CSA C22 3 NO 4-1974 Control of Electrochemical Corrosion of Underground Metallic Structures (Third Edition).pdf

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1、C22.3 No. 4-1974 Control of ElectrochemicalCorrosion of UndergroundMetallic Structures Canadian Electrical Code, PartIIICopyright Canadian Standards Association 1974All rights reserved. No part of this publication may bereproduced in any form, in an electronic retrieval systemor otherwise, without t

2、he prior permission of thepublisher.Standards Update ServiceC22.3 No. 4-1974Title: Control of Electrochemical Corrosion of Underground Metallic StructuresPagination: 20 pages To register for e-mail notification about any updates to this publicationgo to shop.csa.caclick on CSA Update ServiceThe List

3、 ID that you will need to register for updates to this publication is 2001513.If you require assistance, please e-mail techsupportcsagroup.org or call 416-747-2233.Visit CSA Groups policy on privacy at csagroup.org/legal to find out how we protect your personal information.ContentsCOMMITTEE ON CANAD

4、IAN ELECTRICAL CODE, PART IIISUBCOMMITTEE ON GROUND CURRENT COORDINATIONTASK GROUP ON ELECTROCHEMICAL CORROSION OF UNDERGROUND METALLIC STRUCTURESPREFACE1. SCOPE2. SAFETY REQUIREMENT3. DEFINITIONS4. TYPES OF CORROSION4.1 General.4.2 Stray Current Corrosion4.2.1 Anodic Corrosion.4.2.2 Cathodic Corros

5、ion (Corrosion by Cathodic Products).4.3 Localized Corrosion4.3.1 General.4.3.2 Galvanic Corrosion.4.3.3 Local Action.4.3.4 Differential Aeration.4.3.5 Concentration Cell.4.4 Chemical Attack.5. PRINCIPLES5.1 General5.2 Stray Current Corrosion5.2.1 Mitigation of Stray Current Corrosion5.2.2 Electroly

6、sis Surveys.5.2.3 Maintenance of Protective System.5.3 Non-Stray Current Corrosion5.3.1 Corrosion in Non-Stray Current Areas.5.3.2 Mitigation of Non-Stray Current Corrosion5.3.3 Surveys in Non-Stray Areas5.4 Cooperative Arrangements.6. PRACTICES6.1 General.6.2 Limitation of Stray Currents.6.3 Limita

7、tion of Stray Current Discharged to Earth.6.3.1 Track Construction and Bonding6.3.2 Track Insulation6.3.3 Electrical Reinforcement of Tracks and Other Return Conductors6.4 Limitations of Stray Current Picked up from Earth6.4.1 General.6.4.2 Location of Underground Structures with Respect to Tracks6.

8、4.3 Avoidance of Contact Between Underground Structures.6.4.4 Conduit Construction6.4.5 Protective Coatings or Jackets on Pipes and Cables.6.4.6 Insulating Joints in Pipes and Cable Sheaths.6.5 Drainage of Cable Sheaths and Pipes6.5.1 General.6.5.2 Application of Drainage.6.5.3 Location of Drainage

9、Connections.6.5.4 Bonding of Cable Sheaths.6.5.5 Measurement of Drainage Currents.6.5.6 Reverse Current Blocking.6.5.7 Forced Drainage.6.5.8 Drainage of Pipes.Copyright CSA International26.6 Protection Against Cathodic Corrosion (Corrosion by Cathodic Products)6.6.1 General.6.6.2 Restriction of Nega

10、tive Potentials.6.6.3 Flushing of Ducts.6.7 Mitigative Measures Applicable in Non-Stray Areas6.7.1 Cathodic Protection.6.7.2 Current Required for Cathodic Protection.6.7.3 Location of Current Supply Points.6.7.4 Current Supply.6.7.5 Type of Anodes.6.7.6 Location of Anodes.6.7.7 Joint Cathodic Protec

11、tion.APPENDIX A VOLTAGE AND CURRENT DISTRIBUTION IN STRAY CURRENT AREASAPPENDIX B DRAINAGE SYSTEMSCopyright CSA International3COMMITTEE ON CANADIAN ELECTRICAL CODE, PART IIIJ. E. GILLESPIE (Chairman)Hydro-Quebec, MontrealN. J. DUNLOP (Vice-Chairman)British Columbia Telephone Company, Vancouver (Repr

12、esenting Canadian Telecommunications Carriers Association)J. D. ADAMManitoba Telephone System, WinnipegN. J. DUNLOPBritish Columbia Telephone Company, VancouverB. C. NOWLANBell Canada, MontrealJ. F. NOYES.Newfoundland Telephone Co. Ltd., St. Johns (Representing Provincial Electrical Inspection Autho

13、rities)K. L. BELLAMY.Ontario Hydro, Toronto (Representing Canadian Transport Commission)H. H. BLAKNEY.Canadian Transport Commission, Ottawa (Representing Railways)R. T. BRADLEY.Canadian National Telecommunications, TorontoB. T. POWER.Canadian Pacific Telecommunications, Montreal (Representing Canadi

14、an Cable Television Association)K. J. EASTONCable Consultants, Clarkson (Representing Canadian Electrical Association)M. FRARESSO.Ontario Hydro, TorontoJ. E. GILLESPIE.Hydro-Quebec, MontrealW. G. MCMICHAEL.British Columbia Hydro and Power Authority, VancouverG. H. WELDONManitoba Hydro, Winnipeg (Rep

15、resenting Association of Municipal Electrical Utilities)J. A. TORRANCEEtobicoke Hydro-Electric Commission, EtobicokeC. D. HOLMESRoads and Transport Association of Canada, OttawaG. YORKE SLADER.The National Energy Board, OttawaH. M. ROBINSON (Secretary non-voting)Canadian Standards Association, Rexda

16、le In addition to the members of the Committee, the following made valuable contribution to the development of thisStandard in their capacities as noted:J. G. CASSAN (Associate)Ontario Hydro, TorontoM. P. GUNNING (Associate).Hydro Quebec, MontrealW. J. MEESE (Associate).National Bureau of Standards,

17、 Washington D.C.B. C. NOWLAN (Associate)Bell Canada, MontrealC. POULIOT (Alternate)Hydro Quebec, MontrealR. E. TREEN (Associate).Ontario Hydro, Toronto Copyright CSA International4SUBCOMMITTEE ON GROUND CURRENT COORDINATIONJ. G. CASSAN (Chairman).Ontario Hydro, Toronto(Representing Canadian Electric

18、al Association)M. E. CARLSON.TransCanada PipeLines Limited, Toronto(Representing Canadian Gas Association)C. DEGRANDMONTHydro Quebec, Montreal(Representing Canadian Electrical Association)W. J. HARDERSaskatchewan Telecommunications, Regina(Representing Canadian Telecommunications Carriers Associatio

19、n)G. W. LAWSONDepartment of Manpower and Labour, Edmonton(Representing Provincial Electrical Impaction Authorities)W. M. MCCOWAN.Toronto Hydro-Electric System, Toronto(Representing Association of Municipal Electrical Utilities)J. SOLINASBell Canada, Montreal(Representing Canadian Telecommunications

20、Carriers Association)T. R. THOMPSONOntario Hydro, Toronto(Representing Canadian Electrical Association)A. TILT.Public Utilities Commission, Scarborough(Representing American Water Works Association)R. TRUSSLER.City of Calgary Electric System, CalgaryB. C. WATTSON.Canadian National Telecommunications

21、, Toronto(Representing Canadian National Railways)H. A. WEBSTER.Corrosion Service Company Limited, TorontoCopyright CSA International5TASK GROUP ON ELECTROCHEMICAL CORROSION OF UNDERGROUNDMETALLIC STRUCTURESH. A. WEBSTER (Chairman)Corrosion Service Company Limited, TorontoH. T. ANDERSENCanadian West

22、ern Natural Gas Company Limited, CalgaryR. T. CROTHERSBell Canada, Toronto(Representing Canadian Telecommunications Carriers Association)R. C. JACOBSENOntario Hydro, Toronto Copyright CSA International6PREFACEThis is the third edition of C22.3 No. 4, it supersedes previous editions published in 1936

23、 and 1958.In the first edition, major emphasis was placed upon the corrosive effects of stray currents originating indirect-current electric railway systems. In fact, the title of the first edition was “Principles and Practices for ProtectingUnderground Structures from the Effects of Stray Currents

24、Originating in Direct-Current Electric Railway Systems“.In preparing the second edition of C22.3 No. 4, the Committee recognized certain major changes that were occurringthroughout the country. Many transportation systems had discontinued operation of electrically operated railwaysemploying grounded

25、 rails, or were in the process of eliminating this type of system. For this reason, the stray currentsituation was undergoing a radical change, and often this change resulted in more severe corrosion problems thanexisted during the operation of the electric railway. For example, many street railways

26、 have in the past cooperatedextensively with the owners of other subsurface structures by, designing their systems to limit stray currents and bypermitting the installation of drainage bonds between the two systems at strategic locations. The net result of thiscooperation has been a large measure of

27、 cathodic protection to the other system. With the elimination of the streetrailway, however, this protection has been withdrawn, and corrosion due to other causes has been permitted to takeplace.It should be recognized that electrically operated railways employing grounded rail returns are not the

28、only source ofstray currents. Other types Of systems utilizing grounded direct-current circuits often act as sources of stray currents inthe earth. One such source that is becoming of major importance is the pipeline equipped with cathodic protection.While the electric railway is becoming of decreas

29、ing importance as a source of stray currents, considerableexperience in the mitigation of corrosion due to stray currents originating in such railways has accumulated over theyears. For this reason some of the Rules contained in this Code apply specifically to railways. It should be realized,however

30、, that these Rules apply in general to all systems which originate stray earth currents, and that railways arementioned specifically merely for convenience.The Committee charged with the preparation of the second edition foresaw the gradual abolition of electric railwaysand attempted to emphasize ca

31、thodic protection systems as a new and important source of stray dc current. In theinterim between the publication of the second edition and the preparation of the third edition it is now apparent thatelectric traction systems may see increasing use in urban and inter-urban service. With the advent

32、of high voltagedirect current transmission for the long distance transportation of power and the almost universal use of cathodicprotection on oil and gas piping systems the up-dating of this Standard is most timely.This Standard was prepared by the Task Group on Electrochemical Corrosion of Undergr

33、ound Metallic Structuresunder the jurisdiction of the Subcommittee on Ground Current Coordination and the Committee on Canadian ElectricalCode, Part III and was formally approved by these Committees.REXDALE, APRIL, 1974NOTE: In order to keep abreast of progress in the industries concerned, CSA Publi

34、cations are subject to periodic review. Suggestions forimprovement will be welcomed at all times. They will be recorded and in due course brought to the attention of the appropriate Committee forconsideration.Also, requests for interpretation will be accepted by the Committee. They should be worded

35、in such a manner as to permit a simple “yes“ or“no“ answer based on the literal text of the requirements concerned.All enquiries regarding this Standard should be addressed to Canadian Standards Association, 178 Rexdale Boulevard, Rexdale, OntarioM9W IR3. Copyright CSA International71. SCOPE1.1The p

36、rovisions of this Standard, forming a part of the Canadian Electrical code, Part III, embody the applicableprinciples and general practices where underground metallic structures are subject to the risk of electro-chemicalcorrosion.1.2This Standard is issued for the guidance of all parties owning, co

37、ntrolling, or operating grounded electric systems andsubsurface structures such as metallic pipes, metallic cable sheaths, or other structures with underground metalliccomponents.2. SAFETY REQUIREMENT2.1Where corrosion of underground systems or structures could result in a hazard to persons preventi

38、ve measures shall beinstituted. This demands the cooperation of all parties concerned.NOTE: If any of the parties concerned are not sufficiently familiar wish the engineering details involved in the mitigationof electrochemical corrosion as set forth in the principles and practices contained therein

39、, such party should obtaintechnical advice from qualified experts. information on the formation of Electrolysis Committees, as well as a directoryof existing Committees, can be obtained from the National Association of Corrosion Engineers.3. DEFINITIONS3.1The following definitions apply in this Stan

40、dard: Anode means an electrode through which current enters an electrolyte. In corrosion processes, the anode is theelectrode that usually has the greater tendency to go into solution, or to corrode;Cathode means an electrode through which current leaves an electrolyte. In corrosion processes, the c

41、athode is usuallythe area that is not attacked;Cathodic corrosion (corrosion by cathodic products) means corrosion occurring on the surface of a cathode due tothe chemicals released there by electrolytic action, usually when the surrounding electrolyte is alkaline;Cathodic protection means reduction

42、 or prevention of corrosion of a metal surface by making it all cathodic:Concentration cell means an electrolytic cell, the emf of which is due to differences in strength or composition of theelectrolyte at anode and cathode areas;Corrosion means the deterioration of a substance, usually a metal, be

43、cause of a reaction with its environment;Differential aeration cell means an electrolytic cell, the emf of which is due to a difference in oxygen concentration attwo otherwise similar electrodes; Drainage means a technique whereby a metallic conductor is installed between structures to provide a pre

44、ferential pathfor stray currents which would otherwise pass through the soil or other electrolyte; Electrolysis means the production of chemical changes by the passage of current through an electrolyte. This termcommonly refers to corrosion problems caused by stray currents;Electrolysis survey means

45、 the operation of determining by means of measurements, relevant facts pertaining toelectrolysis conditions. These measurements include determination of voltages, currents, voltage gradients, condition ofthe soil surrounding underground structures, the extent of corrosion that may have occurred, and

46、 other factors, so thatthe risk of corrosion may be assessed and suitable mitigative measures determined;Electrolyte means a chemical substance, usually liquid containing ions which migrate in an electric field. For thepurposes of this Standard electrolyte refers to the soil adjacent to and in conta

47、ct with an underground metallic structure,including the moisture and other chemicals contained therein;Forced drainage means the use of a rectifier or other dc source in a drainage bond to overcome an IR drop in the bonddue to the passage of drainage current;Galvanic anode means an anode constructed

48、 of a metal high in the galvanic series, usually magnesium, sometimeszinc. A galvanic anode is used to protect an underground structure of metal lower in the galvanic series. The galvanicCopyright CSA International8potential generated by the combination of the two metals makes the protected structur

49、e a cathode. Since a galvanicanode is subjected to anodic corrosion, it must be replaced periodically;Galvanic cell means a cell in which chemical change is the source of electric energy. It usually consists of twodissimilar conductors in contact with each other and with an electrolyte, or two similar conductors in contact with eachother and with dissimilar electrolytes, or combinations thereof;Galvanic corrosion means the corrosion of the anode of a galvanic cell;Galvanic series means a list of metals and alloys arranged according to thei