Testing device and method for simulating dynamic interface metal corrosion of supercritical CO2 and aqueous solution

Abstract

The invention discloses a metal corrosion testing device and method for simulating a dynamic interface of supercritical CO2 and an aqueous solution, and belongs to the technical field of metal corrosion testing. The metal corrosion testing device comprises a reaction kettle, a temperature control system, a gas control system, a supercritical CO2 / aqueous solution interface simulation control system and an electrochemical testing system, the supercritical CO2 / water solution interface simulation control system comprises an electric push rod, a time relay and a sample holder; one end of the electric push rod penetrates through the kettle cover of the reaction kettle and is connected with the time relay; the time relay is used for controlling periodic reciprocating motion of the electric push rod; the electrochemical testing system comprises an electrochemical workstation and an electrochemical probe; the electrochemical workstation is connected with an electrochemical probe, and the electrochemical probe is arranged on the corrosion exposure experiment sample; the temperature control system is arranged in the reaction kettle, and the gas control system is connected with the reaction kettle. The technical problem that the metal corrosion of the dynamic interface of the supercritical CO2 and the aqueous solution cannot be accurately analyzed in the prior art is solved.

Description

Technical Field

[0001] This invention belongs to the field of metal corrosion testing technology, specifically relating to a metal corrosion testing device and method that simulates the dynamic interface between supercritical CO2 and aqueous solution. Background Technology

[0002] Carbon dioxide capture, utilization, and storage (CCUS) technology is a crucial technology for oil and gas field companies to enhance oil recovery. CO2 sequestration involves injecting collected CO2 into saline aquifers or depleted oil and gas fields via pipelines, utilizing the geological reservoir to preserve the CO2. However, due to impurities in the gas source, the interaction between the gas and formation water can easily trigger corrosion of pipelines and tubing. Furthermore, while CO2-based enhanced oil recovery (EOR) is an effective way to utilize CO2, as crude oil development progresses into its later stages, the increasing water content in crude oil, coupled with the effects of supercritical CO2 within pipelines, exacerbates pipeline corrosion problems.

[0003] Oil pipelines, as crucial transportation channels, play a vital role in transporting supercritical carbon dioxide. The service environment of oil pipelines is complex, involving not only direct contact with supercritical CO2 and formation water, but also the interface region between the two—the supercritical CO2 / formation water interface zone. Due to the interaction between CO2 and oil / water, as well as the influence of impurities in the gas, the corrosion characteristics of this region differ significantly from other areas. Especially during CO2-assisted oil recovery, the use of gas-water alternation inevitably leads to the formation of the supercritical CO2 / formation water interface zone.

[0004] Currently, the corrosion mechanism of metal pipes in supercritical CO2 environments has become a research hotspot in recent years. Studies on supercritical CO2 corrosion mainly involve immersion in aqueous solutions or complete exposure to supercritical CO2 for weight loss testing and surface characterization. However, these methods cannot accurately analyze the influence mechanism and patterns of pipe corrosion at the gas-liquid interface.

[0005] The corrosion of metallic materials in a supercritical CO2 environment is an electrochemical process. How to establish an in-situ electrochemical testing system in a supercritical CO2 environment to fully reveal the metal corrosion mechanism at the supercritical CO2 / formation water interface and provide necessary scientific support for pipe material selection is a challenging problem that deserves further exploration in current research. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a test device and method for simulating the dynamic interface metal corrosion of supercritical CO2 and aqueous solution, and solve the technical problem that the prior art cannot accurately analyze the dynamic interface metal corrosion of supercritical CO2 and aqueous solution.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] This invention provides a test device for simulating the dynamic interface metal corrosion of supercritical CO2 and aqueous solution, including a reaction vessel, a temperature control system, a gas control system, a supercritical CO2 / aqueous solution interface simulation control system, and an electrochemical testing system;

[0009] The supercritical CO2 / aqueous solution interface simulation control system includes an electric push rod, a time relay, and a sample holder;

[0010] One end of the electric push rod passes through the lid of the reactor and is connected to a time relay, while the other end is connected to a sample holder in the reactor; the time relay is used to control the periodic reciprocating motion of the electric push rod.

[0011] The electrochemical testing system includes an electrochemical workstation and an electrochemical probe;

[0012] The electrochemical workstation is connected to the electrochemical probe, which is placed on the corrosion exposure test sample.

[0013] The temperature control system is located inside the reactor, and the gas control system is connected to the reactor.

[0014] In specific implementation, the sample holder includes a lower disc, a sample groove, an upper disc, and a support.

[0015] The support has a lower disk and an upper disk at its two ends, and the sample groove is correspondingly opened on the lower disk and the upper disk.

[0016] In the specific implementation process, several of the corrosion exposure test samples are fixed on the sample holder, and several of the electrochemical probes are respectively located in the supercritical CO2 / water solution interface region and the water solution immersion region on the corrosion exposure test samples.

[0017] In practice, the electrochemical probe includes an auxiliary electrode and a reference electrode.

[0018] The auxiliary electrode, reference electrode, and corrosion exposure test sample constitute a three-electrode system.

[0019] In practice, the electrochemical probe also includes a support, epoxy resin, and an adjustable sleeve.

[0020] The auxiliary electrode and the reference electrode are placed parallel and aligned between the two pillars, and the auxiliary electrode and the reference electrode are encapsulated with epoxy resin. The adjustable sleeve is located below the auxiliary electrode and the reference electrode, and the adjustable sleeve is used to fix the auxiliary electrode and the reference electrode.

[0021] In the specific implementation process, the reference electrode is an Ag / AgCl reference electrode; the auxiliary electrode is a Pt auxiliary electrode.

[0022] In specific implementation, the temperature control system includes a heating resistance wire, a thermocouple, and a temperature control module in the controller;

[0023] The heating resistance wire is installed on the inner wall of the reactor, the thermocouple is inserted into the reactor, and the heating resistance wire and the thermocouple are electrically connected to the temperature control module in the controller.

[0024] In practice, the gas control system includes a booster pump, a pressure gauge, a CO2 cylinder, and a pressure control module in the controller.

[0025] The outlet of the CO2 cylinder is connected to the inlet on the lid of the reactor via an inlet pipe. The booster pump is installed on the inlet pipe, and the outlet of the inlet pipe extends below the liquid surface inside the reactor.

[0026] The pressure gauge is installed on the lid of the reactor and is electrically connected to the pressure control module in the controller.

[0027] This invention provides a method for testing metal corrosion at a simulated dynamic interface between supercritical CO2 and aqueous solution, based on a simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion testing device, comprising the following steps:

[0028] The corrosion exposure test specimens are assembled into the specimen holder. One of the corrosion exposure test specimens is equipped with an electrochemical probe. The specimen holder is placed in a reaction vessel containing a simulated formation aqueous solution. The height of the specimen holder is adjusted so that several electrochemical probes are located in the supercritical CO2 / aqueous solution interface region and the fully immersed aqueous solution region on the corrosion exposure test specimen.

[0029] Inert gas is introduced to remove oxygen from the reactor and the simulated formation aqueous solution in the reactor; the reactor is heated to the set temperature through a temperature control system; high-pressure dense-phase CO2 is introduced into the reactor through a gas control system until the set pressure is reached;

[0030] After the experiment begins, the time relay is controlled to make the electric push rod drive the sample holder and the corrosion exposure test sample to make a periodic reciprocating motion of immersion and removal from the water surface, simulating the changes of the gas-liquid interface on the pipe surface.

[0031] An electrochemical workstation and an electrochemical probe were used to test the electrochemical kinetics of the corrosion-exposed test samples and obtain the electrochemical test results.

[0032] After immersion, the corrosion exposure test sample was removed and corrosion characteristics were obtained. The interfacial electrochemical reaction process and mechanism of the metal surface during corrosion exposure were analyzed by combining the corrosion characteristics and electrochemical test results.

[0033] In the specific implementation process, the electrochemical test results include open circuit potential and electrochemical impedance; the corrosion characteristics include surface formation state, corrosion rate, corrosion morphology and corrosion film properties.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] This invention provides a testing device for simulating the dynamic interface corrosion of metals at a supercritical CO2 / aqueous solution. Through a supercritical CO2 / aqueous solution interface simulation control system, it simulates the water-gas interface and the fully immersed region, thereby simulating the environment of pipes in an alternating water-gas interface, filling a gap in the simulation environment of alternating interfaces in ordinary reactors. A high-temperature, high-pressure electrochemical testing system acquires the corrosion kinetics information of samples at the water-gas interface and in the fully immersed region. Combined with immersion experiments, it achieves integrated measurement of corrosion rate, corrosion morphology, and electrochemical kinetics.

[0036] Another aspect of this invention provides a method for simulating the dynamic interface corrosion test of supercritical CO2 and aqueous solution. This method can analyze the differences in corrosion behavior between the water-air interface region and the fully immersed region, explore the influence mechanism of different corrosion potentials in different regions on the macroscopic corrosion cell, clarify the influence mechanism of the water-air alternating interface on pipe corrosion, and simultaneously conduct parallel experiments of immersion tests. Combined with surface analysis methods, this method explores the formation mechanism of corrosion products in corrosion tests, laying a theoretical foundation for a deeper understanding of the local corrosion damage mechanism of the supercritical CO2 / formation water interface. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion testing device of the present invention.

[0038] Figure 2 This is a schematic diagram of the sample holder structure of the present invention;

[0039] Figure 3 This is a schematic diagram of the electrochemical probe structure of the present invention;

[0040] Figure 4 This is a schematic diagram showing the corrosion exposure test specimen of the present invention in the gas phase region, the liquid / gas interface region, and the liquid phase region;

[0041] Figure 5 This is a morphology image of the surface corrosion of N80 pipe material used as a corrosion exposure test sample in an embodiment of the present invention after immersion for ten days.

[0042] Figure 6 The impedance spectra of different regions were obtained by using N80 pipe as a corrosion exposure test sample in an embodiment of the present invention after immersion for ten days.

[0043] Wherein: 1-Boost pump; 2-Pressure gauge; 3-Heating resistance wire; 4-Thermocouple; 5-Electric push rod; 6-Time relay; 7-Electrochemical workstation; 8-Electrochemical probe; 9-Controller; 10-Lower disk; 11-Sample tank; 12-Upper disk; 13-Auxiliary electrode; 14-Reference electrode; 15-Support column; 16-Epoxy resin; 17-Adjustable sleeve; 18-Threaded outer shell; 19-Shielded cable; 20-Sample rack; 21-Reaction vessel. Detailed Implementation

[0044] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0045] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0046] The present invention will now be described in further detail with reference to the accompanying drawings:

[0047] See Figure 1 This invention provides a test device and method for simulating the dynamic interface metal corrosion of supercritical CO2 and aqueous solution. The test device mainly consists of a reaction vessel 21, a supercritical CO2 / aqueous solution interface simulation control system, an electrochemical test system, a temperature control system, and a gas control system.

[0048] The reactor 21 provides the reaction site for metallic materials and gas-liquid interaction. The temperature control system and gas control system provide the required temperature and gas environment. Corrosion exposure test samples with and without electrochemical probes 8 are mounted on the sample holder 20 of the supercritical CO2 / water interface simulation control system and undergo periodic reciprocating motion inside the reactor 21. The electrochemical workstation 7, provided by the high-temperature, high-pressure electrochemical testing system, is connected to the electrochemical probes 8 to measure the electrochemical information of the reaction. This invention enables in-situ electrochemical information measurement of metallic material corrosion in the supercritical CO2 / water interface region and the fully immersed water region, for analyzing corrosion mechanisms in different areas. The simultaneous in-situ electrochemical testing and corrosion immersion experiments lay a theoretical foundation for a deeper understanding of the localized corrosion damage mechanism at the supercritical CO2 / formation water interface.

[0049] This invention provides a metal corrosion testing device that simulates the dynamic interface between supercritical CO2 and aqueous solution. Through a supercritical CO2 / aqueous solution interface simulation control system, the water-gas interface and the fully immersed region are simulated. Through an electrochemical testing system, the corrosion kinetics information of the sample at the water-gas interface and the fully immersed region is obtained.

[0050] Specifically, the simulated supercritical CO2 / aqueous solution dynamic interface metal corrosion testing device includes: a reaction vessel 21, a temperature control system, a gas control system, a supercritical CO2 / aqueous solution interface simulation control system, and an electrochemical testing system. The supercritical CO2 / aqueous solution interface simulation control system includes an electric actuator 5, a time relay 6, and a sample holder 20. One end of the electric actuator 5 passes through the lid of the reaction vessel 21 and is connected to the time relay 6, while the other end is connected to the sample holder 20 inside the reaction vessel 21. The time relay 6 controls the periodic reciprocating motion of the electric actuator 5. The sample holder 20 is used to fix the corrosion exposure test sample. The electrochemical testing system includes an electrochemical workstation 7 and an electrochemical probe 8. The electrochemical workstation 7 is connected to the electrochemical probe 8, which is placed on the corrosion exposure test sample. The temperature control system is located inside the reaction vessel 21, and the gas control system is connected to the reaction vessel 21.

[0051] The number of corrosion exposure test samples is greater than or equal to 2 groups, and an electrochemical probe 8 is installed on one group of corrosion exposure test samples.

[0052] In the specific implementation process, the temperature control system is placed inside the reaction vessel 21, and the specific connection method between the gas control system and the reaction vessel 21 is as follows:

[0053] The reactor 21 includes a nickel-based alloy or stainless steel body, and the lid is connected to the body by bolts and nuts. The body is equipped with a built-in heating resistance wire 3 for heating the reactor 21. The body contains a thermocouple 4 for monitoring the internal temperature. The heating resistance wire 3 and the thermocouple 4 are connected to the controller 9, and the internal temperature of the reactor 21 is controlled through a feedback system. The lid is equipped with a reactor inlet for introducing gas into the reactor 21. The lid is also equipped with a reactor outlet for discharging gas from the reactor. The lid is also equipped with a pressure gauge 2, which is connected to the controller 9. The control module monitors the internal pressure of the reactor in real time.

[0054] In the specific implementation process, the supercritical CO2 / water interface simulation control system consists of an electric push rod 5, a time relay 6, and a sample holder 20. One end of the electric push rod 5 is fixed to the lid of the reactor 21, and the other end is connected to the sample holder 20. The sample holder 20 is a cylindrical sample holder made of polytetrafluoroethylene, which can hold multiple corrosion exposure test samples. The time relay 6 is located outside the reactor body of the reactor 21 and is used to control the periodic movement of the electric push rod 5.

[0055] In practice, the electrochemical testing system mainly consists of an electrochemical probe 8 and an electrochemical workstation 7. The electrochemical probe 8 can be an encapsulated Ag / AgCl reference electrode and a Pt auxiliary electrode (two samples placed parallel and aligned, encapsulated in epoxy resin 16), forming a three-electrode system with the corrosion exposure test sample. The electrochemical probe 8 is mounted on one of the corrosion exposure test sample pieces and moves periodically back and forth along with it. The electrochemical workstation 7 is located outside the reactor and is used to test the kinetic information of the three-electrode system.

[0056] In the specific testing process, several corrosion exposure test samples were fixed on the sample holder 20, and several electrochemical probes 8 were respectively located in the supercritical CO2 / water solution interface region and the fully immersed water solution region on the corrosion exposure test samples. Schematic diagrams of the specific locations in the gas phase region, liquid / gas interface region, and liquid phase region are shown below. Figure 4 As shown.

[0057] Furthermore, such as Figure 2 As shown, the sample holder 20 includes a lower disc 10, a sample slot 11, an upper disc 12, and a support. The lower disc 10 and the upper disc 12 are respectively disposed at both ends of the support, and the sample slots 11 are correspondingly opened on the lower disc 10 and the upper disc 12. Among them, a through hole is opened at the center of the upper disc 12 of the sample holder 20, which is used to fix the electric push rod 5 and the sample holder 20; a number of sample slots 11 are symmetrically opened around the through hole.

[0058] Furthermore, such as Figure 3As shown, the electrochemical probe 8 includes an auxiliary electrode 13, a reference electrode 14, a support 15, an epoxy resin 16, an adjustable sleeve 17, a threaded outer shell 18, and a shielded cable 19.

[0059] The auxiliary electrode 13, the reference electrode 14, and the corrosion exposure test sample constitute a three-electrode system. The auxiliary electrode 13 and the reference electrode 14 are placed parallel and aligned between two pillars 15, and the auxiliary electrode 13 and the reference electrode 14 are encapsulated with epoxy resin 16. An adjustable sleeve 17 is set below the auxiliary electrode 13 and the reference electrode 14, and the adjustable sleeve 17 is used to fix the auxiliary electrode 13 and the reference electrode 14.

[0060] Furthermore, the threaded housing 18 is located below the adjustable sleeve 17, and the shielded cable 19 is located below the threaded housing 18.

[0061] In the specific testing process, the reference electrode 14 can be an Ag / AgCl reference electrode; the auxiliary electrode 13 can be a Pt auxiliary electrode.

[0062] Furthermore, the temperature control system includes a heating resistance wire 3, a thermocouple 4, and a temperature control module in the controller 9; the heating resistance wire 3 is installed on the inner wall of the reactor 21, the thermocouple 4 is inserted into the reactor 21, and the heating resistance wire 3 and the thermocouple 4 are electrically connected to the temperature control module in the controller 9.

[0063] Furthermore, the gas control system includes a booster pump 1, a pressure gauge 2, a CO2 cylinder, and a pressure control module in the controller 9; the outlet of the CO2 cylinder is connected to the inlet on the lid of the reactor 21 through an inlet pipe, the booster pump 1 is installed on the inlet pipe, and the outlet of the inlet pipe extends below the liquid surface inside the reactor 21; the pressure gauge 2 is installed on the lid of the reactor 21, and the pressure gauge 2 is electrically connected to the pressure control module in the controller 9.

[0064] Another aspect of the present invention provides a method for simulating the dynamic interface corrosion test of supercritical CO2 and aqueous solution, comprising the following steps:

[0065] The corrosion exposure test specimen is assembled into the specimen holder 20. One of the corrosion exposure test specimens is equipped with an electrochemical probe 8. The specimen holder 20 is fixed on the electric push rod 5 and placed in the reaction vessel 21 containing simulated formation aqueous solution. The height of the specimen holder 20 is adjusted so that several electrochemical probes 8 are located in the supercritical CO2 / aqueous solution interface region and the aqueous solution full immersion region on the corrosion exposure test specimen, respectively. The electrochemical probes 8 are connected to the electrochemical workstation 7.

[0066] Inert gas is introduced to remove oxygen from the reactor 21 and the simulated formation aqueous solution in the reactor 21; the reactor 21 is heated to the set temperature through the temperature control system; high-pressure dense-phase CO2 is introduced into the reactor 21 through the gas control system until the set pressure is reached;

[0067] After the experiment begins, the control time relay 6 causes the electric push rod 5 to drive the sample holder 20 and the corrosion exposure test sample to perform a periodic reciprocating motion of immersion and removal from the water surface, simulating the changes in the gas-liquid interface on the pipe surface.

[0068] Electrochemical workstation 7 and electrochemical probe 8 were used to test the electrochemical kinetics of the corrosion-exposed test samples and obtain electrochemical test results; the electrochemical test results include open circuit potential and electrochemical impedance.

[0069] After immersion, the corrosion exposure test sample was removed and corrosion characteristics were obtained. The corrosion characteristics included surface formation state, corrosion rate, corrosion morphology and corrosion film properties. By combining the corrosion characteristics and electrochemical test results, the interfacial electrochemical reaction process and mechanism of the metal surface during corrosion exposure were analyzed.

[0070] In the specific implementation process, inert gas is introduced to remove oxygen from the reactor 21 and the simulated formation aqueous solution in the reactor 21; the reactor 21 is heated to the set temperature through a temperature control system; and high-pressure dense-phase CO2 is introduced into the reactor 21 through a gas control system until the set pressure is reached, as follows:

[0071] The reactor 21 is sealed, nitrogen is introduced to remove residual air inside the reactor 21, the exhaust port and the inlet port of the reactor 21 are closed, and the reactor 21 is heated to the set temperature through the temperature control system; the gas control system introduces high-pressure dense phase CO2 into the reactor 21 through the inlet port of the reactor 21 until the set pressure is reached.

[0072] In the specific implementation process, the chemical workstation 7 performs open circuit potential measurement to monitor the potential difference between the working electrode, i.e., the corrosion exposure test sample and the reference electrode 14, in real time.

[0073] The more specific test method for simulating the dynamic interface corrosion of metals at supercritical CO2 and aqueous solution is as follows:

[0074] Step 1: After the polished corrosion exposure test sample and the corrosion exposure test sample with electrochemical probe 8 are installed together in the sample holder 20, they are placed in the high temperature and high pressure reaction vessel 21 containing a certain amount of simulated formation aqueous solution, and inert gas is introduced to remove oxygen from the reaction vessel 21 and the simulated formation aqueous solution.

[0075] Step 2: CO2 is introduced through the inlet of reactor 21, and the required experimental conditions are reached through the temperature control system and pressure control system.

[0076] Step 3: After the experiment begins, by controlling the electric push rod 5 and the time relay 6, the polished corrosion exposure test sample and the corrosion exposure test sample with electrochemical probe 8 on the sample holder 20 are kept in a periodic reciprocating motion in the "immersion-removal" water surface to simulate the changes in the gas-liquid interface on the pipe surface.

[0077] Step 4: Using an electrochemical workstation 7 and two electrochemical probes 8 (placed in the supercritical CO2 / formation water interface zone and the formation water fully immersed zone), the electrochemical kinetics information of the sample is tested to obtain the electrochemical test results;

[0078] Step 5: After the immersion time is over, the corrosion exposure test sample is taken out to determine the corrosion rate, observe the corrosion morphology, and analyze the characteristics of the corrosion film; combined with the electrochemical impedance spectroscopy at different times, the interfacial electrochemical reaction process and mechanism of the metal surface during corrosion are analyzed.

[0079] Furthermore, in step 1, the material of the corrosion exposure test sample is J55, P110, N80, 3Cr, 5Cr, 13Cr, 18Cr alloy steel or 2205 stainless steel, etc., and the size is 12.5cm long, 5cm wide and 0.3cm high. The water tank in the reaction vessel 21 contains a simulated formation aqueous solution with a volume of 10L.

[0080] Furthermore, in step 2, during the introduction of CO2, CO2 is replenished gradually to avoid a rapid decrease in pressure due to the dissolution of CO2.

[0081] Furthermore, in step 3, the motion is periodic and reciprocating, with a step length of 5cm and a time of 30s for each up-and-down movement.

[0082] Furthermore, such as Figure 4 The gas-liquid interface distribution in the reactor 21 shown is as follows: In step 3, the periodic reciprocating motion keeps the metal sample in the gas phase region, water-gas interface region, and fully immersed region at heights of 5, 5, and 2.5 cm, respectively.

[0083] Furthermore, in step 4, the electrochemical information includes corrosion potential and information contained in the electrochemical impedance spectroscopy.

[0084] The above testing methods can analyze the differences in corrosion behavior between the water-air interface zone and the fully immersed zone, explore the influence mechanism of different corrosion potentials in different regions on macroscopic corrosion cells, and lay a theoretical foundation for a deeper understanding of the local corrosion damage mechanism of the supercritical CO2 / formation water interface.

[0085] Example

[0086] This embodiment provides a test device for simulating the dynamic interface metal corrosion of supercritical CO2 and aqueous solution, such as... Figure 1 As shown.

[0087] The simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion test device includes a reaction vessel 21, which includes a vessel body and a vessel cover connected to the vessel body by bolts and nuts.

[0088] The simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion test device includes a temperature control system, which is placed inside the reaction vessel 21. The temperature control system includes a heating resistance wire 3, a thermocouple 4, and a temperature control module in the controller 9. The heating resistance wire 3 is built into the vessel body and is used to heat the reaction vessel 21. The temperature inside the reaction vessel 21 is controlled by the temperature control module in the controller 9. The thermocouple 4 is inserted into the vessel body and is used to obtain the temperature inside the reaction vessel 21. The thermocouple 4 works in conjunction with the built-in heating resistance wire 3 to adjust the temperature inside the reaction vessel.

[0089] The simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion testing device includes a gas control system connected to the reactor 21. The gas control system includes a booster pump 1, a pressure gauge 2, a CO2 cylinder, and a pressure control module in the controller 9. More specifically, the reactor lid has a reactor inlet for introducing gas into the reactor 21; the reactor lid also has a reactor exhaust port for discharging gas from the reactor. The outlet of the CO2 cylinder is connected to the inlet on the reactor lid via an inlet pipe. The booster pump 1 is located on the inlet pipe, and the outlet of the inlet pipe extends below the liquid level inside the reactor 21. The pressure gauge 2 is located on the reactor lid and is used to monitor the pressure inside the reactor 21. The pressure gauge 2 is electrically connected to the pressure control module in the controller 9.

[0090] The simulated supercritical CO2 / aqueous solution dynamic interface metal corrosion testing device includes a supercritical CO2 / aqueous solution interface simulation control system and a water-gas interface simulation control system. The supercritical CO2 / aqueous solution interface simulation control system includes an electric actuator 5, a time relay 6, and a sample holder 20. One end of the electric actuator 5 is fixed to the lid of the reactor 21, and the other end is connected to the sample holder 20. The time relay 6 is located outside the reactor 21 and is used to control the periodic reciprocating motion of the electric actuator 5. The sample holder 20 is cylindrical and horizontally fixed in the reactor 21. The sample holder 20 is used to fix the electrodes and corrosion exposure test samples in the electrochemical testing system.

[0091] The sample holder 20 is a cylindrical sample holder made of polytetrafluoroethylene. The sample holder 20 has a central through hole for connecting and fixing to the electric push rod 5. Four sample slots 11 are symmetrically distributed around the through hole for mounting corrosion exposure test samples. The corrosion exposure test samples are 5, 5 and 2.5 cm in size. The central through hole can lead out wires.

[0092] The simulated supercritical CO2-aqueous dynamic interface metal corrosion testing device includes an electrochemical testing system, which comprises an electrochemical workstation 7 and an electrochemical probe 8. The electrochemical probe 8 is an encapsulated Ag / AgCl reference electrode and a Pt auxiliary electrode (the Ag / AgCl reference electrode and Pt auxiliary electrode are placed parallel and aligned, encapsulated in epoxy resin 16), forming a three-electrode system with the corrosion exposure test sample. The electrochemical probe 8 is mounted on the corrosion exposure test sample and moves with it. The electrochemical workstation 7 is located outside the reactor and is used to test the kinetic information of the three-electrode system.

[0093] This embodiment also provides a testing method based on the above-mentioned simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion testing device, including the following steps:

[0094] S1: Assemble the corrosion exposure test sample with the test electrode in the electrochemical probe 8 and the corrosion exposure test sample without the electrochemical probe 8 into the sample holder 20, then insert and fix the sample holder 20 onto the electric push rod 5, adjust the height of the sample holder 20 so that several electrochemical probes 8 are respectively located in the supercritical CO2 / water interface region and the water solution immersion region on the corrosion exposure test sample, and pass the two copper wires of the test electrode in the electrochemical probe 8 out through the wire hole on the lid and connect them to the electrochemical workstation 7.

[0095] S2: Cover the vessel with the lid, seal the reactor 21, open the exhaust port of the reactor 21, and continuously introduce high-purity N2 through the air inlet of the reactor 21 for two hours to remove residual air in the reactor 21; close the air inlet and exhaust port of the reactor 21, and control the vessel body to heat up to the set temperature through the temperature control module in the controller 9.

[0096] S3: High-pressure dense-phase CO2 is introduced through the air inlet of reactor 21, and the pressure inside the reactor is monitored in real time by the pressure control module in pressure gauge 2 and controller 9 until the set pressure is reached;

[0097] S4: Open-circuit potential measurement is performed using electrochemical workstation 7 to monitor the potential difference between the working electrode (corrosion exposure test sample) and the reference electrode 14 in real time. Since no continuous water film forms on the surfaces of the two electrodes, they are not conductive, resulting in a large and drastic fluctuation in the monitored potential difference. Related electrochemical tests, such as electrochemical impedance spectroscopy, are then performed using electrochemical workstation 7.

[0098] S5: After exposure experiments at different times, the corrosion exposure test samples are taken out, the surface formation state is observed, the corrosion rate is measured, the corrosion morphology is observed, and the corrosion film characteristics are analyzed. Combined with the electrochemical impedance spectroscopy at different times, the interfacial electrochemical reaction process and mechanism of the metal surface during corrosion exposure can be analyzed.

[0099] Figure 5 The image shown depicts the surface corrosion morphology of a sample after immersion for ten days in a corrosion exposure test. From... Figure 5 As can be seen, the surface of the corrosion exposure test specimens was covered by a dense corrosion product film, and localized corrosion was also observed to be severe. This indicates that under supercritical CO2 conditions, N80 carbon steel has relatively low corrosion resistance and severe localized corrosion, and the dense corrosion product film on the surface cannot provide adequate protection.

[0100] Figure 6 The images shown are electrochemical impedance spectroscopy spectra of different regions of the corrosion exposure test sample after immersion for ten days. Figure 6 As can be seen, the impedance spectra in different regions are all composed of a capacitive arc. The radius of the capacitive arc of the sample at the gas / liquid interface is smaller than that in the liquid phase region, indicating that the N80 pipe at the gas / liquid interface is less corrosion resistant. This may be related to the continuous dissolution of carbon dioxide in the aqueous solution, providing a continuous source of cathodic depolarizer.

[0101] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A test device for simulating the dynamic interface corrosion of metals at supercritical CO2 and aqueous solution, characterized in that, It includes a reaction vessel (21), a temperature control system, a gas control system, a supercritical CO2 / water interface simulation control system, and an electrochemical testing system; The supercritical CO2 / water interface simulation control system includes an electric push rod (5), a time relay (6), and a sample holder (20); One end of the electric push rod (5) passes through the lid of the reactor (21) and is connected to the time relay (6), and the other end is connected to the sample holder (20) in the reactor (21); the time relay (6) is used to control the periodic reciprocating motion of the electric push rod (5); The electrochemical testing system includes an electrochemical workstation (7) and an electrochemical probe (8); The electrochemical workstation (7) is connected to the electrochemical probe (8), which is placed on the corrosion exposure test sample; The temperature control system is placed inside the reactor (21), and the gas control system is connected to the reactor (21).

2. The simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion testing device according to claim 1, characterized in that, The sample holder (20) includes a lower disc (10), a sample slot (11), an upper disc (12), and a support; The support has a lower disk (10) and an upper disk (12) at its two ends, and the sample groove (11) is opened on the lower disk (10) and the upper disk (12) respectively.

3. The simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion testing device according to claim 1, characterized in that, Several corrosion exposure test specimens are fixed on a specimen holder (20), and several electrochemical probes (8) are located in the supercritical CO2 / water solution interface region and the water solution immersion region on the corrosion exposure test specimens, respectively.

4. The simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion testing device according to claim 1, characterized in that, The electrochemical probe (8) includes an auxiliary electrode (13) and a reference electrode (14); The auxiliary electrode (13), the reference electrode (14), and the corrosion exposure test sample constitute a three-electrode system.

5. The simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion testing device according to claim 4, characterized in that, The electrochemical probe (8) also includes a support (15), epoxy resin (16), and an adjustable sleeve (17); The auxiliary electrode (13) and the reference electrode (14) are placed parallel and aligned between the two pillars (15), and the auxiliary electrode (13) and the reference electrode (14) are encapsulated with epoxy resin (16); the adjustable sleeve (17) is located below the auxiliary electrode (13) and the reference electrode (14), and the adjustable sleeve (17) is used to fix the auxiliary electrode (13) and the reference electrode (14).

6. The simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion testing device according to claim 4, characterized in that, The reference electrode (14) is an Ag / AgCl reference electrode; the auxiliary electrode (13) is a Pt auxiliary electrode.

7. The simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion testing device according to claim 1, characterized in that, The temperature control system includes a heating resistance wire (3), a thermocouple (4), and a temperature control module in the controller (9); The heating resistance wire (3) is set on the inner wall of the reactor (21), the thermocouple (4) is inserted into the reactor (21), and the heating resistance wire (3) and the thermocouple (4) are electrically connected to the temperature control module in the controller (9).

8. The simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion testing device according to claim 1, characterized in that, The gas control system includes a booster pump (1), a pressure gauge (2), a CO2 cylinder, and a pressure control module in the controller (9); The outlet of the CO2 cylinder is connected to the inlet on the lid of the reactor (21) through an inlet pipe. The booster pump (1) is installed on the inlet pipe, and the outlet of the inlet pipe extends below the liquid surface inside the reactor (21). The pressure gauge (2) is installed on the lid of the reactor (21), and the pressure gauge (2) is electrically connected to the pressure control module in the controller (9).

9. A method for testing metal corrosion at a simulated dynamic interface between supercritical CO2 and aqueous solution, characterized in that, The simulated supercritical CO2 and aqueous solution dynamic interface metal corrosion testing device according to any one of claims 1 to 8 includes the following steps: The corrosion exposure test specimens are assembled into the specimen holder (20), one of which is equipped with an electrochemical probe (8). The specimen holder (20) is placed in the reaction vessel (21) containing simulated formation aqueous solution. The height of the specimen holder (20) is adjusted so that several electrochemical probes (8) are located in the supercritical CO2 / aqueous solution interface region and the aqueous solution immersion region on the corrosion exposure test specimen, respectively. Inert gas is introduced to remove oxygen from the reactor (21) and the simulated formation aqueous solution in the reactor (21); the reactor (21) is heated to the set temperature through the temperature control system; high-pressure dense phase CO2 is introduced into the reactor (21) through the gas control system until the set pressure is reached; After the experiment begins, the control time relay (6) causes the electric push rod (5) to drive the sample holder (20) and the corrosion exposure test sample to perform a periodic reciprocating motion of immersion and removal from the water surface, simulating the changes in the gas-liquid interface on the pipe surface. Electrochemical workstation (7) and electrochemical probe (8) were used to test the electrochemical kinetics of the corrosion-exposed test sample and obtain the electrochemical test results. After immersion, the corrosion exposure test sample was removed and corrosion characteristics were obtained. The interfacial electrochemical reaction process and mechanism of the metal surface during corrosion exposure were analyzed by combining the corrosion characteristics and electrochemical test results.

10. The method for testing metal corrosion at the simulated supercritical CO2 and aqueous solution dynamic interface according to claim 9, characterized in that, The electrochemical test results include open circuit potential and electrochemical impedance; the corrosion characteristics include surface formation state, corrosion rate, corrosion morphology and corrosion film properties.

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