Device and method for testing pitting corrosion of metal material in seawater

Abstract

The invention discloses a device and method for testing pitting corrosion of a metal material in seawater, and belongs to the technical field of metal corrosion prevention, the device comprises a testing device main body, a gas conveying device and a flow simulation device, the gas conveying device is arranged on the left side of the testing device main body, and the flow simulation device is located on the right side of the testing device main body; the test device main body comprises a container kettle, an air outlet is formed in the container kettle, and the side surface of the container kettle is communicated with a drain valve. According to the invention, pitting corrosion of the metal material can be simulated by coating the surface of the metal material with the epoxy anticorrosive paint, two sample clamps are provided, the first sample clamp is installed in a circulating pipeline with a hole, and a metal sample for a flow corrosion test is fixed; the second device is arranged at the bottom of the test container kettle and is used for fixing a metal sample for a static corrosion test; the first sample clamp can be used for fixing four metal samples at the same time; the second sample clamp can be used for fixing six metal samples in a horizontal or vertical state at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of metal anticorrosion, and in particular relates to a pitting corrosion test device and method for metal materials in seawater. Background Art

[0002] The main reason for the failure of metal materials working in seawater is corrosion. Taking oil and gas pipelines as an example, the corrosion of metal materials will cause oil and gas leakage due to perforation, environmental pollution, and waste of materials and manpower due to shutdown and maintenance, resulting in huge property losses.

[0003] Three influencing factors of corrosion simulation: corrosive medium environment. Affected by seawater and the medium in the working environment, there are many reasons for the corrosion of metal materials in seawater, mainly including seawater corrosion, dissolved oxygen corrosion, carbon dioxide corrosion, hydrogen sulfide corrosion, and joint corrosion of carbon dioxide and hydrogen sulfide; pitting corrosion. Pitting corrosion is a form of corrosion that is not easy to be found, destructive and has great hidden dangers. Pitting corrosion of submarine pipelines will cause holes in the wall thickness, causing leakage of oil, gas and other media, resulting in economic losses and environmental pollution; flow-accelerated corrosion. The corrosion rate of metal materials in a flowing environment is significantly higher than that in a static environment. This phenomenon is usually called flow-accelerated corrosion.

[0004] Based on this, a new test device and method are needed to meet the needs of enterprises and related personnel to explore the corrosion mechanism of metal materials and improve the corrosion resistance of metal materials. Summary of the invention

[0005] The purpose of the present invention is to solve the above technical problems and to provide a pitting corrosion test device and method for metal materials in seawater.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A pitting corrosion test device for metal materials in seawater, comprising a test device body, a gas delivery device and a flow simulation device, wherein the gas delivery device is arranged on the left side of the test device body, and the flow simulation device is arranged on the right side of the test device body;

[0008] The main body of the test device includes a container kettle, an air outlet is provided in the container kettle, a drain valve is connected to the side of the container kettle, a rotatable sample fixture is connected to the container kettle, an exhaust valve is connected to the top of the container kettle, a pressure gauge is connected to the side of the container kettle, a thermometer is connected through the top position of the container kettle, and a temperature-controlled heating tube is connected through the side wall position of the container kettle.

[0009] As a further description of the above technical solution: the gas delivery device includes a nitrogen gas cylinder and a test gas cylinder, the gas outlet end of the nitrogen gas cylinder is provided with a gas pipeline, the gas pipeline and the test gas cylinder are respectively provided with a No. 1 gas inlet valve and a No. 2 gas inlet valve, the ends of the No. 1 gas inlet valve and the No. 2 gas inlet valve are connected to a main gas inlet valve, and the end of the main gas inlet valve is connected to the gas outlet.

[0010] As a further description of the above technical solution: the flow simulation device includes an inlet valve connected to the container kettle, a centrifugal pump is provided on the pipeline on the right side of the inlet valve, a circulation pipeline is provided at the end of the centrifugal pump, a flow meter is provided on the circulation pipeline, an outflow valve is provided at the end of the circulation pipeline, and the outflow valve is connected to the container kettle.

[0011] As a further description of the above technical solution: the rotatable sample clamp comprises six sample clamps in total, and corrosion tests of six samples can be carried out simultaneously, and each sample clamp can be rotated independently.

[0012] As a further description of the above technical solution: when the No. 1 air intake valve or the No. 2 air intake valve cannot be closed and when the gas cylinder is not connected to the left side of the test device body, the main air intake valve can be closed to prevent the gas from flowing out and causing changes in the test environment parameters.

[0013] As a further description of the above technical solution: a threaded opening is provided on the pipeline between the inlet valve and the centrifugal pump, and a screw-in sample clamp is provided in the threaded opening, so that corrosion tests of four samples can be carried out simultaneously.

[0014] The invention discloses a pitting corrosion test method for metal materials in seawater. The sample is prepared for pitting corrosion test by sample pretreatment, and the parameters of the test environment can be changed by operating the test device.

[0015] As a further description of the above technical solution: different types of pitting corrosion tests can be carried out by preparing different test solutions according to different test requirements; the required test gas can be introduced into the container through the test gas delivery unit; the test pressure can be selected through the pressure control unit; the test temperature can be selected through the temperature control unit; and the pitting corrosion test in a static or flowing state can be carried out by selecting sample fixtures in different positions.

[0016] As a further description of the above technical solution: the test sample is coated with epoxy anti-corrosion paint so as to be a test sample with only the porous surface contacting the atmosphere.

[0017] As a further description of the above technical solution: a corrosion rate calculation method suitable for this test method is provided.

[0018] The present invention provides a set of test methods adapted to the test device, and the static corrosion test method is as follows:

[0019] S1: Sample pretreatment: grind the working surface of the metal material sample to a mirror surface, then use acetone ultrasonic cleaning and anhydrous ethanol ultrasonic cleaning for 5 minutes, then blow dry with cold air from a hair dryer or dry naturally, wrap the sample with filter paper and place it in a dryer for 24 hours; cover the sample with N circular baffles with an area of ​​S, then apply epoxy anti-corrosion paint on the surface of the sample, remove the circular baffles, and make a metal sample with a corrodible area in the shape of a hole, and weigh the mass of the treated sample;

[0020] S2: Test solution preparation: The user selects the appropriate solution for the test according to different test requirements. There are two options for solution preparation: (1) artificially preparing seawater to simulate the corrosion of metal materials by seawater; (2) the corrosion of metal materials in seawater will also occur on the contact surface with the medium in the working environment, so it is necessary to prepare medium solutions with different components required for the test to conduct corrosion tests caused by other factors;

[0021] S3: Sample immersion: open the container kettle and fix the sample on the rotatable sample fixture at the bottom, rotate the rotatable sample fixture to the target angle according to the test requirements; ensure that the inlet valve and the outflow valve are closed; add the prepared solution into the container kettle; when the exhaust valve is open, open the No. 1 inlet valve to introduce nitrogen for deoxygenation, and close the exhaust valve after deoxygenation; open the No. 2 inlet valve to introduce the test gas; observe the pressure gauge in the container kettle, open the No. 1 inlet valve to introduce nitrogen to adjust to the test pressure; open the temperature control heating tube to set the test temperature; start the test, and the immersion time is T;

[0022] S4: Test result detection: After the test, turn off the temperature control heating tube, open the exhaust valve, reduce the pressure and temperature; open the drain valve to discharge the solution; open the container kettle and take out the sample; soak the sample in the pickling solution (the ratio of the pickling solution is 500mL HCl, density 1.19g / mL, 500mL deionized water + 3.5g hexamethylenetetramine) for 10min, then gently scrub the surface of the test piece with a soft brush, rinse the test piece with clean water, dehydrate with anhydrous ethanol, blow dry with cold air, and finally dry it in a drying oven for 24h before weighing the sample mass;

[0023] S5: Corrosion rate calculation: The average corrosion rate is calculated by weight loss method using formula (1):

[0024]

[0025] Where: v is the average corrosion rate, mm / a; W 1 is the weight of the sample before the test, g; W 2 is the weight of the sample after the corrosion products are removed after the test, g; N is the number of pitting holes; S is the area of ​​a single pitting hole, cm2; T is the test time, h; ρ is the density of the metal sample, g / cm3;

[0026] S6: Corrosion behavior study: The morphology of the corroded samples was observed by scanning electron microscopy (SEM), the composition of the corrosion products was analyzed by X-ray diffractometer (XRD) and energy dispersive spectrometer (EDS), and the surface corrosion state of the samples was analyzed by electrochemical detection to explore the corrosion mechanism of metal materials in the service environment.

[0027] The present invention provides a set of test methods adapted to the test device, and the flow corrosion test method is as follows:

[0028] S1: Sample pretreatment: grind the working surface of the metal material sample to a mirror surface, then use acetone ultrasonic cleaning and anhydrous ethanol ultrasonic cleaning for 5 minutes, then blow dry with a hair dryer or dry naturally, wrap the sample with filter paper and place it in a dryer for 24 hours; cover the sample with N circular baffles with an area of ​​S, then apply epoxy anti-corrosion paint on the surface of the sample, remove the circular baffles, and make a metal sample with a corrodible area as a hole. Weigh the mass of the treated sample as W 1 ;

[0029] S2: Test solution preparation: The user selects the appropriate solution for the test according to different test requirements. There are two options for solution preparation: (1) artificially preparing seawater to simulate the corrosion of metal materials by seawater; (2) the corrosion of metal materials in seawater will also occur on the contact surface with the medium in the working environment, so it is necessary to prepare medium solutions with different components required for the test to conduct corrosion tests caused by other factors;

[0030] S3: Sample immersion: Fix the sample on the screw-in sample clamp, then screw the sample clamp into the threaded opening of the pipeline, add the prepared solution into the container kettle, and the liquid level should be higher than the outflow valve; open the inflow valve and the outflow valve to connect the test device body and the flow simulation device; when the exhaust valve is in the open state, open the No. 1 air inlet valve to introduce nitrogen for deoxygenation, and close the exhaust valve after deoxygenation; open the No. 2 air inlet valve to introduce the test gas; observe the pressure gauge in the container kettle, open the No. 1 air inlet valve to introduce nitrogen and adjust it to the test pressure; open the temperature control heating tube to set the test temperature; observe the flow meter and set the centrifugal pump to the test flow rate; start the test, and the immersion time is T;

[0031] S4: Test result detection: After the test, turn off the temperature control heating tube, open the exhaust valve, reduce the pressure and temperature; open the drain valve to discharge the solution; screw out the screw-in sample clamp and take out the sample; soak the sample in the pickling solution (the ratio of the pickling solution is 500mL HCl, density 1.19g / mL, 500mL deionized water + 3.5g hexamethylenetetramine) for 10 minutes, then gently brush the surface of the test piece with a soft brush, rinse the test piece with clean water, dehydrate with anhydrous ethanol, blow dry with cold air, and finally dry it in a drying oven for 24 hours and weigh the sample mass W 2 ;

[0032] S5: Corrosion rate calculation: The average corrosion rate is calculated by weight loss method using formula (1);

[0033] S6: Corrosion behavior study: The morphology of the corroded samples was observed by scanning electron microscopy (SEM), the composition of the corrosion products was analyzed by X-ray diffractometer (XRD) and energy dispersive spectrometer (EDS), and the surface corrosion state of the samples was analyzed by electrochemical detection to explore the corrosion mechanism of metal materials in the service environment.

[0034] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0035] 1. In the present invention, the pitting corrosion of metal materials can be simulated by coating the surface of the metal materials with epoxy anti-corrosion coating, and two kinds of sample fixtures are provided. The first kind is installed in the open circulation pipeline to fix the metal sample for the flow corrosion test; the second kind is installed at the bottom of the test container kettle to fix the metal sample for the static corrosion test; the first kind of sample fixture can fix four metal samples at the same time; the second kind of sample fixture can fix six metal samples in the horizontal or vertical state at the same time; a variety of different tests can be carried out by changing the test conditions. First, when artificial seawater is selected in the solution preparation, the seawater corrosion of metal materials can be simulated; when salt solution is selected in the solution preparation, the corrosion of metal materials in seawater dominated by other factors can be simulated. The specific implementation method is to introduce a certain amount of gas that dominates the corrosion test into the solution through a gas delivery unit.

[0036] 2. The present invention provides abundant controllable test conditions for corrosion tests of metal materials in seawater, so that the results obtained from the corrosion tests are closer to the actual situation, and provides a strong basis for enterprises to formulate corrosion control measures and improve metal materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the overall structure of a pitting corrosion test device and method for metal materials in seawater proposed by the present invention;

[0038] Figure 2 A schematic diagram of the structure of a test device for pitting corrosion of metal materials in seawater proposed by the present invention;

[0039] Figure 3 This is a schematic diagram of the main structure of a test device for pitting corrosion of metal materials in seawater proposed by the present invention;

[0040] Figure 4 This is a schematic diagram of the structure of a gas conveying device for a metal material pitting corrosion test device and method in seawater proposed by the present invention;

[0041] Figure 5The present invention provides a schematic structural diagram of a flow simulation device for testing pitting corrosion of metal materials in seawater.

[0042] Legend:

[0043] 1. Container kettle; 2. Exhaust valve; 3. Thermometer; 4. Pressure gauge; 5. Rotatable sample fixture; 6. Temperature control heating tube; 7. Gas outlet; 8. Drain valve; 9. Gas pipeline; 10. No. 2 inlet valve; 11. No. 1 inlet valve; 12. Main inlet valve; 13. Nitrogen cylinder; 14. Test gas cylinder; 15. Outflow valve; 16. Pipeline threaded opening; 17. Screw-in sample fastener; 18. Flow meter; 19. Circulation pipeline; 20. Centrifugal pump; 21. Inflow valve. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Please see attached Figure 1 -Attached Figure 5 , the present invention provides a technical solution: a pitting corrosion test device for metal materials in seawater, comprising a test device body, a gas delivery device and a flow simulation device, wherein the gas delivery device is arranged on the left side of the test device body, and the flow simulation device is arranged on the right side of the test device body;

[0046] The main body of the test device includes a container kettle 1, an air outlet 7 is provided in the container kettle 1, a drain valve 8 is connected to the side of the container kettle 1, a rotatable sample fixture 5 is connected to the container kettle 1, an exhaust valve 2 is connected to the top of the container kettle 1, a pressure gauge 4 is connected to the side of the container kettle 1, a thermometer 3 is connected through the top position of the container kettle 1, and a temperature control heating tube 6 is connected through the side wall position of the container kettle 1.

[0047] The gas delivery device includes a nitrogen gas cylinder 13 and a test gas cylinder 14. A gas pipeline 9 is provided at the gas outlet end of the nitrogen gas cylinder 13. A No. 1 gas inlet valve 11 and a No. 2 gas inlet valve 10 are provided outside the gas pipeline 9 and the test gas cylinder 14, respectively. The ends of the No. 1 gas inlet valve 11 and the No. 2 gas inlet valve 10 are connected to a main gas inlet valve 12, and the end of the main gas inlet valve 12 is connected to the gas outlet 7.

[0048] The flow simulation device includes an inlet valve 21 connected to the container kettle 1. A centrifugal pump 20 is provided on the pipeline on the right side of the inlet valve 21. A circulation pipeline 19 is provided at the end of the centrifugal pump 20. A flow meter 18 is provided on the circulation pipeline 19. An outflow valve 15 is provided at the end of the circulation pipeline 19. The outflow valve 15 is connected to the container kettle 1.

[0049] The rotatable sample fixture 5 comprises six sample clamps in total, and can carry out corrosion tests on six samples at the same time, and each sample clamp can rotate independently.

[0050] When the No. 1 air intake valve 11 or the No. 2 air intake valve 10 cannot be closed and when the gas cylinder is not connected to the left side of the test device body, the main air intake valve 12 can be closed to prevent the test environment parameters from changing due to the outflow of gas.

[0051] A threaded opening 16 is provided on the pipeline between the inflow valve 21 and the centrifugal pump 20. A screw-in sample clamp 17 is provided in the threaded opening 16, so that corrosion tests of four samples can be carried out simultaneously.

[0052] The invention discloses a pitting corrosion test method for metal materials in seawater. The sample is prepared for pitting corrosion test by sample pretreatment, and the parameters of the test environment can be changed by operating the test device.

[0053] Different types of pitting corrosion tests can be carried out by preparing different test solutions according to different test requirements; the required test gas can be introduced into the container through the test gas delivery unit; the test pressure can be selected through the pressure control unit; the test temperature can be selected through the temperature control unit; and the pitting corrosion test can be carried out in a static or flowing state by selecting sample fixtures in different positions.

[0054] The test specimens were coated with epoxy anticorrosive paint so that only the porous surface was exposed to the atmosphere.

[0055] A method for calculating the corrosion rate applicable to this test method is provided.

[0056] Provide a set of test methods suitable for this test device. The static corrosion test method is as follows:

[0057] S1: Sample pretreatment: grind the working surface of the metal material sample to a mirror surface, then use acetone ultrasonic cleaning and anhydrous ethanol ultrasonic cleaning for 5 minutes, then blow dry with cold air from a hair dryer or dry naturally, wrap the sample with filter paper and place it in a dryer for 24 hours; cover the sample with N circular baffles with an area of ​​S, then apply epoxy anti-corrosion paint on the surface of the sample, remove the circular baffles, and make a metal sample with a corrodible area in the shape of a hole, and weigh the mass of the treated sample;

[0058] S2: Test solution preparation: The user selects the appropriate solution for the test according to different test requirements. There are two options for solution preparation: (1) artificially preparing seawater to simulate the corrosion of metal materials by seawater; (2) the corrosion of metal materials in seawater will also occur on the contact surface with the medium in the working environment, so it is necessary to prepare medium solutions with different components required for the test to conduct corrosion tests caused by other factors;

[0059] S3: Sample immersion: open the container kettle and fix the sample on the rotatable sample fixture at the bottom, rotate the rotatable sample fixture to the target angle according to the test requirements; ensure that the inlet valve and the outflow valve are closed; add the prepared solution into the container kettle; when the exhaust valve is open, open the No. 1 inlet valve to introduce nitrogen for deoxygenation, and close the exhaust valve after deoxygenation; open the No. 2 inlet valve to introduce the test gas; observe the pressure gauge in the container kettle, open the No. 1 inlet valve to introduce nitrogen to adjust to the test pressure; open the temperature control heating tube to set the test temperature; start the test, and the immersion time is T;

[0060] S4: Test result detection: After the test, turn off the temperature control heating tube, open the exhaust valve, reduce the pressure and temperature; open the drain valve to discharge the solution; open the container kettle and take out the sample; soak the sample in the pickling solution (the ratio of the pickling solution is 500mL HCl, density 1.19g / mL, 500mL deionized water + 3.5g hexamethylenetetramine) for 10min, then gently scrub the surface of the test piece with a soft brush, rinse the test piece with clean water, dehydrate with anhydrous ethanol, blow dry with cold air, and finally dry it in a drying oven for 24h before weighing the sample mass;

[0061] S5: Corrosion rate calculation: The average corrosion rate is calculated by weight loss method using formula (1):

[0062]

[0063] Where: v is the average corrosion rate, mm / a; W 1 is the weight of the sample before the test, g; W 2 is the weight of the sample after the corrosion products are removed after the test, g; N is the number of pitting holes; S is the area of ​​a single pitting hole, cm2; T is the test time, h; ρ is the density of the metal sample, g / cm3;

[0064] S6: Corrosion behavior study: The morphology of the corroded samples was observed by scanning electron microscopy (SEM), the composition of the corrosion products was analyzed by X-ray diffractometer (XRD) and energy dispersive spectrometer (EDS), and the surface corrosion state of the samples was analyzed by electrochemical detection to explore the corrosion mechanism of metal materials in the service environment.

[0065] The present invention provides a set of test methods adapted to the test device, and the flow corrosion test method is as follows:

[0066] S1: Sample pretreatment: grind the working surface of the metal material sample to a mirror surface, then use acetone ultrasonic cleaning and anhydrous ethanol ultrasonic cleaning for 5 minutes, then blow dry with a hair dryer or dry naturally, wrap the sample with filter paper and place it in a dryer for 24 hours; cover the sample with N circular baffles with an area of ​​S, then apply epoxy anti-corrosion paint on the surface of the sample, remove the circular baffles, and make a metal sample with a corrodible area as a hole. Weigh the mass of the treated sample as W 1 ;

[0067] S2: Test solution preparation: The user selects the appropriate solution for the test according to different test requirements. There are two options for solution preparation: (1) artificially preparing seawater to simulate the corrosion of metal materials by seawater; (2) the corrosion of metal materials in seawater will also occur on the contact surface with the medium in the working environment, so it is necessary to prepare medium solutions with different components required for the test to conduct corrosion tests caused by other factors;

[0068] S3: Sample immersion: Fix the sample on the screw-in sample clamp, then screw the sample clamp into the threaded opening of the pipeline, add the prepared solution into the container kettle, and the liquid level should be higher than the outflow valve; open the inflow valve and the outflow valve to connect the test device body and the flow simulation device; when the exhaust valve is in the open state, open the No. 1 air inlet valve to introduce nitrogen for deoxygenation, and close the exhaust valve after deoxygenation; open the No. 2 air inlet valve to introduce the test gas; observe the pressure gauge in the container kettle, open the No. 1 air inlet valve to introduce nitrogen and adjust it to the test pressure; open the temperature control heating tube to set the test temperature; observe the flow meter and set the centrifugal pump to the test flow rate; start the test, and the immersion time is T;

[0069] S4: Test result detection: After the test, turn off the temperature control heating tube, open the exhaust valve, reduce the pressure and temperature; open the drain valve to discharge the solution; screw out the screw-in sample clamp and take out the sample; soak the sample in the pickling solution (the ratio of the pickling solution is 500mL HCl, density 1.19g / mL, 500mL deionized water + 3.5g hexamethylenetetramine) for 10 minutes, then gently brush the surface of the test piece with a soft brush, rinse the test piece with clean water, dehydrate with anhydrous ethanol, blow dry with cold air, and finally dry it in a drying oven for 24 hours and weigh the sample mass W 2 ;

[0070] S5: Corrosion rate calculation: The average corrosion rate is calculated by weight loss method using formula (1);

[0071] S6: Corrosion behavior study: The morphology of the corroded samples was observed by scanning electron microscopy (SEM), the composition of the corrosion products was analyzed by X-ray diffractometer (XRD) and energy dispersive spectrometer (EDS), and the surface corrosion state of the samples was analyzed by electrochemical detection to explore the corrosion mechanism of metal materials in the service environment.

[0072] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A pitting corrosion test device for metal materials in seawater, comprising a test device body, a gas delivery device and a flow simulation device, characterized in that: The gas delivery device is arranged on the left side of the test device body, and the flow simulation device is arranged on the right side of the test device body; The main body of the test device comprises a container kettle (1), wherein the container kettle (1) is provided with an air outlet (7), the side of the container kettle is connected to a drain valve (8), the container kettle (1) is connected to a rotatable sample fixture (5), the container kettle (1) is connected to an exhaust valve (2), the side of the container kettle (1) is connected to a pressure gauge (4), the top position of the container kettle (1) is connected through a thermometer (3), and the side wall position of the container kettle (1) is connected through a temperature control heating tube (6).

2. A pitting corrosion test device for metal materials in seawater according to claim 1, characterized in that: The gas delivery device comprises a nitrogen gas cylinder (13) and a test gas cylinder (14); a gas pipeline (9) is provided at the gas outlet end of the nitrogen gas cylinder (13); a first gas inlet valve (11) and a second gas inlet valve (10) are provided outside the gas pipeline (9) and the test gas cylinder (14), respectively; ends of the first gas inlet valve (11) and the second gas inlet valve (10) are connected to a main gas inlet valve (12); an end of the main gas inlet valve (12) is connected to a gas outlet (7).

3. A pitting corrosion test device for metal materials in seawater according to claim 1, characterized in that: The flow simulation device comprises an inflow valve (21) connected to a container kettle (1); a centrifugal pump (20) is provided on a pipeline on the right side of the inflow valve (21); a circulation pipeline (19) is provided at the end of the centrifugal pump (20); a flow meter (18) is provided on the circulation pipeline (19); an outflow valve (15) is provided at the end of the circulation pipeline (19); and the outflow valve (15) is connected to the container kettle (1).

4. A pitting corrosion test device for metal materials in seawater according to claim 1, characterized in that: The rotatable sample clamp (5) comprises a total of six sample clamps, and can carry out corrosion tests on six samples simultaneously, and each sample clamp can rotate independently.

5. The pitting corrosion test device for metal materials in seawater according to claim 2, characterized in that: When the No. 1 air intake valve (11) or the No. 2 air intake valve (10) cannot be closed and when the left side of the test device body is not connected to a gas cylinder, the main air intake valve (12) can be closed to prevent the gas from flowing out and causing changes in the test environment parameters.

6. A pitting corrosion test device for metal materials in seawater according to claim 3, characterized in that: A threaded opening (16) is provided on the pipeline between the inlet valve (21) and the centrifugal pump (20), and a screw-in sample clamp (17) is provided in the threaded opening (16), so that corrosion tests of four samples can be carried out simultaneously.

7. A method for testing pitting corrosion of metal materials in seawater, characterized in that: The sample pretreatment makes the sample meet the conditions for pitting corrosion test, and the parameters of the test environment can be changed by operating the test device.

8. A method for testing pitting corrosion of metal materials in seawater according to claim 7, characterized in that: Different types of pitting corrosion tests can be carried out by preparing different test solutions according to different test requirements; the required test gas can be introduced into the container through the test gas delivery unit; the test pressure can be selected through the pressure control unit; the test temperature can be selected through the temperature control unit; and the pitting corrosion test can be carried out in a static or flowing state by selecting sample fixtures in different positions.

9. A method for testing pitting corrosion of metal materials in seawater according to claim 8, characterized in that: The test specimens were coated with epoxy anticorrosive paint so that only the porous surface was exposed to the atmosphere.

10. A method for testing pitting corrosion of metal materials in seawater according to claim 9, characterized in that: A method for calculating the corrosion rate applicable to this test method is provided.

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