JP2013127389A - Corrosion testing device and corrosion testing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corrosion testing device and a corrosion testing method that can conduct a long-time corrosion test even in a high-density-impurity environment.SOLUTION: The corrosion testing device includes: a water storage tank 2 in which high-concentration dissolved oxygen water 3 is reserved; dissolved oxygen concentration adjusting means 14 of adjusting the dissolved oxygen concentration of the high-concentration dissolved oxygen water 3 in the water storage tank; an autoclave 9 in which high-concentration salt water 18 is reserved and a test-piece 19 is dipped in the high-concentration salt water; feed means 17 of feeding the high-concentration dissolved oxygen water into the autoclave; evacuation means 26 of evacuating the interior of the autoclave; dissolved oxygen concentration measuring means 31 of measuring the dissolved oxygen concentration of the high-concentration salt water; and heating means 32 of heating the autoclave.

Description

  The present invention relates to a corrosion test apparatus and a corrosion test method for simulating metal corrosion in a high-temperature water environment at a temperature having a saturated vapor pressure higher than atmospheric pressure, for example, a boiler water environment and a light water reactor environment.

  Normally, in order to predict the degree of corrosion of materials used in boiler water environments or materials used in light water reactor environments, the test specimens are corroded with a hydrostatic or circulating corrosion tester that simulates the boiler environment or light water reactor environment. A corrosion test is performed.

  The hydrostatic corrosion tester defines and adjusts the dissolved oxygen concentration or dissolved hydrogen concentration involved in the corrosion of the test water in the test tank, and adjusts the dissolved oxygen concentration that changes depending on the corrosion reaction of the test piece under test. It has a structure that detects the degree of corrosion by change, and is used when the test time is short or the rate of the corrosion reaction is slow.

  In addition, the circulation type corrosion test apparatus allows water with controlled dissolved oxygen concentration or dissolved hydrogen concentration to flow into an autoclave, which is a sealed pressure vessel, using a pressurizable plunger pump or diaphragm pump. Controls the dissolved oxygen concentration of the test water in the autoclave, and returns the water whose dissolved oxygen concentration has decreased due to the corrosion reaction to the test pieces in the autoclave to the supply tank. Used when speed is high.

  In addition, since the circulation type corrosion test apparatus needs to cool the water heated in the autoclave, for example, it has a heat exchanger that cools the water in the return path using the water in the forward path. Even when testing is performed using pure water and controlling impurities, there is almost no damage to the autoclave or heat exchanger because it is in the ppb order.

  However, for example, when controlling the dissolved oxygen concentration and performing a test with high-temperature water having a high impurity concentration, the autoclave itself is often made of a highly corrosion-resistant alloy such as Hastelloy (registered trademark) or titanium. Circulation loop piping and heat exchangers are rarely made of highly corrosion-resistant alloys. As a result, there is a problem that impurities are concentrated at the stage of cooling the heated high-temperature water, and the piping and the heat exchanger are easily corroded.

  Therefore, when the impurity concentration of water is high, the dissolved oxygen concentration is controlled before the test and the test is often performed with a static water type corrosion tester. Since the oxygen concentration changes with time, there is a problem that the test environment cannot be kept constant.

  In Patent Document 1, after the test water extracted from the test water storage tank is pressurized to a predetermined pressure corresponding to the target saturated gas concentration by the adjustment pump and fed to the dissolved gas adjustment tank, Supply the gas for aeration from the gas supply source to the test water, dissolve the gas for aeration until the saturation concentration corresponding to the pressure of the test water is reached, raise the temperature to the test temperature with a heater, and after the corrosion test A configuration is disclosed in which test water is returned to the test water storage tank via a desalting filter.

JP-A 63-285445

  In view of such circumstances, the present invention provides a corrosion test apparatus and a corrosion test method capable of performing a long-time corrosion test even in a high concentration impurity environment.

  The present invention provides a water storage tank for storing high concentration dissolved oxygen water, a dissolved oxygen concentration adjusting means for adjusting the dissolved oxygen concentration of the high concentration dissolved oxygen water in the water storage tank, and high concentration salt water being stored. An autoclave in which a test piece is submerged in the high-concentration salt water, a feeding means for feeding the high-concentration dissolved oxygen water into the autoclave, a vacuum exhaust means for evacuating the autoclave, and a solution of the high-concentration salt water The present invention relates to a corrosion test apparatus including a dissolved oxygen concentration measuring means for measuring an oxygen concentration and a heating means for heating the autoclave.

  The present invention also includes a step of injecting high-concentration salt water into the autoclave and sinking a test piece in the high-concentration salt water, a step of evacuating the autoclave by vacuum evacuation means, and heating the autoclave by heating means. A step, a step of adjusting the dissolved oxygen concentration of the high-concentration dissolved oxygen water in the water tank by the dissolved oxygen concentration adjusting means, a step of feeding the high-concentration dissolved oxygen water into the autoclave by the feeding means, and a set time When the dissolved oxygen concentration in the high-concentration salt water decreases during the lapse of time, the feeding means has a step of pouring the high-concentration dissolved oxygen water into the high-concentration salt water.

  According to the present invention, a water storage tank in which high-concentration dissolved oxygen water is stored, a dissolved oxygen concentration adjusting means for adjusting the dissolved oxygen concentration in the water storage tank, and high-concentration salt water are stored. And an autoclave in which a test piece is submerged in the high-concentration salt water, a feeding means for feeding the high-concentration dissolved oxygen water into the autoclave, a vacuum exhaust means for evacuating the autoclave, and the high-concentration salt water Since the dissolved oxygen concentration measuring means for measuring the dissolved oxygen concentration and the heating means for heating the autoclave are provided, it is not necessary to circulate the high-concentration salt water, and corrosion of parts can be prevented and the high-concentration salt water can be prevented. By controlling the dissolved oxygen concentration, a long-term corrosion test can be performed while keeping the test environment constant or substantially constant.

  According to the present invention, the step of injecting high-concentration salt water into the autoclave and submerging the test piece in the high-concentration salt water, the step of evacuating the autoclave by a vacuum exhaust means, and the autoclave by the heating means A step of heating, a step of adjusting the dissolved oxygen concentration of the high-concentration dissolved oxygen water in the water tank by a dissolved oxygen concentration adjusting means, a step of feeding the high-concentration dissolved oxygen water into the autoclave by a feeding means, When the dissolved oxygen concentration in the high-concentration salt water decreases when a set time has elapsed, the feeding means has a step of injecting the high-concentration dissolved oxygen water into the high-concentration salt water, so that the high-concentration salt water is circulated. It is possible to prevent the corrosion of parts without losing the effect, and to exhibit an excellent effect that a long-time corrosion experiment is possible.

It is a block diagram which shows the corrosion test apparatus which concerns on the Example of this invention. It is a flowchart explaining the corrosion test based on the Example of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  With reference to FIG. 1, a corrosion test apparatus 1 according to an embodiment of the present invention will be described.

  In FIG. 1, reference numeral 2 denotes a water storage tank, in which high-concentration dissolved oxygen water 3 is stored.

  The water tank 2 is connected to a circulation pipe 4, an oxygen supply pipe 5, a nitrogen supply pipe 6, and an exhaust pipe 7, and is connected to an autoclave 9 described later via a supply pipe 8.

  One end of the circulation pipe 4 is connected to the lower end of the water tank 2, and the other end passes through the top plate of the water tank 2 and extends into the water tank 2, and communicates with the gas part. The circulation pipe 4 is provided with a DO meter (dissolved oxygen concentration measuring instrument) 10, a DH meter (dissolved hydrogen concentration measuring instrument) 11, and a circulation pump 12. The circulation pipe 4, the dissolved oxygen concentration measuring instrument 10, and the dissolved The hydrogen concentration measuring device 11 and the circulation pump 12 constitute a circulation system 13.

  The circulation pump 12 has a function of circulating the high-concentration dissolved oxygen water 3 in the water storage tank 2 through the circulation pipe 4. The dissolved oxygen concentration measuring device 10 has a function of measuring the dissolved oxygen concentration in the high concentration dissolved oxygen water 3 circulating through the circulation pipe 4, and the dissolved hydrogen concentration measuring device 11 circulates through the circulation pipe 4. It has a function of measuring the dissolved hydrogen concentration in the high-concentration dissolved oxygen water 3.

  The oxygen supply pipe 5 is connected to an oxygen supply source (not shown), and the tip penetrates the top plate of the water storage tank 2 and is submerged in the high-concentration dissolved oxygen water 3. It is designed to supply oxygen directly.

  The nitrogen supply pipe 6 is connected to a nitrogen supply source (not shown), and the tip penetrates the top plate of the water tank 2 and is submerged in the high-concentration dissolved oxygen water 3. Nitrogen is supplied directly to

  The exhaust pipe 7 is connected to the top plate of the water tank 2 so that oxygen and nitrogen that are supplied into the high-concentration dissolved oxygen water 3 and are not separated from the water are exhausted to the outside of the water tank 2. It has become.

  The oxygen supply pipe 5, the nitrogen supply pipe 6, the exhaust pipe 7, and the circulation system 13 constitute a dissolved oxygen concentration adjusting means 14.

  The feed pipe 8 is provided with a high-pressure pump 15 and a valve 16, and the high-pressure pump 15 feeds the high-concentration dissolved oxygen water 3 in the water storage tank 2 into the autoclave 9. The valve 16 can close the feed pipe 8. The feeding pipe 8, the high pressure pump 15 and the valve 16 constitute a feeding means 17.

  The autoclave 9 is a sealed pressure vessel made of a highly corrosion-resistant alloy having a predetermined thickness. The autoclave 9 stores high-concentration salt water 18 as test water in which high-concentration impurities are dissolved, A metal test piece 19 is submerged in the high-concentration salt water 18.

  A drain pipe 21 for draining the high-concentration salt water 18 is connected to the autoclave 9, and an exhaust pipe 22 for evacuating the inside of the autoclave 9 is connected to the exhaust pipe 22. A pump 24 is provided, and a pressure gauge 25 for measuring the pressure in the autoclave 9 is provided. The exhaust pipe 22, the valve 23, and the rotary pump 24 constitute a vacuum exhaust means 26.

  The autoclave 9 is provided with a reference electrode 27 immersed in the high-concentration salt water 18 and platinum electrodes 28 and 28 polarized on the cathode side and immersed in the high-concentration salt water 18. The platinum electrodes 28, 28 are electrically connected to a potentiostat (potentiostat) 29, so that the dissolved oxygen concentration in the high-concentration salt water 18 can be measured by the potentiostat 29. The reference electrode 27, the platinum electrodes 28 and 28, and the potentiostat 29 constitute a dissolved oxygen concentration measuring means 31.

  Further, a heater 32 is provided around the autoclave 9 as heating means for surrounding the autoclave 9.

  Next, a corrosion test using the corrosion test apparatus 1 will be described using the flowchart of FIG. In the corrosion test in the present embodiment, the dissolved hydrogen concentration measuring instrument 11 is not used.

  STEP: 01 When performing a corrosion test using the corrosion test apparatus 1, first, a predetermined amount, for example, 1 L of the high-concentration salt water 18 is injected so that the autoclave 9 does not become full, and the high-concentration salt water 18 is injected into the high-concentration salt water 18. After the test piece 19 is submerged, the autoclave 9 is closed.

  (Step 02) After the autoclave 9 is airtightly closed, the valve 23 is opened and the rotary pump 24 is driven to evacuate the autoclave 9.

  (Step 03) After evacuating the autoclave 9, the valve 23 is closed and the autoclave 9 is heated by the heater 32. Due to the heating of the heater 32, the inside of the autoclave 9 is saturated at a high temperature, the temperature of the high-concentration salt water 18 rises to, for example, 290 ° C., and the pressure in the autoclave 9 rises to, for example, 7.5 MPa.

  Note that the heating of the autoclave 9 at STEP: 03 may be performed in parallel with STEP: 01 or STEP: 02 in order to shorten the time.

  At this time, the potentiostat 29 is operated, and the saturation value of the cathode current density is measured by the potentiostat 29, and the saturation value of the cathode current density is measured to measure the diffusion limit current density of oxygen, The dissolved oxygen concentration of the high-concentration salt water 18 is measured.

  (Step 04) Next, the dissolved oxygen concentration of the high-concentration dissolved oxygen water 3 in the water storage tank 2 is adjusted. When oxygen is supplied into the high-concentration dissolved oxygen water 3 from the oxygen supply pipe 5, the dissolved oxygen concentration in the high-concentration dissolved oxygen water 3 increases, and the high-concentration dissolved oxygen from the nitrogen supply pipe 6. By supplying nitrogen into the water 3, the dissolved oxygen concentration in the high-concentration dissolved oxygen water 3 is lowered, and the circulating pump 12 is driven to cause the dissolved oxygen concentration measuring instrument 10 to dissolve oxygen. By supplying oxygen and nitrogen while measuring the concentration, the high-concentration dissolved oxygen water 3 is set to a predetermined dissolved oxygen concentration, for example, 32 ppm.

  The adjustment of the dissolved oxygen concentration of the high-concentration dissolved oxygen water 3 in STEP: 04 may be performed in parallel with STEP: 01 to STEP: 03 in order to shorten the time.

  (Step 05) After adjusting the dissolved oxygen concentration of the high-concentration dissolved oxygen water 3, the valve 16 is opened and the high-pressure pump 15 is driven to bring the high-concentration dissolved oxygen water 3 into the autoclave 9 at high temperature and high pressure. To send.

  STEP: 06 The high-concentration dissolved oxygen water 3 was fed, and it was confirmed by the potentiostat 29 that the dissolved oxygen concentration of the high-concentration salt water 18 reached a set value in a corrosion test, for example, 0.2 ppm. Thereafter, the valve 16 is closed and the high-pressure pump 15 is stopped. Thus, the preparation for the corrosion test on the test piece 19 is completed, and the corrosion test is started. The chloride concentration of the high-concentration brine 18 at the start of the corrosion test is, for example, 100 ppm.

  STEP: 07 When a preset time, for example, 24 hours has elapsed after the start of the corrosion test, the current dissolved oxygen concentration of the high-concentration salt water 18 is measured by the potentiostat 29.

  (Step 08) When the dissolved oxygen concentration of the high-concentration salt water 18 is measured, it is then determined whether or not a preset corrosion test time, for example, 500 hours has elapsed.

  STEP: 09 If it is determined that the corrosion test time has not elapsed in STEP 08, whether or not the dissolved oxygen concentration of the high-concentration salt water 18 measured next is equal to the set value, that is, in this example. In this case, it is determined whether or not the concentration is 0.2 ppm. When the measured dissolved oxygen concentration of the high-concentration salt water 18 coincides with the set value, the processing of STEP 07 is performed again.

  STEP: 10 The dissolved oxygen concentration of the high-concentration salt water 18 does not match the set value in STEP: 09, that is, the measured dissolved oxygen concentration of the high-concentration salt water 18 is, for example, 0.1 ppm, which is less than 0.2 ppm. When it is determined that the high-pressure pump 15 is driven, the high-concentration dissolved oxygen water 3 in the water storage tank 2 is introduced into the autoclave 9 through the supply pipe 8. A predetermined amount, for example, 3.1 mL of water is injected.

  The dissolved oxygen concentration of the high-concentration salt water 18 is recovered from 0.1 ppm to 0.2 ppm by pouring the high-concentration dissolved oxygen water 3, but 3.1 mL of the high-concentration salt water 18 is added to 3.1 mL of the high-concentration salt water 18. Since only the concentration of dissolved oxygen water 3 is poured, the chloride concentration in the high-concentration salt water 18 is reduced only from 100 ppm to only 99.7 ppm, and the influence on the corrosion test due to the chloride concentration reduction is extremely small. .

  After injecting the high-concentration dissolved oxygen water 3 into the high-concentration salt water 18 at STEP: 10, the processing of STEP: 07 is performed again, and it is judged that the corrosion test time has elapsed at STEP: 08. The corrosion test ends.

  After completion of the corrosion test, the valve 23 is opened to reduce the pressure in the autoclave 9, the high-concentration salt water 18 is drained from the drain pipe 21, the autoclave 9 is opened, and the autoclave 9 is opened. The test piece 19 is taken out.

  As described above, since the corrosion test apparatus 1 in the present embodiment is a static water type corrosion test apparatus, the high-concentration salt water 18 is always stored in the autoclave 9 and the high-concentration salt water 18 is circulated. Therefore, it is possible to prevent the pipe and the heat exchanger from being corroded.

  Further, the corrosion test apparatus 1 in this embodiment can inject the high-concentration dissolved oxygen water 3 into the high-concentration salt water 18 during the corrosion test. The dissolved oxygen concentration can be kept constant or substantially constant, and a long-time corrosion test can be performed.

  Therefore, by using the corrosion test apparatus 1 of the present embodiment, pipes and the like are not corroded even in a corrosion test under a concentrated impurity environment, and the test environment is kept constant or substantially constant. A time corrosion test can be performed.

DESCRIPTION OF SYMBOLS 1 Corrosion test apparatus 2 Water storage tank 3 High concentration dissolved oxygen water 5 Oxygen supply pipe 6 Nitrogen supply pipe 8 Supply pipe 9 Autoclave 13 Circulation system 14 Dissolved oxygen concentration adjustment means 17 Supply means 18 High concentration salt water 19 Test piece 26 Vacuum exhaust Means 31 Dissolved oxygen concentration measurement means 32 Heater

Claims (2)

  A water storage tank for storing high-concentration dissolved oxygen water, a dissolved oxygen concentration adjusting means for adjusting a dissolved oxygen concentration of the high-concentration dissolved oxygen water in the water storage tank, a high-concentration salt water being stored and the high-concentration salt water An autoclave in which a test piece is submerged, a feeding means for feeding the high-concentration dissolved oxygen water into the autoclave, a vacuum exhaust means for evacuating the autoclave, and a dissolved oxygen concentration of the high-concentration salt water are measured. A corrosion test apparatus comprising: a dissolved oxygen concentration measuring means for heating; and a heating means for heating the autoclave.   Injecting high-concentration salt water into the autoclave and sinking a test piece in the high-concentration salt water; evacuating the autoclave with vacuum evacuation means; heating the autoclave with heating means; A step of adjusting the dissolved oxygen concentration of the high concentration dissolved oxygen water in the autoclave by the dissolved oxygen concentration adjusting means, a step of feeding the high concentration dissolved oxygen water into the autoclave by the feeding means, and the high concentration when the set time elapses. A corrosion test method, comprising: the step of feeding the high-concentration dissolved oxygen water into the high-concentration salt water when the dissolved oxygen concentration in the salt water is lowered.

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