Corrosion testing apparatus and corrosion testing method

Abstract

To provide a corrosion test device and corrosion test method, which allow for conducting a test simulating an environment with a corrosive fluid, such as condensed ammonia water, flowing through piping.SOLUTION: A corrosion test device 1 with a first test line 20, second test line 30, and third test line 40 for allowing a corrosion test solution to flow therethrough is provided. A supply line 10 connected upstream of the test lines is provided with a flow rate adjustment valve 11 for adjusting the flow rate of the corrosion test solution distributed to the test lines, and the test lines are provided with object-under-test connection units 22, 32, 42, respectively, for removably connecting a tubular object under test.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a corrosion test apparatus and a corrosion test method.

Background Art

[0002] Pipes used in factory wastewater treatment facilities and the like are required to have excellent corrosion resistance. For example, in a coke factory, the exhaust gas discharged from a coke oven is treated with aqueous ammonia (ammonia water). The ammonia water containing harmful substances such as ammonia and hydrogen sulfide after exhaust gas treatment is treated in a denitrification facility equipped with a distillation column or the like, and ammonia and the like are removed. The condensed ammonia water obtained by condensing the steam distilled from the distillation column of the denitrification facility is particularly highly corrosive, and it is necessary to ensure excellent corrosion resistance for the pipes.

[0003] Regarding metal members used in a highly corrosive environment, it has been proposed to conduct a test simulating the corrosive environment to predict the degree of progress of corrosion Patent Document 1 discloses a corrosion test apparatus for testing the stress corrosion cracking resistance of a metal material by introducing an inert gas and a corrosive gas into a test solution while immersing a specimen made of the metal material in the test solution. Patent Document 2 discloses an apparatus for measuring the corrosion rate as a corrosion test apparatus for measuring atmospheric corrosion. The apparatus fills a test tank in which a metal sample is disposed with an electrolyte solution, contacts a pressure element with the metal sample, and measures the corrosion rate by performing electrochemical measurement while moving the pressure element.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, corrosion testing apparatuses such as those described in Patent Documents 1 and 2 are designed to test corrosion of metal materials caused by corrosive gases or atmospheric corrosion, and do not simulate environments in which corrosive liquids such as condensed ammonia water flow through pipes.

[0006] The present invention aims to provide a corrosion testing apparatus and a corrosion testing method that can perform tests simulating an environment in which corrosive liquids such as condensed ammonium solution flow through pipes. [Means for solving the problem]

[0007] The present invention includes the following embodiments. [1] A test line through which the corrosion test solution is distributed, The system includes a flow control valve for adjusting the flow rate of the corrosion test solution circulating in the test line, The aforementioned test line is a corrosion testing apparatus equipped with a test specimen connection section to which tubular test specimens are detachably connected. [2] comprising a supply line for supplying the corrosion test solution, and three test lines branching off from the supply line, The corrosion testing apparatus according to [1], wherein each of the three aforementioned test lines is provided with a check valve. [3] Each of the three test lines is provided with a dissolved oxygen meter for measuring the dissolved oxygen concentration of the corrosion test solution flowing through each test line, as described in [2]. [4] The corrosion test apparatus according to [2] or [3], wherein each of the three test lines is provided with a thermometer for measuring the temperature of the corrosion test solution flowing through each test line. [5] An oxygen supply line that supplies oxygen-containing gas to one of the three test lines, A corrosion testing apparatus according to any one of [2] to [4], comprising a flow indicator and a pressure indicator provided in the oxygen supply line for measuring the flow rate and pressure, respectively, of the oxygen-containing gas to be supplied. [6] A deoxidizing agent supply line that supplies a deoxidizing agent-containing liquid to one of the three test lines, A pump provided in the oxygen absorber supply line for pumping the oxygen absorber-containing liquid toward the test line, A corrosion testing apparatus according to any one of [2] to [5], comprising: an oxygen absorber storage tank connected to the opposite side of the oxygen absorber supply line from the test line, for storing the oxygen absorber-containing liquid. [7] The corrosion testing apparatus according to any one of [1] to [6], wherein two or more test specimens of different diameters are connected to the test line by a joint at the test specimen connection section. A corrosion test method using a corrosion test apparatus described in any of [8][1] to [7], A corrosion test method comprising connecting a tubular test specimen to the test specimen connection section of the test line, circulating a corrosion test solution through the test line, and measuring the corrosion rate of the inner surface of the test specimen. [Effects of the Invention]

[0008] According to the present invention, a corrosion testing apparatus and a corrosion testing method can be provided that can perform tests simulating an environment in which corrosive liquids such as condensed ammonium solution flow through pipes. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing a corrosion testing apparatus as an example of an embodiment. [Figure 2] This is a schematic diagram showing an example of the connection configuration of test specimens at the test specimen connection section of a test line. Figure 2(A) shows a configuration in which one test specimen is connected, and Figure 2(B) shows a configuration in which two test specimens of different diameters are connected. [Figure 3] This graph summarizes the corrosion test results for Examples 1-3, plotting the corrosion rate against the flow rate of condensed ammonia. [Figure 4] This graph summarizes the corrosion test results from Examples 4 and 5, plotting the corrosion rate against the flow rate of condensed ammonia. [Modes for carrying out the invention]

[0010] [Corrosion testing equipment] The corrosion test apparatus of the present invention includes a test line through which a corrosion test solution flows, and a flow rate adjustment valve for adjusting the flow rate of the corrosion test solution flowing through the test line, and the test line is an apparatus including a test body connection portion to which a tubular test body is detachably connected. The corrosion test apparatus of the present invention can be suitably used for corrosion tests of piping through which corrosive liquids such as condensed ammonia water flow.

[0011] Hereinafter, an example of the corrosion test apparatus of the present invention will be described with reference to the drawings. In addition, the dimensions and the like of the drawings illustrated in the following description are examples, and the present invention is not necessarily limited thereto, and can be appropriately modified and implemented without changing the gist thereof.

[0012] As shown in FIG. 1, the corrosion test apparatus 1 of the present embodiment includes a supply line 10, a first test line 20, a second test line 30, a third test line 40, an oxygen supply line 50, and a deoxidizer supply line 60.

[0013] The first test line 20, the second test line 30, and the third test line 40 are connected to the downstream side of the supply line 10 so as to branch into three from the supply line 10. The oxygen supply line 50 is connected to the downstream side of the branch point of the second test line 30 with the supply line 10. The deoxidizer supply line 60 is connected to the downstream side of the branch point of the third test line 40 with the supply line 10.

[0014] The pipes constituting the supply line 10, the first test line 20, the second test line 30, the third test line 40, the oxygen supply line 50, and the deoxidizer supply line 60 are not particularly limited, and known pipes capable of feeding a corrosion test solution can be used. Examples of the pipe material include stainless steel, titanium, and Hastelloy.

[0015] The supply line 10 is a line for supplying a corrosion test solution to each of the first test line 20, the second test line 30, and the third test line 40. The connection on the upstream side of the supply line 10 is not particularly limited as long as it can supply the corrosion test solution. For example, the upstream side of the supply line 10 can be connected to the piping of the equipment to be tested. Specifically, an example is a mode of connecting to the piping of a denitrification facility that removes ammonia and the like from the diluted water obtained by treating the exhaust gas discharged from a coke oven. A mode of connecting to the piping through which condensed water in which ammonia gas is dissolved at a high concentration, that is, condensed diluted ammonia water, flows is preferable. Thus, if the upstream side of the supply line 10 is connected to the piping of the actual machine, it is possible to suppress a change in the composition of the corrosion test solution due to contact with the atmosphere between sampling from the actual machine and using it for the test.

[0016] A flow rate adjustment valve 11 is provided in the supply line 10. By adjusting the flow rate of the corrosion test solution supplied through the supply line 10 with the flow rate adjustment valve 11, the flow rate of the corrosion test solution flowing through the tubular test body installed in each test line can be adjusted.

[0017] The first test line 20, the second test line 30, and the third test line 40 are lines for measuring the corrosion rate of a tubular test body (hereinafter, also simply referred to as "test body") to be tested, and the corrosion test solution supplied from the supply line 10 flows through them. A check valve 21 is provided on the downstream side of the branch point of the first test line 20 with the supply line 10. Similarly, a check valve 31 is provided on the downstream side of the branch point of the second test line 30 with the supply line 10, and a check valve 41 is provided on the downstream side of the branch point of the third test line 40 with the supply line 10. Thus, by providing check valves in each test line, it is possible to suppress the reverse flow of the corrosion test solution flowing through each test line and its inflow into other test lines.

[0018] A test body connection part 22 to which the test body is detachably connected is provided on the downstream side of the check valve 21 of the first test line 20. The configuration of the test specimen connection section 22 is not particularly limited as long as it can connect to the test specimen. For example, in the test specimen connection section 22, as shown in Figure 2(A), the test specimen 80 and the piping constituting the first test line 20 can be connected by a joint 70.

[0019] Alternatively, as shown in Figure 2(B), a joint 71 capable of connecting pipes of different diameters may be used to connect multiple test specimens 80 of different diameters to each other, and these specimens may be connected to the piping constituting the first test line 20. By adopting the configuration shown in Figure 2(B), test specimens of different diameters can be tested simultaneously. Therefore, the flow velocity dependence of the corrosion rate can be easily investigated in a short time. Furthermore, the test specimen connection section 22 may be connected to the first test line 20 with three or more test specimens linked together.

[0020] Downstream of the check valve 31 in the second test line 30, there is a test specimen connection section 32 to which a test specimen can be detachably connected. Similarly, downstream of the check valve 41 in the third test line 40, there is a test specimen connection section 42 to which a test specimen can be detachably connected. The description of the specimen connection section 22 of the first test line 20 also applies to the specimen connection section 32 of the second test line 30 and the specimen connection section 42 of the third test line 40.

[0021] As shown in Figure 1, the first test line 20 is equipped with a dissolved oxygen meter 23 and a thermometer 24. Similarly, the second test line 30 is equipped with a dissolved oxygen meter 33 and a thermometer 34, and the third test line 40 is equipped with a dissolved oxygen meter 43 and a thermometer 44. This allows for the measurement of the dissolved oxygen concentration and temperature of the corrosion test solution flowing through each test line.

[0022] The configuration in which a dissolved oxygen meter is installed in a test line is not particularly limited. For example, one configuration may involve providing a removable lid on the piping of the test line and inserting the dissolved oxygen meter into the portion where the lid has been removed. The manner in which a thermometer is installed on the test line is not particularly limited, and examples include the same manner as in which a dissolved oxygen concentration meter is installed on the test line.

[0023] The oxygen supply line 50 is a line that supplies oxygen-containing gas to the second test line 30. By blowing oxygen-containing gas into the corrosion test solution flowing through the second test line 30 via the oxygen supply line 50, the dissolved oxygen (DO) concentration of the corrosion test solution flowing through the second test line 30 can be increased.

[0024] In this example, the oxygen supply line 50 is equipped with a flow indicator 51 and a pressure indicator 52. This allows for the measurement of the flow rate and pressure of the oxygen-containing gas supplied through the oxygen supply line 50. In one example shown in Figure 1, a flow rate adjustment valve 53 is provided near the confluence point of the oxygen supply line 50 with the second test line 30. This allows for adjustment of the flow rate of oxygen-containing gas injected into the corrosion test solution flowing through the second test line 30.

[0025] In this example, a connection port 54 is provided on the oxygen supply line 50 opposite the second test line, to which a hose for supplying oxygen-containing gas is connected. For example, by connecting a blower to the end of the hose connected to the connection port 54, air can be supplied as the oxygen-containing gas. Alternatively, an oxygen storage tank for storing oxygen gas may be connected to the end of the hose connected to the connection port 54 to supply oxygen gas. Furthermore, on the side of the oxygen supply line 50 opposite the second test line, a means for supplying oxygen-containing gas, such as a blower, may be directly connected to the piping without using a hose.

[0026] The oxygen absorber supply line 60 is a line that supplies the oxygen absorber-containing liquid to the third test line 40. The end of the oxygen absorber supply line 60 opposite the third test line 40 is connected to an oxygen absorber storage tank 61 that stores the oxygen absorber-containing liquid. The oxygen absorber supply line 60 is also equipped with a pump 62 that pumps the oxygen absorber-containing liquid towards the third test line 40. This allows the oxygen absorber-containing liquid to be supplied to the third test line 40 through the oxygen absorber supply line 60, thereby lowering the DO concentration of the corrosion test solution flowing through the third test line 40.

[0027] In one example shown in Figure 1, a flow rate adjustment valve 63 is provided between the oxygen absorber storage tank 61 and the pump 62 in the oxygen absorber supply line 60. This allows for adjustment of the flow rate of the oxygen absorber-containing liquid injected into the corrosion test solution flowing through the second test line 30.

[0028] Any oxygen absorber that can lower the DO concentration of the corrosion test solution is acceptable, such as sodium sulfite and hydrazine. Of these, sodium sulfite is preferred from a safety standpoint. One oxygen absorber may be used alone, or two or more may be used in combination.

[0029] Any solvent that does not affect the corrosion test can be used in the oxygen absorber-containing solution; for example, pure water can be used.

[0030] In terms of maintaining dissolved oxygen removal capacity, the content of the oxygen absorber in the oxygen absorber-containing liquid is preferably 20% by mass or more, and more preferably 22% by mass or more, based on the total mass of the oxygen absorber-containing liquid.

[0031] As described above, the corrosion testing apparatus 1 is equipped with a test line to which tubular test specimens can be detachably connected, and the flow rate of the corrosion test solution flowing through the test line can be adjusted by the flow rate adjustment valve 11. Therefore, corrosion tests can be conducted that simulate the corrosion environment in actual equipment.

[0032] Furthermore, in the corrosion testing apparatus 1, the supply line 10 branches off to the first test line 20, the second test line 30, and the third test line 40, allowing oxygen-containing gas to be supplied to the second test line 30 and an oxygen scavenger to the third test line 40. Therefore, in each test line, corrosion tests using the target corrosion test solution, corrosion tests using a corrosion test solution with a high DO concentration, and corrosion tests using a corrosion test solution with a low DO concentration can be performed simultaneously using the same corrosion test solution. This makes it possible to conduct corrosion tests with corrosion test solutions of various DO concentrations while suppressing changes in the composition of the corrosion test solution due to contact with the atmosphere, etc., and to explore the conditions under which sufficient corrosion resistance can be obtained.

[0033] [Corrosion Test Method] The corrosion testing method of the present invention is a method for performing a corrosion test using the corrosion testing apparatus of the present invention, wherein a tubular test specimen is connected to the test specimen connection part of the test line, and a corrosion test solution is circulated through the test line to measure the corrosion rate on the inner surface of the test specimen.

[0034] The corrosion test solution is not particularly limited, and examples include ammonia, hydrogen sulfide, and other harmful substances contained in ammonia water after processing exhaust gas discharged from a coke oven, and condensed ammonia water obtained by processing that ammonia water in a distillation column of a denitrification facility.

[0035] The tubular test specimen is not particularly limited; for example, a test specimen made of the same material as piping used in various facilities where corrosion may occur can be used. Specifically, examples include piping made of materials such as stainless steel, titanium, and Hastelloy.

[0036] For example, in stainless steel piping, when an aqueous solution such as condensed ammonium solution flows through it, the chromium in the piping reacts with oxygen and water, forming a Cr oxide film (passivation film) several nanometers thick on the inner surface of the piping, which is known to provide corrosion resistance. This Cr oxide film can be removed by the shear force of the liquid flowing through the piping, but it can also be regenerated by the oxygen and water in the liquid. Therefore, the corrosion resistance of stainless steel piping is affected by the flow velocity (shear rate) of the liquid flowing through the piping and the DO concentration of the liquid. Furthermore, if hydrogen sulfide such as condensed ammonium solution is present, the formation of sulfide scale on the Cr oxide film adversely affects the regeneration rate of the Cr oxide film. Due to these factors, if the regeneration rate of the Cr oxide film exceeds the removal rate, excellent corrosion resistance is obtained, and if the removal rate exceeds the regeneration rate, corrosion resistance decreases.

[0037] For example, in a corrosion test method using corrosion testing apparatus 1, the flow rate of the corrosion test solution flowing through each test line can be adjusted by the flow rate adjustment valve 11 to investigate the dependence of the corrosion rate of the test specimen on the flow velocity of the corrosion test solution. Furthermore, by conducting corrosion tests with corrosion test solutions of different DO concentrations in the first test line 20, the second test line 30, and the third test line 40, the dependence of the corrosion rate of the test specimen on the DO concentration of the corrosion test solution can be investigated.

[0038] Furthermore, the present invention is not limited to the corrosion testing apparatus 1 and the corrosion testing method using the corrosion testing apparatus 1 described above. For example, the corrosion testing apparatus of the present invention may be an apparatus with one or two test lines, or an apparatus equipped with four or more test lines.

[0039] Furthermore, the corrosion testing apparatus of the present invention may be an apparatus equipped with only one of the following: a test line that performs corrosion testing without adding oxygen-containing gas and oxygen-absorbing agent-containing liquid to the target corrosion test solution; a test line that performs corrosion testing by adding oxygen-containing gas to the corrosion test solution; and a test line that performs corrosion testing by adding oxygen-absorbing agent-containing liquid to the corrosion test solution. Alternatively, it may be an apparatus equipped with any combination of two of these.

[0040] The corrosion testing apparatus of the present invention may be one or both of the following: a dissolved oxygen meter and a thermometer in the test line. Furthermore, without departing from the spirit of the present invention, the components in the above embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Examples]

[0041] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description.

[0042] [Corrosion rate] The weight change of the test specimen before and after the corrosion test was measured using an electronic balance. From the weight change and the contact area of ​​the test specimen with the test liquid (internal surface area of ​​the test specimen), the thickness of the test specimen decreased in each corrosion test was determined and converted to the thickness per year to determine the corrosion rate.

[0043] [Example 1] Using the corrosion test apparatus 1 illustrated in Figure 1, stainless steel (SUS316L) test specimens (nominal diameter: 20A) were placed in each test line, and condensed amphibious water was flowed at a flow rate of 0.142 m / s to measure the corrosion rate. Air was supplied as the oxygen-containing gas to the second test line, and a 22 wt% sodium sulfite aqueous solution was supplied as the oxygen-absorbing agent-containing liquid to the third test line. The DO concentration of the condensed amphibious water in the first test line was 65 ppb, the DO concentration of the condensed amphibious water in the second test line was 4,266 ppb, and the DO concentration of the condensed amphibious water in the third test line was 4 ppb. The test durations (time during which condensed ammonium solution was flowed through the test specimen) were set to 192 hours and 384 hours. The results are shown in Table 1.

[0044] [Table 1]

[0045] As shown in Table 1, the DO concentration of condensed ammonium solution could be controlled in each test line. Furthermore, no corrosion of the test specimens was observed at any of the DO concentrations.

[0046] [Example 2] The corrosion rate was measured in the same manner as in Example 1, except that the conditions shown below were changed. One test specimen with a nominal diameter of 20A and two test specimens with a nominal diameter of 8A were connected and installed in each test line, and the flow velocities of the condensed ammonia water were adjusted to 0.213 m / s, 1.66 m / s, and 1.66 m / s, respectively. The DO concentration of the condensed ammonia water in the first test line was controlled to 8 ppb, the DO concentration in the second test line to 5,650 ppb, and the DO concentration in the third test line to 0 ppb. The test duration was 71.5 hours. The results are shown in Table 2.

[0047] [Table 2]

[0048] As shown in Table 2, in all test lines, the smaller the nominal diameter and the higher the flow rate of condensed ammonia water, the higher the corrosion rate of the test specimen.

[0049] [Example 3] The corrosion rate was measured in the same manner as in Example 1, except that the conditions shown below were changed. Four test specimens with nominal diameters of 20A, 15A, 10A, and 8A were connected and installed in each test line. The flow velocities of the condensed ammonia water in each test line were adjusted to 0.213 m / s, 0.522 m / s, 0.873 m / s, and 1.66 m / s, respectively. The DO concentration of the condensed ammonia water in the first test line was controlled to 1,161 ppb, in the second test line to 5,560 ppb, and in the third test line to 42 ppb. The test duration was 102 hours. The results are shown in Table 3.

[0050] [Table 3]

[0051] As shown in Table 3, in the first and second test lines, where the DO concentration of the condensed ammonia water was high, the corrosion rate of the test specimens was low regardless of the nominal diameter of the specimen, i.e., regardless of the flow rate of the condensed ammonia water. On the other hand, in the third test line, where the DO concentration of the condensed ammonia water was low, the corrosion rate of the test specimens was higher as the nominal diameter of the specimen and the flow rate of the condensed ammonia water increased.

[0052] Figure 3 shows a graph summarizing the corrosion test results for Examples 1-3, plotting the corrosion rate against the flow velocity of condensed ammonia. As shown in Figure 3, under conditions where the flow velocity of condensed ammonia water was 0.82 m / s or less, regeneration of the Cr oxide film was dominant over removal, and excellent corrosion resistance was exhibited, preventing corrosion from progressing regardless of the DO concentration of the condensed ammonia water. On the other hand, under conditions where the flow velocity of condensed ammonia water was greater than 0.82 m / s, corrosion progressed when the DO concentration of the condensed ammonia water was less than 100 ppb, and the corrosion rate tended to increase as the flow velocity of the condensed ammonia water increased or the DO concentration of the condensed ammonia water decreased.

[0053] [Example 4] The material of the test specimen was changed to titanium (Ti), and the corrosion rate was measured in the same manner as in Examples 1 to 3. The results were summarized, and a graph plotting the corrosion rate against the flow velocity of condensed ammonia is shown in Figure 4.

[0054] [Example 5] The material of the test specimen was changed to Hastelloy, and the corrosion rate was measured in the same manner as in Examples 1 to 3. The results were summarized, and a graph plotting the corrosion rate against the flow rate of condensed ammonia is shown in Figure 4.

[0055] As shown in Figure 4, when the test specimen was made of titanium or Hastelloy, the corrosion rate was extremely low regardless of the flow rate and DO concentration of the condensed ammonia water. [Explanation of Symbols]

[0056] 1...Corrosion testing apparatus, 10...Supply line, 11...Flow rate control valve, 20...First test line, 30...Second test line, 40...Third test line, 21, 31, 41...Check valves, 22, 32, 42...Test specimen connection parts, 23, 33, 43...Dissolved oxygen concentration meter, 24, 34, 44...Thermometer, 50...Oxygen supply line, 51...Flow rate indicator, 52...Pressure indicator, 54...Connection port, 60...Oxygen absorber supply line, 61...Oxygen absorber storage tank, 62...Pump, 70, 71...Fittings, 80...Test specimen.

Claims

1. A supply line for supplying corrosion test solution, Three test lines branched off from the aforementioned supply line, A flow control valve for adjusting the flow rate of the corrosion test solution flowing through each of the three aforementioned test lines, Each of the three aforementioned test lines is provided with a check valve, An oxygen supply line that supplies oxygen-containing gas to one of the three test lines, The oxygen supply line is provided with a flow indicator and a pressure indicator, which measure the flow rate and pressure of the oxygen-containing gas to be supplied, respectively. The three aforementioned test lines are equipped with test specimen connectors to which tubular test specimens are detachably connected, and the apparatus is a corrosion testing device.

2. The corrosion testing apparatus according to claim 1, wherein each of the three test lines is provided with a dissolved oxygen meter for measuring the dissolved oxygen concentration of the corrosion test solution flowing through each test line.

3. The corrosion testing apparatus according to claim 1 or 2, wherein each of the three test lines is provided with a thermometer for measuring the temperature of the corrosion test solution flowing through each test line.

4. In the corrosion testing apparatus according to any one of claims 1 to 3, A deoxidizing agent supply line that supplies a deoxidizing agent-containing liquid to one of the two test lines that does not have an oxygen supply line that supplies oxygen-containing gas to the aforementioned test line, A pump provided in the oxygen absorber supply line for pumping the oxygen absorber-containing liquid toward the test line, A corrosion testing apparatus comprising: an oxygen absorber storage tank connected to the oxygen absorber supply line on the opposite side from the test line, for storing the oxygen absorber-containing liquid.

5. The corrosion testing apparatus according to any one of claims 1 to 4, wherein at the test specimen connection section, two or more test specimens of different diameters are connected to the test line by a joint.

6. A corrosion test method using a corrosion test apparatus according to any one of claims 1 to 5, A corrosion test method comprising connecting a tubular test specimen to the test specimen connection section of the test line, circulating a corrosion test solution through the test line, and measuring the corrosion rate of the inner surface of the test specimen.

Images