A device and method for quickly and accurately evaluating corrosion inhibitor efficiency and corrosion rate analysis

Abstract

The present invention relates to a device and method for quickly and accurately evaluating the efficiency of corrosion inhibitors and analyzing corrosion rates, which are used in the field of petrochemicals to quickly and accurately evaluate corrosion inhibitors and conduct corrosion mechanism analysis, filling the gap in the field of rapid corrosion analysis under high temperature and high pressure corrosion environment conditions. The device includes a corrosion reactor system, an electrochemical analysis system, an injection system, and a control system. The method of the present invention provides a rapid means for evaluating corrosion inhibitors from multiple aspects such as corrosion potential, corrosion current, and corrosion rate by constructing a three-electrode corrosion system and using an electrochemical method. The device involved in the present invention can simulate a real corrosion environment, and can complete the analysis and evaluation of the corrosion conditions of various steel materials of different grades at one time in a complex corrosive medium environment in a temperature range of 0°C to 220°C and a pressure range of normal pressure to 10.0MPa, and quickly analyze the corrosion rate, effectively replacing the traditional mass loss method.

Description

Technical Field

[0001] The invention belongs to the technical field of simulated corrosion test devices, and in particular relates to a device and method for quickly and accurately evaluating the efficiency of corrosion inhibitors and analyzing corrosion rates. Background Art

[0002] As the trend of crude oil deterioration intensifies, there are many complex corrosive components such as H2S, CO2, and organic acids in the process of crude oil extraction, storage, transportation, and processing. The coexistence with water can form a complex corrosive environment, involving a wide range of corrosion temperatures, causing serious corrosion to pipelines and equipment. As a corrosion inhibitor, the presence of corrosion inhibitors in the corrosion system at a concentration of ppm does not significantly change the properties of the corrosive medium on the one hand, but can significantly reduce the corrosion rate on the other hand. Therefore, adding corrosion inhibitors is an important and relatively economical anti-corrosion measure.

[0003] The evaluation of corrosion inhibitors adopts the test method of metal corrosion rate, that is, to determine the corrosion rate of metal in the corrosive medium with a certain corrosion inhibitor added, and compare it with the corrosion rate of the metal in the corrosive medium without corrosion inhibitor, so as to determine the corrosion inhibition efficiency and the best conditions of use. At present, the commonly used corrosion inhibitor evaluation methods are mainly: static method and dynamic method. The static method is to place the sample coupons in the corrosive environment and compare the corrosion rates of blank samples and samples with corrosion inhibitors; the dynamic method is to place the sample coupons in the corrosive environment with a certain amount of stirring, and the equipment used mainly includes high-temperature and high-pressure dynamic kettles and high-temperature and high-pressure rotating cages. Since corrosion occurs through electrochemical reactions, electrochemical technology is an ideal method for studying the corrosion process. In electrochemical research, the metal sample is immersed in a solution similar to the real metal corrosion environment, and the additional electrode is also immersed in the solution, and all electrodes are connected to a constant potential instrument. Using electrochemical kinetic theory and testing methods, the polarization characteristics of the metal surface in the corrosive medium before and after the addition of corrosion inhibitors are studied to evaluate the corrosion characteristics of metals under different conditions, which can effectively replace the traditional mass loss analysis method and overcome the problem of long test cycles.

[0004] Currently, the commonly used methods for evaluating the performance of corrosion inhibitors include "SY / T 5273-2014 Performance Evaluation Method of Corrosion Inhibitors for Oilfield Produced Water". Although this method is time-saving, it can only qualitatively evaluate the film-forming effect of the corrosion inhibitor, and cannot evaluate key corrosion inhibition effect indicators such as the durability of the corrosion inhibitor film. It also has great limitations and poor repeatability.

[0005] Patent CN 201621429404.3 is a device for testing the corrosion rate of the gas phase in a high-temperature and high-pressure gas-liquid two-phase environment. The corrosion test piece is cooled by circulating cooling water so that the surface temperature of the corrosion test piece is lower than the temperature inside the autoclave. It can well simulate the corrosion of the top of the pipeline by the flowing corrosive medium, but this method is limited to analyzing the corrosion rate under low temperature conditions. Patent CN 106680196 A relates to a system for evaluating the corrosion inhibition efficiency of corrosion inhibitors. It uses a temperature-resistant and pressure-resistant solution to simulate a high-temperature and high-pressure corrosion environment, and simulates the airflow scouring of a high-speed corrosive medium. It is used to study the corrosion inhibition mechanism of corrosion inhibitors under dynamic corrosion conditions. However, the resistance probe is used in the high-temperature and high-pressure corrosion analysis in this method, and the corrosion mechanism cannot be examined in detail; when it is a hanging sample, a three-electrode system is used, but the system cannot withstand high temperature and high pressure. In summary, there is no effective means and method in the field of simulated corrosion test technology that takes into account high temperature, high pressure, fastness and accuracy. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a device and method for quickly and accurately evaluating the efficiency of corrosion inhibitors and analyzing corrosion rates. The device and method can simulate a real corrosive medium environment, and by constructing a three-electrode corrosion system and adopting electrochemical methods, a rapid means is provided for evaluating corrosion inhibitors from multiple aspects such as corrosion potential, corrosion current and corrosion rate.

[0007] At present, the existing technology for corrosion rate analysis and corrosion inhibition efficiency analysis of corrosion inhibitors adopts the mass loss method (the cycle is generally 7 days), and the devices involved include weighing (metering) facilities, constant temperature facilities, pipettes, etc. Specifically, 1. polishing, cleaning, drying, and weighing the test piece; 2. corrosion treatment in a constant temperature facility; 3. weighing and other treatments on the corroded test piece, and calculating the corrosion rate and corrosion inhibition efficiency.

[0008] The device and method for quickly and accurately evaluating the efficiency of corrosion inhibitors and analyzing corrosion rates involved in the present invention include metering facilities (precision electronic balance, desktop acidity meter, pressure gauge, etc.), constant temperature facilities (corrosion reactor system), and electrochemical analysis system. The specific method is 1. Connecting a three-electrode system in a corrosion reactor; 2. Setting corrosion conditions, including temperature, pressure, rotation speed, and pH; 3. Starting the electrochemical test.

[0009] The specific technical solutions are as follows:

[0010] A device for quickly and accurately evaluating the efficiency of corrosion inhibitors and analyzing corrosion rates, the device comprising a kettle cover, a kettle body, a heating facility, a thermocouple, a pressure gauge, a metal hollow shaft with a sleeve, a drain valve, a rotor, a pH probe, a magnetic stirrer, a disc electrode holder, a reference electrode, a counter electrode, an electrode fixing frame, an electrochemical workstation, a corrosive medium pump, a nitrogen source, an H2S gas source, a CO2 gas source, a filter, and an injection tube. The kettle cover is connected to the kettle body through a flange, the heating facility is in close contact with the outer wall of the kettle body and surrounds the outer wall of the kettle body, the thermocouple is located between the heating facility and the kettle body, the pressure gauge, the metal hollow shaft with a sleeve, and the pH probe are threadedly connected to the kettle cover, the sleeve is used for insulation of the metal hollow shaft, the drain valve is threadedly connected to the lower part of the kettle body, the rotor is located in the center of the bottom of the kettle body, and the magnetic stirrer is located below the kettle body.

[0011] The disc electrode holder is threadedly connected to a metal hollow shaft with a sleeve, and grooves are evenly arranged on the bottom and the disc electrode holder. The reference electrode and the counter electrode are threadedly connected to the kettle cover, and the electrode fixing frame is welded to the kettle cover. The working electrode end, the counter electrode end and the reference electrode end of the electrochemical workstation are respectively connected to a terminal of the electrode fixing frame, the counter electrode and the reference electrode by wires; the injection pipe is threadedly connected to the kettle cover, the corrosive medium pump, the nitrogen source, the H2S gas source and the CO2 gas source are respectively connected to the inlet of the injection pipe through pipelines, and the filter is threadedly connected to the outlet of the injection pipe.

[0012] The present invention provides a method for quickly and accurately evaluating the efficiency of corrosion inhibitors and analyzing corrosion rates, comprising the following steps:

[0013] 1) Connect the three-electrode system, prepare the working electrode with corroded steel as the raw material, and place it in the groove of the disc electrode holder, then connect the working electrode, counter electrode and reference electrode to the electrochemical workstation, tighten the kettle cover, and replace the gas in the kettle with nitrogen;

[0014] 2) Simulate the corrosion environment. According to the corrosion environment to be tested, the corrosive medium is pumped into the corrosion reactor through the corrosive medium pump, H2S or CO2 or other gases and gas mixtures are flushed into the corrosion reactor, and the heating temperature, pressure and stirring rate are set and started;

[0015] 3) Electrochemical test: When the temperature, pressure, speed and pH of the corrosion reactor meet the requirements of the corrosion environment, start the electrochemical workstation to perform electrochemical testing to test the corrosion current density.

[0016] The method for quickly and accurately evaluating the efficiency of corrosion inhibitors and analyzing corrosion rates is described. The corrosive medium is a medium contacted by the corroded parts of an oil refining and chemical plant, which is an acidic aqueous solution, an oil-water mixture, a desulfurizer aqueous solution, sulfur-containing wastewater, or a corrosive medium specified in industry standards or national standards; the corrosion inhibitor is a corrosion inhibitor used to evaluate and examine its corrosion inhibition performance, with a concentration of 1 μg / g-1000 μg / g, and the corrosion inhibitor is diluted to the use requirements with a specific solvent according to the solubility characteristics of the corrosion inhibitor; the pH of the corrosive medium is adjusted to the use requirements with an organic amine.

[0017] The temperature range of the simulated corrosion environment is 0°C to 220°C, and the pressure range is normal pressure to 10.0MPa. The electrochemical test includes a blank test and a corrosion inhibition test. The blank test is to test the corrosion current density in the simulated corrosion environment without adding any corrosion inhibitor; the corrosion inhibition test is to add a corrosion inhibitor of a mass concentration required for the use of the corrosion inhibitor to the simulated corrosion environment to test the corrosion current density.

[0018] The electrochemical test method is to first determine the corrosion potential E C , the corrosion potential E C Keep the fluctuation less than 1mV within 3min-10min, then conduct a potentiodynamic polarization curve test to determine the corrosion current density I of the system. c The dynamic potential scanning range is [EC-200mv, EC+200mv], the scanning rate is 10mV / min-20mV / min, and finally according to the corrosion current density I c Calculate the corrosion rate C R and corrosion inhibition efficiency η.

[0019] The specific instructions are as follows:

[0020] The present invention is similar to the prior art in that the test piece needs to be polished, cleaned, dried and weighed. The difference is that the principles of corrosion analysis are different. The prior art uses a mass loss method, while the present invention uses an electrochemical method.

[0021] The present invention discloses a device and method for quickly and accurately evaluating the efficiency of corrosion inhibitors and analyzing corrosion rates, characterized in that the device can be divided into a corrosion reactor system, an electrochemical analysis system, an injection system, and a control system. The reactor system is used to simulate a high-temperature and high-pressure corrosion environment, and includes a reactor cover (1), a reactor body (2), a heating facility (3), a thermocouple (4), a pressure gauge (5), a metal hollow shaft with a sleeve (6), a drain valve (7), a rotor (8), a pH probe (9), and a magnetic stirrer (10). The reactor cover (1) and the reactor body (2) are flange-connected. The heating facility (3) is a heating sleeve that is tightly attached to the outer wall of the reactor body 1 and surrounds the outer wall of the reactor body 1. The thermocouple (4) is placed between the heating facility (3) and the reactor body 1 to measure the temperature. The pressure gauge (5) is located on the reactor cover (1) and has a measuring range of ≤16MPa, a metal hollow shaft (6) with a sleeve is placed in the center of the kettle cover (1), and a drain valve (7) is threadedly connected to the lower part of the kettle body (2); a rotor (8) is located in the center of the bottom of the kettle body (2), a pH probe (9) is threadedly connected to the kettle cover (1), and a magnetic stirrer (10) is located below the insulation layer of the kettle body (2) and can drive the upper 8 to rotate; the electrochemical analysis system includes a disk electrode holder (11), a reference electrode (12), a counter electrode (13), an electrode fixing frame (14), and an electrochemical workstation (15), wherein the disk electrode holder (11) is provided with a plurality of grooves The disc electrode holder (11) is threadedly connected to the bottom of the metal hollow shaft (6) with a sleeve, the reference electrode (12) and the counter electrode (13) are threadedly connected to the kettle cover (1), the electrode fixing frame (14) is provided with a plurality of terminals, which correspond to the grooves of the disc electrode holder (11) one by one and are connected through metal conductors, the electrode fixing frame (14) is welded to the kettle cover (1), and the working electrode end, the counter electrode end and the reference electrode end of the electrochemical workstation (15) are respectively connected to a terminal of the electrode fixing frame (14), the counter electrode (13) and the reference electrode (12); injection The system comprises a corrosive medium pump (16), a nitrogen source (17), an H2S gas source (18), a CO2 gas source (19), a filter (20), and an injection pipe (21), wherein the injection pipe (21) is threadedly connected to the top of the reactor cover (1), the corrosive medium pump (16), the nitrogen source (17), the H2S gas source (18), and the CO2 gas source (19) are respectively connected to the inlet of the injection pipe (21) through pipelines, and the filter (20) is threadedly connected to the bottom of the injection pipe (21); the control system centrally controls the temperature, pressure, medium rotation speed, medium pH, etc. of the corrosion reactor.The method for evaluating the efficiency of the corrosion inhibitor and analyzing the corrosion rate is as follows: first, connecting a three-electrode system, preparing a working electrode using the corroded steel material as a raw material, and placing it in the groove of a disc electrode holder (11), then installing a counter electrode (13) and a reference electrode (12), tightening the kettle cover (1), and replacing the gas in the kettle (2) with nitrogen; second, simulating a corrosion environment, according to the corrosion environment to be tested, pumping a corrosion medium into a corrosion reactor (2) through a corrosion medium pump (16), flushing H2S or CO2 or other gases and gas mixtures into the corrosion reactor, setting a heating temperature according to the temperature of the corrosion medium and slowly heating to a given temperature, according to the pressure of the corrosion medium, replenishing the pressure to a specified pressure through an N2 bottle, turning on stirring, and setting the stirring rate; third, performing an electrochemical test, when the temperature, pressure, rotation speed, and pH of the corrosion reactor reach specified requirements, starting an electrochemical workstation to perform an electrochemical test.

[0022] The lid (1) and the body (2) of the corrosion reactor are made of 316L or higher grade steel, and are lined with anti-corrosion materials. The lining is polytetrafluoroethylene or other high temperature resistant anti-corrosion coatings. A sealing gasket is provided between the lid (1) and the body (2). The nitrogen source (17) is filled with nitrogen at 5MPa-10MPa to adjust and control the pressure in the corrosion reactor. The CO2 gas source (19) has a pressure of 1MPa-3MPa, and the H2S gas source (18) has a pressure of 0.1MPa-1MPa, respectively. to adjust and control the partial pressure of the corrosive medium; the corrosive medium pump (16) is a metering pump, which is used to inject the corrosive medium, corrosion inhibitor, organic amine, etc. into the corrosion reaction kettle; the sleeve of the metal hollow shaft with a sleeve (6) is made of insulating and heat-resistant material, which is used to provide electrical insulation protection for the outside of the metal hollow shaft with a sleeve below the high-temperature and high-pressure kettle cover; the drain valve (7) is used to discharge the waste liquid in the kettle after the experiment is completed and to send the gas after decompression to harmless treatment; the stirring is magnetically driven stirring, specifically relying on a magnetic stirrer ( 10) drives the rotor (8) to rotate, thereby driving the corrosive medium to rotate; the rotor (8) is an iron material sealed with a plastic tube or a glass tube; the magnetic stirrer (10) is installed at the bottom of the reactor and is insulated from the reactor body, and is a permanent magnet connected to the rotating shaft of the motor; the groove of the electrode holder (11) is used to place the working electrode, and a vertical guide pin is provided at the center of the groove to fix the working electrode and conduct electricity, and the conductive wire is a copper lead wire to transmit the current signal; the counter electrode (13) is a platinum sheet electrode or a platinum mesh electrode, etc., and the area is determined according to the general requirements of the field; the reference electrode (12) can be a saturated calomel electrode, a silver-silver chloride electrode reference electrode, or a high-temperature reference electrode according to the temperature requirements, and the reference electrode works close to the disc electrode holder (11); the electrode fixing frame (14) is provided with a plurality of terminals respectively connected to the groove of the disc electrode holder (11) through metal wires; the material of the working electrode can be various grades of steel, and it is made into a bottom area of ​​100mm according to the general requirements of the field 2The shape of the cylinder is a cylinder, the height of the cylinder is 2mm-5mm, and there is a needle-shaped hole with a diameter running through the center. The cylindrical surface and a circular surface of the cylinder are evenly coated with insulation resin, so that the corroded surface faces upward and is placed in the groove of the disc electrode holder (11); the conductive wire is an insulated copper wire, which is used to connect the groove and the terminal. One end of the conductive wire is connected to the groove, and the other end is led out from the cavity of the disc electrode holder (11), and is led to the terminal of the electrode fixing frame (14) on the upper surface of the kettle cover through the hollow of the metal hollow shaft 6 with a sleeve, and finally led to the working electrode end of the electrochemical workstation; the cover is provided with a temperature control heating switch, a rotary switch and a temperature and pressure display, etc.; the electrochemical test includes a blank test and a corrosion inhibition test, the test temperature range is 0°C to 220°C, the test pressure range is normal pressure to 10.0MPa, and the test flow rate range is 0m / s-22m / s; the blank test is without adding any The corrosion rate in a simulated corrosion environment is tested under the conditions of any corrosion inhibitor; the corrosion inhibition test is to add the corrosion inhibitor of the mass concentration required by the use of the corrosion inhibitor into the corrosion reactor to measure the corrosion rate; the working electrode needs to be immersed in the corrosion solution for a period of time before the corrosion reactor test to ensure that the electrode reaches a stable state; the pressure of the nitrogen replacement is normal pressure, and the number of replacements is more than 6 times; the corrosive medium is the medium contacted by the corroded part of the oil refining and chemical equipment, which can be an acidic aqueous solution, an oil-water mixture, a desulfurizer aqueous solution, or a corrosive medium specified in the industry standard or national standard; the corrosion inhibitor is a corrosion inhibitor used to evaluate and examine its corrosion inhibition performance, and the concentration can be determined according to the use requirements of the corrosion inhibitor; the pH of the corrosive medium can be adjusted by organic amine or inorganic ammonia according to the use requirements; the method of the electrochemical test is to first determine the corrosion potential E C Then the potentiodynamic polarization curve test was carried out to determine the corrosion current density I of the system. c Finally, according to the corrosion current density I c Calculate the corrosion rate C R and corrosion inhibition efficiency η, the calculation method of the corrosion rate is:

[0023]

[0024] The calculation formula of the corrosion inhibition efficiency is: C R ——Corrosion rate, mm / a; I c ——Corrosion current density, A / cm 2 ; M——atomic weight of the corroded metal; ρ——density, g / cm 3 ; F——Faraday constant, 96485C / mol; n——number of electrons transferred in electrochemical reaction (generally 2 for iron corrosion); η ε ——Corrosion inhibition efficiency, %; C R0 ——Blank test corrosion rate, mm / a; CR1 ——Corrosion rate of corrosion inhibition test, mm / a.

[0025] The device and method for quickly and accurately evaluating the efficiency of corrosion inhibitors and analyzing corrosion rates described in the present invention have the following characteristics: 1. The device involved in the present invention can simulate a real corrosion environment (covering a temperature range of 0°C to 220°C and a pressure range of normal pressure to 10.0MPa), and can complete the corrosion analysis of a specific complex corrosive medium on a variety of different grades of steel materials at one time, and quickly analyze the corrosion rate (taking only 10min-30min), effectively replacing the traditional mass loss method; 2. The device and method in the present invention construct a three-electrode corrosion system and adopt an electrochemical method to provide a rapid means for evaluating corrosion inhibitors from multiple aspects such as corrosion potential, corrosion current and corrosion rate, judge the type of corrosion inhibition, analyze the corrosion inhibition mechanism and quickly obtain the corrosion inhibition efficiency of the corrosion inhibitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a high temperature and high pressure corrosion reactor.

[0027] Figure 2 It is the cover of the high temperature and high pressure corrosion reactor.

[0028] Figure 3 This is a cross-sectional view of the disc electrode holder.

[0029] Figure 4 This is a top view of the disc electrode holder.

[0030] Figure 5 This is the evaluation of corrosion inhibitor A.

[0031] Figure 6 This is the evaluation of corrosion inhibitor B.

[0032] Among them, 1 is the kettle cover, 2 is the kettle body, 3 is the heating facility, 4 is the thermocouple, 5 is the pressure gauge, 6 is the metal hollow shaft with the sleeve, 7 is the drain valve, 8 is the stirring setting, 9 is the pH probe, 10 is the magnetic stirrer; 11 is the disc electrode holder, 12 is the reference electrode, 13 is the counter electrode, 14 is the electrode fixing frame, 15 is the electrochemical workstation; 16 is the corrosive medium pump, 17 is the nitrogen source, 18 is the H2S gas source, 19 is the CO2 gas source, 20 is the filter, 21 is the injection tube. DETAILED DESCRIPTION

[0033] In order to make the purpose and advantages of the present invention clearer, the implementation steps of the present invention are described in detail below with reference to examples. The precision electronic balance (Mettler Toledo), desktop acidity meter (Ramagnetic PHS-3C), electrochemical workstation (Gamary), organic needle, precision metering pump (BT100M), hair dryer, etc. involved in the experiment, as well as hydrochloric acid (mass fraction of 36% to 38%), petroleum ether (chemically pure), anhydrous ethanol (chemically pure), corrosion inhibitor (industrial product), sodium hydroxide standard solution (0.5mol / L) and other reagents related terms do not limit the present invention, but are only for the purpose of describing specific embodiments, and are not intended to limit the present invention, and should not be understood as being limited to the embodiments described herein. Obviously, the following embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present invention.

[0034] In this embodiment, the number of grooves in the disc electrode holder (11) is selected to be 6, namely 1#, 2#, 3#, 4#, 5# and 6#, and the number of terminals of the corresponding electrode fixing frame (14) is also 6. Figure 4 and Figure 2 .

[0035] Example 1 - Simulating the Corrosive Environment of the Stripper Air Cooler

[0036] Step 1, connect the three-electrode system. The air cooler at the top of the H2S stripping tower of a residual oil hydrogenation unit is seriously corroded. In order to investigate the corrosion of the air cooler in the corrosive medium environment, a corrosion environment is established according to the corrosive medium conditions of the air cooler (see Table-1). Six different materials are selected (see Table-2, 25#, 20#, 304, 316, 321, C276), and they are all made into cylindrical corrosion test pieces with a bottom diameter of 11.28mm and a surface height of 2mm as working electrodes. Then the bottom surface is polished with water sandpaper, cleaned with petroleum ether, blown dry with a hair dryer, and the cylindrical surface and one of the bottom surfaces are coated with epoxy resin for insulation. The six working electrodes of different materials are placed in the six grooves of the disc electrode holder. The 1# placed in the disc electrode holder as required is used as the working electrode, the platinum sheet electrode is used as the counter electrode, and the high-temperature reference electrode is used as the reference electrode.

[0037] Table-1 Corrosive media conditions of H2S stripping tower air cooler in a residue oil hydrotreating unit

[0038]

[0039] Table-2 Six different steel materials

[0040]

[0041] Step 2, simulate the corrosive environment. Install the kettle cover, tighten the main bolts step by step in multiple times according to symmetry and diagonal direction, and apply force evenly without deflection to achieve a good sealing effect. Connect the nitrogen source to the feed port, turn on the nitrogen source, and punch to check the air tightness of the reactor. Replace the air in the reactor with nitrogen for no less than 6 times to reduce the oxygen content to below 0.3%. According to the corrosive medium conditions in Table-1, use the corrosive medium pump to pump naphtha and water into the reactor respectively, soak the three electrodes, turn on the H2S gas source to flush H2S into the reactor, and measure the amount of H2S to ensure that the medium H2S concentration is 10000mg / L. Adjust the temperature, pressure and flow rate of the system. Set the temperature to 120℃, and slowly heat to 120℃. After stabilizing for 10 minutes, turn on the nitrogen source to replenish the pressure to the simulated environment pressure of 0.72mPa. According to the medium flow rate of the simulated environment of 7 m / s, the speed of the electromagnetic stirrer at the bottom of the reactor was set to 100 r / s to achieve the purpose of simulating the medium flow rate of 7 m / s.

[0042] Step 3, electrochemical test. Wait for the system pressure to stabilize at 0.72mPa and the temperature to stabilize at 120℃ and remain stable. Turn on the electrochemical workstation, connect 12 to the reference electrode interface of the electrochemical workstation, connect 13 to the counter electrode interface of the electrochemical workstation, and connect 14-1 to the working electrode interface of the electrochemical workstation. Wait for the open circuit potential E O After stabilization, a potentiodynamic polarization curve test was performed in a three-electrode system with a scanning range of [EC-200mv, EC+200mv] and a scanning rate of 10mV / min to measure the corrosion potential Ec1 and corrosion current density Ic1 of the system. Then, 14-2, 14-3, 14-4, 14-5 and 14-6 were connected to the working electrode interface of the electrochemical workstation in turn to determine the corrosion potential and corrosion current density, and calculate the corrosion rate C R . See Table-3.

[0043] Table-3 Corrosion rates of six materials under corrosive medium conditions in the air cooler of H2S stripper of a residue oil hydrotreating unit

[0044]

[0045] Example 2 - Simulated acidic water corrosion

[0046] Establish the corrosion environment of acidic water to 20# carbon steel according to No. 1 in Table-4. Step 1, connect the three-electrode system. Make 20# carbon steel into a cylindrical corrosion test piece with a bottom diameter of 11.28mm and a surface height of 2mm as the working electrode, polish the bottom surface with water sandpaper, clean it with petroleum ether, blow it dry with a hair dryer, and coat the cylindrical surface and one of the bottom surfaces with epoxy resin for insulation. Then place it in the 2# groove of the disc electrode holder, use the platinum mesh electrode as the counter electrode, and the silver / silver chloride reference electrode as the reference electrode.

[0047] Table-4 Simulated acidic water corrosion medium conditions

[0048]

[0049] Step 2, simulate the corrosion environment. Install the kettle cover, tighten the main bolts symmetrically and diagonally in multiple times, and apply force evenly without deflection to achieve a good sealing effect. Connect the nitrogen source and the feed port, turn on the nitrogen source, and punch to check the air tightness of the reactor. Replace the air in the reactor with nitrogen for no less than 6 times to reduce the oxygen content to below 0.3%. Use the corrosion medium pump to pump deionized water into the reactor, soak the three electrodes, open the H2S gas source valve and the CO2 gas source valve respectively, and flush H2S and CO2 gases into the corrosion reactor to 1000mg / L and 500mg / L, set the temperature to 30℃ and slowly heat to 30℃, open the N2 gas source valve, and pressurize the corrosion reactor to 0.1mPa. Set the speed of the electromagnetic stirrer at the bottom of the reactor to 13r / s, and the simulated medium flow rate to 1m / s.

[0050] Step 3, electrochemical test. After the system pressure reaches the specified temperature and pressure and remains stable, turn on the electrochemical workstation, connect 12 to the reference electrode interface of the electrochemical workstation, connect 13 to the counter electrode interface of the electrochemical workstation, and connect 14-1 to the working electrode interface of the electrochemical workstation. O After stabilization, a potentiodynamic polarization curve test was carried out in a three-electrode system with a scanning range of [EC-200mv, EC+200mv] and a scanning rate of 15mV / min. The corrosion potential and corrosion current density of the system were measured, as shown in Table 5. According to the calculated corrosion rate C R .

[0051]

[0052] Example 3 - Simulated acidic water corrosion

[0053] According to No. 2 in Table 4, the corrosion environment of acidic water for 20# carbon steel was established. According to the method and steps of Example 2, the scanning rate was 20mV / min, and the corrosion potential Ec1 and corrosion current density Ic1 of the system were measured respectively, and the corrosion rate C was calculated. R .

[0054] Example 4 - Simulated acidic water corrosion

[0055] According to No. 3 in Table 4, the corrosion environment of acidic water on 20# carbon steel was established. According to the method and steps of Example 2, the corrosion potential Ec1 and corrosion current density Ic1 of the system were measured respectively, and the corrosion rate C was calculated. R .

[0056] Example 5 - Simulated acidic water corrosion

[0057] According to No. 4 in Table 4, the corrosion environment of acidic water on 20# carbon steel was established. According to the method and steps of Example 2, the corrosion potential Ec1 and corrosion current density Ic1 of the system were measured respectively, and the corrosion rate C was calculated. R .

[0058] Example 6 - Simulated acidic water corrosion

[0059] According to No. 5 in Table 4, the corrosion environment of acidic water on 20# carbon steel was established. According to the method and steps of Example 2, the corrosion potential Ec1 and corrosion current density Ic1 of the system were measured respectively, and the corrosion rate C was calculated. R .

[0060] Table-5 Corrosion rate of 20# carbon steel by acidic water under different conditions (method in the present invention)

[0061]

[0062]

[0063] Comparative Example 1

[0064] In the embodiment of the present invention, the corrosion rate is correlated by testing the corrosion current density. The experimental period is very short, about within 30 minutes. In the comparative example, the corrosion rate tested by this method is compared with the corrosion rate tested by the traditional mass loss method. In the traditional corrosion reactor, the corresponding corrosion environment is established according to the requirements of Example 2-Example 6. After grinding and weighing, 20# steel is immersed in the above-mentioned corrosive medium for 72 hours. The test piece specifications are After the test, remove the corrosion product film on the surface of the test piece, clean it in an ultrasonic instrument, dry it with filter paper and weigh it. Calculate the corrosion rate by weight loss. The corrosion rate is calculated according to the formula recommended by GB / T19292.4-2003, that is:

[0065] Where v is the corrosion rate mm / a; Δm is the weight loss of metal in g; ρ is the metal density 7.85 g / cm 3 ; A is the surface area of ​​the test piece cm 2 ; Δt is the corrosion time h.

[0066] Table-6 Corrosion rate of 20# carbon steel in acidic water under different conditions (mass loss method)

[0067]

[0068] It can be seen from the above results that, under the same corrosion environment, the corrosion rate measured in the present invention has the same law as the corrosion rate measured by the traditional mass loss method, and the values ​​are close, so the traditional mass loss method can be replaced.

[0069] Example 7 - Static Corrosion Inhibitor Evaluation Example:

[0070] Blank test, step 1: prepare electrodes. Make a cylindrical corrosion test piece of 20# carbon steel with a bottom diameter of 11.28mm and a surface height of 2mm as the working electrode, polish the bottom with water sandpaper, clean it with petroleum ether, blow it dry with a hair dryer, and coat the cylindrical surface and one of the bottom surfaces with epoxy resin for insulation. Then place it in the 1# groove of the disc electrode holder, use the platinum mesh electrode as the counter electrode, and the silver / silver chloride reference electrode as the reference electrode. Step 2: Fill the medium. Install the kettle cover, tighten the main bolts step by step in a symmetrical and diagonal manner in multiple times, and apply force evenly without deflection to achieve a good sealing effect. Connect the nitrogen source to the feed port, turn on the nitrogen source, and punch to check the air tightness of the reactor. Replace the air in the reactor with nitrogen for no less than 6 times to reduce the oxygen content to below 0.3%. Take the 15% hydrochloric acid solution described in the standard SY / T5405-1996 as the corrosion medium, pump it into the corrosion reactor described in the present invention, immerse the three electrodes, set the temperature to 60°C, and slowly heat to 60°C and stabilize for 10 minutes. Step 3: Electrochemical test. Wait for the pressure and temperature of the system to remain stable. Turn on the electrochemical workstation, connect 12 to the reference electrode interface of the electrochemical workstation, connect 13 to the counter electrode interface of the electrochemical workstation, and connect 14-1 to the working electrode interface of the electrochemical workstation. Wait for the open circuit potential E O After stabilization, a potentiodynamic polarization curve test was performed in a three-electrode system with a scanning range of [EC-200mv, EC+200mv] and a scanning rate of 10mV / min-20mV / min to measure the corrosion potential Ec and corrosion current density Ic of the system. The trend of corrosion potential over time was recorded.

[0071] Corrosion inhibition test: Inhibitor A with a concentration of 0.1%, 0.3%, 0.5% and 1.0% by mass was added to the corrosive medium at intervals of 30 minutes. After the corrosion inhibitor was evenly dispersed in the corrosive medium, electrochemical testing was performed after the corrosion inhibitor was pre-filmed on the corrosion surface of the working electrode 10 minutes later. The corrosion potential Ec and corrosion current density Ic of the system were measured respectively, and the corrosion inhibition efficiency η was calculated.

[0072] Figure 5This is the change in the corrosion potential of the working electrode after adding corrosion inhibitor A. It can be seen that after adding corrosion inhibitor A (concentration is 0.1%wt), the corrosion potential of the system drops from -128mV to -169mV. The decrease in corrosion potential indicates that the corrosion inhibitor inhibits the cathode and is a cathodic corrosion inhibitor.

[0073] Example 8 - Static Corrosion Inhibitor Evaluation Example

[0074] The corrosion inhibitor B was rapidly evaluated according to the method steps of Example 7. Figure 6 To evaluate the corrosion inhibitor B,

[0075] Knowable

[0076] After adding the corrosion inhibitor B (concentration of 0.1% wt), the corrosion potential of the system hardly changed, and it can be judged that the corrosion inhibitor is a mixed inhibition type corrosion inhibitor. According to the calculation formula of corrosion inhibition efficiency, the corrosion inhibition of corrosion inhibitor A and corrosion inhibitor B is calculated (the results are shown in Table 7).

[0077] Table-7 Static corrosion inhibition effect of corrosion inhibitors A and B

[0078]

[0079]

[0080] Example 9 - Dynamic Corrosion Inhibitor Evaluation Implementation

[0081] Based on the static evaluation of corrosion inhibitor B in Example 7, the rotation speed of the electromagnetic stirrer at the bottom of the reactor was set to 100 r / s to achieve a simulated medium flow rate of 7 m / s, and corrosion inhibitors A and B were dynamically evaluated respectively.

[0082] Table-8 Dynamic corrosion inhibition effect of corrosion inhibitors A and B

[0083]

[0084] The technical solutions disclosed and proposed by the present invention can be realized by those skilled in the art by referring to the contents of this article and appropriately changing the conditions, routes and other links. Although the methods and preparation techniques of the present invention have been described through preferred embodiments, relevant technicians can obviously modify or re-combine the methods and technical routes described herein without departing from the content, spirit and scope of the present invention to realize the final preparation technology. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the spirit, scope and content of the present invention.

Claims

1. A method for quickly and accurately evaluating the efficiency of corrosion inhibitors and analyzing corrosion rates. The device of the method includes a kettle cover, a kettle body, a heating facility, a thermocouple, a pressure gauge, a metal hollow shaft with a sleeve, a drain valve, a rotor, a pH probe, a magnetic stirrer, a disc electrode holder, a reference electrode, a counter electrode, an electrode fixing frame, an electrochemical workstation, a corrosive medium pump, a nitrogen source, an H2S gas source, a CO2 gas source, a filter, and an injection pipe; the kettle cover is connected to the kettle body through a flange, the heating facility is in close contact with the outer wall of the kettle body and surrounds the outer wall of the kettle body, the thermocouple is located between the heating facility and the kettle body, the pressure gauge, the metal hollow shaft with a sleeve, the pH probe, the injection pipe, the reference electrode and the counter electrode are threadedly connected to the kettle cover, the electrode fixing frame is welded to the kettle cover, and the drain valve is threadedly connected to the kettle body. The lower part of the kettle body, the magnetic stirrer is located below the kettle body, the rotor is located in the center of the bottom of the kettle body, the corrosive medium pump, nitrogen source, H2S gas source, CO2 gas source are respectively connected to the inlet of the injection pipe through pipelines, the filter is threadedly connected to the outlet of the injection pipe, and the disc electrode holder is threadedly connected to the bottom of the metal hollow shaft with a sleeve; the disc electrode is provided with a groove, the electrode fixing frame is provided with the same number of terminals as the groove, the terminals and the grooves are correspondingly connected by conductive wires, the conductive wires are insulated copper wires, which are led out from the cavity of the disc electrode holder, and are led to the terminals of the electrode fixing frame on the kettle cover through the hollow of the metal hollow shaft with a sleeve, and the working electrode end, the counter electrode end and the reference electrode end of the electrochemical workstation are respectively connected to a terminal of the electrode fixing frame, the counter electrode and the reference electrode by wires; It is characterized in that The method comprises the following steps: 1) Connect the three-electrode system, prepare the working electrode with corroded steel as the raw material, and place it in the groove of the disc electrode holder, then connect the working electrode, counter electrode and reference electrode to the electrochemical workstation, tighten the kettle cover, and replace the gas in the kettle with nitrogen; 2) Simulate the corrosion environment. According to the corrosion environment to be tested, pump the corrosive medium into the corrosion reactor through the corrosive medium pump, flush H2S or CO2 or other gases and gas mixtures into the corrosion reactor, set the heating temperature, set the pressure, set the stirring rate and start; 3) Electrochemical test: When the temperature, pressure, speed and pH of the corrosion reactor meet the requirements of the corrosion environment to be tested, start the electrochemical workstation to perform electrochemical test and test the corrosion current density; The electrochemical test method is to first determine the corrosion potential E C , the corrosion potential E C Keep the fluctuation less than 1mV within 3min-10min, then conduct a potentiodynamic polarization curve test to determine the corrosion current density I of the system. c The dynamic potential scanning range is [EC-200mv, EC+200mv], the scanning rate is 10mV / min-20mV / min, and finally according to the corrosion current density I c Calculate the corrosion rate C R , the corrosion rate C R The calculation formula is: ； C R ——Corrosion rate, mm / a; I c ——Corrosion current density, A / cm 2 ; M——atomic weight of the corroded metal; ρ——density, g / cm 3 ; F——Faraday constant, 96485 C / mol; n——number of electrons transferred in electrochemical reaction; η ε ——Corrosion inhibition efficiency; The calculation formula of corrosion inhibition efficiency η is: ； C R0 ——Blank test corrosion rate, mm / a; C R1 ——Corrosion rate of corrosion inhibition test, mm / a.

2. The method according to claim 1, characterized in that The corrosive medium is the medium that the corroded parts of the oil refining and chemical equipment are in contact with, which is an acidic aqueous solution, an oil-water mixture, and a desulfurizer aqueous solution; the corrosion inhibitor is a corrosion inhibitor used to evaluate and examine its corrosion inhibition performance, with a concentration of 1μg / g-1000μg / g. The corrosion inhibitor is diluted to the use requirements with a specific solvent according to the solubility characteristics of the corrosion inhibitor; the pH of the corrosive medium is adjusted to the use requirements with an organic amine.

3. The method according to claim 1, characterized in that The temperature range of the simulated corrosion environment is 0°C~220°C, and the pressure range is normal pressure~10.0MPa. The electrochemical test includes a blank test and a corrosion inhibition test. The blank test is to test the corrosion current density in the simulated corrosion environment without adding any corrosion inhibitor; the corrosion inhibition test is to add a corrosion inhibitor of a mass concentration required for the use of the corrosion inhibitor to the simulated corrosion environment to test the corrosion current density.

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