JPH09229892A - Method for monitoring anticorrosion of stainless steel piping and indoor piping system made of stainless steel - Google Patents
Method for monitoring anticorrosion of stainless steel piping and indoor piping system made of stainless steelInfo
- Publication number
- JPH09229892A JPH09229892A JP6209796A JP6209796A JPH09229892A JP H09229892 A JPH09229892 A JP H09229892A JP 6209796 A JP6209796 A JP 6209796A JP 6209796 A JP6209796 A JP 6209796A JP H09229892 A JPH09229892 A JP H09229892A
- Authority
- JP
- Japan
- Prior art keywords
- stainless steel
- potential
- corrosion
- steel pipe
- pipe
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 239000010935 stainless steel Substances 0.000 title claims abstract description 65
- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 65
- 238000012544 monitoring process Methods 0.000 title claims abstract description 8
- 238000000034 method Methods 0.000 title claims description 10
- 238000005260 corrosion Methods 0.000 claims abstract description 70
- 230000007797 corrosion Effects 0.000 claims abstract description 70
- 230000002269 spontaneous effect Effects 0.000 claims description 14
- 239000011810 insulating material Substances 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 34
- 239000000463 material Substances 0.000 abstract description 11
- 239000000460 chlorine Substances 0.000 description 18
- 238000012360 testing method Methods 0.000 description 13
- 229910052801 chlorine Inorganic materials 0.000 description 11
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 10
- 238000003466 welding Methods 0.000 description 8
- 229910000831 Steel Inorganic materials 0.000 description 7
- 239000010959 steel Substances 0.000 description 6
- 239000007800 oxidant agent Substances 0.000 description 5
- 239000002184 metal Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000008399 tap water Substances 0.000 description 4
- 235000020679 tap water Nutrition 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 239000011324 bead Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- -1 chlorine ions Chemical class 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical class Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 2
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 241000894007 species Species 0.000 description 2
- 230000001954 sterilising effect Effects 0.000 description 2
- 238000004659 sterilization and disinfection Methods 0.000 description 2
- 241001163841 Albugo ipomoeae-panduratae Species 0.000 description 1
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 1
- 229940123973 Oxygen scavenger Drugs 0.000 description 1
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 229910001431 copper ion Inorganic materials 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000010612 desalination reaction Methods 0.000 description 1
- 235000020188 drinking water Nutrition 0.000 description 1
- 239000003651 drinking water Substances 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 235000020681 well water Nutrition 0.000 description 1
- 239000002349 well water Substances 0.000 description 1
Landscapes
- Testing Resistance To Weather, Investigating Materials By Mechanical Methods (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、屋内配管用に使用され
るステンレス鋼管の耐食性をモニタリングする方法及び
そのモニタリング手段を備えたステンレス鋼管製屋内配
管システムに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for monitoring the corrosion resistance of a stainless steel pipe used for indoor piping and a stainless steel pipe indoor piping system equipped with the monitoring means.
【０００２】[0002]
【従来の技術】ホテル，マンション等のビルの給水，給
湯用屋内配管には、Ｚｎめっき鋼管，塩化ビニルライニ
ング鋼管，銅管等が使用されている。地域によっては使
用水の水質が変化し、水質の変化に対応した水処理が施
されている。そのため、たとえば使用原水の汚染が進ん
でいるところでは、塩素イオンや滅菌のための残留塩素
の濃度増加等によって配管の腐食が進行し易くなる環境
にある。Ｚｎめっき鋼管では、赤水や白錆の沈澱による
機器の目詰り対策が望まれる。ライニング鋼管は、継手
等の異種金属接触部でガルバニック腐食を起こし、長期
にわたる使用では赤水発生の虞れがある。銅管は、主と
して給湯用途に使用されているが、孔食等が発生し、腐
食に伴い銅イオンの溶出に起因して青水を発生させる虞
れがある。腐食に起因したトラブルを解消するため、最
近では屋内配管に対してステンレス鋼管が適用され始め
ている。現在使用されている屋内配管用のステンレス鋼
管は、オーステナイト系のＳＵＳ３０４が主流である。2. Description of the Related Art Zn-plated steel pipes, vinyl chloride lining steel pipes, copper pipes and the like are used for indoor water supply and hot water supply pipes of buildings such as hotels and condominiums. Depending on the region, the quality of the water used changes, and water treatment is applied in response to changes in water quality. Therefore, for example, where the raw water used is contaminated, there is an environment in which the corrosion of the pipes easily progresses due to an increase in the concentration of chlorine ions or residual chlorine for sterilization. For Zn-plated steel pipes, it is desired to take measures against clogging of equipment due to precipitation of red water or white rust. The lining steel pipe causes galvanic corrosion at a dissimilar metal contact portion such as a joint, and there is a risk of red water generation during long-term use. Copper pipes are mainly used for hot water supply, but there is a risk that pitting corrosion and the like will occur, and that blue water will be generated due to the elution of copper ions due to corrosion. Recently, stainless steel pipes have begun to be applied to indoor pipes in order to eliminate problems caused by corrosion. Austenitic SUS304 is the mainstream stainless steel pipe currently used for indoor piping.
【０００３】[0003]
【発明が解決しようとする課題】配管にステンレス鋼管
を使用した場合でも、配管を取り巻く環境，特に水質に
よっては腐食発生の虞れがある。ステンレス鋼は、不動
態皮膜をもつ材料であることから、腐食の形態は局部的
なものになりやすく、一旦腐食が発生するとその部分に
腐食が集中する。配管用に使用されるステンレス鋼管で
は、配管内に形成される腐食電池に起因したマクロセル
腐食が主である。腐食電池は、配管接続に伴って形成さ
れる。すなわち、ステンレス鋼配管の接続は、一般に大
口径管ではフランジ継手を使用することが多い。具体的
には、スタブエンドとよばれるフランジ継手と直管とを
溶接接合することにより配管接続している。小口径管で
は、金属製のメカニカルジョイントを使用することが一
般的である。これら溶接部や隙間部がアノードになり、
素管の健全部がカソードとなり、腐食電池が形成され
る。Even when a stainless steel pipe is used as the pipe, corrosion may occur depending on the environment surrounding the pipe, particularly the water quality. Since stainless steel is a material having a passive film, the form of corrosion tends to be localized, and once corrosion occurs, the corrosion concentrates on that part. In a stainless steel pipe used for piping, macro cell corrosion caused by a corrosion battery formed in the piping is mainly. Corrosion batteries are formed with the piping connections. That is, for connection of stainless steel pipes, in general, flange joints are often used in large-diameter pipes. Specifically, a flange joint called a stub end and a straight pipe are welded and connected to each other for pipe connection. For small diameter pipes, it is common to use metal mechanical joints. These welds and gaps become anodes,
The sound part of the raw tube serves as the cathode, forming a corrosion battery.
【０００４】そこで、屋内配管用にステンレス鋼管を適
用する場合、配管内でマクロセル腐食を起こさないよう
な施工及び環境の管理が重要な問題となる。しかし、屋
内配管環境におけるステンレス鋼管の適用性を把握する
手段及びその具体的な方策は明確でない。本発明は、こ
のような問題を解消すべく案出されたものであり、ステ
ンレス鋼管の自然電位をモニタリングし、自然電位が常
に腐食発生電位より低くなるような水質，接続部の状
態，配管材料等に関する指標を得、ステンレス鋼製配管
系の腐食を未然に防止することを目的とする。Therefore, when a stainless steel pipe is used for indoor piping, it is an important problem to control the construction and environment so as not to cause macrocell corrosion in the piping. However, the means to grasp the applicability of stainless steel pipes in the indoor piping environment and its concrete measures are not clear. The present invention has been devised to solve such a problem, and monitors the natural potential of a stainless steel pipe, and the water quality, the state of the connection part, and the piping material such that the natural potential is always lower than the corrosion generation potential. It aims to prevent corrosion of the stainless steel piping system in advance by obtaining indicators related to the above.
【０００５】[0005]
【課題を解決するための手段】本発明の耐食性モニタリ
ング方法は、その目的を達成するため、配管系を構成す
るステンレス鋼管に参照電極を取り付け、該参照電極と
電位差計とを通る測定回路の一端を前記ステンレス鋼管
に接続し、前記電位差計で前記ステンレス鋼管の自然電
位を測定することを特徴とする。参照電極は、ステンレ
ス鋼製の絶縁短管に取り付けることができる。また、一
方の絶縁短管に参照電極を取り付け、該絶縁短管に隣接
し且つ内面を酸洗仕上げした他方の絶縁短管の自然電位
を測定してもよい。測定された自然電位は、腐食発生電
位と比較され、腐食発生に影響を及ぼす水質，接続部の
状態，配管材料等の調整に活用される。In order to achieve the object, the corrosion resistance monitoring method of the present invention has a reference electrode attached to a stainless steel pipe constituting a piping system, and one end of a measurement circuit passing through the reference electrode and a potentiometer. Is connected to the stainless steel pipe, and the natural potential of the stainless steel pipe is measured by the potentiometer. The reference electrode can be attached to an insulating short tube made of stainless steel. Alternatively, a reference electrode may be attached to one of the insulating short tubes, and the natural potential of the other insulating short tube adjacent to the insulating short tube and having the inner surface pickled may be measured. The measured spontaneous potential is compared with the corrosion generation potential, and is utilized for adjusting the water quality, the condition of the connection part, the piping material, etc. that affect the corrosion generation.
【０００６】[0006]
【実施の形態】配管のマクロセル腐食は、溶接継手部や
パッキンとの隙間部がアノードになり、素管部がカソー
ドとして作用し、この間の電位差によって形成された電
池により発生する。一般にステンレス鋼管素材部の腐食
発生電位は、アノードとなる溶接部や隙間部の腐食発生
電位より貴である。対象とする環境でステンレス鋼は到
達する自然電位より溶接部や隙間部の腐食発生電位が高
い場合、腐食が発生しない。しかし、腐食発生電位が自
然電位より低いと、腐食が発生する。この腐食発生電位
と自然電位との比較から、ステンレス鋼管が腐食を起こ
すか否かを推定できる。このような前提に立って、本発
明者等は、ステンレス鋼管における自然電位及び溶接部
等の腐食発生電位の関連から、屋内配管に使用されるス
テンレス鋼管の耐食性推定方法を検討した。BEST MODE FOR CARRYING OUT THE INVENTION Macrocell corrosion of piping is caused by a battery formed by the potential difference between the weld joint and the gap between it and the packing serving as the anode, and the blank tube acting as the cathode. In general, the corrosion generation potential of the stainless steel pipe material is nobler than the corrosion generation potential of the welded portion or the gap that serves as the anode. Corrosion does not occur in stainless steel in the target environment when the corrosion generation potential of the welded portion or the gap is higher than the natural potential that reaches it. However, when the corrosion generation potential is lower than the natural potential, corrosion occurs. From the comparison between the corrosion generation potential and the natural potential, it can be estimated whether or not the stainless steel pipe will corrode. Based on such a premise, the present inventors have examined a corrosion resistance estimation method for a stainless steel pipe used for indoor piping from the relationship between the spontaneous potential of the stainless steel pipe and the corrosion generation potential of the welded portion.
【０００７】給水，給湯水等の中性環境におけるステン
レス鋼管の自然電位は、材料側では合金組成や皮膜の状
態、環境側では残留塩素や溶存酸素等の酸化剤の種類や
濃度、水の流動状態，温度等に応じて変化する。ステン
レス鋼のように不動態を示す合金や金属では、酸化剤の
量や種類によって自然電位が大きく変動する。たとえ
ば、給湯配管システムをシミュレートした流動循環試験
におけるステンレス鋼管の自然電位の測定結果を図１に
示す。なお、自然電位は、配管内に基準電極となる飽和
カロメル電極を設置し、電位差計を使用して測定した。
酸化剤として残留塩素及び溶存酸素を含む８０℃の上水
を１ｍ／秒で循環した場合、ステンレス鋼配管の自然電
位はおよそ２００ｍＶ. SCE であった。酸化剤として溶
存酸素だけを含む上水を１ｍ／秒で循環した場合の自然
電位は、およそ−５０ｍＶ. SCE であった。また、静止
環境では、およそ−１００ｍＶ. SCE で自然電位が定常
状態になった。このように、屋内給湯配管環境における
ステンレス鋼管の自然電位は、水の流動状態や酸化剤の
有無に応じて−１００〜２００ｍＶ. SCE まで変動し、
特に残留塩素の存在により自然電位が大きく上昇するこ
とが判る。The natural potential of a stainless steel pipe in a neutral environment such as water supply and hot water supply depends on the alloy composition and film state on the material side, the type and concentration of the oxidizer such as residual chlorine and dissolved oxygen on the environment side, and the flow of water. It changes according to the condition and temperature. In the case of alloys and metals that show a passive state such as stainless steel, the self-potential changes greatly depending on the amount and type of oxidizer. For example, FIG. 1 shows the result of measuring the self-potential of a stainless steel pipe in a flow circulation test simulating a hot water supply piping system. The spontaneous potential was measured by using a potentiometer with a saturated calomel electrode serving as a reference electrode installed in the pipe.
If the 80 ° C. of tap water containing residual chlorine and dissolved oxygen as an oxidizing agent was circulated at 1 m / sec, self-potential of the stainless steel pipe was about 200 mV. SCE. Natural potential when the clean water containing only dissolved oxygen as an oxidizing agent was circulated at 1 m / sec, was approximately -50 mV. SCE. In the static environment, the self-potential became a steady state at about -100 mV. SCE . In this way, the natural potential of the stainless steel pipe in the indoor hot water supply piping environment varies from −100 to 200 mV. SCE depending on the flow state of water and the presence or absence of an oxidant,
In particular, it can be seen that the presence of residual chlorine greatly increases the spontaneous potential.
【０００８】腐食電位も、自然電位と同様に材料側では
化学成分や表面状態、環境側ではＣｌ- 等のハロゲンイ
オンの存在や液温等によって変わる。Ｃｌ- の高い環境
では、不動態皮膜が破壊され易くなり、腐食発生電位が
低くなる。耐食性を高めるＣｒ，Ｍｏ等の元素を多く含
有する材料は、不動態皮膜が強固になり、腐食発生電位
が高くなる。溶接部等のように酸化スケール生成に伴
い、スケール直下の表面にＣｒ欠乏層が存在すると腐食
発生電位が低くなる。たとえば、ステンレス鋼管ＳＵＳ
３０４，３１６の円周溶接部の８０℃における腐食発生
電位とＣｌ- 濃度の関係を図２に示すように、Ｃｌ- 濃
度が高くなり溶接状態が悪くなるに従って腐食発生電位
が低くなる。上水中のＣｌ- 濃度上限値を２００ｐｐｍ
Ｃｌ- とすると、溶接状態及び鋼種によっては腐食発生
電位が自然電位よりも卑になることがあり、腐食発生の
虞れが生じる。Similarly to the natural potential, the corrosion potential also changes depending on the chemical composition and surface condition on the material side and the presence of halogen ions such as Cl − and the liquid temperature on the environment side. In an environment with high Cl −, the passivation film is easily broken and the corrosion generation potential becomes low. A material containing a large amount of elements such as Cr and Mo that enhances corrosion resistance has a strong passive film and a high corrosion generation potential. If a Cr-deficient layer is present on the surface immediately below the scale due to the generation of oxide scale such as in a welded portion, the corrosion generation potential becomes low. For example, stainless steel pipe SUS
As shown in FIG. 2, the relationship between the corrosion generation potential and the Cl − concentration at the circumferential welds of 304 and 316 at 80 ° C. becomes lower as the Cl − concentration increases and the welding condition deteriorates. Upper limit of Cl - concentration in tap water is 200ppm
If Cl − is used, the corrosion generation potential may become baser than the natural potential depending on the welding state and steel type, and there is a risk of corrosion generation.
【０００９】上水の使用水質基準には、Ｃｌ- 濃度の上
限が２００ｐｐｍに、総硬度の上限が３００ｐｐｍに、
滅菌のための残留塩素の存在が定められており、その他
のイオン種に関する基準はない。また、給湯に対しては
上水のみでなく、震災時等も考慮して井戸水使用も進め
られており、総硬度や金属アルカリ度が高くなるケース
も増えてきている。その結果、それらのイオン種の存在
によって自然電位が上がったり、腐食発生電位が下がっ
たりする可能性もある。ステンレス鋼管の腐食発生電位
は、たとえば腐食形態が孔食の場合、ＪＩＳＧ０５７７
「ステンレス鋼の孔食電位測定方法」や定電位測定法に
より、予め実験室的に測定できる。そこで、実配管シス
テムにおけるステンレス鋼管の自然発生電位が測定でき
ると、ステンレス鋼管の適用可否が見極められる上、適
用後の環境側における維持管理の指標が得られる。According to the water quality standards for tap water, the upper limit of Cl - concentration is 200 ppm, the upper limit of total hardness is 300 ppm,
The presence of residual chlorine for sterilization is defined, and there are no standards for other ionic species. In addition to tap water for hot water supply, well water is being used in consideration of the earthquake and other cases, and the total hardness and metal alkalinity are increasing in many cases. As a result, the presence of these ionic species may increase the spontaneous potential or decrease the corrosion generation potential. The corrosion generation potential of a stainless steel pipe is JIS G0577 when the corrosion form is pitting corrosion, for example.
It can be preliminarily measured in a laboratory by "a measuring method of pitting corrosion potential of stainless steel" or a constant potential measuring method. Therefore, if the spontaneously generated potential of the stainless steel pipe in the actual piping system can be measured, the applicability of the stainless steel pipe can be determined, and an index of maintenance management on the environment side after application can be obtained.
【００１０】配管システムにおける自然電位を最も簡便
に測定する手段としては、図３に示す構成が採用され
る。この場合、貯水槽や給湯タンク１に接続した出側の
ステンレス配管２に２０Ｓｕ程度の枝管３及びバルブ４
を設け、枝管３に飽和カロメル電極等の参照電極５を設
置する。試料電極であるステンレス配管２と参照電極５
との間に電位差計６を接続し、電位差計６によってステ
ンレス配管２の自然電位を測定する。自然電位をより正
確に測定するためには、参照電極５や試料電極２等の測
定器周辺に溶接部や隙間形成部がない方が好ましい。こ
の場合には図４に示すように、長さ１ｍ程度のステンレ
ス鋼製絶縁フランジ短管７の中央部に参照電極５を埋め
込み、リード線８を絶縁フランジ短管７に接続した構造
が採用される。この方法で得られる自然電位は短管７以
外のステンレス鋼管の状態や構造による影響を受けない
ため、環境側の変化のみを把握することができる。ま
た、試料電極となるステンレス配管２の表面状態によっ
ても測定される自然電位が異なることから、予め内面を
酸洗した鋼管を測定用に使用することも、変動要因をで
きるだけ除いて自然電位を得る手段として有効である。The configuration shown in FIG. 3 is adopted as the most simple means for measuring the natural potential in the piping system. In this case, a branch pipe 3 and a valve 4 of about 20 Su are attached to the stainless steel pipe 2 on the outlet side connected to the water storage tank or the hot water supply tank 1.
And a reference electrode 5 such as a saturated calomel electrode is installed on the branch pipe 3. Stainless steel pipe 2 as a sample electrode and reference electrode 5
A potentiometer 6 is connected between the and, and the potentiometer 6 measures the natural potential of the stainless steel pipe 2. In order to measure the natural potential more accurately, it is preferable that there is no welded portion or gap forming portion around the measuring device such as the reference electrode 5 and the sample electrode 2. In this case, as shown in FIG. 4, a structure is adopted in which the reference electrode 5 is embedded in the central portion of a stainless steel insulating flange short tube 7 having a length of about 1 m and the lead wire 8 is connected to the insulating flange short tube 7. It Since the self-potential obtained by this method is not affected by the state and structure of the stainless steel pipes other than the short pipe 7, it is possible to understand only the change on the environment side. In addition, since the measured spontaneous potential varies depending on the surface state of the stainless steel pipe 2 serving as the sample electrode, it is possible to obtain the natural potential by removing the fluctuation factors as much as possible by using a steel pipe whose inner surface is pickled in advance for measurement. It is effective as a means.
【００１１】自然電位を測定する箇所としては、最も残
留塩素濃度が高いタンク１の出側直近部にある配管部分
が好適である。この部分は、水が循環する間に消耗され
る残留塩素の減少による影響が少ない。ただし、環境側
の変化を確実に捉え、各箇所におけるステンレス配管の
耐食性を把握するためには、配管からの分岐箇所等にも
測定部を設けることが有効である。自然電位測定箇所を
複数設置し、各測定箇所での測定値を比較することによ
り、材料側の変化も把握できると共に、より信頼性の高
い自然電位を検出できる。このようにして測定された自
然電位が腐食発生電位を超え、腐食の発生が予測される
とき、使用水の変更，飲料用水処理剤，脱酸素剤の使
用，脱塩装置の設置等の対策によってステンレス鋼配管
の耐食性を確保し、健全な配管系が維持される。As a location for measuring the natural potential, a pipe portion in the immediate vicinity of the outlet side of the tank 1 having the highest residual chlorine concentration is suitable. This part is less affected by the reduction of residual chlorine consumed during water circulation. However, in order to grasp the changes on the environment side surely and to grasp the corrosion resistance of the stainless steel pipe at each place, it is effective to provide a measuring unit also at a branch point from the pipe. By installing a plurality of natural potential measuring points and comparing the measured values at the respective measuring points, it is possible to grasp the change on the material side and detect a more reliable natural potential. When the spontaneous potential measured in this way exceeds the corrosion potential and corrosion is predicted to occur, countermeasures such as changing the water used, using drinking water treatment agents, oxygen scavengers, and installing desalination equipment The corrosion resistance of stainless steel piping is secured and a sound piping system is maintained.
【００１２】[0012]
【実施例】塩素イオン濃度２００ｐｐｍの環境において
自然電位を変化させるため残留塩素濃度が種々異なる試
験液を使用し、モニター試験配管により耐食性試験を実
施した。モニター試験配管としては、市販のＳＵＳ３０
４ＴＰＤ管２０Ｓｕ（肉厚１ｍｍ）及びＳＵＳ３１６Ｔ
ＰＤ管２０Ｓｕ（肉厚１ｍｍ）を使用した。試験管の長
さは１ｍであり、管の中央部を円周溶接した。溶接状態
は、溶接スケールがなくビード形状が良好なもの
（Ａ），溶接スケールがありビード形状が良好なもの
（Ｂ），溶接スケールがありビード形状が不良なもの
（Ｃ）の３水準で評価した。自然電位の測定には、図４
に示すように絶縁短管７を直列に２本挿入し、一方の絶
縁短管７に電位測定用の参照電極５を設置し、他方の絶
縁短管として内面９を酸洗したものを使用した。そし
て、絶縁短管７の自然電位を測定し、６か月後の自然電
位の定常値と図２に示す腐食発生電位との比較から予測
される耐食性と試験管の腐食発生の有無との関係を調査
した。[Examples] Corrosion resistance tests were carried out through monitor test pipes using test liquids having different residual chlorine concentrations in order to change the natural potential in an environment having a chlorine ion concentration of 200 ppm. As the monitor test pipe, commercially available SUS30
4TPD tube 20Su (wall thickness 1mm) and SUS316T
PD tube 20Su (wall thickness 1 mm) was used. The length of the test tube was 1 m, and the central portion of the tube was welded circumferentially. Welded condition is evaluated in 3 levels: one with no weld scale and good bead shape (A), one with weld scale and good bead shape (B), and one with weld scale and poor bead shape (C). did. Figure 4
As shown in Fig. 2, two insulating short tubes 7 were inserted in series, a reference electrode 5 for potential measurement was installed in one insulating short tube 7, and the inner surface 9 was pickled as the other insulating short tube. . Then, the spontaneous potential of the insulated short tube 7 is measured, and the relationship between the corrosion resistance predicted by the comparison between the steady value of the spontaneous potential after 6 months and the corrosion occurrence potential shown in FIG. investigated.
【００１３】調査結果を示す表１にみられるように、耐
食性の予測結果は、実際の腐食発生有無の状況に一致し
ていた。すなわち、自然電位が低い場合、ＳＵＳ３１６
に腐食が検出されなかった。また、溶接状態が悪いＳＵ
Ｓ３０４には、腐食が検出された。これは、その試験条
件における自然電位が溶接状態の悪いＳＵＳ３０４の腐
食発生電位より高く、他の被試験管の腐食発生電位より
低いためである。他方、自然電位が高い場合には、ＳＵ
Ｓ３１６，ＳＵＳ３０４共に溶接状態に拘らず、腐食が
検出された。これは、その試験条件における自然電位が
全ての被試験管の腐食発生電位より高くなるためであ
る。このように、自然電位とステンレス鋼配管の耐食性
に密接な相関性があることが確認された。以上の結果に
基づき、測定された自然電位に応じ、水質に関しては残
留塩素濃度を減らし、接合面に関してはスケールが残ら
ないような溶接に変更し、材質に関してはＳＵＳ３０４
からＳＵＳ３１６に変更することによって、ステンレス
鋼配管の腐食発生電位が配管環境における自然電位より
貴になることから、腐食発生が防止される。すなわち、
それらの対策を講じる指針が本発明に従って得られ、そ
れらの対策を講じた結果として長期間にわたってステン
レス鋼を健全な状態に維持できる。As can be seen from Table 1 showing the investigation results, the corrosion resistance prediction results were in agreement with the actual presence or absence of corrosion. That is, when the natural potential is low, SUS316
No corrosion was detected. Also, SU with poor welding condition
Corrosion was detected in S304. This is because the spontaneous potential under the test condition is higher than the corrosion generation potential of SUS304 having a poor welding state and lower than the corrosion generation potential of other test pipes. On the other hand, when the natural potential is high, SU
Corrosion was detected in both S316 and SUS304 regardless of the welding state. This is because the spontaneous potential under the test conditions is higher than the corrosion generation potentials of all the test tubes. Thus, it was confirmed that there is a close correlation between the natural potential and the corrosion resistance of stainless steel piping. Based on the above results, according to the measured self-potential, the residual chlorine concentration was reduced for water quality, welding was changed so that no scale remained on the joint surface, and SUS304 for the material.
By changing from SUS316 to SUS316, the corrosion occurrence potential of the stainless steel pipe becomes nobler than the natural potential in the piping environment, so that the corrosion occurrence is prevented. That is,
Guidelines for taking these measures are obtained in accordance with the present invention, and as a result of taking these measures, the stainless steel can be kept in a healthy state for a long period of time.
【００１４】 [0014]
【００１５】[0015]
【発明の効果】以上に説明したように、本発明において
は、配管システム内で自然電位を測定し、測定値と腐食
発生電位とを比較することにより、ステンレス配管にお
ける腐食発生の可能性が予測できる。予測結果に応じて
残留塩素濃度の低下，溶接状態の改善，配管用鋼種の変
更等の対策を施す指標が得られ、腐食の発生が未然に防
止される。また、屋内配管システムにおけるステンレス
鋼管の耐食性及び配管系の寿命延長に対する信頼性の高
い屋内配管システムが構築される。更には、自然電位を
定期的に測定し環境を把握することにより、水質の維持
管理の指針としても効果的なデータが得られる。As described above, in the present invention, the spontaneous potential is measured in the piping system and the measured value is compared with the corrosion occurrence potential to predict the possibility of corrosion occurrence in stainless steel piping. it can. According to the prediction result, an index for taking measures such as reduction of residual chlorine concentration, improvement of welding condition, and change of steel grade for piping can be obtained, and corrosion can be prevented in advance. In addition, an indoor piping system having high reliability for corrosion resistance of stainless steel pipes in the indoor piping system and extension of life of the piping system is constructed. Furthermore, by periodically measuring the natural potential and grasping the environment, effective data can be obtained as a guideline for water quality maintenance.
【図１】 給湯配管システムをシミュレートした流動循
環試験におけるステンレス配管の自然電位を経時的に調
査したグラフFIG. 1 is a graph in which the self-potential of stainless steel piping in a flow circulation test simulating a hot water supply piping system is investigated over time.
【図２】 塩素イオン濃度及び溶接状態が腐食電位に及
ぼす影響を表したグラフFIG. 2 is a graph showing the influence of chlorine ion concentration and welding condition on corrosion potential.
【図３】 給湯配管システムをシミュレートしてステン
レス配管の自然電位を測定する流動循環試験を説明する
図FIG. 3 is a diagram for explaining a flow circulation test for simulating a hot water supply piping system and measuring a spontaneous potential of stainless steel piping.
【図４】 絶縁フランジ短管を使用して自然電位を測定
する流動循環試験を説明する図FIG. 4 is a diagram for explaining a flow circulation test in which a self-potential is measured using an insulating flange short tube.
１：貯水槽又は給湯タンク ２：ステンレス配管
３：枝管 ４：バルブ ５：参照電極 ６：電
位差計 ７：絶縁フランジ管 ８：リード線 ９：予め酸洗した絶縁フランジ管の内面1: Water tank or hot water supply tank 2: Stainless steel piping
3: Branch pipe 4: Valve 5: Reference electrode 6: Potentiometer 7: Insulating flange pipe 8: Lead wire 9: Inner surface of insulating flange pipe pre-pickled
───────────────────────────────────────────────────── フロントページの続き (72)発明者 原田 和加大 山口県新南陽市野村南町4976番地 日新製 鋼株式会社技術研究所内 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Waka Harada 4976 Nomura-Minamimachi, Shinnanyo-shi, Yamaguchi Nisshin Steel Co., Ltd.
Claims (4)
電極を取り付け、該参照電極と電位差計とを通る測定回
路の一端を前記ステンレス鋼管に接続し、前記電位差計
で前記ステンレス鋼管の自然電位を測定するステンレス
鋼製配管の耐食性モニタリング方法。1. A stainless steel pipe constituting a piping system is provided with a reference electrode, one end of a measuring circuit passing through the reference electrode and a potentiometer is connected to the stainless steel pipe, and the potentiometer is used to measure the natural potential of the stainless steel pipe. A method for monitoring the corrosion resistance of stainless steel pipes to be measured.
取り付け、該参照電極と電位差計とを通る測定回路の一
端を、前記絶縁短管に隣接するステンレス鋼管に接続
し、前記電位差計で前記ステンレス鋼管の自然電位を測
定するステンレス鋼製配管の耐食性モニタリング方法。2. A stainless steel insulated short tube is attached with a reference electrode, one end of a measuring circuit passing through the reference electrode and the potentiometer is connected to a stainless steel tube adjacent to the insulated short tube, and the potentiometer is used. A method for monitoring corrosion resistance of a stainless steel pipe, which comprises measuring the spontaneous potential of the stainless steel pipe.
テンレス鋼製絶縁短管を配管系内に挿入し、一方の絶縁
短管に参照電極を取り付け、該参照電極と電位差計とを
通る測定回路の一端を、前記絶縁短管に隣接し且つ内面
を酸洗仕上げした他方の絶縁短管に接続し、前記電位差
計で前記他方の絶縁短管の自然電位を測定するステンレ
ス鋼製配管の耐食性モニタリング方法。3. A stainless steel insulated short pipe connected in series via an insulating material is inserted into a piping system, a reference electrode is attached to one insulating short pipe, and the reference electrode and potentiometer are connected to each other. One end of a measuring circuit passing through is connected to the other insulating short pipe adjacent to the insulating short pipe and whose inner surface is pickled, and a stainless steel pipe for measuring the natural potential of the other insulating short pipe with the potentiometer. Corrosion resistance monitoring method.
を備えたステンレス鋼管製屋内配管システム。4. An indoor piping system made of stainless steel pipe, comprising the measuring circuit according to claim 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6209796A JPH09229892A (en) | 1996-02-23 | 1996-02-23 | Method for monitoring anticorrosion of stainless steel piping and indoor piping system made of stainless steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6209796A JPH09229892A (en) | 1996-02-23 | 1996-02-23 | Method for monitoring anticorrosion of stainless steel piping and indoor piping system made of stainless steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09229892A true JPH09229892A (en) | 1997-09-05 |
Family
ID=13190215
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6209796A Pending JPH09229892A (en) | 1996-02-23 | 1996-02-23 | Method for monitoring anticorrosion of stainless steel piping and indoor piping system made of stainless steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09229892A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100750895B1 (en) * | 2005-12-20 | 2007-08-22 | 삼성중공업 주식회사 | Stress Corrosion Cracking Test Method and Test Equipment of Aluminum-Brass Heating Coil |
| JP2013160654A (en) * | 2012-02-06 | 2013-08-19 | Seiko Epson Corp | Sensor device |
| JP5481699B1 (en) * | 2013-04-04 | 2014-04-23 | 札幌施設管理株式会社 | Piping evaluation method |
| JP5640286B2 (en) * | 2013-12-26 | 2014-12-17 | 札幌施設管理株式会社 | Piping evaluation method |
-
1996
- 1996-02-23 JP JP6209796A patent/JPH09229892A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100750895B1 (en) * | 2005-12-20 | 2007-08-22 | 삼성중공업 주식회사 | Stress Corrosion Cracking Test Method and Test Equipment of Aluminum-Brass Heating Coil |
| JP2013160654A (en) * | 2012-02-06 | 2013-08-19 | Seiko Epson Corp | Sensor device |
| JP5481699B1 (en) * | 2013-04-04 | 2014-04-23 | 札幌施設管理株式会社 | Piping evaluation method |
| JP5640286B2 (en) * | 2013-12-26 | 2014-12-17 | 札幌施設管理株式会社 | Piping evaluation method |
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