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1、Standard Test Method Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Piping Systems This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions.Its acceptance do
2、es not in any respect preclude anyone, whether he has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE International standard is to be construed as granting any ri
3、ght, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents minimum requirements and should in no
4、way be interpreted as a restriction on the use of better procedures or materials.Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances.NACE International assumes no responsibility
5、for the interpretation or use of this standard by other parties and accepts responsibilityforonlythoseofficialNACEInternationalinterpretationsissuedbyNACE International in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual volunteers. U
6、sers of this NACE International standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use.This NACE International standard may not necessarily address all potential
7、health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard. Users of this NACE International standard are also responsible for establishing appropriate health, safety, and environmental protectio
8、n practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revised or withd
9、rawn at any time without prior notice. NACE International requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication. The user is cautioned to obtain the latest edition. Purchasers of NACE International standards may rec
10、eive current information on all standards and other NACE International publications by contacting the NACE International Membership Services Department, 1440 South Creek Drive, Houston, Texas 77084-4906 (telephone +1 281/228-6200). Reaffirmed 2002-04-11 Approved 1997-12-22 NACE International 1440 So
11、uth Creek Drive Houston, Texas 77084-4906 +1 281/228-6200 ISBN 1-57590-047-5 2002, NACE International NACE Standard TM0497-2002 Item No. 21231 Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/05/2007 19:31
12、:56 MSTNo reproduction or networking permitted without license from IHS -,-,- TM0497-2002 NACE Internationali _ Foreword This NACE International standard test method provides descriptions of the measurement techniques and cautionary measures most commonly used on underground piping to determine whet
13、her a specific criterion has been complied with at a test site. This test method includes only those measurement techniques that relate to the criteria or special conditions, such as a net protective current, contained in NACE Standard RP0169.1This test method is intended for use by corrosion contro
14、l personnel concerned with the corrosion of buried underground or submerged piping systems, including oil, gas, water, and similar structures. The measurement techniques described require that the measurements be made in the field. Because the measurements are obtained under widely varying circumsta
15、nces of field conditions and pipeline design, this standard is not as prescriptive as those NACE standard test methods that use laboratory measurements.Instead, this standard gives the user latitude to make testing decisions in the field based on the technical facts available. This standard contains
16、 instrumentation and general measurement guidelines. It includes methods for voltage drop considerations when making pipe-to-electrolyte potential measurements and provides guidance to prevent incorrect data from being collected and used. The measurement techniques provided in this standard were com
17、piled from information submitted by committee members and others with expertise on the subject. Variations or other techniques not included may be equally effective. The complexity and diversity of environmental conditions may require the use of other techniques. Appendix A contains information on t
18、he common types, use, and maintenance of reference electrodes. Appendix B contains information for the net protective current technique, which, while not a criterion, is a useful technique to reduce corrosion.Appendix C contains information regarding the use of coupons to evaluate cathodic protectio
19、n. While some engineers use these techniques, they are not universally accepted practices. However, there is ongoing research into their use. The test methods in this standard were originally prepared by NACE Task Group T-10A-3 on Test Methods and Measurement Techniques Related to Cathodic Protectio
20、n Criteria, a component of Unit Committee T-10A on Cathodic Protection. It was reviewed by Task Group 020 and reaffirmed in 2002 by Specific Technology Group (STG) 35 on Pipelines, Tanks, and Well Casings.This standard is issued by NACE under the auspices of STG 35. In NACE standards, the terms shal
21、l, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements. Should is used to state that which is considered good and is recommended but is not absolute
22、ly mandatory.May is used to state that which is considered optional. _ Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/05/2007 19:31:56 MSTNo reproduction or networking permitted without license from IHS
23、-,-,- TM0497-2002 iiNACE International _ NACE International Standard Test Method Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Piping Systems Contents 1. General. 1 2. Definitions. 1 3. Safety Considerations 3 4. Instrumentation and Measureme
24、nt Guidelines. 3 5. Pipe-to-Electrolyte Potential Measurements 4 6. Causes of Measurement Errors . 7 7. Voltage Drops Other Than Across the Pipe Metal/Electrolyte Interface. 8 8. Test Method 1Negative 850 mV Pipe-to-Electrolyte Potential of Steel and Cast Iron Piping With Cathodic Protection Applied
25、 10 9. Test Method 2Negative 850 mV Polarized Pipe-to-Electrolyte Potential of Steel and Cast Iron Piping. 11 10. Test Method 3100 mV Cathodic Polarization of Steel, Cast Iron, Aluminum, and Copper Piping. 13 References 17 Bibliography 17 Appendix A: Reference Electrodes 18 Appendix B: Net Protectiv
26、e Current. 19 Appendix C: Using Coupons to Determine Adequacy of Cathodic Protection. 25 Figures Figure 1: Instrument Connections 6 Figure 2: Pipe-to-Electrolyte Potential Corrections for Pipeline Current Flow 9 Figure 3: Cathodic Polarization Curves 14 Figure B1: Surface Potential Survey 23 Figure
27、B2: Pipe-to-Electrolyte Potential Survey of a Noncathodically Protected Pipeline. 24 _ Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/05/2007 19:31:56 MSTNo reproduction or networking permitted without l
28、icense from IHS -,-,- TM0497-2002 NACE International1 _ Section 1: General 1.1 This standard provides testing procedures to comply with the requirements of a criterion at a test site on a buried or submerged steel, cast iron, copper, or aluminum pipeline. 1.2 The provisions of this standard shall be
29、 applied by personnel who have acquired by education and related practical experience the principles of cathodic protection of buried and submerged metallic piping systems. 1.3 Special conditions in which a given test technique is ineffective or only partially effective sometimes exist. Such conditi
30、ons may include elevated temperatures, disbonded dielectricorthermallyinsulatingcoatings,shielding, bacterialattack,andunusualcontaminantsinthe electrolyte. Deviation from this standard may be warranted in specific situations.In such situations corrosion control personnel should be able to demonstra
31、te that adequate cathodic protection has been achieved. _ Section 2: Definitions(1) Anode: The electrode of an electrochemical cell at which oxidation occurs. Electrons flow away from the anode in the external circuit.Corrosion usually occurs and metal ions enter the solution at the anode. Cable: A
32、bound or sheathed group of insulated conductors. Cathode: The electrode of an electrochemical cell at which reduction is the principal reaction. Electrons flow toward the cathode in the external circuit. Cathodic Disbondment:The destruction of adhesion between a coating and the coated surface caused
33、 by products of a cathodic reaction. Cathodic Polarization: The change of electrode potential in the active (negative) direction caused by current across the electrode/electrolyte interface. See also Polarization. Cathodic Protection: A technique to reduce the corrosion of a metal surface by making
34、that surface the cathode of an electrochemical cell. CathodicProtectionCoupon:Ametalsample representing the pipeline at the test site, used for cathodic protection testing, and having a chemical composition approximating that of the pipe. The coupon size should be small to avoid excessive current dr
35、ain on the cathodic protection system. Coating:A liquid, liquefiable, or mastic composition that, after application to a surface, is converted into a solid protective, decorative, or functional adherent film. Conductor:A bare or insulated material suitable for carrying electric current. Corrosion: T
36、he deterioration of a material, usually a metal, that results from a reaction with its environment. Corrosion Potential (Ecorr):The potential of a corroding surface in an electrolyte relative to a reference electrode under open-circuit conditions (also known as rest potential, open-circuit potential
37、, or freely corroding potential). Criterion: A standard for assessment of the effectiveness of a cathodic protection system. Current Density: The current to or from a unit area of an electrode surface. Electrical Isolation:The condition of being electrically separated from other metallic structures
38、or the environment. Electrode: A conductor used to establish contact with an electrolyte and through which current is transferred to or from an electrolyte. Electrode Potential:The potential of an electrode in an electrolyte as measured against a reference electrode. (The electrode potential does no
39、t include any resistance losses in potential in either the electrolyte or the external circuit.It represents the reversible work to move a unit charge from the electrode surface through the electrolyte to the reference electrode.) Electrolyte:A chemical substance containing ions that migrate in an e
40、lectric field.(For the purpose of this standard, electrolyte refers to the soil or liquid, including contained moisture and other chemicals, next to and in contact with a buried or submerged metallic piping system.) Foreign Structure:Any metallic structure that is not intended as part of a system un
41、der cathodic protection. _ (1)Definitions in this section reflect common usage among practicing corrosion control personnel and apply specifically to how terms are used in this standard.As much as possible, these definitions are in accord with those in the “NACE Glossary of Corrosion-Related Terms”
42、(Houston, TX: NACE). Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/05/2007 19:31:56 MSTNo reproduction or networking permitted without license from IHS -,-,- TM0497-2002 2NACE International Free Corrosi
43、on Potential: See Corrosion Potential. GalvanicAnode:Ametalthatprovidessacrificial protection to another metal that is more noble when electrically coupled in an electrolyte. This type of anode is the current source in one type of cathodic protection. Holiday:A discontinuity in a protective coating
44、that exposes unprotected surface to the environment. Impressed Current:An electric current supplied by a device employing a power source that is external to the electrode system. (An example is direct current for cathodic protection.) “Instant Off” Potential:A measurement of a pipe-to- electrolytepo
45、tentialmadewithoutperceptibledelay following the interruption of cathodic protection. Interference:Any electrical disturbance on a metallic structure as a result of stray current. Isolation: See Electrical Isolation. Long-Line Current: Current through the earth between an anodicandacathodicareathatr
46、eturnsalongan underground metallic structure. Long-Line Current Voltage Drop Error: That voltage drop error in the “off” potential that is caused by current flow in the soil due to potential gradients along the pipe surface. “Off” or “On”:A condition whereby cathodic protection current is either tur
47、ned off or on. Pipe-to-Electrolyte Potential:The potential difference between the pipe metallic surface and electrolyte that is measured with reference to an electrode in contact with the electrolyte. This measurement is commonly termed pipe-to- soil (P/S). Pipe-to-Soil: See Pipe-to-Electrolyte Potential. Polarization: The change from the open-circuit potential as a result of current across the electrode/electrolyte interface. PolarizedPotential:Thepotentialacrossthe structure/electrolyteinterfacethatisthesumofthe corrosion potential and the cathodic polarization. Poten