws and fastening gaskets. The material of the fastening device chucks is 316 austenitic stainless steel; the fastening device chucks include a first horizontal section, a vertical section and a second horizontal section, and the upper surface of the second horizontal section is provided with a fastening gasket with a thickness of 2-3 mm. There are 6-8 fastening screw positioning grooves, the diameter of the fastening screw positioning grooves is 4-5 mm, and the depth is 0.5-0.6 mm. The fastening screw positioning grooves are used to position the fastening screws. Another function of the stainless steel positioning ring is to bear the fastening force exerted by the fastening screws, so as to prevent the fastening screws from damaging the reaction tank cover; The number of threaded holes in the intake pipe is 3 to 4, the number of threaded holes in the exhaust pipe is 1 to 2, the number of threaded holes in the Lujin capillary is 1, the number of threaded holes in the auxiliary electrode is 1, and the number of threaded holes in the digital display thermometer probe is 1 to 2; correspondingly, the number of intake pipes is 3 to 4, the number of exhaust pipes is 1 to 2, the number of Lujin capillaries is 1, the number of auxiliary electrodes is 1, and the number of digital display thermometer probes is 1 to 2; The auxiliary electrode and the digital display thermometer probe are respectively provided with sealing rings after they are connected with the threaded hole of the intake pipe, the threaded hole of the exhaust pipe, the threaded hole of the Lujin capillary, the threaded hole of the auxiliary electrode, and the threaded hole of the digital display thermometer probe; The inlet pipe and the exhaust pipe are glass pipes with external threads; one end of the inlet pipe is equipped with porous foam for bubble dispersion, the purpose is to disperse the input gas and accelerate its dissolution in the corrosive medium; the inlet pipe is passed into one of high-purity nitrogen or carbon dioxide or hydrogen sulfide, and the high-purity nitrogen deoxidizes the corrosive medium. In the Lujin capillary, the liquid injection port of the Lujin capillary has a structure with internal and external double threads, the external thread of the Lujin capillary is connected with the Lujin capillary threaded hole on the glass pool, the internal thread of the Lujin capillary is connected with the external thread of the reference electrode through a thread structure, and is sealed by a rubber sealing ring; the opening of the Lujin capillary tip is aligned with the center of the test surface of the sample, and is kept at a distance of 0.5 to 1 mm from the sample to be tested; the number of the temperature sensors is 1 to 8; The heating device uses a resistance heating water bath or oil bath to heat the electrolytic cell. The temperature sensor automatically controls the heating rate and the temperature of water or oil through a closed-loop method. Put the reaction cell into the water or oil in the heating and heat preservation device. within ±0.1°C of the target temperature. 2. the electrochemical testing device of a kind of acoustic emission detection material corrosion performance according to claim 1, it is characterized in that: the diameter of the test surface of sample is 5 ± 0.01mm, and length is 7～8mm; Step thread waveguide rod is metal material, and described metal material is ferritic stainless steel; Primary sleeve, secondary sleeve, tertiary sleeve are all insulating materials, and described insulating material is polytetrafluoroethylene; Described sealing ring is rubber sealing ring; on the fixed end. 3. The application of an electrochemical testing device for acoustic emission detection of material corrosion performance in electrochemical corrosion testing as claimed in claim 1 or 2, characterized in that: the second external thread of the stepped thread waveguide is connected to the internal thread of the sample, a couplant layer is set on the circumferential surface of the sample, and the fixed end of the stepped thread waveguide is rotated, so that the test surface of the sample connected to the second external thread of the stepped thread waveguide is flush with the first alignment surface of the first-level sleeve and the second alignment surface of the third-level sleeve; The sample is fixedly connected, and the electrochemical corrosion test is carried out on the sample. The sample is used as the working electrode, and the wire is connected to the stepped threaded waveguide rod located outside the test device to collect the electrochemical corrosion signal on the sample; the acoustic emission elastic wave emitted by the sample during the corrosion process is transmitted to the acoustic emission sensor through the stepped threaded waveguide rod, and the displacement signal is converted into an electrical signal, which is transmitted outward; the digital display thermometer probe and the temperature sensor cooperate to detect the actual temperature of the corrosive medium in the electrolytic cell.