WO2000034759A1 - Evaluation de la corrosion - Google Patents

Evaluation de la corrosion Download PDF

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Publication number
WO2000034759A1
WO2000034759A1 PCT/GB1999/004048 GB9904048W WO0034759A1 WO 2000034759 A1 WO2000034759 A1 WO 2000034759A1 GB 9904048 W GB9904048 W GB 9904048W WO 0034759 A1 WO0034759 A1 WO 0034759A1
Authority
WO
WIPO (PCT)
Prior art keywords
corrosion
electrode
plant
sensor electrode
stern
Prior art date
Application number
PCT/GB1999/004048
Other languages
English (en)
Inventor
David Anthony Eden
Original Assignee
Integriti Investments Limited
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from GBGB9826836.0A external-priority patent/GB9826836D0/en
Application filed by Integriti Investments Limited filed Critical Integriti Investments Limited
Priority to CA002353937A priority Critical patent/CA2353937A1/fr
Priority to AU16663/00A priority patent/AU1666300A/en
Priority to GB0113862A priority patent/GB2367630A/en
Publication of WO2000034759A1 publication Critical patent/WO2000034759A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
    • G01N17/04—Corrosion probes

Definitions

  • This invention relates to corrosion monitoring of process or production plant in circumstances where the metal surfaces of the plant are, or may in the course of plant operations be, exposed to a liquid environment that is corrosive to them.
  • the liquid environment may be contained, conveyed or stored process liquid or it may be heat-transfer media or even transient condensate.
  • the liquid will be aqueous.
  • the invention is directed to electrochemical methods of monitoring such corrosion in which the liquid environment to which plant surfaces are or may become exposed serves at pre-selected locations as an electrolyte of an Electrochemical Corrosion Cell .
  • Electrochemical methods known in the prior art investigate responses of corroding electrodes under chosen conditions of imposed potential or current flow and include those known as polarisation; linear polarisation resistance; electrochemical impedance; electrochemical noise (potential or current noise); and harmonic analysis. All of these investigative methods are part of the armoury of the skilled corrosion engineer and the underlying science of each is now well established. For practical applications in industrial plant preference will be given to methods that intrude as little as possible, both in the sense of avoiding the imposition of irreversible changes in reference material and in the sense of minimal effect on plant conditions or operations.
  • harmonic analysis has come increasingly to the fore as a practical tool with the advent of instruments capable of performing precise, sensitive measurement and data manipulation, and of PCs able to run sophisticated computer software so as to derive values of derivatives and functions and then to printout or display pertinent information graphically, such as trends or sudden sporadic excursions.
  • the theory underlying harmonic analysis was developed in the late 70s, early 80s but practical field use is more recent.
  • Harmonic analysis is an extension of electrochemical impedance determination. It involves applying a small ac sinusoidal voltage of selected frequency to a corroding electrode and observing the current response, which here comprises not only the fundamental (i.e. the impedance measurement) but also upper harmonics. Measurement of the fundamental and first and second harmonic components of the Faradaic impedance response is possible with an analyser with harmonic selection. The practical challenge is to apply a perturbation signal of sufficient amplitude to produce a measurable second harmonic without excessively disturbing the system, as the second harmonic may be found to lie within the noise level of the instrumentation.
  • the resulting measurements (which relate the corrosion current i C o rr and the Tafel Slopes with the Stern-Geary Constant) provide the information needed to derive values for i corr/ the charge transfer resistance Ret, and the Stern-Geary constant. (Note: three equations and three unknowns) .
  • the applied perturbation might be a voltage amplitude of around 25 mV at a frequency of around 0.1 Hz.
  • the present invention stems from a finding that it is in fact possible to monitor both general corrosion rates and the occurrence of pitting or crevice corrosion in an operating plant by using a single introduced sensor electrode and the plant itself (including within the term "plant” the probe structure that may in chosen configurations carry the sensor electrode) as the second electrode of the required electrochemical cell.
  • a test electrode of the same or electrochemically similar material to that of the plant would form one electrode (the working electrode) , a second electrode (an auxiliary electrode) which may be the same or a different material to the working electrode used to support the current flow, and a third electrode (a reference electrode) against which the polarisation of the working electrode is controlled.
  • the plant liquid would provide the electrolyte.
  • the use of two electrodes of the same/similar metals would not be considered because a symmetrical response would be expected with loss of the second harmonic (rectified) component.
  • an electrochemical corrosion monitoring cell comprising the introduced sensor electrode, the local plant structure, as a second electrode, and the liquid medium as the electrolyte.
  • the surface area of the sensor electrode is (and is typically required to be) at least an order of magnitude smaller than the effective or apparent local surface area of the plant electrode. (It is of no material consequence that the plant structure is earthed) .
  • the present invention in its broadest aspect, provides a method of establishing the probable, or equivalent, corrosion behaviour of plant metal surface in contact with corrosive liquid (e.g. process/ production liquid media) , the method comprising the following procedures:
  • a preferred method of monitoring comprises at least one of the following procedures: -
  • the polarising voltage has a magnitude that is less than, but a substantial fraction (equal to or greater than 10%) of the prevailing Stern-Geary constant value.
  • the current noise measured may be correlated with the general corrosion rate. It can reveal localised corrosion (for example pitting or crevice attack) by correlation of the background general corrosion rate (per harmonic analysis) with transient excursions in the current signal.
  • the value of the current flow measured under (4) is equal to, or a fraction of, the corrosion current in the same proportion as the applied voltage bears to the Stern - Geary constant.
  • the sensor electrode should preferably have an effective surface area that is, at least, an order of magnitude (e.g. at least 1/lOth) smaller than the apparent, or 'effective', surface area of the plant electrode.
  • Figure 1 shows schematically an in-line arrangement of a sensor electrode for a stretch of pipework, the electrode being part of a gasket at a flange coupling in the pipe-line
  • Figure 2 shows schematically a cut-away view of a sensor electrode mounting at a boundary wall of a vessel and in the form of a lateral probe.
  • the gasket 4 comprises an annular sensor electrode disc (or ring) 4 electrically insulated from the flanges 2a and 2b by spacing insulating material 5.
  • the insulating material is shown as two separate plates on opposite sides of a plate electrode 4.
  • the electrode 4 might equally be a ring, or part ring, embedded in the radially inward surface of a cylindrical block of insulating material 5 such that the innermost surface of the electrode 4 is exposed to fluid in the pipeline.
  • Electrical connecting leads are shown at 6, one coupled to the electrode 4 and the other to the flange 2a.
  • a localised part of a vessel wall is indicated by arrow 7. It is in contact with fluid indicated by arrow 8.
  • An intrusive probe assembly shown generally by arrow 9 is affixed to the vessel wall 7 at a flanged port 10 in the vessel wall 7 such that a sensor electrode 11 is exposed at its inner end surface 11a to the fluid 8 at the vessel wall boundary.
  • the electrode 11 is coupled to an end plate 12 that is clamped by bolts 13 to the flanged port 10.
  • the electrode 11 is insulated from the vessel wall 7 and from the flanged port 10 by a layer of suitable insulating material (not numbered) . Electrical connections are shown at 14.
  • the exposed surface areas of electrodes 4 and 11 are precisely known and are very small relative to the apparent, or effective, areas of the reference 'plant' electrodes.
  • the materials from which the electrodes are made are the same as, or are electrochemically correlated to, the metals of the pipework or vessel, respectively.
  • the measured responses of the electrochemical cells which these arrangements form are essentially (or may be taken to be) the responses of the sensor electrodes to conditions encountered and these by design mirror those of the plant structures at the monitored locations.
  • reference 'plant' electrode surface may be introduced at sensor electrode installation either as a specific item or as a feature of sensor probe design.
  • the electrochemical current noise of the sensor versus the plant metal surface was measured for a period of not less than 300 seconds, with a sampling period of 1 second.
  • We then calculated statistical moments of the current signal i.e. mean, variance, third and fourth moments.
  • the skew and kurtosis of the current signal were then calculated from the moments.
  • We also calculated a value for the localisation index of the signal (I mean divided by I r.m.s.) . This step was repeated later in the procedure .
  • a dc potential signal of a value 50% of the Stern-Geary value, measured electrochemical current noise of the sensor versus the plant metal surface for a period of not less than 300 seconds, with a sampling period of 1 second, and calculated statistical moments of the current signal, i.e. mean, variance, third and fourth moments.
  • the mean current flow was of a value of ca 50% of the general corrosion current, and the higher moments indicated the stability of the corrosion current which relates to the probability of localised corrosion.

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  • Life Sciences & Earth Sciences (AREA)
  • Biodiversity & Conservation Biology (AREA)
  • Ecology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Environmental Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Testing Resistance To Weather, Investigating Materials By Mechanical Methods (AREA)

Abstract

L'invention concerne un procédé permettant d'évaluer la corrosion générale et localisée dans des installations. Ce procédé consiste à utiliser une sonde électrode de diagnostic unique, référencée par rapport à la structure de l'installation, et à analyser ses réactions à des stimuli imposés afin d'obtenir des indications sur le comportement de l'installation vis-à-vis de la corrosion.
PCT/GB1999/004048 1998-12-07 1999-12-07 Evaluation de la corrosion WO2000034759A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
CA002353937A CA2353937A1 (fr) 1998-12-07 1999-12-07 Evaluation de la corrosion
AU16663/00A AU1666300A (en) 1998-12-07 1999-12-07 Corrosion monitoring
GB0113862A GB2367630A (en) 1998-12-07 1999-12-07 Corrosion monitoring

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9826836.0A GB9826836D0 (en) 1998-11-14 1998-12-07 Corrosion monitoring using a single element sensor probe
GB9826836.0 1998-12-07

Publications (1)

Publication Number Publication Date
WO2000034759A1 true WO2000034759A1 (fr) 2000-06-15

Family

ID=10843743

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1999/004048 WO2000034759A1 (fr) 1998-12-07 1999-12-07 Evaluation de la corrosion

Country Status (4)

Country Link
AU (1) AU1666300A (fr)
CA (1) CA2353937A1 (fr)
GB (1) GB2367630A (fr)
WO (1) WO2000034759A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002073169A1 (fr) * 2001-03-08 2002-09-19 Intercorr Holdings Limited Estimation de la penetration de la corrosion localisee
WO2006059133A1 (fr) * 2004-12-03 2006-06-08 Capcis Limited Mesure de la corrosivite
WO2007064567A2 (fr) * 2005-11-30 2007-06-07 General Electric Company Dispositif et procede permettant de mesurer la corrosion en temps reel
US7239156B1 (en) 2006-07-13 2007-07-03 Pepperl & Fuchs, Inc. Configurable corrosion measurement field device
US7245132B1 (en) 2006-07-12 2007-07-17 Pepperl & Fuchs, Inc. Intrinsically safe corrosion measurement and history logging field device
US7282928B1 (en) 2006-07-13 2007-10-16 Pepperl & Fuchs, Inc. Corrosion measurement field device with improved LPF, HDA, and ECN capability
CN114839233A (zh) * 2021-02-01 2022-08-02 中国石油化工股份有限公司 一种用于模拟大型管道流动及腐蚀的试验管路系统及方法

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2006437A (en) * 1977-10-07 1979-05-02 Tokyo Shibaura Electric Co Method of evaluating the corrosion rate of metal and apparatus for evaluating the same
US4395318A (en) * 1982-01-15 1983-07-26 Petrolite Corporation Pitting corrosion meter
WO1987007022A1 (fr) * 1986-05-12 1987-11-19 The University Of Manchester Institute Of Science Controle de la corrosion
WO1988001052A1 (fr) * 1986-07-25 1988-02-11 The University Of Manchester Institute Of Science Sonde de controle de la corrosion
EP0258170A2 (fr) * 1986-08-29 1988-03-02 CITIES SERVICE OIL & GAS CORPORATION Capteur de corrosion et méthode pour mesurer des vitesses de corrosion
EP0287348A2 (fr) * 1987-04-14 1988-10-19 Electric Power Research Institute, Inc Surveillance in situ de la vitesse de corrosion de métaux polarisés ou non
GB2298926A (en) * 1995-03-14 1996-09-18 Petroleo Brasileiro Sa Electrochemical sensor and process for assessing hydrogen permeation

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2006437A (en) * 1977-10-07 1979-05-02 Tokyo Shibaura Electric Co Method of evaluating the corrosion rate of metal and apparatus for evaluating the same
US4395318A (en) * 1982-01-15 1983-07-26 Petrolite Corporation Pitting corrosion meter
WO1987007022A1 (fr) * 1986-05-12 1987-11-19 The University Of Manchester Institute Of Science Controle de la corrosion
WO1988001052A1 (fr) * 1986-07-25 1988-02-11 The University Of Manchester Institute Of Science Sonde de controle de la corrosion
EP0258170A2 (fr) * 1986-08-29 1988-03-02 CITIES SERVICE OIL & GAS CORPORATION Capteur de corrosion et méthode pour mesurer des vitesses de corrosion
EP0287348A2 (fr) * 1987-04-14 1988-10-19 Electric Power Research Institute, Inc Surveillance in situ de la vitesse de corrosion de métaux polarisés ou non
GB2298926A (en) * 1995-03-14 1996-09-18 Petroleo Brasileiro Sa Electrochemical sensor and process for assessing hydrogen permeation

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002073169A1 (fr) * 2001-03-08 2002-09-19 Intercorr Holdings Limited Estimation de la penetration de la corrosion localisee
WO2006059133A1 (fr) * 2004-12-03 2006-06-08 Capcis Limited Mesure de la corrosivite
WO2007064567A2 (fr) * 2005-11-30 2007-06-07 General Electric Company Dispositif et procede permettant de mesurer la corrosion en temps reel
WO2007064567A3 (fr) * 2005-11-30 2007-08-02 Gen Electric Dispositif et procede permettant de mesurer la corrosion en temps reel
CN101341390B (zh) * 2005-11-30 2012-02-01 通用电气公司 测量实时腐蚀的装置和方法
US7245132B1 (en) 2006-07-12 2007-07-17 Pepperl & Fuchs, Inc. Intrinsically safe corrosion measurement and history logging field device
US7239156B1 (en) 2006-07-13 2007-07-03 Pepperl & Fuchs, Inc. Configurable corrosion measurement field device
US7282928B1 (en) 2006-07-13 2007-10-16 Pepperl & Fuchs, Inc. Corrosion measurement field device with improved LPF, HDA, and ECN capability
CN114839233A (zh) * 2021-02-01 2022-08-02 中国石油化工股份有限公司 一种用于模拟大型管道流动及腐蚀的试验管路系统及方法
CN114839233B (zh) * 2021-02-01 2024-03-29 中国石油化工股份有限公司 一种用于模拟大型管道流动及腐蚀的试验管路系统及方法

Also Published As

Publication number Publication date
GB0113862D0 (en) 2001-08-01
GB2367630A (en) 2002-04-10
AU1666300A (en) 2000-06-26
CA2353937A1 (fr) 2000-06-15

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