US2483397A - Cathodic protection system - Google Patents

Cathodic protection system Download PDF

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Publication number
US2483397A
US2483397A US610643A US61064345A US2483397A US 2483397 A US2483397 A US 2483397A US 610643 A US610643 A US 610643A US 61064345 A US61064345 A US 61064345A US 2483397 A US2483397 A US 2483397A
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US
United States
Prior art keywords
circuit
underground
rectifier
current
track
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
US610643A
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English (en)
Inventor
Walter F Bonner
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.)
STC PLC
Federal Telephone and Radio Corp
Original Assignee
Standard Telephone and Cables PLC
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 to NL65387D priority Critical patent/NL65387C/xx
Application filed by Standard Telephone and Cables PLC filed Critical Standard Telephone and Cables PLC
Priority to US610643A priority patent/US2483397A/en
Priority to FR939377D priority patent/FR939377A/fr
Priority to CH275450D priority patent/CH275450A/fr
Application granted granted Critical
Publication of US2483397A publication Critical patent/US2483397A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • 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

Definitions

  • the present invention relates to a system for protecting underground metallic structures against electrolytic corrosion and more particularly to the so-called cathodic system of electrolytic corrosion prevention in which the potential of the buried structure is depressed below that of the surrounding earth.
  • Electrolytic corrosion of underground metallic structures is occasioned by the presence in such structures of electric currents. These arise in some cases from a galvanic action between the metallic structure and the surrounding soil in which it is embedded, due to the chemical nature of the soil and the fact that the surrounding earth, particularly when moist, is a conductor of electricity.
  • the currents within the underground metallic structure also commonly are caused by stray currents from such sources as electric railway tracks which are employed as one of the conductors for the supply of energy to the railway rolling equipment.
  • the tendency of underground metallic structures to undergo electrolytic corrosion can be overcome by the cathodic system of protection.
  • This system is based on creating and maintaining a difference of potential between the underground metallic structure and the immediately surrounding earth such that the metal structure is at a lower potential than the earth, wherefore current flow from the metal structure to the earth is substantially prevented.
  • Such systems commonly provide the desired difference of potential between the underground metallic structure and the surrounding earth by connecting the negative side of a rectified alternating current circuit to the buried structure.
  • the positive side may be connected to a suitable electrode buried in the earth nearby, or in the case when the principal cause of the electrolysis is a nearby electric railway, to the railway track. In some instances the positive connection is made to the negative bus bar at the generating station.
  • the current required varies with soil conditions, but, ordinarily, currents of the order of amperes have proven adequate in practice.
  • the current flow may fluctuate due to various changes in the conditions such as changes in the conductivity of the soil due to rainfall and to changes in the potential of the track work of the railway.
  • Rise of the current above values which are adequate to substantially prevent electrolytic action represents'an expenditure of energy which does not produce a corresponding beneficial result. Also, such large currents cause unnecessary heating and other undesired effects in the rectifiers.
  • a further object is to provide an electrolytic corrosion control circuit which is automatically responsive to rise of current above a predetermined value to limit the current flow.
  • the electrolytic corrosion control system includes a circuit connected to the underground structure which includes means for producing a difference of potential to depress the potential of the structure and means responsive to the value of the current in the circuit connected to the structure to render inoperative the means for producing the difference of potential.
  • the system of the present invention includes a circuit connecting the underground metallic structure with the earth adjacent the structure, with the rails of an electric railway in the vicinity of the underground metallic structure or with the negative bus bar at the generating station.
  • An electromotive force is impressed on this circuit in a direction to tend to cause current flow from the underground structure to the earth, the track, or the bus bar, as the case may be.
  • the current supply in practice is an alternating source which is connected to the circuit by means of a transformer whose secondary winding is in series with the circuit, in which case a suitable rectifier is provided in series with the transformer secondary winding.
  • a shunt circuit is arranged across the rectifier and the transformer secondary winding.
  • the shunt circuit contains a set of normally open relay contacts which are adapted to be closed by a relay operating winding, connected in series with the transformer secondary winding and the rectifier, when the current in the circuit exceeds a predetermined value.
  • the relay may be provided with a second set of contacts arranged to open the supply circuit to the transformer primary winding simultaneously with the short cir- 3 cuiting of the rectifier and the transformer secondary winding.
  • the underground pipe which is to be protected is illustrated at I.
  • a rail of an adjacent electric railway track is illustrated at 2.
  • the pipe I would be gradually eroded by the action of stray currents from the track 2 which would flow into the pipe at points at which the pipe is of lower potential than the adjacent earth and would then leave the pipe at points where the potential of the adjacent earth is less than the potential of the pipe.
  • a negative potential with respect to the earth is impressed on the pipe from a suitable source of alternating electromotive force 3.
  • Alternating current from the source 3 is supplied to the primary winding 4 of a transformer 5 whose secondary winding 6 is connected between the pipe I and the track 2 by a circuit 8.
  • a rectifier i is included in the circuit 8 in series with the secondary winding 6 of the transformer 5.
  • the rectifier is so arranged as to permit current now in the direction from the pipe i to the track 2.
  • the rectifier illustrated symbolically at I may be of any suitable type and may be a single rectifier or a set of rectifiers connected in the well-known Wheatstone bridge arrangement.
  • a shunt circuit 9 is provided, connected in parallel with the rectifier I and the secondary winding 6 of the transformer.
  • a relay in has its operating winding ll connected in the circuit 6, in series with the transformer secondary winding 6 and the rectifier 1, to be responsive to the current in this circuit.
  • Relay III is provided with a set of normally-open contacts I! connected in the shunt circuit 9 which are adapted to be closed upon operation of the relay to close the shunt circuit 9. This operation will occur when the current flowing in circuit 8, and consequently through the operating winding H of relay I0, exceeds a preselected value which is determined by the characteristics of the relay l0.
  • the alternating current source and the rectifier are for all practical purposes rendered inoperative and the connection between the pipe and the track is a direct grounding connection through the shunt circuit 9.
  • the relay it opens the shunt circuit 9.
  • a cathodic protective system for protecting underground structures against electrolytic corrosion including, in combination, an underground structure, an electric railway track in the vicinity of the structure, a circuit connecting the track and the underground structure, means for impressing an electromotive force on said circuit, and means for rendering said first-named means inoperative upon rise of current in said circuit above a predetermined value, and operative when said potential difierence falls below said value.
  • a cathodic protective system for protecting underground structures from electrolytic corrosion including, in combination, an underground structure, a grounding circuit connected to said structure, a source of electromotive force connected in series in said circuit, and means for short circuiting said source of electromotive force upon rise of current in said circuit above a predetermined value.
  • a cathodic protective system for protecting underground metallic structures from electrolytic corrosion including, in combination, an underground metallic structure, an electric railway track in the vicinity of the structure, a circuit connecting the track and the underground structure, a rectifier and a source of alternating electromotive force connected in series in said circuit and means for short circuiting said rectifier and source of electromotive force upon rise of current in said circuit above a predetermined value.
  • a cathodic protective system for protecting underground metallic structures from electrolytic corrosion including, in combination, an underground metallic structure, an electric railway track in the vicinity of the underground structure, a circuit connecting the track and the underground structure, a rectifier connected in said circuit, a source of electromotive force, a transformer having a primary winding connected to said source and a secondary winding connected in said circuit in series with said rectifier, a relay having an operating winding connected in said circuit in series with the rectifier and the transformer winding, a pair of normally-open contacts connected to said circuit in shunt with said rectifier and transformer secondary winding, and a set of normally-closed contacts connected in the supply circuit to said transformer primary winding, whereby said relay operates upon rise of current in said circuit above a predetermined value to short circuit the rectifier and transformer secondary winding and to disconnect said source of electromotive force from the transformer primary winding.

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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)
US610643A 1945-08-13 1945-08-13 Cathodic protection system Expired - Lifetime US2483397A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL65387D NL65387C (enrdf_load_stackoverflow) 1945-08-13
US610643A US2483397A (en) 1945-08-13 1945-08-13 Cathodic protection system
FR939377D FR939377A (fr) 1945-08-13 1946-10-11 Perfectionnements à la protection de structures métalliques souterraines
CH275450D CH275450A (fr) 1945-08-13 1947-06-06 Installation de protection d'une structure métallique souterraine.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US610643A US2483397A (en) 1945-08-13 1945-08-13 Cathodic protection system

Publications (1)

Publication Number Publication Date
US2483397A true US2483397A (en) 1949-10-04

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ID=24445861

Family Applications (1)

Application Number Title Priority Date Filing Date
US610643A Expired - Lifetime US2483397A (en) 1945-08-13 1945-08-13 Cathodic protection system

Country Status (4)

Country Link
US (1) US2483397A (enrdf_load_stackoverflow)
CH (1) CH275450A (enrdf_load_stackoverflow)
FR (1) FR939377A (enrdf_load_stackoverflow)
NL (1) NL65387C (enrdf_load_stackoverflow)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3055813A (en) * 1958-11-17 1962-09-25 Pure Oil Co Current controller for use in cathodic protection of steel structures
US3098026A (en) * 1958-10-08 1963-07-16 Engelhard Ind Inc Cathodic protection system
US3182007A (en) * 1958-12-01 1965-05-04 Continental Oil Co Electrode assembly for the anodic passivation of metals
US3208925A (en) * 1960-01-07 1965-09-28 Continental Oil Co Anodic protection against corrosion
US5321318A (en) * 1992-02-05 1994-06-14 Michel Montreuil Stray current neutralizing method and device
US5541459A (en) * 1992-03-05 1996-07-30 Stri Ab Device for compensation of an alternating voltage which occurs between a medium and a metallic pipeline disposed in the medium
US5825170A (en) * 1997-01-24 1998-10-20 Filtre-Expert Magnetically coupled alternating stray current neutralizing method and system
US7064459B1 (en) * 2001-08-20 2006-06-20 Brunswick Corporation Method of inhibiting corrosion of a component of a marine vessel

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1962696A (en) * 1934-03-01 1934-06-12 George I Rhodes Method of and means for protecting pipe lines and other buried metallic structures from corrosion
US1971146A (en) * 1933-02-20 1934-08-21 Western Union Telegraph Co Electrical protective device
US2053214A (en) * 1934-04-21 1936-09-01 Union Carbide & Carbon Corp Electrode resistant to anodic attack
US2395833A (en) * 1943-01-09 1946-03-05 Int Standard Electric Corp Electrolysis switch

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1971146A (en) * 1933-02-20 1934-08-21 Western Union Telegraph Co Electrical protective device
US1962696A (en) * 1934-03-01 1934-06-12 George I Rhodes Method of and means for protecting pipe lines and other buried metallic structures from corrosion
US2053214A (en) * 1934-04-21 1936-09-01 Union Carbide & Carbon Corp Electrode resistant to anodic attack
US2395833A (en) * 1943-01-09 1946-03-05 Int Standard Electric Corp Electrolysis switch

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3098026A (en) * 1958-10-08 1963-07-16 Engelhard Ind Inc Cathodic protection system
US3055813A (en) * 1958-11-17 1962-09-25 Pure Oil Co Current controller for use in cathodic protection of steel structures
US3182007A (en) * 1958-12-01 1965-05-04 Continental Oil Co Electrode assembly for the anodic passivation of metals
US3208925A (en) * 1960-01-07 1965-09-28 Continental Oil Co Anodic protection against corrosion
US5321318A (en) * 1992-02-05 1994-06-14 Michel Montreuil Stray current neutralizing method and device
US5541459A (en) * 1992-03-05 1996-07-30 Stri Ab Device for compensation of an alternating voltage which occurs between a medium and a metallic pipeline disposed in the medium
US5825170A (en) * 1997-01-24 1998-10-20 Filtre-Expert Magnetically coupled alternating stray current neutralizing method and system
US7064459B1 (en) * 2001-08-20 2006-06-20 Brunswick Corporation Method of inhibiting corrosion of a component of a marine vessel

Also Published As

Publication number Publication date
FR939377A (fr) 1948-11-12
NL65387C (enrdf_load_stackoverflow)
CH275450A (fr) 1951-05-31

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