JP2013011564A - Corrosion fatigue test apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corrosion fatigue test apparatus capable of accurately evaluating corrosion fatigue characteristics of a metallic material in a marine environment.SOLUTION: A corrosion fatigue test apparatus 10 includes: a test apparatus body 14 for applying a repeated load to a metal specimen 12; a testing cell 20 filled with a corrosive liquid 22 in which the metal specimen is immersed; a specimen simulated electrode 28 and a reference electrode 30 arranged in the testing cell to be immersed in the corrosive liquid; a potential measuring instrument 32; a corrosive liquid storage container 40; corrosive liquid conveyance means 44, 46, 48; and control means 60. The corrosive liquid includes artificial sea water stored in the corrosive liquid storage container and algae propagated by marine creatures 56 put in the artificial sea water. The control means controls conveyance of the corrosive liquid to the testing cell and apples a repeated load to the metal specimen while making an immersion potential of the metal specimen be the same as a reference immersion potential obtained by previously immersing a metal electrode made of the same material as that of the metal specimen in natural sea water.

Description

  The present invention relates to a corrosion fatigue test apparatus, and more particularly to a corrosion fatigue test apparatus for evaluating the corrosion fatigue of a metal material in a marine environment.

  In recent years, many metal structures and metal devices are used in the marine environment, and it is necessary to evaluate the corrosion fatigue resistance characteristics of metal materials in the marine environment. Metal materials, for example, stainless steel, are used in various corrosive environments because of the base protection (excellent corrosion resistance) of the passive film made of Cr oxide formed on the surface. However, if chloride is present in the environment where stainless steel is used, the passive film is broken and local corrosion such as pitting corrosion and crevice corrosion occurs. Then, corrosion fatigue occurs and progresses from the point where pitting corrosion or crevice corrosion occurs.

  In Non-Patent Document 1, a 2.5% Mo-containing high-strength austenitic stainless steel developed for use in a marine environment or the like is subjected to a corrosion fatigue test in a 3% NaCl aqueous solution. It is described that it is relatively small.

Shoichiro Ehara et al., “Corrosion Fatigue Behavior of High Strength Austenitic Stainless Steel Containing 2.5% Mo”, Proceedings of the 30th Fatigue Symposium (October 28-30, 2010), Japan Society for Materials Science Fatigue Division Committee Pages 67-70

  By the way, the conventional corrosion fatigue property evaluation of a metal material under the marine environment is performed using artificial seawater as shown in Non-Patent Document 1 and the like. However, in an actual marine environment, microorganisms such as algae adhere to the surface of a metal structure or metal device. If algae adheres to a metal structure or metal equipment immersed in natural seawater, the immersion potential of the part where the algae adheres becomes higher, causing local corrosion such as pitting corrosion and crevice corrosion. It becomes easy to do.

  When evaluating the corrosion fatigue of metal materials using artificial seawater, the artificial seawater does not contain microorganisms such as algae, so the corrosion fatigue characteristics of metal materials in the marine environment may not be evaluated accurately. There is.

  Accordingly, an object of the present invention is to provide a corrosion fatigue test apparatus capable of more accurately evaluating the corrosion fatigue characteristics of a metal material in a marine environment.

  A corrosion fatigue test apparatus according to the present invention is a corrosion fatigue test apparatus for evaluating the corrosion fatigue of a metal material. The test apparatus main body applies a repeated load to a metal test piece, and is disposed in the test apparatus main body. A test cell in which a corrosive solution into which the test piece is immersed is placed, and the corrosive solution includes artificial seawater containing sodium chloride, and the immersion potential of the metal test piece immersed in the corrosive solution is naturally increased in advance. It is characterized in that a repeated load is applied to the metal test piece at the same potential as a reference immersion potential obtained by immersing a metal electrode formed of the same material as the metal test piece in seawater.

  A corrosion fatigue test apparatus according to the present invention is a test piece simulation electrode that is disposed in the test cell so as to be immersed in the corrosion solution, and is formed of the same material as the metal test piece, and the corrosion solution in the test cell. A reference electrode immersed in the electrode, a potential measuring instrument connected to the test piece simulation electrode and the reference electrode, a corrosive liquid storage container storing the corrosive liquid, and the corrosive liquid storage container Control means for controlling the corrosive liquid transporting means for transporting the corrosive liquid to the test cell, the test apparatus main body, the potential measuring instrument, and the corrosive liquid transporting means, and the corrosive liquid includes: The artificial seawater stored in a corrosive liquid storage container, and algae propagated by marine organisms stored in the artificial seawater, the control means controls the transport of the corrosive liquid to the test cell, The metal test immersed in the corrosive liquid. The immersion potential of the piece may be set to the same potential as the reference immersion potential obtained by previously immersing a metal electrode made of the same material as that of the metal test piece in natural seawater, and a repeated load may be applied to the metal test piece. preferable.

  A corrosion fatigue test apparatus according to the present invention is a test piece simulation electrode that is disposed in the test cell so as to be immersed in the corrosion solution, and is formed of the same material as the metal test piece, and the corrosion solution in the test cell. A reference electrode soaked in the electrode, a potential measuring instrument connected to the test piece simulation electrode and the reference electrode, an artificial seawater storage container storing the artificial seawater, and the artificial seawater storage container Artificial seawater transport means for transporting the artificial seawater to a test cell, an oxidant storage container storing an oxidant, an oxidant transport means for transporting the oxidant from the oxidant storage container to the test cell, and A control device for controlling a test apparatus main body, the potential measuring instrument, the artificial seawater transporting means, and the oxidant transporting means, and the corrosive liquid is added to the artificial seawater put in the test cell. Add the oxidizing agent The control means controls the transport of the oxidant to the test cell, and the immersion potential of the metal test piece immersed in the corrosive liquid is previously set in natural seawater with the same material as the metal test piece. It is preferable to apply a load repeatedly to the metal test piece at the same potential as the reference immersion potential obtained by immersing the formed metal electrode.

  In the corrosion fatigue test apparatus according to the present invention, the oxidant is preferably hypochlorous acid, hypochlorite, hydrogen peroxide or ozone.

  A corrosion fatigue test apparatus according to the present invention is provided in the test cell and is disposed by being immersed in the corrosive liquid, and a reference electrode is provided in the test cell and is immersed in the corrosive liquid. And a control means for controlling the potentiostat connected to the platinum electrode, the reference electrode, and the metal test piece, the test apparatus main body, and the potentiostat, and the corrosive liquid comprises: The artificial seawater, the control means controls the potentiostat, and the immersion potential of the metal test piece immersed in the corrosive liquid is previously formed in natural seawater with the same material as the metal test piece. It is preferable to apply a load repeatedly to the metal test piece at the same potential as the reference immersion potential obtained by immersing the metal electrode.

  In the corrosion fatigue testing apparatus according to the present invention, the metal material is preferably a metal material that forms a passive film.

  In the corrosion fatigue test apparatus according to the present invention, the reference immersion potential is preferably determined based on the immersion potential of a metal electrode to which algae in the natural seawater adheres.

  In the corrosion fatigue test apparatus according to the present invention, it is preferable that the reference immersion potential is determined based on the amount of algae attached to the metal electrode.

  In the corrosion fatigue test apparatus according to the present invention, when the metal test piece is formed of stainless steel, the reference immersion potential is +0.6 V vs. SHE (standard hydrogen electrode) or more, and the metal test piece is When formed of a titanium material, the reference immersion potential is preferably +0.7 V vs. SHE (standard hydrogen electrode) or more.

  According to the corrosion fatigue test apparatus having the above configuration, the influence of chloride contained in artificial seawater and the influence of an increase in immersion potential due to adhesion of microorganisms such as algae are evaluated in combination. It is possible to evaluate the corrosion fatigue characteristics of metal materials with higher accuracy.

In embodiment of this invention, it is a schematic diagram which shows the structure of the corrosion fatigue test apparatus. In embodiment of this invention, it is a schematic diagram which shows the structure of a test cell. In embodiment of this invention, it is the graph which measured the immersion potential of the stainless steel electrode. In embodiment of this invention, it is the graph which measured the immersion potential of the titanium electrode immersed in natural seawater under the marine environment. In embodiment of this invention, it is a graph which shows the temperature and pH dependence in the immersion potential (natural corrosion potential Esp) of stainless steel and titanium. 5 is a flowchart showing a procedure of a corrosion fatigue test method in the embodiment of the present invention. In other embodiment of this invention, it is a schematic diagram which shows the structure of a test cell. In other embodiment of this invention, it is a flowchart which shows the procedure of the corrosion fatigue test method. In another embodiment of this invention, it is a schematic diagram which shows the structure of a test cell. In another embodiment of this invention, it is a flowchart which shows the procedure of the corrosion fatigue test method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the corrosion fatigue test apparatus 10.

  The corrosion fatigue test apparatus 10 includes a test apparatus main body 14 that applies a repeated load to the metal test piece 12 and a hydraulic pressure source 16. The test apparatus main body 14 has rods 18a and 18b for holding both ends of the metal test piece 12 and applying a repeated load. A test cell 20 for immersing the metal test piece 12 in a corrosive liquid is attached to the test apparatus main body 14.

  In addition, although the metal material which evaluates corrosion fatigue is not specifically limited, It is preferable that it is a metal material which forms a passive film. This is because these metal materials are susceptible to local corrosion such as pitting corrosion and crevice corrosion because the passive film is locally broken by chloride present in the environment. The metal material that forms the passive film is, for example, a titanium material or stainless steel.

  FIG. 2 is a schematic diagram showing the configuration of the test cell 20. The test cell 20 is formed in a hollow shape and has a space into which the corrosive liquid 22 can be injected. For example, about 200 cc of the corrosive liquid 22 can be injected into the test cell 20.

  The test cell 20 is provided with an opening 24 through which the rods 18a and 18b of the test apparatus body 14 can be inserted on the upper and lower surfaces thereof. A seal member 26 is provided between the test cell 20 and the rods 18 a and 18 b so that the corrosive liquid 22 does not leak from the test cell 20. The test cell 20 is provided with a heater (not shown) for heating the corrosive liquid 22.

  A test piece simulation electrode 28 and a reference electrode 30 are attached to the test cell 20. The test piece simulation electrode 28 and the reference electrode 30 are connected to the potential measuring device 32 by an insulating coated metal lead wire.

  The test piece simulation electrode 28 is made of the same material as the metal test piece 12 and is formed into small pieces in order to obtain the immersion potential of the metal test piece 12 immersed in the corrosive liquid 22. For example, when the metal test piece 12 is formed of general-purpose stainless steel SUS304, the test piece simulation electrode 28 is also formed of general-purpose stainless steel SUS304. When the metal test piece 12 is formed of industrial pure titanium Ti—Gr1, the test piece simulation electrode 28 is also formed of industrial pure titanium Ti—Gr1.

  As the reference electrode 30, a general Ag / AgCl electrode can be used. As the potential measuring device 32, a general electrometer (potentiometer) or the like is used. The immersion potential of the metal test piece 12 immersed in the corrosive liquid 22 is obtained by measuring the potential difference between the test piece simulated electrode 28 immersed in the corrosive liquid 22 and the reference electrode 30 to obtain the immersion potential of the test specimen simulated electrode 28. Can be requested.

  On the lower surface of the test cell 20, an injection port 34 for injecting the corrosive liquid 22 into the test cell 20 is provided. The test cell 20 is provided with an overflow pipe 36 for preventing the overflow of the corrosive liquid 22 and circulating the corrosive liquid 22 between the test cell 20 and a corrosive liquid storage container 40 described later. The overflow tube 36 is disposed so that the tip 38 of the overflow tube 36 is positioned above the upper end of the metal test piece 12 in the vertical direction so that the entire metal test piece 12 is immersed in the corrosive liquid 22.

  The corrosive liquid storage container 40 stores a corrosive liquid 22 to be injected into the test cell 20. The corrosive liquid storage container 40 is disposed below the test cell 20 in the vertical direction. For example, about 50 L of the corrosive liquid 22 can be stored in the corrosive liquid storage container 40.

  The liquid supply port 42 of the corrosive liquid storage container 40 and the injection port 34 of the test cell 20 are connected by a pipe 44. The pipe 44 is provided with a pump 46, a valve 48, a flow meter (not shown), and the like. A general liquid feed pump or the like is used for the pump 46. As the valve 48, a general electromagnetic valve or the like is used.

  The pipe 44, the pump 46, and the valve 48 have a function as a corrosive liquid conveying means. By operating the pump 46 and the valve 48, the corrosive liquid 22 is removed from the corrosive liquid storage container 40 to the test cell 20. Can be transported to. Further, a filter 50 is provided at the liquid supply port 42 of the corrosive liquid storage container 40 so that marine organisms 56 to be described later do not flow out. The filter 50 is formed in a mesh shape with synthetic resin or the like, for example.

  The pipe 44 is preferably provided with a branch pipe 52 for returning a part of the transported corrosive liquid 22 to the corrosive liquid storage container 40. One end of the branch pipe 52 is connected to the valve 48, and the other end of the branch pipe 52 is connected to the upper surface of the corrosive liquid storage container 40. When the branch pipe 52 is provided, a three-way valve or the like is used as the valve 48. By adjusting the valve 48, the ratio between the amount of the corrosive liquid 22 conveyed to the test cell 20 and the amount of the corrosive liquid 22 returned to the corrosive liquid storage container 40 can be changed. By providing the branch pipe 52, a part of the corrosive liquid 22 injected into the test cell 20 can be returned to the corrosive liquid storage container 40, so that the amount of the corrosive liquid 22 injected into the test cell 20 is more accurate. Can be adjusted well.

  A liquid receiving port 54 connected to the overflow pipe 36 is provided on the upper surface of the corrosive liquid storage container 40. The corrosive liquid 22 injected into the test cell 20 is returned to the corrosive liquid storage container 40 from the liquid receiving port 54 through the overflow pipe 36. Thus, the corrosive liquid 22 can be circulated between the test cell 20 and the corrosive liquid storage container 40.

  The corrosive liquid 22 is produced by putting marine organisms 56 in artificial seawater stored in the corrosive liquid storage container 40. Algae such as diatoms can be propagated in artificial seawater by placing marine organisms 56 in artificial seawater stored in the corrosive liquid storage container 40 and rearing, for example, so that the corrosive liquid 22 closer to natural seawater can be obtained. Can be produced.

  The corrosive liquid storage container 40 is provided with an air blowing device 58, a heater (not shown), a water temperature gauge, a hydrometer, and the like for breeding marine organisms 56 and the like. In addition, it is preferable that the corrosive liquid storage container 40 is comprised with the synthetic resin container and glass container which were formed with synthetic resins, such as a transparent acrylic, in order to confirm the reproduction of algae visually from the outside.

  Artificial seawater contains an aqueous salt solution containing chemical components (sodium chloride, magnesium chloride, magnesium sulfate, calcium sulfate, potassium chloride, sodium sulfate, etc.) substantially the same as natural seawater in order to breed marine organisms 56 and the like. Used. As the artificial seawater, for example, generally available aquamarine (manufactured by Hachishu Pharmaceutical Co., Ltd.) or the like can be used.

  The marine organism 56 is not particularly limited, but it is preferable to use marine fish, seaweed and the like generally bred for ornamental purposes. For example, a damselfish, butterflyfish, or puffer fish may be used as the saltwater fish.

  The control means 60 is electrically connected to the test apparatus main body 14, the hydraulic source 16, the test cell 20, the potential measuring device 32, the corrosive liquid storage container 40, the pump 46, the valve 48, and the like, and functions to control these devices. have. Further, the control means 60 can control the pump 46 and the valve 48 to adjust the conveyance amount of the corrosive liquid 22 into the test cell 20. The control means 60 is composed of, for example, a general personal computer.

  The control means 60 includes a calculation processing unit 62 that performs calculation processing of data, a storage unit 64 that stores data, and a determination unit 66 that determines whether or not a repeated load can be applied to the metal test piece 12. .

  In the calculation processing unit 62, the immersion potential of the test piece simulation electrode 28 is calculated based on the data sent from the potential measuring device 32.

  The storage unit 64 stores an immersion potential obtained by immersing a metal electrode formed of the same material as the metal test piece 12 in natural seawater (natural seawater) in advance. The previously determined immersion potential constitutes a reference immersion potential for determining whether or not a repetitive load can be applied to the metal test piece 12.

  The determination unit 66 determines whether or not a repetitive load can be applied to the metal test piece 12 based on the immersion potential of the test piece simulation electrode 28. In the determination unit 66, the immersion potential of the test piece simulation electrode 28 is compared with the reference immersion potential. Then, when the immersion potential of the test piece simulation electrode 28 becomes equal to the reference immersion potential, it is determined that a repeated load can be applied to the metal test piece 12.

  Next, how to obtain the reference immersion potential will be described. The reference immersion potential is obtained by immersing a metal electrode formed of the same material as the metal test piece 12 in natural seawater in advance.

FIG. 3 is a graph obtained by measuring the immersion potential of the stainless steel electrode, and FIG. 3A is a graph obtained by measuring the immersion potential of the stainless steel electrode immersed in natural seawater under the marine environment. during artificial seawater (air-saturated solution of 3.5% [NaCl] + 5 g / L _[Na 2 SO _4], pH 8.2, solution temperature 20 ° C.) is a graph of immersion potential of stainless steel electrodes were immersed in . 3A and 3B, the horizontal axis represents the immersion time (s) of the stainless steel electrode, and the left vertical axis of the graph represents the immersion potential (V vs. V) based on the standard hydrogen electrode. SHE), the right vertical axis of the graph represents the immersion potential (V vs. SCE) based on the saturated calomel electrode.

As is apparent from the graph of FIG. 3A, when the stainless steel electrode is immersed in natural seawater, the amount of algae attached to the electrode surface of the stainless steel electrode increases with the increase of the immersion time from the start of immersion, and the immersion potential increases. Rises. When about 1 × 10 ⁶ s (278 hrs) elapses, the immersion potential becomes substantially constant at +0.6 V vs. SHE (standard hydrogen electrode).

  In contrast, when the stainless steel electrode is immersed in artificial seawater, the immersion potential is +0.15 to +0.25 V vs. SHE (standard) from the start of immersion, as is apparent from the graph of FIG. The hydrogen electrode is substantially constant. Thus, since artificial seawater does not contain algae, there is no adhesion of algae to the electrode surface, and no increase in immersion potential is observed.

  FIG. 4 is a graph obtained by measuring the immersion potential of a titanium electrode immersed in natural seawater under the marine environment. The titanium electrode was immersed in natural seawater for a predetermined period (300 hrs to 500 hrs) in a marine environment to allow algae to adhere to the electrode surface, and then the immersion potential of the titanium electrode was measured in natural seawater. The horizontal axis of the graph of FIG. 4 shows the measurement time of the immersion potential, and the vertical axis of the graph shows the immersion potential based on the standard hydrogen electrode. The titanium electrode is made of industrial pure titanium Ti-Gr. 1 was used, and an Ag / AgCl electrode was used as a reference electrode.

  First, it was immersed in natural seawater for a predetermined period (300 hrs to 500 hrs), and then immersed in natural seawater with algae attached to the surface of the titanium electrode, and the immersion potential was measured. The immersion potential of the titanium electrode 68a attached with algae was +0.7 V vs. SHE (standard hydrogen electrode).

  Next, after removing large algae clumps adhering to the titanium electrode 68a (the fine algae remained adhering to the titanium electrode), it was immersed in natural seawater and the immersion potential was measured. The immersion potential of the titanium electrode 68b from which large algae clusters were removed was +0.6 V vs. SHE (standard hydrogen electrode).

  Furthermore, after polishing the surface of the titanium electrode 68b (a state in which fine algae were almost removed from the titanium electrode), the surface was immersed in natural seawater and the immersion potential was measured. The immersion potential of the titanium electrode 68c whose surface was polished was +0.25 V vs. SHE (standard hydrogen electrode).

  The immersion potentials of the titanium electrodes 68a and 68b to which the algae adhered were higher than the immersion potential of the titanium electrode 68c whose surface was polished. Moreover, the immersion potential of the titanium electrode 68a with a large amount of algae attached showed a higher immersion potential than the titanium electrode 68b with a small amount of algae attached.

  FIG. 5 is a graph showing temperature and pH dependency of the immersion potential (natural corrosion potential Esp) of stainless steel and titanium. The horizontal axis of the graph in FIG. 5 represents the pH value, the left vertical axis of the graph represents the immersion potential (mV vs. SHE) with respect to the standard hydrogen electrode, and the right vertical axis of the graph represents the saturated calomel electrode. The immersion potential (mV vs. SCE) is shown.

  From the graph of FIG. 5, the immersion potential of stainless steel and titanium at pH 8.2, which is the pH value of standard natural seawater at 20 ° C., was substituted for pH 8.2 for Esp = 0.733-0.059 pH. It is + 0.25V vs. SHE (standard hydrogen electrode). This result substantially coincides with the immersion potential of the stainless steel shown in the graph of FIG. 3B and the immersion potential of the titanium electrode 68c shown in the graph of FIG.

  In this way, when the metal material is immersed in natural seawater, the immersion potential of the metal material is increased due to the influence of the amount of algae and the like contained in natural seawater. There is a possibility of accelerating corrosion occurrence.

  Therefore, the reference immersion potential is determined based on the immersion potential of the metal electrode to which algae is attached in natural seawater in consideration of the marine environment where the metal material is used. Further, the reference immersion potential is preferably determined based on the amount of algae attached to the metal electrode per unit area.

  When stainless steel is used in a standard marine environment, the immersion potential is usually +0.6 V vs. SHE (standard hydrogen electrode) as shown in the graph of FIG. +0.6 V vs. SHE (standard hydrogen electrode) or higher. In addition, when stainless steel is used in a marine environment where the generation of algae is relatively small and the immersion potential does not reach +0.6 V vs. SHE (standard hydrogen electrode), the reference immersion potential is set to, for example, +0.4 to +0. .5V vs. SHE (standard hydrogen electrode). Furthermore, when using stainless steel in the marine environment in which the generation of algae hardly occurs, the reference immersion potential is, for example, +0.25 to +0.3 V vs. SHE (standard hydrogen slightly higher than the immersion potential in artificial seawater). Electrode).

  When a titanium material is used in a standard marine environment, the immersion potential is usually +0.7 V vs. SHE (standard hydrogen electrode) as shown in the graph of the titanium electrode 68a in FIG. May be +0.7 V vs. SHE (standard hydrogen electrode) or higher. In addition, when a titanium material is used in a marine environment where the generation of algae is relatively small and the immersion potential does not reach +0.7 V vs. SHE (standard hydrogen electrode), the reference immersion potential is set to +0.6 V vs., for example. SHE (standard hydrogen electrode) may be used. Furthermore, when the titanium material is used in an marine environment in which almost no algae is generated, the reference immersion potential is, for example, +0.25 to +0.3 V vs. SHE (standard hydrogen slightly higher than the immersion potential in artificial seawater). Electrode).

  In addition, although the method of calculating | requiring said reference | standard immersion potential demonstrated stainless steel and titanium material, a reference immersion potential can be calculated | required with the same method also about another metal material.

  Next, the corrosion fatigue test method will be described. FIG. 6 is a flowchart showing the procedure of the corrosion fatigue test method.

  A marine organism such as seawater fish or seaweed is placed in the artificial seawater stored in the corrosive liquid storage container 40, for example, reared, and algae is propagated in the artificial seawater to produce the corrosive liquid 22 (S10). . The growth of algae can be confirmed by, for example, deposits attached to the surface of the corrosive liquid storage container 40.

  The test cell 20 and the metal test piece 12 are set up (S11). The metal test piece 12 is attached to the rods 18 a and 18 b of the test apparatus main body 14, and the test cell 20 is set in the test apparatus main body 14.

  The corrosive liquid 22 is injected into the test cell 20 and circulated (S12). The corrosive liquid 22 is injected into the test cell 20 from the corrosive liquid storage container 40. The pump 46 is operated by the control means 60 and the valve 48 is opened to convey the corrosive liquid 22 to the test cell 20. The corrosive liquid 22 injected into the test cell 20 is returned to the corrosive liquid storage container 40 through the overflow pipe 36. The metal test piece 12, the test piece simulation electrode 28, and the reference electrode 30 in the test cell 20 are immersed in the corrosive liquid 22. Then, by circulating the corrosive liquid 22 between the test cell 20 and the corrosive liquid storage container 40, algae contained in the corrosive liquid 22 adheres to the metal test piece 12 and the test piece simulated electrode 28.

  The immersion potential of the test piece simulation electrode 28 is measured (S13). Data of the test piece simulation electrode 28 is sent from the potential measuring device to the control means 60, and the immersion potential of the test piece simulation electrode 28 is calculated by the calculation processing unit 62. As the amount of algae attached to the surface of the test piece simulation electrode 28 increases, the immersion potential of the test piece simulation electrode 28 increases.

  The immersion potential of the test piece simulation electrode 28 is compared with a reference immersion potential determined in advance to determine whether a repeated load can be applied (S14). The determination unit 66 of the control means 60 compares the immersion potential of the test piece simulation electrode 28 with the reference immersion potential. When the immersion potential of the test piece simulation electrode 28 is lower than the reference immersion potential, the immersion in the corrosive liquid 22 is continued without applying a repeated load to the metal test piece 12.

  When the immersion potential of the test piece simulation electrode 28 becomes equal to the reference immersion potential, the immersion potential of the metal test piece 12 is considered to have reached the reference immersion potential, and a repeated load is applied to the metal test piece 12 to perform a fatigue test. Start (S15). The control means 60 controls the operation of the pump 46 and the valve 48 so that the immersion potential of the test piece simulation electrode 28 becomes the reference immersion potential even while the metal test piece 12 is repeatedly loaded. The amount of the corrosive liquid conveyed from the liquid storage container 40 to the test cell 20 is adjusted. Thereby, since the algae contained in the corrosive liquid 22 are supplied into the test cell 20 even when a load is repeatedly applied to the metal test piece 12, the reference immersion potential can be maintained.

  When the metal test piece 12 is fatigued or has reached the fatigue limit, the repeated load is stopped (S16). The operation of the rods 18a and 18b of the test apparatus main body 14 is stopped by the control means 60, and the load of the repeated load on the metal test piece 12 is stopped. Thus, the corrosion fatigue test is completed.

  According to the above configuration, since the corrosion fatigue test can be performed using a corrosive liquid composed of artificial seawater containing algae, the influence of chloride contained in the artificial seawater and the influence of an increase in immersion potential due to adhesion of algae are combined. It is evaluated and the corrosion fatigue property of the metal material in the marine environment can be evaluated more accurately.

  According to the above configuration, the algae are propagated by marine organisms stored in the artificial seawater stored in the corrosive liquid storage container, so that a repeated load is applied to the metal test piece for a long period (for example, 1 to 3 months). Even when loaded, active algae can be supplied to the test cell. Therefore, it is not necessary to conduct a corrosion fatigue test in an actual marine environment, and corrosion fatigue characteristics can be evaluated in an environment close to the actual marine environment even at a laboratory level.

  Next, another corrosion fatigue test apparatus will be described.

  The other corrosion fatigue test apparatuses are different from the corrosion fatigue test apparatus 10 in the configuration of the test cell, the corrosive liquid conveying means, and the like, and the test apparatus main body 14 and the hydraulic source 16 have the same configuration. In addition, the same code | symbol is attached | subjected to the same element and detailed description is abbreviate | omitted.

  FIG. 7 is a schematic diagram showing the configuration of the test cell 70. The test cell 70 is formed in a hollow shape and has a space into which the corrosive liquid 72 can be injected. The test cell 70 is provided with an opening 24 through which the rods 18a and 18b holding the metal test piece 12 can be inserted. A seal member 26 is provided around the opening 24 so that the corrosive liquid 72 does not leak from between the test cell 70 and the rods 18a and 18b.

  A test cell simulation electrode 28 and a reference electrode 30 are attached to the test cell 70. The test piece simulation electrode 28 and the reference electrode 30 are connected to a potential measuring device 32. Both the test piece simulated electrode 28 and the reference electrode 30 are immersed in the corrosive liquid 72, and the immersion of the metal test piece 12 immersed in the corrosive liquid 72 by measuring the immersion potential of the test piece simulated electrode 28. The potential is determined.

  Artificial seawater is stored in the artificial seawater storage container 74. The artificial seawater storage container 74 and the test cell 70 are connected by a pipe 76 that conveys artificial seawater. The pipe 76 is provided with a pump 78, a valve 80, and the like. The pipe 76, the pump 78, and the valve 80 have a function as an artificial seawater transport unit that transports the artificial seawater from the artificial seawater storage container 74 to the test cell 70. A general liquid feed pump is used for the pump 78, and a general electromagnetic valve or the like is used for the valve 80.

  For the artificial seawater, a salt solution containing sodium chloride is used. For the artificial seawater, it is preferable to use an aqueous salt solution containing chemical components substantially the same as natural seawater, sodium chloride, magnesium chloride, calcium chloride, potassium chloride, sodium sulfate, and the like. As the artificial seawater, for example, the above-mentioned Aquamarine (manufactured by Hachishu Pharmaceutical Co., Ltd.), a salt aqueous solution based on ASTM D1141-52, a salt aqueous solution containing 3-3.5 wt% NaCl, and the like are used.

  An oxidizing agent is stored in the oxidizing agent storage container 82. The oxidant storage container 82 and the test cell 70 are connected by a pipe 84 that conveys the oxidant. The pipe 84 is provided with a pump 86, a valve 88, and the like. The pipe 84, the pump 86, and the valve 88 function as an oxidant transport unit that transports the oxidant from the oxidant storage container 82 to the test cell 70. A general liquid feed pump is used as the pump 86, and a general electromagnetic valve or the like is used as the valve 88.

  As the oxidizing agent, for example, hypochlorous acid or hypochlorite (for example, sodium hypochlorite), hydrogen peroxide, ozone and the like are used. By adding an oxidizing agent to the artificial seawater put in the test cell 70 to produce the corrosive liquid 72, the immersion potential of the metal test piece 12 immersed in the corrosive liquid 72 can be increased. For example, when a stainless steel test piece is used for the metal test piece 12 and hypochlorous acid is used as the oxidizing agent, the immersion potential of the stainless steel test piece is set to +0. 6V vs. SHE (standard hydrogen electrode).

  The control means 90 is electrically connected to the test apparatus main body 14, the hydraulic power source 16, the test cell 70, the artificial seawater storage container 74, the oxidant storage container 82, the potential measuring device 32, the pumps 78 and 86, the valves 80 and 88, and the like. And has a function of controlling these devices. In addition, the control means 90 can control the pumps 78 and 86 and the valves 80 and 88 to adjust the amount of artificial seawater and oxidant transported into the test cell 70.

  The control means 90 is composed of a personal computer or the like, similar to the control means 60, and includes a calculation processing section 62 for calculating and processing the immersion potential of the test piece simulation electrode 28, a storage section 64 for storing the reference immersion potential, and a metal test. And a determination unit 66 for determining whether or not a repeated load can be applied to the piece 12.

  Next, the corrosion fatigue test method will be described. FIG. 8 is a flowchart showing the procedure of the corrosion fatigue test method.

  The test cell 70 and the metal test piece 12 are set up (S20). The metal test piece 12 is attached to the rods 18 a and 18 b of the test apparatus main body 14, and the test cell 70 is set in the test apparatus main body 14.

  Artificial seawater is injected into the test cell 70 (S21). The pump 78 is operated by the control means 90 and the valve 80 is opened, and the artificial seawater is conveyed from the artificial seawater storage container 74 to the test cell 70. And the metal test piece 12, the test piece simulation electrode 28, and the reference electrode 30 in the test cell 70 are immersed in artificial seawater.

  The immersion potential of the test piece simulation electrode 28 is measured (S22). Data of the test piece simulation electrode 28 is sent from the potential measuring device 32 to the control means 90, and the calculation processing unit 62 calculates the immersion potential of the test piece simulation electrode 28.

  An oxidizing agent is added to the test cell 70 (S23). The pump 86 is operated by the control means 90 and the valve 88 is opened to convey the oxidant from the oxidant storage container 82 to the test cell 70. As the amount of the oxidant added to the artificial seawater increases, the immersion potential of the test piece simulation electrode 28 becomes higher.

  The immersion potential of the test piece simulation electrode 28 is compared with a reference immersion potential determined in advance to determine whether or not a repeated load can be applied (S24). The determination unit 66 of the control means 90 compares the immersion potential of the metal test piece 12 with the reference immersion potential. When the immersion potential of the test piece simulation electrode 28 is lower than the reference immersion potential, the addition of the oxidizing agent is continued without applying a repeated load to the metal test piece 12.

  When the immersion potential of the test piece simulation electrode 28 is the same as the reference immersion potential, the immersion potential of the metal test piece 12 is regarded as having reached the reference immersion potential, and a fatigue test is performed by repeatedly applying a load to the metal test piece 12. Start (S25). The control means 90 controls the operation of the pump 86 and the valve 88 to oxidize so that the immersion potential of the test piece simulation electrode 28 becomes the reference immersion potential even while the metal test piece 12 is repeatedly loaded. The amount of oxidant conveyed from the agent storage container 82 to the test cell 70 is adjusted.

  When the metal test piece 12 is subjected to fatigue failure or reaches the fatigue limit, the repeated load is stopped (S26). The operation of the rods 18a and 18b of the test apparatus main body 14 is stopped by the control means 90, and the load of the repeated load on the metal test piece 12 is stopped. Thus, the corrosion fatigue test is completed.

  According to the above configuration, since the corrosion fatigue test can be performed using a corrosive solution obtained by adding an oxidant to artificial seawater, the influence of chloride contained in the artificial seawater and the influence of an increase in immersion potential are evaluated in combination. It is possible to evaluate the corrosion fatigue characteristics of metallic materials in the marine environment more accurately.

  According to the above configuration, by adding an oxidizing agent to increase the immersion potential of the metal test piece, it can be made the same potential as the reference immersion potential in a shorter time than attaching algae to the metal test piece. Save time.

  Next, another corrosion fatigue test apparatus will be described.

  Another corrosion fatigue test apparatus is different from the corrosion fatigue test apparatus 10 in the configuration of a test cell and a corrosive liquid supply system, and the test apparatus main body 14 and the hydraulic source 16 have the same configuration. In addition, the same code | symbol is attached | subjected to the same element and detailed description is abbreviate | omitted.

  FIG. 9 is a schematic diagram showing the configuration of the test cell 92. The test cell 92 is formed in a hollow shape and has a space in which a corrosive solution 94 into which the metal test piece 12 is immersed is placed. The test cell 92 is provided with an opening 24 through which the rods 18a and 18b holding the metal test piece 12 can be inserted. A seal member 26 is provided around the opening 24 so that the corrosive liquid 94 does not leak from the test cell 92.

  Further, an insulating member 96 formed of an insulating resin or the like is inserted between the metal test piece 12 and the grips of the rods 18a and 18b, and the gap between the metal test piece 12 and the rods 18a and 18b is inserted. Insulated.

  A reference electrode 30 and a platinum electrode 98 are attached to the test cell 92. The metal test piece 12, the reference electrode 30, and the platinum electrode 98 are connected to a potentiostat (constant potential electrolysis device) 100 with a metal lead wire with insulation coating. The potentiostat 100 also has a function as a potential measuring device. The metal test piece 12, the reference electrode 30, and the platinum electrode 98 are all immersed in the corrosive liquid 94.

  The corrosive liquid storage container 102 stores a corrosive liquid 94 made of artificial seawater. The corrosive liquid storage container 102 and the test cell 92 are connected by a pipe 104 that conveys the corrosive liquid 94. The pipe 104 is provided with a pump 106, a valve 108, and the like. The pipe 104, the pump 106, and the valve 108 have a function as a corrosive liquid transport unit that transports the corrosive liquid 94 from the corrosive liquid storage container 102 to the test cell 92. A general liquid feed pump is used for the pump 106, and a general electromagnetic valve or the like is used for the valve 108.

  For the artificial seawater, a salt solution containing sodium chloride is used. For the artificial seawater, it is preferable to use an aqueous salt solution containing chemical components substantially the same as natural seawater, sodium chloride, magnesium chloride, calcium chloride, potassium chloride, sodium sulfate, and the like. As the artificial seawater, for example, the above-mentioned Aquamarine (manufactured by Hachishu Pharmaceutical Co., Ltd.), a salt aqueous solution based on ASTM D1141-52, a salt aqueous solution containing 3-3.5 wt% NaCl, and the like are used.

  The control means 110 is electrically connected to the test apparatus main body 14, the hydraulic source 16, the test cell 92, the corrosive liquid storage container 102, the potentiostat 100, the pump 106, and the valve 108. It has a function to control. Further, the control means 110 can control the potentiostat 100 to adjust the immersion potential of the metal test piece 12.

  The control means 110 is composed of a personal computer or the like, similar to the control means 60, and includes a calculation processing section 62 for calculating and processing the immersion potential of the metal test piece 12, a storage section 64 for storing the reference immersion potential, and a metal test piece. And a determination unit 66 that determines whether or not a repetitive load load to 12 is possible.

  Next, the corrosion fatigue test method will be described. FIG. 10 is a flowchart showing the procedure of the corrosion fatigue test method.

  The test cell 92 and the metal test piece 12 are set up (S30). The metal test piece 12 is attached to the rods 18 a and 18 b of the test apparatus main body 14, and the test cell 92 is set in the test apparatus main body 14.

  A corrosive solution 94 made of artificial seawater is injected into the test cell 92 (S31). The pump 106 is operated by the control means 110 and the valve 108 is opened, so that the corrosive liquid 94 made of artificial seawater is conveyed from the corrosive liquid storage container 102 into the test cell 92. The metal test piece 12 and the reference electrode 30 platinum electrode 98 in the test cell 92 are immersed in the corrosive liquid 94.

  The immersion potential of the metal test piece 12 is measured (S32). Measurement data of the metal test piece 12 is sent from the potentiostat 100 to the control means 110, and the immersion potential of the metal test piece 12 is calculated by the calculation processing unit 62.

  A potential is applied to the metal test piece 12 by the potentiostat 100 (S33). As the potential is applied to the metal test piece 12 by the potentiostat 100, the immersion potential of the metal test piece 12 increases.

  The immersion potential of the metal test piece 12 is compared with a reference immersion potential determined in advance, and the possibility of repeated load loading is determined (S34). The determination unit 66 of the control means 110 compares the immersion potential of the metal test piece 12 with the reference immersion potential, and determines whether or not a repeated load can be applied to the metal test piece 12.

  When the immersion potential of the metal test piece 12 becomes the same potential as the reference immersion potential (when the immersion potential reaches the reference immersion potential), the metal test piece 12 is loaded repeatedly and a fatigue test is started (S35). The control means 110 controls the potentiostat 100 so that the immersion potential of the metal test piece 12 becomes the reference immersion potential even while the metal test piece 12 is repeatedly loaded.

  When the metal test piece 12 is fatigued or reaches the fatigue limit, the repeated load is stopped (S36). The control means 110 stops the operation of the rods 18 a and 18 b of the test apparatus main body 14, and the load of the repeated load on the metal test piece 12 is stopped. Thus, the corrosion fatigue test is completed. In addition, in the constant potential holding in the system in which the metal test piece 12 is insulated as described above, if local corrosion occurs and progresses in addition to the passive state holding current that flows constantly, the local corrosion is generated and progressed. Since the corresponding currents are overlapped, it is preferable to monitor the occurrence of corrosion pits and the occurrence / progress of corrosion fatigue cracks by monitoring changes in current over time.

  According to the above configuration, the corrosion fatigue test can be performed by applying a potential with a potentiostat (external power source) by immersing a metal test piece in a corrosive liquid made of artificial seawater, and the influence of chloride contained in the artificial seawater, The influence of the increase in immersion potential is evaluated in combination, and the corrosion fatigue characteristics of the metal material in the marine environment can be more accurately evaluated.

  According to the above configuration, by applying a potential to the metal test piece with a potentiostat (external power source), it can be made the same potential as the reference immersion potential in a shorter time than attaching algae to the metal test piece. Test time can be saved. For example, when algae is attached to a stainless steel test piece to obtain a reference immersion potential +0.6 V vs. SHE (standard hydrogen electrode), 300 to 500 hours are used as shown in FIG. Cost. Therefore, the waiting time from the preparation of the test until the algae adheres to the stainless steel test piece and becomes +0.6 V vs. SHE (standard hydrogen electrode) is 2 weeks to 1 month. According to the above configuration, a waiting time of 2 weeks to 1 month can be saved by maintaining a constant potential at +0.6 V vs. SHE (standard hydrogen electrode) immediately with a potentiostat (external power source).

  DESCRIPTION OF SYMBOLS 10 Corrosion fatigue test apparatus, 12 Metal test piece, 14 Test apparatus main body, 16 Hydraulic source, 18a, 18b Rod 20, 70, 92 Test cell, 22, 72, 94 Corrosion liquid, 26 Seal member, 28 Test piece simulation electrode, 30 Reference electrode, 32 Potential measuring device, 34 Inlet, 36 Overflow pipe, 40, 102 Corrosion liquid storage container, 42 Liquid supply port, 44, 76, 84, 104 Piping, 46, 78, 86, 106 Pump, 48, 80, 88, 108 Valve, 50 Filter, 52 Branch pipe, 54 Liquid inlet, 56 Marine organism, 58 Air blowing device, 60, 90, 110 Control means, 62 Calculation processing unit, 64 Storage unit, 66 Judgment unit, 74 Artificial seawater storage container, 82 Oxidant storage container, 96 Insulating member, 98 Platinum electrode, 100 Potentiostat

Claims (9)

A corrosion fatigue testing apparatus for evaluating the corrosion fatigue of a metal material,
A main body of a test apparatus for repeatedly applying a load to a metal specimen;
A test cell placed in the test apparatus body and containing a corrosive solution into which the metal test piece is immersed;
With
The corrosive liquid includes artificial seawater containing sodium chloride,
The metal test is performed so that the immersion potential of the metal test piece immersed in the corrosive liquid is the same as the reference immersion potential obtained by previously immersing a metal electrode formed of the same material as the metal test piece in natural seawater. Corrosion fatigue testing equipment characterized by repeatedly applying a load to a piece. The corrosion fatigue test apparatus according to claim 1,
A test piece simulation electrode that is disposed in the test cell soaked in the corrosive liquid and is formed of the same material as the metal test piece,
A reference electrode placed in the test cell soaked in the corrosive liquid;
A potential measuring instrument connected to the test piece simulation electrode and the reference electrode;
A corrosive liquid storage container in which the corrosive liquid is stored;
A corrosive liquid transporting means for transporting the corrosive liquid from the corrosive liquid storage container to the test cell;
Control means for controlling the test apparatus main body, the potential measuring instrument, and the corrosive liquid conveying means;
With
The corrosive liquid includes the artificial seawater stored in the corrosive liquid storage container, and algae propagated by marine organisms stored in the artificial seawater,
The control means controls the conveyance of the corrosive liquid to the test cell, and the immersion potential of the metal test piece immersed in the corrosive liquid is previously formed in natural seawater with the same material as the metal test piece. A corrosion fatigue test apparatus characterized in that a repeated load is applied to the metal test piece at the same potential as a reference immersion potential obtained by immersing a metal electrode. The corrosion fatigue test apparatus according to claim 1,
A test piece simulation electrode that is disposed in the test cell soaked in the corrosive liquid and is formed of the same material as the metal test piece,
A reference electrode placed in the test cell soaked in the corrosive liquid;
A potential measuring instrument connected to the test piece simulation electrode and the reference electrode;
An artificial seawater storage container in which the artificial seawater is stored;
Artificial seawater transport means for transporting the artificial seawater from the artificial seawater storage container to the test cell;
An oxidizing agent storage container in which the oxidizing agent is stored;
Oxidant transport means for transporting the oxidant from the oxidant storage container to the test cell;
Control means for controlling the test apparatus main body, the potential measuring instrument, the artificial seawater transfer means, and the oxidant transfer means;
With
The corrosive liquid is prepared by adding the oxidizing agent to the artificial seawater put in the test cell,
The control means controls the transport of the oxidant to the test cell, and the immersion potential of the metal test piece immersed in the corrosive liquid is previously formed in natural seawater with the same material as the metal test piece. A corrosion fatigue test apparatus characterized by applying a load repeatedly to the metal test piece at the same potential as a reference immersion potential obtained by immersing the electrode. The corrosion fatigue test apparatus according to claim 3,
A corrosion fatigue test apparatus, wherein the oxidizing agent is hypochlorous acid, hypochlorite, hydrogen peroxide, or ozone. The corrosion fatigue test apparatus according to claim 1,
A platinum electrode provided in the test cell and disposed immersed in the corrosive liquid;
A reference electrode provided in the test cell and placed immersed in the corrosive liquid;
A potentiostat connected to the platinum electrode, the reference electrode, and the metal specimen;
Control means for controlling the test apparatus main body and the potentiostat;
With
The corrosive liquid consists of the artificial seawater,
The control means controls the potentiostat and determines the immersion potential of the metal test piece immersed in the corrosive liquid by previously immersing a metal electrode made of the same material as the metal test piece in natural seawater. A corrosion fatigue testing apparatus characterized by applying a repeated load to the metal test piece at the same potential as the reference immersion potential. A corrosion fatigue test apparatus according to any one of claims 1 to 5,
The corrosion fatigue test apparatus characterized in that the metal material is a metal material that forms a passive film. The corrosion fatigue test apparatus according to any one of claims 1 to 6,
The corrosion fatigue test apparatus, wherein the reference immersion potential is determined based on an immersion potential of a metal electrode to which algae in the natural seawater adheres. The corrosion fatigue test apparatus according to claim 7,
The corrosion fatigue test apparatus characterized in that the reference immersion potential is determined based on the amount of algae attached to the metal electrode. The corrosion fatigue test apparatus according to claim 7 or 8,
When the metal test piece is formed of stainless steel, the reference immersion potential is +0.6 V vs. SHE (standard hydrogen electrode) or more, and when the metal test piece is formed of a titanium material, The corrosion fatigue test apparatus characterized in that the reference immersion potential is +0.7 V vs. SHE (standard hydrogen electrode) or more.

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