EP0253671B1 - Korrosionsschutz - Google Patents

Korrosionsschutz Download PDF

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Publication number
EP0253671B1
EP0253671B1 EP87306336A EP87306336A EP0253671B1 EP 0253671 B1 EP0253671 B1 EP 0253671B1 EP 87306336 A EP87306336 A EP 87306336A EP 87306336 A EP87306336 A EP 87306336A EP 0253671 B1 EP0253671 B1 EP 0253671B1
Authority
EP
European Patent Office
Prior art keywords
anode
substrate
tube
barrier
electrolyte
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.)
Expired - Lifetime
Application number
EP87306336A
Other languages
English (en)
French (fr)
Other versions
EP0253671A2 (de
EP0253671A3 (en
Inventor
James Patrick Reed
Albert Highe
Michael Masia
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raychem Corp
Original Assignee
Raychem Corp
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
Application filed by Raychem Corp filed Critical Raychem Corp
Priority to EP92103118A priority Critical patent/EP0488995B1/de
Priority to AT87306336T priority patent/ATE80674T1/de
Publication of EP0253671A2 publication Critical patent/EP0253671A2/de
Publication of EP0253671A3 publication Critical patent/EP0253671A3/en
Application granted granted Critical
Publication of EP0253671B1 publication Critical patent/EP0253671B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
    • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
    • C23F13/04—Controlling or regulating desired parameters
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
    • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
    • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
    • C23F13/06—Constructional parts, or assemblies of cathodic-protection apparatus
    • C23F13/08—Electrodes specially adapted for inhibiting corrosion by cathodic protection; Manufacture thereof; Conducting electric current thereto
    • C23F13/16—Electrodes characterised by the combination of the structure and the material

Definitions

  • This invention relates to the corrosion protection of pipes, vessels and other corrodible substrates.
  • a corrosion-protecting potential difference between the substrate and a counter-electrode.
  • a DC power source is used to establish the desired potential difference between the substrate as cathode and an anode which is composed of a material which is resistant to corrosion, eg. platinum, graphite, or a conductive polymer.
  • a material which is resistant to corrosion eg. platinum, graphite, or a conductive polymer.
  • the known corrosion systems suffer from serious disadvantages, in particular a failure to obtain sufficiently uniform current distribution on the substrate.
  • This disadvantage can arise from the use of one or more discrete electrodes; or from the use of a distributed electrode, eg a platinum wire, whose radial resistance to the substrate is low, so that at high currents the current density on the anode decreases rapidly as the distance from the power source increases; and/or because the substrate is shielded (including those situations in which the substrate has a complex shape which results in one part of the substrate being shielded by another part of the substrate).
  • the flexible elongate anodes disclosed in U.S. Patents Nos.
  • 4,502,929 and 4,473,450 which comprise a low resistance core surrounded by a conductive polymer coating, are very useful in mitigating this disadvantage, but they cannot be used at the high current densities which are required in certain situations, for example the protection of structures which have no protective coating thereon.
  • Another disadvantage is the relatively short life of anodes (including the electrical connections thereto), especially when exposed to environments which are highly corrosive or which contain oily contaminants (and in the case of platinum anodes, when exposed to fresh potable water), and the difficulty and expense of repairing or replacing the anodes when this becomes necessary.
  • a barrier which lies between the substrate and the counter-electrode, which is spaced apart from the substrate and the counter-electrode, and which directs the flow of ions between the substrate and the counter-electrode, and thus provides an improved current distribution on the substrate, and/or enables the counter-electrode to be more easily maintained or replaced, and/or reduces the rate at which the current density on an elongate electrode changes with the distance from the power source, and/or provides a controlled environment around the electrode to improve its efficiency, eg. by reducing contamination or by making it possible to surround the counter-electrode with an electrolyte which is different from the electrolyte which contacts the substrate.
  • the present invention provides an assembly for cathodically protecting an electrically conductive substrate from corrosion, the assembly comprising:
  • the present invention provides a method of cathodically protecting an electrically conductive substrate from corrosion by a liquid electrolyte which contacts it, which method comprises establishing a potential difference between the substrate as cathode and an elongate distributed anode such that current flows between the substrate and the anode along current paths which pass through ion permeable sections of a barrier which (i) lies between the substrate and the anode, and (ii) is spaced apart from the substrate and the anode, and (iii) is in the form of a tube which surrounds the anode and has a plurality of ion-permeable sections therein, and in which method a pump drives an electrolyte down the tube and through the ion permeable sections towards the substrate.
  • the barrier which is used in the present invention modifies the way in which current flows between the substrate and the anode so as to produce one or more of the desirable results noted above. In general, this will result in the resistance between the substrate and the anode being substantially higher than it would be in the absence of the barrier, preferably by a factor of at least 10, for example at least 100, or even more, balancing the resulting advantages against the disadvantage of the higher voltages required as the resistance increases.
  • the barrier preferably comprises a plurality of ion-permeable sections.
  • Preferred ion-permeable sections include simple apertures, for example a hole in the wall of a tube, or an opening at the end of a tube.
  • Ion-permeable sections which are composed of an ion-permeable material, eg. a glass frit, can also be used, especially when it is desired to have the anode contacted by an electrolyte which is different from that which contacts the substrate.
  • the size and/or the spacing of the ion-permeable sections can be uniform or non-uniform, depending upon the desired current distribution on the substrate.
  • the ion-permeable sections are preferably of fixed dimensions.
  • the distance between adjacent ion-permeable sections is preferably less than 10 times, particularly less than 4 times, the distance between the ion-permeable sections and the substrate.
  • An important factor in determining the size of the apertures can be the need to ensure that anodic reaction products, eg. gaseous chlorine, do not block the apertures. Unless the conditions of operation are such that anodic reaction products remain dissolved in the electrolyte or can be easily vented, care must be taken to prevent harmful build-up of such reaction products between the anode and the barrier. In some case positive benefit can be derived from such reaction products, eg. to lessen fouling of marine structures.
  • hydrostatic pressure is used to drive the electrolyte through the ion-permeable section(s) towards the substrate.
  • Such hydrostatic pressure which is provided by a pump, can have the alternative and/or additional advantages of (1) reducing the danger that the ion-permeable sections will be blocked by contaminants present in the electrolyte between the barrier and the substrate, for example oily contaminants in the water layer at the bottom of an oil storage tank, and/or (2) making it possible, when it is desired to surround the anode with an electrolyte which is different from the electrolyte which contacts the substrate (eg. when protecting a potable water tank with a platinum anode), to prevent substantial contamination of the anode electrolyte by the substrate electrolyte with minimal contamination of the substrate electrolyte by the anode electrolyte.
  • the barrier must not be electronically connected to the substrate or the anode, and is preferably composed of (including coated by) an electrically insulating material, eg. a plastic.
  • Preferred barriers are in the form of a tube (which may be of round or other cross section) or a plurality of tubes which are joined together to form a branched structure.
  • the branch tubes are preferably of smaller cross-section than the main tube, for example so that the total cross-sectional area of the branch tubes is no greater than the cross-sectional area of the main tube.
  • the tube or tubes can be heated by an internal or external heater to reduce the viscosity of the electrolyte therein (including to prevent it from freezing) and/or to reduce its resistivity.
  • the tube or tubes can be arranged as a continuous loop, so that electrolyte circulates through them, or can simply terminate in an open end (ie. an ion-permeable section) or a closed end.
  • the tube (or at least one of the tubes where a plurality of tubes are joined together) surrounds an elongate anode, for example one whose length is at least 100 times, preferably at least 1000 times, its smallest dimension, typically a metal wire, especially a platinum or platinum-coated wire, having for example a diameter of at least 0.01 inch (0.025 cm), preferably 0.02 to 0.3 inch (0.05 to 0.075 cm).
  • the internal diameter of the tube containing the wire anode is preferably P times the diameter of the wire, where P is 2 to 100, eg. 5 to 30, for example a diameter of 0.125 to 0.6 inch (0.36 to 1.5 cm).
  • the tube containing the wire anode comprises ion-permeable sections, or there are branch tubes comprising ion-permeable sections attached thereto, or both.
  • the branch tubes can comprise perforations and/or can have an open end, which may be fitted with a nozzle. In this way, it is possible to obtain a much more uniform current density on the anode, and hence also on the substrate, than in the absence of the barrier. This desirable result is achieved because the resistance between the substrate and the elongate anode is much greater than it would be in the absence of the tube or tubes, preferably by a factor of at least 10, for example at least 100 or even higher. This is especially valuable when it is desirable to provide a high current from a distributed anode.
  • anode comprising a metal core and a conductive polymer jacket, because such anodes cannot support the high current densities required.
  • a platinum wire anode or the like; such anodes will support very high current densities, but at the currents needed in such circumstances, the current density on the anode decreases rapidly as the distance from the power source increases, as demonstrated for example in Example 1 below.
  • the voltage of the power source is preferably less than 100 volts, particularly less than 50 volts, with the system being designed with this preference in mind.
  • electrolyte When there is a net transfer of electrolyte through the ion-permeable section(s) of the barrier, electrolyte must be supplied to the anode, and this can be done by recycling electrolyte from the vicinity of the substrate and/or by supplying fresh electrolyte.
  • electrolyte When build-up of electrolyte in the vicinity of the substrate must be avoided, eg. in the bottom of an oil storage tank, means must be provided for removing excess electrolyte; the excess electrolyte can be recycled to the anode, if desired or necessary after filtering or otherwise treating it to remove harmful contaminants.
  • Preferred uses for the present invention include the protection of city water tanks, ballast tanks in ships, oil rigs, cooling tanks for power stations, water tanks for secondary recovery in oil wells, oil storage tanks, heat exchangers, condensers, heater treaters, and buried pipes, in particular pipes buried below the permafrost line, for example oil pipes in frozen tundra.
  • Figure 1 shows a DC power source 1 which is connected to an anode 2 and a corrodible substrate 3 which is a cathode.
  • Anode 2 and substrate 3 are separated by a barrier 4 which comprises ion-permeable sections 45, and are connected by electrolyte 5 through sections 45.
  • a positive hydrostatic pressure is maintained from the interior of the barrier 4 across the ion-permeable sections 45 by means of pump 6.
  • Figure 1 is a diagrammatic side view which shows the corrodible substrate 3 within a vessel 7 containing the electrolyte 5.
  • the anode 2 is an elongate anode
  • the barrier 4 is a perforated tube containing the anode.
  • Figure 2 shows in diagrammatic plan view an alternative way of protecting a vessel 3.
  • Tube 44 surround the vessel and contains elongate anode 2.
  • Branch tubes 42 communicate with tube 44, pass through the wall of the vessel, and terminate in open ends or nozzles 45 which can point in one or more desired directions.
  • Figure 3 shows a tube with perforations therein through which ion-containing electrolyte can emerge; the perforations shown are uniformly spaced and of uniform size, but they could be of different sizes and separations in order to provide desired current distribution.
  • Figure 4 shows a tube composed of an ion-conducting membrane through which ions can pass, but non-ionic material cannot.
  • Figure 5 shows a perforated tube which is covered by an ion-conducting membrane.
  • Figure 6 shows a part of a perforated tube in which each perforation is covered by an ion-conducting membrane.
  • Figure 7 shows an open-ended tube through the open end of which ion-containing electrolyte can emerge.
  • Figure 8 shows an open-ended tube whose open end is covered by a porous plug.
  • Figure 9 shows a tube having a plurality of branch nozzles mounted thereon.
  • the invention is illustrated in the following Example.
  • procedures (A) and (B) are comparative examples and procedure (C) is an example of the invention.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Prevention Of Electric Corrosion (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
  • Internal Circuitry In Semiconductor Integrated Circuit Devices (AREA)
  • Thermistors And Varistors (AREA)

Claims (7)

  1. Anordnung zum kathodischen Schutz eines elektrisch leitfähigen Substrats gegen Korrosion, wobei die Anordnung folgendes aufweist:
    (1) ein elektrisch leitfähiges Substrat, das korrosionsanfällig ist;
    (2) eine langgestreckte, verteilte Anode, die eine Form hat, die im allgemeinen der Form des Substrats entspricht; und
    (3) eine Schicht, die (i) zwischen dem Substrat und der Anode liegt, (ii) von dem Substrat und der Anode beabstandet ist und (iii) die Form eines Rohres aufweist, das die Anode umgibt, das aber, wenn die Anode und das Substrat mit entgegengesetzten Polen einer Gleichstromquelle elektrisch verbunden sind und durch einen Elektrolyten zwischen der Anode und dem Substrat ein Schaltkreis geschlossen ist, es ermöglicht, daß ein elektrischer Strom zwischen der Anode und dem Substrat fließt,
    dadurch gekennzeichnet, daß
    (a) die genannte Schicht eine Sperrschicht ist, die eine Vielzahl von Bereichen aufweist, die ionendurchlässig sind, so daß dann, wenn die Anode und das Substrat mit entgegengesetzten Polen einer Gleichstromquelle elektrisch verbunden sind, die Verteilung und/oder die Größe der ionendurchlässigen Bereiche das Fließen von elektrischem Strom zwischen dem Substrat und der Anode begrenzt, verglichen mit dem Strom, der bei Abwesentheit der Sperrschicht fließen würde, so daß der Widerstand zwischen dem Substrat und der Anode das Q-fache des Widerstandes zwischen diesen bei Abwesentheit der Sperrschicht ist, wobei Q wenigstens 1,5, vorzugsweise wenigstens 10, insbesondere wenigestens 100 ist, und
    (b) die Anordnung ferner eine Pumpe aufweist, um flüssigen Elektrolyten durch das Rohr und durch die ionendurchlässigen Bereiche in Richtung auf das Substrat zu pumpen.
  2. Anordnung nach Anspruch 1, wobei die Verteilung und/oder die Größe der ionendurchlässigen Bereiche längs des Rohres ungleichmäßig ist.
  3. Anordnung nach Anspruch 1 oder 2, wobei die Länge der Anode wenigstens das 100-fache, vorzugsweise wenigstens das 1000-fache, ihrer kleinsten Dimension ist, und die Sperrschicht in Form eines Rohres vorliegt, das aus einem Isoliermaterial besteht und in seinen Wandungen Öffnungen aufweist.
  4. Anordnung nach Anspruch 1, 2 oder 3, wobei die Sperrschicht ferner eine Vielzahl von Abzweigrohren aufweist, wobei jedes der Abzweigrohre mit dem Rohr in Verbindung steht und wenigstens eine Öffnung darin hat.
  5. Anordnung nach einem der vorhergehenden Ansprüche, wobei die Anode ein Metalldraht mit einem Durchmesser von 0,05 cm bis 0,75 cm ist und der Innendurchmesser des Rohres das P-fache des Durchmessers des Drahtes ist, wobei P einen Wert von 2 bis 100, vorzugsweise von 5 bis 30 hat.
  6. Anordnung nach einem der vorhergehenden Ansprüche, wobei die Anode eine Platinoberfläche hat.
  7. Verfahren zum kathodischen Schützen eines elektrisch leitfähigen Substrats gegen Korrosion durch einen flüssigen Elektrolyten, der mit ihm in Berührung steht, wobei das Verfahren folgendes aufweist: Ausbilden einer Potentialdifferenz zwischen dem Substrat als Kathode und einer langgestreckten, verteilten Anode, so daß ein Strom zwischen dem Substrat und der Anode längs Strompfaden fließt, die durch ionendurchlässige Bereiche einer Sperrschicht verlaufen, die (i) zwischen dem Substrat und der Anode liegt und (ii) von dem Substrat und der Anode beabstandet ist und (iii) in Form eines Rohres vorliegt, das die Anode umgibt und eine Vielzahl von ionendurchlässigen Bereichen darin hat, und wobei bei dem Verfahren eine Pumpe einen Elektrolyten durch das Rohr und durch die ionendurchlässigen Bereiche in Richtung auf das Substrat fördert.
EP87306336A 1986-07-18 1987-07-17 Korrosionsschutz Expired - Lifetime EP0253671B1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP92103118A EP0488995B1 (de) 1986-07-18 1987-07-17 Korrosionsschutz
AT87306336T ATE80674T1 (de) 1986-07-18 1987-07-17 Korrosionsschutz.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US88819886A 1986-07-18 1986-07-18
US888198 1986-07-18

Related Child Applications (1)

Application Number Title Priority Date Filing Date
EP92103118.3 Division-Into 1992-02-25

Publications (3)

Publication Number Publication Date
EP0253671A2 EP0253671A2 (de) 1988-01-20
EP0253671A3 EP0253671A3 (en) 1988-08-03
EP0253671B1 true EP0253671B1 (de) 1992-09-16

Family

ID=25392719

Family Applications (2)

Application Number Title Priority Date Filing Date
EP92103118A Expired - Lifetime EP0488995B1 (de) 1986-07-18 1987-07-17 Korrosionsschutz
EP87306336A Expired - Lifetime EP0253671B1 (de) 1986-07-18 1987-07-17 Korrosionsschutz

Family Applications Before (1)

Application Number Title Priority Date Filing Date
EP92103118A Expired - Lifetime EP0488995B1 (de) 1986-07-18 1987-07-17 Korrosionsschutz

Country Status (7)

Country Link
EP (2) EP0488995B1 (de)
JP (1) JPS6333587A (de)
AT (2) ATE129529T1 (de)
CA (1) CA1331160C (de)
DE (2) DE3781735T2 (de)
ES (1) ES2033852T3 (de)
NO (1) NO177355C (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9426216D0 (en) * 1994-12-23 1995-02-22 Cathelco Ltd Descaling ships ballast tanks
ES2119692B1 (es) * 1996-07-12 1999-05-16 Lopez Calleja Lopez Jose Luis Dispositivo, sistema y procedimiento para aislar electricamente la estructura metalica de una embarcacion de una masa externa.
DE102014203659A1 (de) * 2014-02-28 2015-09-03 Siemens Aktiengesellschaft Kühlvorrichtung für einen Konverter einer Hochspannungs-Gleichstrom-Übertragungsanlage

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3022242A (en) * 1959-01-23 1962-02-20 Engelhard Ind Inc Anode for cathodic protection systems
NL247246A (de) * 1959-12-17 1900-01-01
GB1108692A (en) * 1964-04-17 1968-04-03 Gordon Ian Russell Method for installing cathodic protection against corrosion
NL6612237A (de) * 1966-08-31 1968-03-01
JPS5137263B1 (de) * 1968-10-28 1976-10-14
US4171254A (en) * 1976-12-30 1979-10-16 Exxon Research & Engineering Co. Shielded anodes
US4318787A (en) * 1980-02-22 1982-03-09 Conoco Inc. Sacrificial anode composition in cathodic protection process
US4457821A (en) * 1983-01-17 1984-07-03 Pennwalt Corporation Cathodic protection apparatus for well coated metal vessels having a gross bare area

Also Published As

Publication number Publication date
NO873015D0 (no) 1987-07-20
ATE129529T1 (de) 1995-11-15
EP0488995B1 (de) 1995-10-25
ES2033852T3 (es) 1993-04-01
DE3751575D1 (de) 1995-11-30
EP0253671A2 (de) 1988-01-20
NO177355B (no) 1995-05-22
EP0488995A3 (en) 1992-07-01
DE3751575T2 (de) 1996-06-27
DE3781735D1 (de) 1992-10-22
EP0488995A2 (de) 1992-06-03
JPS6333587A (ja) 1988-02-13
EP0253671A3 (en) 1988-08-03
DE3781735T2 (de) 1993-04-22
ATE80674T1 (de) 1992-10-15
NO177355C (no) 1995-09-06
NO873015L (no) 1988-01-19
CA1331160C (en) 1994-08-02

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