WO2017007334A1 - Systèmes de protection cathodique - Google Patents

Systèmes de protection cathodique Download PDF

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Publication number
WO2017007334A1
WO2017007334A1 PCT/NO2016/050147 NO2016050147W WO2017007334A1 WO 2017007334 A1 WO2017007334 A1 WO 2017007334A1 NO 2016050147 W NO2016050147 W NO 2016050147W WO 2017007334 A1 WO2017007334 A1 WO 2017007334A1
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WO
WIPO (PCT)
Prior art keywords
magnet
anode
cable
sacrificial anode
protected
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.)
Ceased
Application number
PCT/NO2016/050147
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English (en)
Inventor
Carl Henrik Ahlen
Sven Morten Hesjevik
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.)
Equinor Energy AS
Original Assignee
Statoil Petroleum ASA
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Publication date
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Publication of WO2017007334A1 publication Critical patent/WO2017007334A1/fr
Anticipated expiration legal-status Critical
Ceased 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
    • C23F13/06—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
    • C23F13/18—Means for supporting electrodes
    • 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
    • C23F13/20—Conducting electric current to electrodes
    • 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
    • C23F2213/00—Aspects of inhibiting corrosion of metals by anodic or cathodic protection
    • C23F2213/30—Anodic or cathodic protection specially adapted for a specific object
    • C23F2213/31—Immersed structures, e.g. submarine structures

Definitions

  • the present invention relates to a sacrificial anode assembly and cathodic protection system in which a sacrificial anode is connected to a structure to be protected. More particularly the invention relates to the use of a magnet to provide both physical and electrical connection. The invention also extends to a device for connecting a sacrificial anode to a structure to be protected in a cathodic protection system, comprising a magnet, and a method of connecting a sacrificial anode to a structure.
  • Cathodic protection systems are used to protect metal structures from corrosion, in particular subsea metal structures and components such as pipelines, valves, platforms, ship hulls and offshore wind power structures.
  • Such systems essentially work by making the structure into the cathode of an electrochemical cell.
  • a sacrificial anode(s) made of a more electrochemically active material than the structure (i.e. it is more susceptible to corrosion than the material of the structure) is electrically connected to the structure. Electrons flow from the anode to the structure and negatively polarise the structure, which thereby becomes a cathode.
  • the sacrificial anode corrodes in preference to the structure to be protected, hence the term "sacrificial", thereby protecting the structure from corrosion. When it has corroded to a certain level the sacrificial anode is then replaced with a new anode.
  • Arrays of multiple anodes are often used, with an array being connected to a structure via a connecting cable.
  • Anodes therefore need to be both initially installed (for example retrofitted to existing structures) and then replaced when required, which presents a number of difficulties given the typically subsea environment in which they are used.
  • metal magnets are their limited magnetic power and manufacturing difficulties, resulting in limitations in the size of anodes that they can be used to mount and the size of structures that they can be used to protect.
  • ceramic magnets are resistant to corrosion and moreover do not possess a potential relative to the surface to be protected such that there is no corrosion around or under the magnet. They can also be made of all shapes and sizes and thus assembled into bigger units to provide larger scale protection. However such ceramic magnets cannot provide the electrical connection necessary for sacrificial anodes. Therefore if a ceramic magnet is used, the electrical connection has to be effected separately, such as in US 3513082.
  • a ceramic magnet has a threaded opening into which a threaded bar of a sacrificial anode is fitted. The magnet provides the physical connection to the ship to be protected.
  • the end of the bar of the anode has a contact terminal which is electrically connected by various components to the ship to effect the electrical connection.
  • Such a system is therefore necessarily more complex than one in which an electrically conductive magnet is used, however it was considered necessary to use ceramic magnets to avoid the corrosion problems of electrically conductive metal magnets.
  • US 7402233 also notes problems, in particular corrosion, with the use of metal magnets to physically and electrically attach anodes to the structure to be protected. It aims to solve the problem through the use of a ceramic magnet, however in this invention the ceramic magnet is embedded within the anode and a conductive adhesive is used to provide electrical connection between the anode and the structure.
  • this system is more complex than one in which an electrically conductive magnet is used, however it was considered necessary.
  • US 3772179 is a further example of the general understanding that corrosion prevents good electrical contact between an electrically conductive magnet and a structure to be protected.
  • a ceramic magnet is used to provide physical connection between the anode and the structure, whilst an electrically conductive spring member is used to provide the electrical connection. Parts of the spring member are coated with a soft metal to prevent corrosion.
  • Retroclamp can also carry an anode material itself to form a stand-alone system (as opposed to connecting a cable from an anode array).
  • Anode installation clamps are also described for example in GB 2464213 which teaches a C-shaped clamp that engages and clamps sacrificial anodes to a subsea pipeline to be protected.
  • clamping systems need to be installed and replaced by a diver, involve some expense and complexity and the types of structure that they can be connected to can be limited (e.g. to pipeline applications). There is also the risk of damage to the structure due to the force of the clamp.
  • the present invention provides a sacrificial anode assembly, comprising: a sacrificial anode; and a rare-earth or alnico magnet coupled to the anode via a fastener and arranged to attach the anode, via magnetic force, to a structure to be protected; wherein the magnet is electrically conductive and is arranged to provide electrical connection between the anode and the structure to be protected.
  • the electrical connection between the sacrificial anode and the magnet may preferably be via the fastener.
  • Rare-earth or alnico magnets are particularly preferred as they can supply sufficient magnetic force in order to both achieve good electric contact and to maintain a physical connection between the sacrificial anode and the structure. By using such magnets with good electrical conductivity, the electrical connection provided by the magnet is sufficient without the need for an additional electrical connector.
  • Alnico is a particularly useful magnetic material for the present invention since it has important corrosion resistant properties that help to avoid the problems in the prior art due to corrosion of metal magnets. It also provides a strong magnetic connection which has the advantages mentioned below in relation to neodymium magnets.
  • the most preferred type of rare-earth magnet is a neodymium magnet, e.g. comprising an alloy of neodymium, iron and boron.
  • a neodymium magnet e.g. comprising an alloy of neodymium, iron and boron.
  • This provides a particularly high magnetic force that helps ensure electrical and physical contact between the anode and the structure throughout the lifetime of the system, by avoiding loss of contact due to environmental issues such as high sea currents.
  • the strong magnetic force between the magnet and the structure also helps prevent development of deposits that would reduce electric contact/lead to corrosion.
  • Neodymium magnets may preferably be coated with a more corrosion resistant metal alloy such as nickel or aluminium.
  • the alnico or rare earth magnet is resistant to corrosion to the extent that over the lifetime of the anode it will provide adequate physical and electrical connection to the structure.
  • magnets therefore enables sacrificial anodes to be easily attached to a structure to be protected, without the need for e.g. welding or bolting, whereby the electrical connection is effected via the magnet such that an additional electrical connection is not required.
  • sacrificial anodes can be fitted and replaced quickly, easily and cost-effectively e.g. by a diver or remotely operated vehicle.
  • magnets do not suffer from the corrosion problems and limited strength issues of other metallic magnets recognised in the prior art, which led to the prejudice against the use of conductive metallic magnets in this technology.
  • the exposed surface(s) of the magnet are also provided with corrosion protection by the sacrificial anode.
  • the sacrificial anode may be made from any suitable material such as zinc, magnesium or aluminium, but a particularly preferred material is an Al-Zn-ln alloy.
  • More than one magnet may be provided depending on the attachment force required. Each magnet may be attached by a different fastener, or a single fastener may attach more than one magnet.
  • the shape of the anode assembly can be chosen so as to minimise the effect of undersea forces and thus minimise the magnetic attachment force required.
  • the magnet may be directly coupled to the anode via the fastener or indirectly coupled.
  • the sacrificial anode has a metal strip (e.g. a carbon steel strip) extending therethrough.
  • the anode is cast together with the metal strip during manufacture, for example it may be placed in the mould before the anode material is cast in the mould.
  • the magnet is coupled to the metal strip (and thereby the anode) via the fastener.
  • a second magnet is provided which is coupled to the metal strip via a second fastener, wherein the magnets are coupled to respective ends of the metal strip via the fasteners.
  • This metal strip offers the advantage that it is simpler to attach magnets to the strip than directly to the anode material (in the case of thick anodes it would be particularly difficult to adequately attach the magnets).
  • the fastener comprises a shaft portion and a housing into which the magnet is fitted.
  • the magnet will generally not be welded to the housing by rather be glued for example with epoxy, or be attached by shrink fitting or pressing.
  • the housing may provide mechanical protection against damage, which is particularly useful if the magnet is brittle.
  • the housing and/or the shaft are in contact with the magnet and are preferably electrically conductive so that the magnet and housing and/or shaft are electrically connected.
  • electrical connection between the anode and the structure may be provided by means of the metal strip, housing and/or shaft and magnet.
  • the housing preferably has an annular recess into which an annular magnet is fitted.
  • the shaft portion is arranged through an opening in the metal strip to thereby couple the magnet to the metal strip and thereby the anode.
  • the fastener may therefore be a bolt with magnet housing, with the magnets being bolt-mounted magnets. It may be known as a "magnetic bolt”. Such items may be available commercially, and are typically made of carbon steel, stainless steel or any other metal. A nut and washers may be provided to hold the bolt in place in the opening (hole) in the metal strip.
  • the metal strip and/or the fastener e.g. the bolt and magnet housing
  • the metal strip and/or the fastener will generally be protected from corrosion as they are cathodically protected themselves by the anode material.
  • the invention also provides a cathodic protection system in which a sacrificial anode assembly as described above is connected to a structure to be protected.
  • the structure to be protected is a subsea structure.
  • the structure may be a pipeline, valve, platform, ship's hull or offshore wind power structure. Since most of the structures that it is desired to protect are made from magnetically receptive materials, such as steels, the invention has wide ranging usage.
  • the invention further extends to a method of connecting a sacrificial anode assembly as described above to a structure to be protected, comprising: attaching the magnet to the structure to be protected by way of magnetic force so as to provide both physical attachment and electrical connection between the magnet and the structure; such that the sacrificial anode is electrically connected to the structure via the magnet.
  • the method further comprises cleaning the surface of the structure where the magnet is to be attached, preferably including removing organic coatings and/or marine fouling and/or calcareous deposits.
  • cleaning may be performed by a high pressure water jet operated by a diver or remotely operated subsea vehicle.
  • the present invention provides a device for connecting a sacrificial anode to a structure to be protected in a cathodic protection system, comprising: an electrically conductive cable; an electrically conductive magnetic plate; and an electrically conductive magnet; wherein the electrically conductive cable is for providing an electrical connection between the anode and the magnetic plate, the cable being attached at an end to the magnetic plate;
  • the magnetic plate is attached to the magnet by magnetic force so that the magnetic plate is both physically attached and electrically connected to the magnet, the cable thereby being electrically connected to the magnet via the magnetic plate; wherein the magnet has a surface for attaching to the structure by magnetic force so as to provide both a physical attachment and electrical connection between the magnet and the structure; such that the device can thereby provide an electrical connection between the sacrificial anode and the structure.
  • the electrically conductive cable may be directly connected to the anode, or may be connected via other elements such as other conductive components. If the anode is part of an anode array, the cable will generally be connected to the array at a connection point that provides electrical connection with all the anodes. Thus in this embodiment it can be understood that more than one anode is provided.
  • more than one electrically conductive cable is provided for providing an electrical connection between the anode (e.g. anode array) and the magnetic plate.
  • the electrically conductive magnet will need to supply sufficient magnetic force in order to both achieve good electric contact and to maintain a physical connection between the sacrificial anode and the structure.
  • the magnet is an alnico or rare earth magnet, such as a neodymium magnet comprising an alloy of neodymium, iron and boron.
  • a neodymium magnet comprising an alloy of neodymium, iron and boron.
  • other types of strong magnet can be used.
  • the sacrificial anode will provide some corrosion protection to the magnet (and magnetic plate), in the same way that it protects the structure.
  • the magnet, magnetic plate and connection between the cable and the magnetic plate are at least partially enclosed / encapsulated in a casting, preferably a polymeric casting, and in one embodiment an epoxy casting.
  • a casting preferably a polymeric casting, and in one embodiment an epoxy casting.
  • the casting also adds mechanical and electrical robustness.
  • the casting provides significant advantages both in terms of function and longevity.
  • the polymeric casting encloses the magnet, magnetic plate and connection between the cable and the magnetic plate except for the surface of the magnet for attaching to the structure.
  • the cable protrudes from the casting for connecting to the sacrificial anode.
  • the cable may be a copper, aluminium or steel cable and is preferably an armoured cable. It preferably provides both physical and electrical connection between the sacrificial anode and the magnet.
  • the cable is attached at an end to the magnetic plate, for example it may be welded, soldered, brazed or fitted by mechanical means.
  • the plate may be a steel plate.
  • the use of such a magnetic plate is particularly advantageous (as opposed to say connecting the cable directly to the magnet) because it can be difficult to connect the cable directly to an alnico or neodymium magnet by soldering or welding due to the low curie point.
  • the other side of the plate (opposite that to which the cable is attached) is attached to the magnet by magnetic force, thus providing both physical attachment and electrical connection between the plate and the magnet.
  • the provision of the magnetic plate provides a simple effective means by which the cable can be put in electrical connection with the magnet.
  • the device can be installed on a structure to be protected by a diver or remotely operated vehicle.
  • the entire device e.g. including the anode, cable, magnetic plate and magnet
  • the entire device e.g. including the anode, cable, magnetic plate and magnet
  • the structure to be protected is a subsea structure, for example a pipeline, valve, platform, ship's hull or offshore wind power structure.
  • the device can be retrofitted to existing structures.
  • a cathodic protection system in which a sacrificial anode is connected to a structure to be protected using a device as described above.
  • the structure to be protected may be a subsea structure, preferably a pipeline, valve, ship's hull or offshore wind power structure.
  • the sacrificial anode may be part of a remote array of anodes.
  • the conductive cable provides an electrical connection between the array of anodes and the magnet.
  • the sacrificial anode(s) when the sacrificial anode(s) has been consumed, the sacrificial anode(s) (or in the case of an anode array, the complete array), cable, magnetic plate and magnet are replaced. In this way, these elements can be seen as essentially forming a "replaceable system".
  • the present invention provides a cathodic protection system in which a sacrificial anode is connected to a structure to be protected, comprising: a sacrificial anode; an electrically conductive magnet which is attached to the structure to be protected by means of magnetic force; an electrically conductive magnetic plate attached to the magnet; and an electrically conductive cable; wherein the sacrificial anode is connected to the electrically conductive magnetic plate via the conductive cable secured at one end to the magnetic plate; such that the sacrificial anode is electrically connected to the magnet via the conductive cable and the magnetic plate; the sacrificial anode thereby being electrically connected to the structure via the magnet, cable and plate; and wherein the magnet, magnetic plate and connection between the cable and the magnetic plate are at least partially enclosed in a polymeric casting so as to isolate the connection between the cable and the plate from the environment.
  • the present invention provides a method of connecting a sacrificial anode to a structure to be protected in a cathodic protection system utilising a device as described above; comprising electrically connecting the electrically conductive cable to the sacrificial anode; and attaching the device to the structure by magnetic force so as to provide both physical attachment and electrical connection between the magnet and the structure; such that the sacrificial anode is electrically connected to the structure via the cable, plate and magnet.
  • the anode is part of a remote array of anodes, thus the step of attaching the cable to the anode comprises attaching the cable to the array of anodes, such that the array of anodes is electrically connected to the structure via the cable, plate and magnet.
  • the structure to which the anode is connected may be a subsea structure, preferably a pipeline, valve, platform, ship's hull or offshore wind power structure.
  • the method further comprises cleaning the surface of the structure where the device is to be attached. This may include removing organic coatings and/or marine fouling and/or calcareous deposits using e.g. a high pressure water jet operated by a diver or remotely operated subsea vehicle.
  • the present invention provides a cathodic protection system in which a sacrificial anode is connected to a structure to be protected, comprising: a sacrificial anode; and a rare-earth or alnico magnet;
  • the sacrificial anode is electrically connected to the magnet; and wherein the magnet is attached to the structure to be protected by means of magnetic force so as to provide both physical attachment and electrical connection between the magnet and the structure, such that the sacrificial anode is electrically connected to the structure via the magnet.
  • the sacrificial anode is preferably both electrically and physically connected to the magnet and thereby to the structure.
  • the electrical connection between the sacrificial anode and the magnet may be direct (e.g. direct contact) or indirect (e.g. via other electrically conductive elements such as a plate and/or cable).
  • the physical connection may also be direct or indirect e.g. via other elements such as a plate and/or cable.
  • the electrical connection and physical connection between the anode and the magnet are provided in the same way e.g. by direct contact or via elements such as a plate and/or cable.
  • Rare-earth or alnico magnets are particularly preferred as they can supply sufficient magnetic force in order to both achieve good electric contact and to maintain a physical connection between the sacrificial anode and the structure.
  • Alnico is a particularly useful magnetic material for the present invention since it has important corrosion resistant properties that help to avoid the problems in the prior art due to corrosion of metal magnets. It also provides a strong magnetic connection which has the advantages mentioned below in relation to neodymium magnets.
  • the most preferred type of rare-earth magnet is a neodymium magnet, e.g. comprising an alloy of neodymium, iron and boron.
  • a neodymium magnet e.g. comprising an alloy of neodymium, iron and boron.
  • This provides a particularly high magnetic force that helps ensure electrical and physical contact between the anode and the structure throughout the lifetime of the system, by avoiding loss of contact due to environmental issues such as high sea currents.
  • the strong magnetic force between the magnet and the structure also helps prevent development of deposits that would reduce electric contact/lead to corrosion.
  • Neodymium magnets may preferably be coated with a more corrosion resistant metal alloy such as nickel or aluminium.
  • the alnico or rare earth magnet is resistant to corrosion to the extent that over the lifetime of the anode it will provide adequate physical and electrical connection to the structure. Typically, when the sacrificial anode is replaced at the end of its life, the magnet will also be replaced (although an embodiment can be envisaged in which the magnet is reused).
  • the magnet is an alnico or rare earth magnet, it will be appreciated that other types of strong magnet could be used instead.
  • magnets therefore enables sacrificial anodes to be easily attached to a structure to be protected, whereby the electrical connection is effected via the magnet such that an additional electrical connection is not required.
  • sacrificial anodes can be fitted and replaced quickly, easily and cost- effectively e.g. by a diver or remotely operated vehicle.
  • magnets do not suffer from the corrosion problems and limited strength issues of other metallic magnets recognised in the prior art, which led to the prejudice against the use of conductive metallic magnets in this technology.
  • the exposed surface(s) of the magnet are also provided with corrosion protection by the sacrificial anode.
  • the sacrificial anode may be made from any suitable material such as zinc, magnesium or aluminium, but a particularly preferred material is an Al-Zn-ln alloy.
  • the anode may be directly attached to the magnet thus providing direct physical and electrical connection with the magnet.
  • the anode may be attached to the magnet via one or more interim elements, such as an electrically conductive magnetic plate.
  • the anode may be attached to one side of the magnetic plate (e.g. a steel plate), and the magnetic plate attached at its opposite side via magnetic force to the magnet, such that the anode is physically attached and electrically connected to the magnet via the plate.
  • the sacrificial anode is connected to the magnet via a cable.
  • the cable is preferably a conductive cable, such as a copper, aluminium or steel cable, and provides both electrical and physical connection between the sacrificial anode and the magnet.
  • the cable is preferably an armoured cable. In such an embodiment at one end the cable is attached to the anode.
  • the cable is connected to the magnet via a magnetic plate attached to the magnet, the cable being secured to the magnetic plate.
  • the cable may for example be welded, soldered, brazed or fitted by mechanical means to the plate.
  • the plate may be a steel plate. The use of such a plate is advantageous because it can be difficult to connect the cable directly to the alnico or neodymium magnet by soldering or welding due to the low curie point.
  • the other side of the plate is attached to the magnet by magnetic force, thus providing both physical attachment and electrical connection between the plate and the magnet.
  • the sacrificial anode is part of a remote array of multiple anodes.
  • the conductive cable provides an electrical connection between the array and the magnet.
  • the sacrificial anode will provide some corrosion protection to the magnet
  • the magnet, magnetic plate and connection between the cable and the magnetic plate are enclosed / encapsulated in a casting except for the surface of the magnet for attaching to the structure, so as to isolate the connection between the cable and the plate from the environment.
  • the cable protrudes from the casting so as to be connected to the sacrificial anode.
  • the casting is preferably a polymeric casting, and in one embodiment is an epoxy casting.
  • the structure to be protected by the invention is typically a subsea structure, such as a pipeline, valve, platform, ship's hull or offshore wind power structure. Since most of the structures that it is desired to protect are made from magnetically receptive materials, such as steels, the invention has wide ranging usage.
  • the present invention provides a method of connecting a sacrificial anode to a structure to be protected in a cathodic protection system, comprising: electrically connecting a sacrificial anode to an alnico or rare earth magnet; attaching the magnet to the structure to be protected by way of magnetic force so as to provide both physical attachment and electrical connection between the magnet and the structure; such that the sacrificial anode is electrically connected to the structure via the magnet.
  • a preferred rare earth magnet is neodymium, e.g. comprising an alloy of neodymium, iron and boron.
  • organic coatings, marine fouling and in the case of bare steel oxides, calcareous deposits, that are present on the surface of the structure at the attachment area may be removed, e.g. by a high-pressure water jet, in order to improve the physical and electrical connection.
  • the high pressure water jet may be operated by a diver or remotely operated subsea vehicle (ROV).
  • ROV subsea vehicle
  • the magnet may be attached to the structure by a diver or a remotely operated subsea vehicle.
  • the method further comprises electrically connecting the sacrificial anode to the magnet via an electrically conductive cable either directly or indirectly via other conductive elements.
  • the anode may be electrically (and preferably physically) connected at one end of the cable, with the other end of the cable being directly or indirectly electrically (and preferably physically) connected to the magnet.
  • the method may comprise connecting the cable to the magnet via an electrically conductive magnetic plate, by securing the cable to the magnetic plate and attaching the magnetic plate to the magnet via magnetic force.
  • the magnet, magnetic plate and connection between the cable and the magnetic plate may be enclosed in a casting, preferably a polymeric (e.g. epoxy casting), except for the surface of the magnet for attaching to the structure, so as to isolate the connection between the cable and the plate from the environment, and wherein the cable protrudes from the casting so as to be connected to the sacrificial anode.
  • the sacrificial anode may be part of a remote array of anodes wherein the array is electrically connected to the magnet via the conductive cable.
  • the method may comprise directly connecting the sacrificial anode to the magnet, i.e. without the use of a cable.
  • the invention provides a method of connecting a sacrificial anode to a structure to be protected in a cathodic protection system, comprising: providing an electrical connection between an anode and an electrically conductive magnetic plate by means of an electrically conductive cable, wherein the electrically conductive cable is attached to the magnetic plate;
  • the magnetic plate attaching the magnetic plate to an electrically conductive magnet by magnetic force so that the magnetic plate is both physically attached and electrically connected to the magnet; attaching the magnet to the structure to be protected by magnetic force so as to provide both a physical attachment and electrical connection between the magnet and the structure; such that the sacrificial anode is electrically connected to the structure via the cable, plate and magnet.
  • the magnet is an alnico or rare earth magnet, most preferably a neodymium magnet.
  • the method may further include enclosing the magnet and magnetic plate including the attachment between the cable and the magnetic plate in a polymeric casting, except for a surface of the magnet that is attached to the structure, so as to isolate these parts from the environment, and allowing the cable to protrude from the casting for connection to the sacrificial anode.
  • the present invention provides a method of protecting a structure with an array of sacrificial anodes, comprising: electrically connecting the array of anodes to an electrically conductive magnetic plate by means of an electrically conductive cable; attaching the electrically conductive magnetic plate to an electrically conductive magnet by means of magnetic force so that they are electrically connected; attaching the magnet to the structure by means of magnetic force so that they are electrically connected; such that the array is electrically connected to the structure via the cable, magnetic plate and magnet and can thereby provide cathodic protection to the structure.
  • the structure to be protected by the methods of the invention is typically a subsea structure, such as a pipeline, valve, platform, ship's hull or offshore wind power structure.
  • Figure 1 illustrates a cathodic protection system in which an array of sacrificial anodes is connected to a structure to be protected using a magnetic device, according to an embodiment of the invention
  • Figure 2 illustrates the magnetic device of Figure 1 for attaching a sacrificial anode to a structure to be protected in more detail;
  • Figure 3 is a top view of a sacrificial anode assembly according to an embodiment of the invention.
  • Figure 4 illustrates the sacrificial anode assembly of Figure 3 in side view
  • Figure 5 is a bottom view of the sacrificial anode assembly of Figures 3 and 4, i.e. the side that is attached to a structure;
  • Figure 6 illustrates an alternative anode that may be used in an anode assembly according to an embodiment of the invention.
  • Figure 1 illustrates a cathodic protection system 1 in which a remote anode array 3 of Al-Zn-ln sacrificial anodes 4 is electrically connected and physically attached to a submerged structure to be protected 5 by an armoured aluminium cable 6 and a magnetic connector device 2.
  • the entire system 1 is located under the sea 7.
  • the structure 5 to be protected may be any subsea structure as previously described such as an offshore wind power structure, ship's hull or pipeline.
  • the magnetic connector device 2 is illustrated in more detail in Figure 2.
  • the aluminium cable 6 is welded to a steel plate 8 so as to be both physically attached and electrically connected to the plate.
  • the steel plate 8 is attached by magnetic force to a neodymium electrically conductive permanent magnet 9. Since the steel plate is electrically conductive, it provides an electrical connection between the cable 6 welded thereto and the neodymium magnet 9. Thus, the cable 6 is both physically attached and electrically connected to the magnet 9 via the plate 8.
  • the magnet 9, steel plate 8 and connection between the aluminium cable 6 and the plate 8 are housed within a polymeric epoxy casting 11 so as to be isolated from the environment.
  • the aluminium cable 6 protrudes from the casting 11 to as to extend to and connect with the anode array 3.
  • the side 10 of the magnet 9 to be connected to the structure 5 i.e. the side opposite that to which the plate 8 is attached
  • organic coatings and marine fouling present on the surface of the structure 5 are removed by a diver-controlled or remotely operated vehicle (ROV)-controlled high pressure water jet.
  • ROV remotely operated vehicle
  • the sacrificial anodes 4 of the anode array 3 are electrically and physically connected to the structure 5 by means of the aluminium cable 6, the steel plate 8 and the neodymium magnet 9.
  • the sacrificial anodes corrode preferentially to the structure 5 to be protected (which becomes a cathode), thus protecting the structure 5 from corrosion.
  • the anode array 3 When the sacrificial anodes 4 of the anode array 3 are depleted to such an extent that they no longer provide the structure 5 with adequate protection, the anode array 3 is replaced. The magnetic connector device 2 and the cable 6 are also replaced. Thus, the magnetic connector device 2, cable 6 and sacrificial anode array 3 can essentially be seen as one system: when the anodes 4 are consumed, the entire system will be removed and replaced with a new magnetic connector-cable-array system. An ROV or diver will remove the existing magnetic connector device 2 from the structure 5 and replace it with a new one. The removal and replacement is much easier than in prior art systems due to the magnetic connection rather than e.g. the friction stud welding of the prior art.
  • FIGS 3, 4 and 5 illustrate a sacrificial anode assembly 20 according to an alternative embodiment of the invention.
  • This anode assembly 20 is for direct connection to a structure, i.e. without the use of an anode cable.
  • the assembly 20 comprises a sacrificial anode 21 having a metal (in this embodiment a carbon steel) strip 22 extending therethrough.
  • the anode 21 is cast together with the metal strip 22 during manufacture.
  • holes (not shown) are coupled.
  • Each bolt mounted magnet 23 comprises a shaft 24, a nut 25, washers 26 and 27, a housing 28 and an annular magnet 29 fixed (typically glued with epoxy) within the housing (the magnets 29 are only visible in Figure 5).
  • the shaft 24 extends through the hole (not shown) and is held in place with nut 25.
  • the strip 22, housing 28, shaft 23 and magnet 29 are electrically conductive.
  • the shaft 24 and housing 28 are, in this embodiment, made of carbon steel.
  • the magnet 29 is a neodymium magnet.
  • the underside of the assembly 20 (as shown in Figure 5) is placed against the structure to be protected, the magnets 29 contact the surface of the structure and the assembly is thereby held in place by the magnetic force of magnets 29.
  • the magnets 29 also provide electrical connection between the anode 21 and the structure, since the strip 22, housing 28 and shaft 24 electrically connect the anode with the magnet 29, and the magnet 29 is in direct contact with the structure.
  • FIG. 6 illustrates an alternative anode 31 that may be used in an anode assembly according to an embodiment of the invention.
  • Anode 31 has a hole 32 through which a bolt mounted magnet 23 may be attached.

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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)

Abstract

La présente invention concerne un système de protection cathodique dans lequel une anode sacrificielle (qui peut faire partie d'un ensemble d'anodes) est raccordée à une structure devant être protégée, telle qu'un oléoduc, une soupape, une plate-forme, une coque de bateau, une structure d'énergie éolienne en mer ou une autre structure sous-marine. Le système comprend une anode sacrificielle et un aimant en terres rares ou en AlNiCo. L'anode sacrificielle est raccordée électriquement à l'aimant. L'aimant est fixé à la structure devant être protégée au moyen d'une force magnétique de manière à assurer à la fois une fixation physique et un raccordement électrique entre l'aimant et la structure, de sorte que l'anode sacrificielle est raccordée électriquement à la structure par l'intermédiaire de l'aimant. La présente invention concerne également un ensemble d'anodes, un dispositif et un procédé de raccordement d'une anode sacrificielle à une structure devant être protégée.
PCT/NO2016/050147 2015-07-03 2016-06-29 Systèmes de protection cathodique Ceased WO2017007334A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB1511713.8A GB201511713D0 (en) 2015-07-03 2015-07-03 Magnetic connector for use in cathodic protection of subsea structures
GB1511713.8 2015-07-03

Publications (1)

Publication Number Publication Date
WO2017007334A1 true WO2017007334A1 (fr) 2017-01-12

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GB (1) GB201511713D0 (fr)
WO (1) WO2017007334A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109536968A (zh) * 2018-12-21 2019-03-29 西安英柯迈信息技术有限公司 阴极保护导线与被保护体的免焊接安装装置及检测方法
CN111041495A (zh) * 2019-10-25 2020-04-21 海洋石油工程股份有限公司 水下设施外接阳极保护装置
CN114919720A (zh) * 2022-05-19 2022-08-19 青岛双瑞海洋环境工程股份有限公司 海床式牺牲阳极装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2923825A1 (de) * 1979-06-05 1980-12-18 Ludwig Hoessle Opferanode
JP2008274359A (ja) * 2007-04-27 2008-11-13 Tokyo Electric Power Co Inc:The 流電陽極
WO2013186548A2 (fr) * 2012-06-12 2013-12-19 Fugro Subsea Services Limited Connecteur électrique destiné à une anode
EP2868774A2 (fr) * 2013-11-05 2015-05-06 Magontec GmbH Accessoire pour un dispositif destiné à la protection cathodique contre la corrosion

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2923825A1 (de) * 1979-06-05 1980-12-18 Ludwig Hoessle Opferanode
JP2008274359A (ja) * 2007-04-27 2008-11-13 Tokyo Electric Power Co Inc:The 流電陽極
WO2013186548A2 (fr) * 2012-06-12 2013-12-19 Fugro Subsea Services Limited Connecteur électrique destiné à une anode
EP2868774A2 (fr) * 2013-11-05 2015-05-06 Magontec GmbH Accessoire pour un dispositif destiné à la protection cathodique contre la corrosion

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109536968A (zh) * 2018-12-21 2019-03-29 西安英柯迈信息技术有限公司 阴极保护导线与被保护体的免焊接安装装置及检测方法
CN109536968B (zh) * 2018-12-21 2024-01-26 西安英柯迈信息技术有限公司 阴极保护导线与被保护体的免焊接安装装置及检测方法
CN111041495A (zh) * 2019-10-25 2020-04-21 海洋石油工程股份有限公司 水下设施外接阳极保护装置
CN111041495B (zh) * 2019-10-25 2022-07-01 海洋石油工程股份有限公司 水下设施外接阳极保护装置
CN114919720A (zh) * 2022-05-19 2022-08-19 青岛双瑞海洋环境工程股份有限公司 海床式牺牲阳极装置
CN114919720B (zh) * 2022-05-19 2024-04-30 青岛双瑞海洋环境工程股份有限公司 海床式牺牲阳极装置

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