JP2015227786A - Crevice corrosion testing device and crevice corrosion testing method - Google Patents
Crevice corrosion testing device and crevice corrosion testing method Download PDFInfo
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Abstract
Description
本発明は、フッ化物イオン、塩化物イオン、臭化物イオン及びヨウ化物イオンなどのいわゆるハロゲン化物イオンを含む腐食環境において、金属材料に発生するすきま腐食の進展性を評価する装置及び方法に関するものである。 The present invention relates to an apparatus and a method for evaluating the progress of crevice corrosion generated in a metal material in a corrosive environment containing so-called halide ions such as fluoride ions, chloride ions, bromide ions and iodide ions. .
ハロゲン化物イオンを含有する自然水に接するゲート、堰、配管類、海水ポンプなどや、塩分を含む醤油、味噌、食酢、ドレッシングなどの食品製造設備に使用される機器などに使用される金属材料には、耐食性が求められる。炭素鋼、低合金鋼、ステンレス鋼、Ｎｉ基合金、Ｔｉなどから、適正な金属材料を選定するためには、腐食環境の塩濃度や温度、ｐＨなどに応じて、適正な電気化学的な手法を採用して、耐食性を評価することが必要である。 Metal materials used in gates, weirs, piping, seawater pumps, etc. that come in contact with natural water containing halide ions, and equipment used in food production facilities such as salt-containing soy sauce, miso, vinegar, and dressings Requires corrosion resistance. In order to select an appropriate metal material from carbon steel, low alloy steel, stainless steel, Ni-base alloy, Ti, etc., an appropriate electrochemical method according to the salt concentration, temperature, pH, etc. of the corrosive environment To evaluate corrosion resistance.
また、ハロゲン化物イオンを含む腐食環境で使用される構造物や機器類は、配管つなぎ目のすきま部や溶接欠陥、ゴミの付着物など、潜在的なすきま構造を有しており、ハロゲン化物によるすきま腐食などの腐食損傷が懸念される。 In addition, structures and equipment used in corrosive environments that contain halide ions have potential gap structures such as gaps in pipe joints, weld defects, and dust deposits. There is concern about corrosion damage such as corrosion.
すきま腐食を電気化学的に評価する方法として、ＪＩＳ Ｇ ０５９２（ステンレス鋼の腐食すきま再不動態化電位測定方法）が知られている。また、従来から、腐食すきま再不動態化電位（ＥＲ，ＣＲＥＶ）と自然ポテンシャル（Ｅｓｐ）とを比較し、すきま腐食が自発的に発生するかどうかを判定する試験が行われている（例えば、非特許文献１〜３、参照）。 As a method for electrochemically evaluating crevice corrosion, JIS G 0582 (a method for measuring the corrosion crevice repassivation potential of stainless steel) is known. Further, conventionally, corrosion crevice repassivation potential (E R, CREV) compares the natural potential (E sp), judges test whether crevice corrosion occur spontaneously is performed (e.g. Non-patent documents 1 to 3).
一方、すきま腐食の進展状況を評価するため、ガラス、石英、樹脂等の透明な物質と試験片との間にすきまを形成し、腐食媒中に浸漬した状態で、すきまの腐食状況を直接観察する試験方法が提案されている（例えば、特許文献１、参照）。 On the other hand, in order to evaluate the progress of crevice corrosion, a clearance is formed between a transparent material such as glass, quartz, or resin and a test piece, and the corrosion status of the crevice is directly observed while immersed in a corrosion medium. A test method has been proposed (for example, see Patent Document 1).
更に、光学顕微鏡の対物レンズと試験片との間を電解液で満たし、電気化学的測定を行いながら、すきま腐食の発生状況を観察する方法が提案されている（例えば、特許文献２、参照）。この方法では、微小な領域の観察及び電気化学的測定が可能であり、すきま腐食の発生及び初期の状態については、その場観察が可能である。 Furthermore, a method for observing the occurrence of crevice corrosion while filling the space between the objective lens of the optical microscope and the test piece with an electrolyte and performing electrochemical measurement has been proposed (for example, see Patent Document 2). . In this method, it is possible to observe a minute region and perform electrochemical measurement, and it is possible to observe in situ the occurrence of crevice corrosion and the initial state.
すきま腐食の発生や進展状況を直接観察する特許文献１及び２の方法によれば、すきま腐食の面積の増加、即ち、二次元的な広がりの経時変化を評価することができる。しかし、腐食による金属材料の寿命は、特定の部位での深さ方向への腐食の進展が大きく影響するので、腐食部位の形態及びその経時的な変化を評価することが重要である。 According to the methods of Patent Documents 1 and 2 for directly observing the occurrence and progress of crevice corrosion, it is possible to evaluate the increase in the area of crevice corrosion, that is, change with time of two-dimensional spread. However, since the life of a metal material due to corrosion is greatly affected by the progress of corrosion in a depth direction at a specific site, it is important to evaluate the form of the corrosion site and its change over time.
金属材料の腐食は、重量減や経時的な変化から求められる腐食速度によって評価することが多いが、腐食環境における金属材料の寿命の決定には、特定の部位の板厚の減少、即ち、最大すきま腐食深さの評価が重要である。 The corrosion of metallic materials is often evaluated by the corrosion rate required from weight loss and changes over time, but in determining the life of metallic materials in a corrosive environment, the reduction of the plate thickness at a specific site, that is, the maximum Evaluation of crevice corrosion depth is important.
本発明者らは、自然海水中に浸漬したＳＵＳ３０４鋼やＳＵＳ３１６Ｌ鋼などのステンレス鋼に発生したすきま腐食損傷を観察した。その結果、すきま腐食の形態には、全面腐食的に活性溶解している部位と、孔食的に腐食している部位とが混在することが判明した。すきま腐食の直接観察と電気化学測定とを組み合わせると、すきま腐食の面積と体積の増加などを評価することが可能になるが、特定の部位のすきま腐食の深さを正確に測定することはできない。 The present inventors observed crevice corrosion damage generated in stainless steel such as SUS304 steel and SUS316L steel immersed in natural seawater. As a result, it has been found that the crevice corrosion forms include a part that is actively dissolved in a general corrosion manner and a part that is pitting corrosion in a mixed manner. Combining direct observation of crevice corrosion and electrochemical measurement makes it possible to evaluate the increase in crevice corrosion area and volume, but it is not possible to accurately measure crevice corrosion depth at a specific site. .
特定の部位のすきま腐食の深さを測定するため、すきま腐食試験を中断して形状測定を行い、試験を再開した場合は、その後のすきま腐食の進展に影響が及ぶと考えられる。一方。試験時間を変えて、すきま腐食の進展による形状の変化を評価しようとすると、試験に要する時間が非常に長くなってしまう。 In order to measure the depth of crevice corrosion in a specific part, if crevice corrosion test is interrupted and shape measurement is performed and the test is restarted, it is considered that the progress of crevice corrosion thereafter will be affected. on the other hand. If it is tried to change the test time and evaluate the shape change due to the progress of crevice corrosion, the time required for the test becomes very long.
本発明は、このような実情に鑑み、すきま腐食を発生、進展させながら、すきま腐食の形態、特に深さ方向のプロファイルの測定を行うことにより、すきま腐食による腐食損傷の程度や経時変化を評価できる、すきま腐食試験装置及び方法を提供することを課題とする。 In view of such circumstances, the present invention evaluates the degree of corrosion damage due to crevice corrosion and the change over time by measuring the form of crevice corrosion, particularly the profile in the depth direction, while generating and advancing crevice corrosion. An object of the present invention is to provide a crevice corrosion test apparatus and method that can be used.
本発明者らは、上記の課題を解決すべく、すきま腐食試験を行いながら、試験片に生じるすきま腐食の形態、特に深さ方向のプロファイルの測定を行うため、光学的に物体の三次元形状を測定する装置を利用する方法を検討した。その結果、溶液を満たした腐食セルで、光透過性を有するすきま形成手段と、試験片とを接触させ、試験片の表面に発生するすきま腐食の形状測定を、すきま形成手段を通して行うことで、最大のすきま腐食の深さ及びその時間的な変化を測定できるとの知見を得た。 In order to solve the above problems, the inventors of the present invention optically measured the three-dimensional shape of an object in order to measure the form of crevice corrosion occurring in a test piece, particularly the profile in the depth direction, while conducting a crevice corrosion test. We studied a method of using a device to measure. As a result, in the corrosion cell filled with the solution, the crevice forming means having light transmittance and the test piece are brought into contact with each other, and the shape measurement of crevice corrosion generated on the surface of the test piece is performed through the crevice forming means. It was found that the maximum crevice corrosion depth and its change over time can be measured.
本発明は、上記知見に基づいてなされたもので、その要旨とするところは以下の通りである。
［１］ 試験片の表面観察及び形状測定が可能な光透過性物質からなるすきま形成手段を有し、溶液が充填される腐食セルと、試験片に発生するすきま腐食の深さ方向プロファイルを測定する光学系形状測定手段とを有することを特徴とするすきま腐食試験装置。
［２］ 前記試験片は円柱状であり、前記すきま形成手段は円盤状であり、前記腐食セルの胴体部は円筒状であることを特徴とする上記［１］に記載のすきま腐食試験装置。
［３］ 前記すきま形成手段は、両面が鏡面研磨されていることを特徴とする上記［１］又は［２］に記載のすきま腐食試験装置。
［４］ 前記すきま形成手段は、試験片と対向する面に凸部を有することを特徴とする上記［１］〜［３］のいずれかに記載のすきま腐食試験装置。
［５］ 前記すきま形成手段の前記凸部を除く基部の厚みは３〜５ｍｍであり、前記凸部の厚みは０．３〜３ｍｍであることを特徴とする上記［４］に記載のすきま腐食試験装置。
［６］ 前記試験片と参照電極との電位差を制御する電位制御手段を有することを特徴とする上記［１］〜［５］のいずれかに記載のすきま腐食試験装置。
［７］ 試験片の表面観察及び形状測定が可能な光透過性物質からなるすきま形成手段に接触するように腐食セルの内部に試験片を設置する工程と、前記腐食セルに溶液を充填する工程と、光学系形状測定手段によってすきま腐食の深さ方向プロファイルを測定する工程とを有することを特徴とするすきま腐食試験方法。
［８］ 前記試験片は円柱状であり、前記すきま形成手段は円盤状であることを特徴とする上記［７］に記載のすきま腐食試験方法。
［９］ 前記すきま形成手段は、両面が鏡面研磨されていることを特徴とする上記［７］又は［８］に記載のすきま腐食試験方法。
［１０］ 前記すきま形成手段は、試験片と対向する面に凸部を有することを特徴とする上記［７］〜［９］のいずれかに記載のすきま腐食試験方法。
［１１］ 前記すきま形成手段の前記凸部を除く基部の厚みは３〜５ｍｍであり、前記基部から突出した凸部の厚みは０．３〜３ｍｍであることを特徴とする上記［１０］に記載のすきま腐食試験方法。
［１２］ 前記試験片と参照電極との電位差を制御する電位制御手段によって、前記試験片の電位を一定に保持してすきま腐食を発生させる工程と、前記すきま腐食の発生後、前記試験片の電位をそのまま一定に保持する工程と、前記試験片の電位を、すきま腐食を発生させる工程の電位よりも卑な電位に保持する工程とを有することを特徴とする上記［７］〜［１１］のいずれかに記載のすきま腐食試験方法。
［１３］ 前記すきま腐食を発生させる工程の電位は、１００〜６００ｍＶであり、前記すきま腐食の発生後、前記試験片の電位をそのまま一定に保持する工程の保持時間は５〜６０分であることを特徴とする上記［１２］に記載のすきま腐食試験方法。
The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] It has a crevice forming means consisting of a light-transmitting substance that enables surface observation and shape measurement of the test piece, and measures the depth cell profile of crevice corrosion generated in the corrosion cell filled with the solution and the test piece. And a crevice corrosion test apparatus characterized by having an optical system shape measuring means.
[2] The crevice corrosion test apparatus according to the above [1], wherein the test piece has a columnar shape, the crevice forming means has a disc shape, and the body portion of the corrosion cell has a cylindrical shape.
[3] The crevice corrosion testing apparatus according to [1] or [2], wherein the crevice forming means is mirror-polished on both sides.
[4] The crevice corrosion testing apparatus according to any one of [1] to [3], wherein the crevice forming means has a convex portion on a surface facing the test piece.
[5] The crevice corrosion according to the above [4], wherein a thickness of the base excluding the convex portion of the gap forming means is 3 to 5 mm, and a thickness of the convex portion is 0.3 to 3 mm. Test equipment.
[6] The crevice corrosion test apparatus according to any one of [1] to [5], further including a potential control unit that controls a potential difference between the test piece and the reference electrode.
[7] A step of installing the test piece inside the corrosion cell so as to come into contact with a gap forming means made of a light transmissive material capable of surface observation and shape measurement of the test piece, and a step of filling the corrosion cell with a solution And a step of measuring a depth direction profile of crevice corrosion by an optical system shape measuring means.
[8] The crevice corrosion test method according to the above [7], wherein the test piece has a cylindrical shape, and the gap forming means has a disk shape.
[9] The crevice corrosion test method according to the above [7] or [8], wherein both surfaces of the crevice forming means are mirror-polished.
[10] The crevice corrosion test method according to any one of [7] to [9], wherein the crevice forming means has a convex portion on a surface facing the test piece.
[11] In the above [10], the thickness of the base portion excluding the convex portion of the gap forming means is 3 to 5 mm, and the thickness of the convex portion protruding from the base portion is 0.3 to 3 mm. The crevice corrosion test method described.
[12] A step of generating crevice corrosion by maintaining a constant potential of the test piece by a potential control means for controlling a potential difference between the test piece and a reference electrode; and after the occurrence of crevice corrosion, [7] to [11] above, characterized by comprising a step of keeping the potential constant as it is, and a step of keeping the potential of the test piece at a potential lower than the potential of the step of generating crevice corrosion. The crevice corrosion test method as described in any one of.
[13] The potential of the step of generating crevice corrosion is 100 to 600 mV, and the holding time of the step of holding the potential of the test piece constant as it is after the occurrence of crevice corrosion is 5 to 60 minutes. The crevice corrosion test method as described in [12] above.
本発明によれば、試験片に生じるすきま腐食の形態及び形状、特に深さ方向のプロファイルを測定することが可能になり、すきま腐食の進展による金属材料の使用寿命を精度良く評価することができる。 According to the present invention, it becomes possible to measure the form and shape of crevice corrosion occurring in a test piece, particularly the profile in the depth direction, and the service life of a metal material due to progress of crevice corrosion can be accurately evaluated. .
本発明のすきま腐食試験装置について説明する。 The crevice corrosion test apparatus of the present invention will be described.
本発明のすきま腐食試験装置は、主に、試験片が設置され、溶液が充填される腐食セルと、試験片に発生するすきま腐食の深さ方向プロファイルを測定する光学系形状測定手段と、によって構成される。光学系形状測定手段は、すきま腐食の形状の測定を行う位置を特定するため、すきま腐食の観察を行う機能を兼ね備えている。 The crevice corrosion test apparatus of the present invention mainly includes a corrosion cell in which a test piece is installed and filled with a solution, and an optical system shape measuring means for measuring a depth direction profile of crevice corrosion generated in the test piece. Composed. The optical system shape measuring means also has a function of observing crevice corrosion in order to identify the position where the crevice corrosion shape is measured.
まず、腐食セルについて説明する。 First, the corrosion cell will be described.
図１は、本発明の腐食セルの一例を説明する図である。下方の図が腐食セルの正面図で、上方の図が腐食セルの上面図である。腐食セルは、密閉構造であり、試験片１を設置するネジ付き台座１０と、試験片１を格納し、試験溶液４で満たされる胴体部である外側ネジ付きリング８と、腐食セル内に設置された試験片１にすきま腐食を発生させるすきま形成手段とを有している。すきま形成手段は、光透過性物質５及び光透過性物質凸部６によって構成され、内側ネジ付き押えリング７によって外側ネジ付きリング８に固定される。 FIG. 1 is a diagram for explaining an example of the corrosion cell of the present invention. The lower figure is a front view of the corrosion cell, and the upper figure is a top view of the corrosion cell. The corrosion cell has a hermetically sealed structure, a threaded pedestal 10 on which the test piece 1 is installed, an outer threaded ring 8 that is a body portion that stores the test piece 1 and is filled with the test solution 4, and is installed in the corrosion cell. And crevice forming means for generating crevice corrosion in the test piece 1. The clearance forming means is constituted by the light transmissive material 5 and the light transmissive material convex portion 6 and is fixed to the outer threaded ring 8 by the inner threaded retaining ring 7.
図２は、本発明の腐食セルのネジ切り構造部位を説明する図である。下方の図が腐食セルの正面図で、上方の図が腐食セルの上面図である。ネジ部を太線で示してある。円筒状の外側ネジ付きリング８の外側の上部及び下部にはネジが備えられ、それぞれ、内側ネジ付き押さえリング９の上部の内側及び内側ネジ付き押さえリング７の下部の内側に設けられたネジと螺合することにより、腐食セルは密閉構造となる。 FIG. 2 is a diagram illustrating a threaded structure portion of the corrosion cell according to the present invention. The lower figure is a front view of the corrosion cell, and the upper figure is a top view of the corrosion cell. The threaded portion is indicated by a thick line. Screws are provided at the upper and lower portions of the outer side of the cylindrical outer threaded ring 8, and the screws provided on the inner side of the upper part of the inner threaded retaining ring 9 and the inner side of the lower part of the inner threaded retaining ring 7, respectively. By screwing, the corrosion cell becomes a sealed structure.
また、図１及び２に示した腐食セルは、電位制御や電気化学測定を行うことができるように、電極として対極２（白金電極ＣＥ）及び参照電極３（ＲＥ）を備えている。電極及び試験片１を、図示しない電位制御手段（ポテンショスタット）に接続すれば、定電位電解や電気化学測定による腐食量の評価などを行うことができる。腐食セルの外側ネジ付きリング８に設けられた電極を通す穴は、シール材などによって塞がれ、密閉構造が保たれる。 Further, the corrosion cell shown in FIGS. 1 and 2 includes a counter electrode 2 (platinum electrode CE) and a reference electrode 3 (RE) as electrodes so that potential control and electrochemical measurement can be performed. If the electrode and the test piece 1 are connected to a potential control means (potentiostat) (not shown), the corrosion amount can be evaluated by constant potential electrolysis or electrochemical measurement. The hole through which the electrode provided in the outer threaded ring 8 of the corrosion cell passes is closed by a sealing material or the like, and a sealed structure is maintained.
図３は、試験片を支持するネジ付き台座の一例を説明する図である。下方の図がネジ付き台座の正面図で、上方の図がネジ付き台座の上面図である。試験片１は円柱状であり、下部に設けられたネジと、ネジ付き台座１０の中央の穴に設けられたネジとを螺合することにより、試験片１をネジ付き台座１０に設置する。ネジを回転すると、試験片１とすきま形成手段との距離を調整することができる。腐食セルの外側ネジ付きリング８を円筒状とし、試験片１を円柱状とすることにより、溶液中で腐食セルを組み立てることが可能なり、容易に腐食セル内への空気の混入を防止することができる。腐食セルの外側ネジ付きリング８は、アクリル製が好ましい。 FIG. 3 is a diagram for explaining an example of a threaded base that supports the test piece. The lower figure is a front view of the threaded base, and the upper figure is a top view of the threaded base. The test piece 1 has a cylindrical shape, and the test piece 1 is installed on the screwed base 10 by screwing a screw provided in the lower part with a screw provided in a central hole of the screwed base 10. When the screw is rotated, the distance between the test piece 1 and the gap forming means can be adjusted. By making the outer threaded ring 8 of the corrosion cell cylindrical and the test piece 1 cylindrical, it is possible to assemble the corrosion cell in solution and easily prevent air from entering the corrosion cell. Can do. The outer threaded ring 8 of the corrosion cell is preferably made of acrylic.
図４は、本発明の腐食セルのすきま形成手段の一例を説明する図である。下方の図がすきま形成手段の正面図で、上方の図がすきま形成手段の上面図である。すきま形成手段は、光透過性物質５及び光透過性物質凸部６によって構成されている。光透過性物質５は、光透過性物質の厚みａと、光透過性物質の直径ｂとを有する。光透過性物質凸部６は、光透過性物質凸部の高さｃと、光透過性物質凸部の直径ｄとを有する。しかし、すきま形成手段は、凸部のない単純な円盤状でもよい。 FIG. 4 is a view for explaining an example of the clearance forming means of the corrosion cell according to the present invention. The lower figure is a front view of the gap forming means, and the upper figure is a top view of the gap forming means. The gap forming means is constituted by the light transmissive material 5 and the light transmissive material convex portion 6. The light transmissive material 5 has a thickness a of the light transmissive material and a diameter b of the light transmissive material. The light transmissive substance convex part 6 has the height c of the light transmissive substance convex part, and the diameter d of the light transmissive substance convex part. However, the clearance forming means may be a simple disk shape without a convex portion.
すきま形成手段に光透過性物質凸部６を設ける場合、光透過性物質凸部６を除く基部の厚みである光透過性物質の厚みａを３〜５ｍｍとする。光透過性物質の厚みａを３ｍｍ以上とすることにより、試験片１の位置をネジで調整し、光透過性物質凸部６に接触させる際に、誤って過大な応力が負荷されても、すきま形成手段の破損を防止することができる。また、すきま腐食を観察する場合、光透過性物質の厚みａの厚みを５ｍｍ以下とすれば、光透過性物質凸部６の厚みを加えても、光が透過する厚みは８ｍｍ以下になり、色収差や画像の歪みなどの発生を抑制することができる。 When the light transmissive substance convex part 6 is provided in the gap forming means, the thickness a of the light transmissive substance, which is the thickness of the base excluding the light transmissive substance convex part 6, is set to 3 to 5 mm. By adjusting the thickness a of the light transmissive substance to 3 mm or more and adjusting the position of the test piece 1 with a screw and bringing it into contact with the light transmissive substance convex portion 6, even if an excessive stress is accidentally applied, Breakage of the clearance forming means can be prevented. In addition, when observing crevice corrosion, if the thickness a of the light-transmitting substance is 5 mm or less, even if the thickness of the light-transmitting substance convex portion 6 is added, the thickness at which light is transmitted is 8 mm or less Occurrence of chromatic aberration and image distortion can be suppressed.
そして、基部から突出した部位の厚みである光透過性物質凸部の高さｃを０．３〜３ｍｍにする。腐食セル内に電極を設置し、試験片と標準電極との電位差を制御する電位制御手段によって、定電位電解処理を行う場合、光透過性物質凸部の高さｃを０．３ｍｍ以上にすることにより、金属イオンの蓄積を防止することができる。また、対極２（白金電極ＣＥ）から発生する気泡が、すきまに停滞することを防ぐには、光透過性物質凸部の高さｃを３ｍｍ以下にする。好ましくは、１〜２ｍｍである。 And the height c of the light transmissive substance convex part which is the thickness of the site | part which protruded from the base part shall be 0.3-3 mm. When the electrode is installed in the corrosion cell and the constant potential electrolysis treatment is performed by the potential control means for controlling the potential difference between the test piece and the standard electrode, the height c of the light transmitting substance convex portion is set to 0.3 mm or more. Thus, accumulation of metal ions can be prevented. Further, in order to prevent bubbles generated from the counter electrode 2 (platinum electrode CE) from staying in the gap, the height c of the light transmissive substance convex portion is set to 3 mm or less. Preferably, it is 1-2 mm.
試験片１とすきま形成手段との間にすきまが形成され、すきま腐食が生じ、進展する。このとき、すきま腐食は、すきまの外周部の近傍で進展し易い。光学系形状測定手段で、すきま腐食の深さを測定する場合、すきま腐食が発生する位置よりも外側では、すきま腐食が発生していないことが好ましい。 A gap is formed between the test piece 1 and the gap forming means, and crevice corrosion occurs and progresses. At this time, crevice corrosion tends to progress in the vicinity of the outer periphery of the crevice. When measuring the depth of crevice corrosion with the optical system shape measuring means, it is preferable that crevice corrosion does not occur outside the position where crevice corrosion occurs.
すきま形成手段に光透過性物質凸部６を設けると、すきま腐食は、光透過性物質凸部６よりも外側では進行しないため、すきま腐食の形状測定を精度良く行うことが可能になる。 If the light transmissive substance convex part 6 is provided in the crevice forming means, the crevice corrosion does not proceed outside the light transmissive substance convex part 6, so that the shape measurement of the crevice corrosion can be accurately performed.
すきま腐食の形状測定は、光学的な原理に基づく光学系形状測定手段で行うことから、すきま形成手段の材質は、光透過性の物質とする。 Since the crevice corrosion shape measurement is performed by an optical system shape measurement means based on an optical principle, the material of the crevice formation means is a light-transmitting substance.
光透過性の物質としては、例えば、石英製ガラス板、パイレックス(登録商標)ガラス、鉛ガラスなどガラス類や、アクリル、ポリカーボネイトなどの樹脂類、ホタル石、人工ルビーや人工ジルコンなどの鉱石又は人工鉱石類を用いることができる。このうち、石英製ガラス板は、入手が容易で、強度が高く、耐薬品性が高いなどの利点があるため、好ましい素材である。 Examples of the light-transmitting substance include glass such as quartz glass plate, Pyrex (registered trademark) glass, lead glass, resins such as acrylic and polycarbonate, ores such as fluorite, artificial ruby and artificial zircon, or artificial Ore can be used. Among these, a quartz glass plate is a preferable material because it has advantages such as easy availability, high strength, and high chemical resistance.
すきま腐食の発生及び進展や試験溶液の変化を観察するためには、すきま形成手段の試験片１に接する側の面と、その反対側の空気に触れる側の面との両面に、鏡面研磨を施すことが好ましい。 In order to observe the occurrence and progress of crevice corrosion and changes in the test solution, mirror polishing is applied to both the surface of the crevice forming means that is in contact with the test piece 1 and the opposite surface that is in contact with air. It is preferable to apply.
図５は、本発明の腐食セルの押さえリングの一例を説明する図である。下方の図が押さえリングの正面図で、上方の図が押さえリングの上面図である。図５に示すように、腐食セルの押さえリング７、９が円筒状であるため、それに合わせて、すきま形成手段は円盤状である。 FIG. 5 is a view for explaining an example of the pressing ring of the corrosion cell of the present invention. The lower figure is a front view of the pressing ring, and the upper figure is a top view of the pressing ring. As shown in FIG. 5, since the pressing rings 7 and 9 of the corrosion cell are cylindrical, the gap forming means is disk-shaped accordingly.
図６は、本発明の腐食セルの外側ネジ付きリングの一例を説明する図である。外側ネジ付きリング８は、ゴム製のパッキン溝１１を備えている。 FIG. 6 is a diagram for explaining an example of the outer threaded ring of the corrosion cell of the present invention. The outer threaded ring 8 includes a rubber packing groove 11.
図７は、本発明の試験片の一例を説明する図である。上方の図が試験片の正面図で、下方の図が試験片の下面図である。試験片１の下部側面にネジ切り１２が施されており、試験片１を設置するネジ付き台座１０と連結させ、光透過性物質凸部６と試験片1との間に生じるすきま部の締め付け具合を調製できるように工夫してある。また、試験片1下部には、マイナス溝１３があり、光透過性物質凸部６と試験片1との間に生じるすきま部の締め付けを容易なものとした。 FIG. 7 is a diagram for explaining an example of the test piece of the present invention. The upper figure is a front view of the test piece, and the lower figure is a bottom view of the test piece. The lower side surface of the test piece 1 is threaded 12, and is connected to a threaded base 10 on which the test piece 1 is installed, and tightens a gap formed between the light-transmitting substance convex portion 6 and the test piece 1. It is devised so that the condition can be adjusted. In addition, a minus groove 13 is provided at the lower part of the test piece 1 to facilitate tightening of a gap portion formed between the light transmitting substance convex portion 6 and the test piece 1.
次ぎに、光学系形状測定手段について説明する。 Next, the optical system shape measuring means will be described.
図８は、本発明のすきま腐食試験装置の光学系形状測定手段の一例を説明する図である。光学系形状測定手段は、胴体１４と、その上部略中央に配置される観察レンズ１５と、観察レンズ１５の両側に配置する計測レンズ１６とを含んでいる。そして、胴体１４の略中央のＸＹステージ上に、試験片１７を格納した腐食セル１８を設置し、試験片１７の表面に複数の異なる方向に設置したＬＥＤ光源から光を照射し、反射光を捉えて、三角測量の原理により、表面の凹凸を計測する。 FIG. 8 is a diagram for explaining an example of the optical system shape measuring means of the crevice corrosion test apparatus of the present invention. The optical system shape measuring means includes a body 14, an observation lens 15 disposed substantially at the upper center thereof, and measurement lenses 16 disposed on both sides of the observation lens 15. And the corrosion cell 18 which accommodated the test piece 17 is installed on the XY stage of the substantially center of the fuselage | body 14, and it irradiates light from the LED light source installed in the several different direction on the surface of the test piece 17, and reflects light Measure surface irregularities using the principle of triangulation.
光学系形状測定手段は、市販の装置を用いることができるが、マクロ的な観察機能を有することが好ましい。光学系形状測定手段に、試験片及び溶液を格納した腐食セルを設置し、すきま腐食試験を行いながら、深さ方向の形状を測定することができる。光学系形状測定手段として、例えば、キーエンス社製ＶＲ−３０００ ３Ｄマクロスコープを好適に用いることができる。 A commercially available apparatus can be used as the optical system shape measuring means, but it is preferable to have a macroscopic observation function. It is possible to measure the shape in the depth direction while performing a crevice corrosion test by installing a corrosion cell storing a test piece and a solution in the optical system shape measuring means. For example, a VR-3000 3D macroscope manufactured by Keyence Corporation can be suitably used as the optical system shape measuring means.
本発明のすきま腐食試験方法について説明する。 The crevice corrosion test method of the present invention will be described.
本発明のすきま腐食試験方法は、主に、光透過性物質からなるすきま形成手段に接触するように、腐食セルの内部に試験片を設置し、腐食セルに溶液を充填し、光学系形状測定手段によって、すきま腐食の深さ方向プロファイルを測定して、試験するものである。そして、すきま腐食は、次に説明するように、試験片の電位を制御して発生させる。 In the crevice corrosion test method of the present invention, a test piece is installed inside a corrosion cell so as to be in contact with a gap forming means mainly made of a light-transmitting substance, the solution is filled in the corrosion cell, and an optical system shape measurement is performed. By means, the depth profile of crevice corrosion is measured and tested. The crevice corrosion is generated by controlling the potential of the test piece as described below.
電位を制御しながらすきま腐食試験を行う場合、自然浸漬状態で起こるすきま腐食現象における電位の変化を模擬する。そのために、すきま腐食の発生後、電位をしばらく保持してから、卑な電位とすることが好ましい。これは、本発明者らが、海水中での金属材料の自然電位の解析を行った結果に基づいている。 When a crevice corrosion test is performed while controlling the potential, the potential change in the crevice corrosion phenomenon that occurs in the natural immersion state is simulated. Therefore, it is preferable to maintain the potential for a while after the occurrence of crevice corrosion, and then to make the base potential. This is based on the result of the present inventors analyzing the natural potential of a metal material in seawater.
図９は、海水に漬浸されたステンレス鋼の自然電位の変化を説明する図であり、ステンレス鋼を海水に浸漬し、すきま腐食を発生させた際の、自然電位の経時変化である。自然電位は、卑な電位から徐々に貴な電位になり、ほぼ一定値となるが、ある時間経つと、自然電位は急激に卑な電位方向にシフトする。これは、すきま腐食の発生により、発生部位とその周辺の領域の電位が卑な電位になり、試験片の全体の電位が卑化したものと考えられる。 FIG. 9 is a diagram for explaining a change in natural potential of stainless steel immersed in seawater, and shows a change in natural potential with time when stainless steel is immersed in seawater to cause crevice corrosion. The natural potential gradually becomes a noble potential from the base potential and becomes a substantially constant value, but after a certain period of time, the natural potential suddenly shifts toward the base potential. This is thought to be due to the occurrence of crevice corrosion, in which the potential at the site of occurrence and the surrounding area becomes a low potential, and the overall potential of the test piece is low.
図１０は、自然浸漬状態で発生するすきま腐食と電位の変化を模擬する定電位電解処理を説明する図である。自然浸漬状態で発生するすきま腐食と電位の変化を模擬するため、試験の初期には、貴な電位Ｅ１に保持し、すきま腐食の発生後もしばらく電位Ｅ１で保持してから、電位Ｅ１よりも卑な電位Ｅ２に保持することが好ましい。 FIG. 10 is a diagram for explaining a constant-potential electrolysis process that simulates crevice corrosion and potential change that occur in a natural immersion state. To simulate changes in the crevice corrosion and potential generated by the natural immersion state, the initial test, held in the noble potentials E 1, and held there while the potential E 1 after the occurrence of crevice corrosion, the potential E It is preferable to maintain the potential E 2 which is lower than 1 .
本発明者らは、一般的な金属材料の場合、Ｅ１は概ね１００〜６００ｍＶであり、例えば、ＳＵＳ３０４鋼では、概ね１００ｍＶ以上であることを知見した。したがって、自然浸漬状態のすきま腐食を模擬するため、Ｅ１を１００ｍＶ以上とする。Ｅ１を高くすれば、すきま腐食が発生するまでの時間を短縮することができる。一方、孔食など、すきま腐食以外の腐食の発生を抑制するために、Ｅ１を６００ｍＶ以下とする。好ましくは、１５０〜５００ｍＶ、より好ましくは、２００〜４００ｍＶである。 The present inventors have found that when a general metal material, E 1 is generally 100～600MV, for example, in SUS304 steel was found that is approximately 100mV or more. Therefore, in order to simulate crevice corrosion in a natural immersion state, E 1 is set to 100 mV or more. If higher E 1, it is possible to shorten the time until the crevice corrosion is generated. On the other hand, in order to suppress the occurrence of corrosion other than crevice corrosion such as pitting corrosion, E 1 is set to 600 mV or less. Preferably, it is 150-500 mV, More preferably, it is 200-400 mV.
また、すきま腐食が発生してから、卑な電位とするまでの保持時間ｔ１を、３００秒（５分）以上とする。また、保持時間ｔ１を長くすると、すきま腐食の進展度合いが増大するが、時間的な制約の観点から、３６００秒（６０分）以下とする。 Further, the holding time t 1 from the occurrence of crevice corrosion until the base potential is reached is set to 300 seconds (5 minutes) or more. A longer holding time t 1, but the progress degree of crevice corrosion is increased, in terms of time constraints, and 3600 seconds (60 minutes) or less.
その後の定電位値Ｅ２は、例えば、一般的なＳＵＳ３０４鋼の場合、１００〜２５０ｍＶであることが知見された。この時の保持時間ｔ２も任意であるが、時間的制約の観点からは２５０００秒（約４２０分）以内が望ましい。 Subsequent constant potential values E 2 are, for example, for a typical SUS304 steel, it has been found to be 100～250MV. The holding time t 2 at this is arbitrary, in terms of time constraints 25,000 seconds (about 420 minutes) is desirably within.
次に、本発明のすきま腐食試験装置及びすきま腐食試験方法の実施例について説明するが、実施例での条件は、本発明の実施可能性及び効果を確認するために採用した一条件例であり、本発明は、この一条件例に限定されるものではない。本発明は、本発明の要旨を逸脱せず、本発明の目的を達成する限りにおいて、種々の条件を採用し得るものである。 Next, examples of the crevice corrosion test apparatus and crevice corrosion test method of the present invention will be described. The conditions in the examples are one example of conditions used to confirm the feasibility and effects of the present invention. The present invention is not limited to this one condition example. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.
ＳＵＳ３０４鋼を直径２０ｍｍ、高さ３９ｍｍの円柱状の試験片に加工し、試験片全体を３０％硝酸、５０℃の溶液に約１ｈ間浸漬して、試験片の表面全体を不動態化させた。硝酸水溶液浸漬による不動態化処理は、試験片のすきま部以外の部位での、腐食の発生を防止するために行った。その後、試験片の下端にリード線をビスで固定した。試験片のすきま形成手段側の面（試験面）は、試験を開始する直前に、湿式で♯４００番研磨した。 SUS304 steel was processed into a cylindrical test piece having a diameter of 20 mm and a height of 39 mm, and the entire test piece was immersed in a solution of 30% nitric acid and 50 ° C. for about 1 h to passivate the entire surface of the test piece. . Passivation treatment by immersion in a nitric acid aqueous solution was performed in order to prevent the occurrence of corrosion at sites other than the gaps of the test piece. Then, the lead wire was fixed to the lower end of the test piece with a screw. The surface on the gap forming means side (test surface) of the test piece was polished # 400 by wet just before starting the test.
試験片の周囲に白金電極（対極ＣＥ）を配置し、小型の参照電極（飽和ＫＣｌ溶液を用いた銀−塩化銀電極、ＲＥ）を装着した。円筒状の外側ネジ付きリングと、試験片を設置したネジ付き台座と、すきま形成手段を固定する内側ネジ付き押さえリングで腐食セルを形成し、人工海水を充填した。その後、ネジ付き台座の穴に設けたネジと螺合する試験片の下部に設けたネジによって、石英ガラス製のすきま形成手段の光透過性物質凸部に試験片を接触させた。 A platinum electrode (counter electrode CE) was arranged around the test piece, and a small reference electrode (a silver-silver chloride electrode using a saturated KCl solution, RE) was attached. Corrosion cells were formed with a cylindrical outer threaded ring, a threaded pedestal on which a test piece was installed, and an inner threaded retaining ring for fixing the gap forming means, and filled with artificial seawater. Thereafter, the test piece was brought into contact with the light transmitting substance convex portion of the gap forming means made of quartz glass with a screw provided at a lower portion of the test piece to be screwed with a screw provided in a hole of the screwed base.
電極及び試験片をリード線によって、ポテンショスタットに接続し、キーエンス社のＶＲ−３０００型３Ｄ マクロスコープのＸＹステージ上に腐食セルを設置した。２５℃、空気飽和条件で、１０分間、自然電位を測定した。その後、電位Ｅ１を４９９ｍＶとして第一の定電位電解を行い、試験片にすきま腐食の発生が確認されてから約１０分間、Ｅ１の電位に保持した。続いて、Ｅ２の電位を、それぞれ、２４９ｍＶ、１９９ｍＶ、１４９ｍＶ及び９９ｍＶとし、２２０００秒間保持する第二定電位電解を行った。すきま腐食試験を行いながら、すきま腐食の観察及びすきま部の深さ測定を行った。 The electrode and the test piece were connected to a potentiostat with lead wires, and a corrosion cell was installed on the XY stage of a VR-3000 3D macroscope manufactured by Keyence Corporation. The natural potential was measured for 10 minutes at 25 ° C. under air saturation. Thereafter, the first constant potential electrolysis potential E 1 as 499MV, about 10 minutes after the occurrence of crevice corrosion was confirmed in the test piece was held at a potential of E 1. Subsequently, the potential of E 2, respectively, and 249mV, 199mV, and 149mV and 99 mV, was carried out a second constant potential electrolysis for holding 22000 seconds. While conducting the crevice corrosion test, the crevice corrosion was observed and the depth of the crevice portion was measured.
図１１は、本発明の試験方法によって測定された電位−時間曲線及びそれに対応した電流−時間曲線の一例を説明する図である。ここで、すきま腐食進展時間とは、全測定時間ｔから、すきま腐食の発生が目視確認された時間ｔＶＩを引いた（ｔ−ｔＶＩ）で示される時間である。ｔＶＩに達してから６００秒経過すると同時に、試験片の電位Ｅ２を各電位に保持した。Ｅ２に応じて、これに対応する電位は種々に変化するが、概して、Ｅ２が貴な電位ほど試験片に流れる電流は大きくなっている。 FIG. 11 is a diagram for explaining an example of a potential-time curve and a corresponding current-time curve measured by the test method of the present invention. Here, the crevice corrosion progress time is a time indicated by (t−t VI ) obtained by subtracting a time t VI at which occurrence of crevice corrosion was visually confirmed from the total measurement time t. At the same time as 600 seconds had elapsed after reaching t VI , the potential E 2 of the test piece was held at each potential. Depending on E 2 , the corresponding potential changes variously, but generally, the current flowing through the test piece increases as the potential of E 2 becomes higher.
図１２は、本発明のすきま腐食試験装置によって撮影されたすきま内の画像の一例を説明する図である。この画像は、図１１の結果のうち、Ｅ１＝４９９ｍＶ、Ｅ２＝２４９ｍＶの電位−すきま腐食進展時間曲線と、これに対応するすきま内の観察画像である。すきま腐食が、時間の経過と共に徐々に広がってゆく様子を観察することができた。 FIG. 12 is a diagram for explaining an example of an image in a gap photographed by the crevice corrosion test apparatus of the present invention. This image is a potential-crevice corrosion progress time curve of E 1 = 499 mV and E 2 = 249 mV among the results of FIG. 11 and an observation image in the gap corresponding thereto. It was possible to observe the crevice corrosion gradually spreading over time.
図１３は、本発明のすきま腐食試験装置によって測定されたすきま腐食深さ断面プロフィールの一例を説明する図であり、Ｅ２＝２４９ｍＶ、２２０００ｓ後のすきま腐食部画像と、二次元及び三次元のすきま腐食深さ分布である。そして、すきま部の最も腐食が進行している位置での概観を示している。Ｅ２＝２４９ｍＶ、２２０００ｓ後のすきま腐食深さ分布では、円で示した位置での腐食深さが最も深くなっている。グラフは、すきま腐食深さ断面プロフィールの一例であり、図中に円で示した位置を通る直線上の深さを示している。 FIG. 13 is a diagram for explaining an example of a crevice corrosion depth cross-sectional profile measured by the crevice corrosion test apparatus according to the present invention. An image of crevice corrosion portion after E 2 = 249 mV and 22000 s and two-dimensional and three-dimensional images are shown. Crevice corrosion depth distribution. Then, an overview is shown at the position where the corrosion of the gap portion is most advanced. In the crevice corrosion depth distribution after E 2 = 249 mV and 22000 s, the corrosion depth at the position indicated by the circle is the deepest. The graph is an example of a crevice corrosion depth cross-sectional profile, and indicates a depth on a straight line passing through a position indicated by a circle in the drawing.
このような測定を複数回繰り返すことにより、最も深い箇所の特定が可能であり、また、腐食面積及び体積を求めることができる。図１４は、すきま腐食の総面積及び総体積の測定方法及び測定結果の一例を説明する図である。図１４は、図１３と同じ位置での結果である。深さ閾値を５μｍに設定し、これより深いものだけを表示している。 By repeating such measurement a plurality of times, the deepest part can be specified, and the corrosion area and volume can be obtained. FIG. 14 is a diagram for explaining an example of the measurement method and measurement result of the total area and total volume of crevice corrosion. FIG. 14 shows the result at the same position as in FIG. The depth threshold is set to 5 μm and only deeper than this is displayed.
図１４の計測領域指定の図に示すＮｏ．１〜３において測定した、体積、断面積、表面積、平均深さ、最大深さの結果を表１に示す。 No. shown in the measurement area designation diagram of FIG. Table 1 shows the results of volume, cross-sectional area, surface area, average depth, and maximum depth measured in 1 to 3.
図１５は、本発明のすきま腐食試験装置によって測定された、図１３のすきま腐食深さ断面プロフィールを拡大して説明する図である。すなわち、図１５は、すきま部の一番深い位置（図１３に円で示した位置）の高倍率解析結果を示しており、すきま腐食深さは、２７０μｍであった。図１５は、最も深くなる箇所のすきま腐食深さ断面プロフィールであり、この位置を定点とし、測定初期からの深さプロフィールの時間変化を求めることも可能である。 FIG. 15 is an enlarged view illustrating the crevice corrosion depth cross-sectional profile of FIG. 13 measured by the crevice corrosion test apparatus of the present invention. That is, FIG. 15 shows a high-magnification analysis result at the deepest position of the gap (position indicated by a circle in FIG. 13), and the crevice corrosion depth was 270 μm. FIG. 15 shows a crevice corrosion depth cross-sectional profile at the deepest point. With this position as a fixed point, it is also possible to obtain the time change of the depth profile from the initial measurement.
図１６は、すきま腐食深さの経時変化の一例を説明する図であり、Ｅ２＝２４９ｍＶ、１９９ｍＶ、１４９ｍＶ及び９９ｍＶでの最大すきま腐食深さＤｍａｘを、すきま腐食進展時間（ｔ−ｔＶＩ）に対してプロットしたものである。いずれも、定電位値をＥ１からＥ２に切り替え直後のすきま腐食進展時間６００秒の時点では、本測定ではＤｍａｘは近似的に０である。これは、測定閾値を５μｍとしているためで、工学的に問題とならないほど小さい。すきま腐食進展時間の増加とともに、いずれのＥ２においても、徐々にＤｍａｘは増加し、Ｅ２の電位が貴な電位ほど明らかに、Ｄｍａｘは高くなることが明確になった。 Figure 16 is a diagram illustrating an example of a change with time of crevice corrosion depth, E 2 = 249mV, 199mV, maximum crevice corrosion depth D max, crevice corrosion progress time at 149mV and 99mV (t-t VI ). In any case, at the time point of the crevice corrosion progress time 600 seconds immediately after switching the constant potential value from E 1 to E 2 , D max is approximately 0 in this measurement. This is because the measurement threshold value is 5 μm, and is small enough not to cause an engineering problem. With increasing crevice corrosion progress time, in any of the E 2, D max is increased gradually, the potential of the E 2 is clearly the more noble potential, D max became clear that high.
本発明によれば、試験片に生じるすきま腐食の形態及び形状、特に深さ方向のプロファイルを測定することが可能になり、すきま腐食の進展による金属材料の使用寿命を精度良く評価することができる。よって、本発明は、産業上の利用可能性が大きいものである。 According to the present invention, it becomes possible to measure the form and shape of crevice corrosion occurring in a test piece, particularly the profile in the depth direction, and the service life of a metal material due to progress of crevice corrosion can be accurately evaluated. . Therefore, the present invention has great industrial applicability.
１ 試験片（円筒状ＷＥ）
２ 対極（白金電極ＣＥ）
３ 参照電極（ＲＥ）
４ 試験溶液
５ 光透過性物質（円盤状）
６ 光透過性物質凸部
７ 内側ネジ付き押さえリング
８ 外側ネジ付きリング（円筒状）
９ 内側ネジ付き押さえリング
１０ ネジ付き台座（円盤状）
１１ ゴム製パッキン溝
１２ ネジ切り
１３ マイナス溝
１４ 胴体
１５ 観察レンズ
１６ 計測レンズ
１７ 試験片
１８ 腐食セル
ａ 光透過性物質の厚み
ｂ 光透過性物質の直径
ｃ 光透過性物質凸部の高さ
ｄ 光透過性物質凸部の直径
1 Test piece (cylindrical WE)
2 Counter electrode (Platinum electrode CE)
3 Reference electrode (RE)
4 Test solution 5 Light transmissive substance (disk shape)
6 Light transmissive substance convex part 7 Inner threaded retaining ring 8 Outer threaded ring (cylindrical)
9 Inner threaded retaining ring 10 Threaded base (disc shape)
DESCRIPTION OF SYMBOLS 11 Rubber packing groove 12 Thread cutting 13 Minus groove 14 Body 15 Observation lens 16 Measurement lens 17 Test piece 18 Corrosion cell a Thickness of light transmissive substance b Diameter of light transmissive substance c Height of convex part of light transmissive substance d Diameter of convex part of light-transmitting substance
Claims (13)
試験片に発生するすきま腐食の深さ方向プロファイルを測定する光学系形状測定手段と
を有することを特徴とするすきま腐食試験装置。 A corrosion cell having a gap forming means made of a light-transmitting substance capable of observing the surface and measuring the shape of the test piece, and filled with a solution;
A crevice corrosion testing apparatus comprising an optical system shape measuring means for measuring a depth direction profile of crevice corrosion generated in a test piece.
前記すきま形成手段は円盤状であり、
前記腐食セルの胴体部は円筒状である
ことを特徴とする請求項１に記載のすきま腐食試験装置。 The test piece is cylindrical,
The clearance forming means is disk-shaped,
The crevice corrosion test apparatus according to claim 1, wherein the body portion of the corrosion cell is cylindrical.
ことを特徴とする請求項１又は２に記載のすきま腐食試験装置。 The crevice corrosion testing apparatus according to claim 1 or 2, wherein the crevice forming means is mirror-polished on both sides.
前記基部から突出した凸部の厚みは０．３〜３ｍｍである
ことを特徴とする請求項４に記載のすきま腐食試験装置。 The thickness of the base portion excluding the convex portion of the gap forming means is 3 to 5 mm,
5. The crevice corrosion test apparatus according to claim 4, wherein a thickness of the convex portion protruding from the base portion is 0.3 to 3 mm.
前記腐食セルに溶液を充填する工程と、
光学系形状測定手段によってすきま腐食の深さ方向プロファイルを測定する工程と
を有することを特徴とするすきま腐食試験方法。 A step of placing the test piece inside the corrosion cell so as to come into contact with a gap forming means made of a light-transmitting substance capable of observing the surface and measuring the shape of the test piece;
Filling the corrosion cell with a solution;
A crevice corrosion test method comprising: measuring a crevice corrosion depth direction profile by an optical system shape measuring means.
前記すきま形成手段は円盤状である
ことを特徴とする請求項７に記載のすきま腐食試験方法。 The test piece is cylindrical,
The crevice corrosion test method according to claim 7, wherein said crevice formation means is disk shape.
ことを特徴とする請求項７又は８に記載のすきま腐食試験方法。 9. The crevice corrosion test method according to claim 7, wherein the crevice forming means is mirror-polished on both sides.
前記凸部の厚みは０．３〜３ｍｍである
ことを特徴とする請求項１０に記載のすきま腐食試験方法。 The thickness of the base portion excluding the convex portion of the gap forming means is 3 to 5 mm,
The crevice corrosion test method according to claim 10, wherein the thickness of the convex part is 0.3-3 mm.
前記すきま腐食の発生後、前記試験片の電位をそのまま一定に保持する工程と、
前記試験片の電位を、すきま腐食を発生させる工程の電位よりも卑な電位に保持する工程と
を有することを特徴とする請求項７〜１１のいずれか１項に記載のすきま腐食試験方法。 A step of generating crevice corrosion by holding the potential of the test piece constant by potential control means for controlling the potential difference between the test piece and the reference electrode;
A step of maintaining the potential of the test piece constant as it is after the occurrence of crevice corrosion;
The crevice corrosion test method according to any one of claims 7 to 11, further comprising a step of maintaining the potential of the test piece at a lower potential than the potential of the step of generating crevice corrosion.
前記すきま腐食の発生後、前記試験片の電位をそのまま一定に保持する工程の保持時間は５〜６０分である
ことを特徴とする請求項１２に記載のすきま腐食試験方法。 The potential of the step of generating crevice corrosion is 100 to 600 mV,
The crevice corrosion test method according to claim 12, wherein after the crevice corrosion occurs, a holding time of the step of holding the potential of the test piece constant as it is is 5 to 60 minutes.
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| JP7312239B2 (en) | 2016-07-19 | 2023-07-20 | エコラブ ユーエスエイ インク | Control of industrial water treatment by digital imaging |
| US11946841B2 (en) | 2016-07-19 | 2024-04-02 | Ecolab Usa Inc. | Control of industrial water treatment via digital imaging |
| US11953445B2 (en) | 2016-07-19 | 2024-04-09 | Ecolab Usa Inc. | Control of industrial water treatment via digital imaging |
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