1、 Standard Test Method Measurement Techniques Related to Criteria for Cathodic Protection of Underground Storage Tank Systems This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any
2、respect preclude anyone, whether he or she 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 right, by
3、 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 way be
4、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 for t
5、he interpretation or use of this standard by other parties and accepts responsibility for only those official NACE International interpretations issued by NACE International in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual voluntee
6、rs. Users 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 pote
7、ntial 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 pro
8、tection 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 CAUTIONARY NOTICE: NACE standards are subject to periodic review, and may be revised or withdrawn at
9、any time in accordance with NACE technical committee procedures. 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 and subsequently from the date of each reaffirmation or revision. The user is
10、 cautioned to obtain the latest edition. Purchasers of NACE International standards may receive current information on all standards and other NACE International publications by contacting the NACE International FirstService Department, 1440 South Creek Dr., Houston, Texas 77084-4906 (telephone +1 2
11、81-228-6200). Revised 2012-03-10 Approved 2001-11-07 NACE International 1440 South Creek Drive Houston, TX 77084-4906 +1 281-228-6200 ISBN 1-57590-137-4 2012, NACE International NACE Standard TM0101-2012 Item No. 21240 TM0101-2012 NACE International i _ Foreword This NACE International standard test
12、 method provides descriptions of the measurement techniques most commonly used on underground storage tank (UST) systems to determine whether a specific cathodic protection (CP) criterion has been complied with at a test site. This standard includes only those measurement techniques that relate to t
13、he criteria or special conditions contained in NACE SP0285.1 The measurement techniques described in this standard require that measurements be made in the field. Because these measurements are obtained under widely varying circumstances of field conditions and tank design, this standard is not as p
14、rescriptive 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 is intended for use by corrosion control personnel concerned with the external
15、 corrosion of UST systems or similar structures, including those used to contain oil, gas, and water. This standard was prepared by Task Group (TG) 209 (formerly Work Group T-10A-14b), and was revised by TG 364, Testing of Cathodic Protection Systems of Underground Storage Tanks, in 2012. TG 364 is
16、administered by Specific Technology Group (STG) 35, Pipelines, Tanks, and Well Casings, and is sponsored by STG 05, Cathodic/Anodic Protection. The measurement techniques provided in this standard were compiled from information submitted by committee members and others with expertise on the subject.
17、 Variations or other techniques not included may be equally effective. This standard is issued by NACE under the auspices of STG 35. In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual. The terms s
18、hall and must are used to state a requirement, and are considered mandatory. The term should is used to state something good and is recommended, but is not considered mandatory. The term may is used to state something considered optional. _ TM0101-2012 ii NACE International _ NACE International Stan
19、dard Test Method Measurement Techniques Related to Criteria for Cathodic Protection of Underground Storage Tank Systems Contents 1. General 1 2. Definitions 1 3. Safety Considerations 3 4. Instrumentation and Measurement Guidelines 3 5. Structure-to-Electrolyte Potential Measurements .5 6. Causes of
20、 Measurement Errors . 9 7. Voltage Drops Other Than Across the Structure-to-Electrolyte Interface . 10 8. Test Method 1Negative 850 mV Structure-to-Electrolyte Potential of Steel Underground Storage Tank Systems with Cathodic Protection Applied . 11 9. Test Method 2Negative 850 mV Polarized Structur
21、e-to-Electrolyte Potential of Steel Underground Storage Tank Systems 13 10. Test Method 3100 mV Cathodic Polarization of Steel Underground Storage Tank Systems . 15 11. Test Methods for Continuity Testing of Steel Underground Storage Tank Systems 20 12. Piping and Appurtenances . 22 13. Records . 23
22、 References 23 Bibliography . 23 Appendix A: Using CP Coupons to Determine the Adequacy of Cathodic Protection (Nonmandatory) . 24 Appendix B: Checklists for CP Systems (Nonmandatory) 28 FIGURES: Figure 1: Instrument Connections 5 Figure 2: Cathodic Polarization Curves 15 TABLE: Table 1: Conversion
23、of Other Potential Measurements to CSE Equivalents6 _ TM0101-2012 NACE International 1 _ Section 1: General 1.1 This standard provides procedures to test compliance with the CP criteria presented in NACE SP02851 on UST systems. Included are instrumentation and general measurement guidelines, procedu
24、res for three commonly used test methods, practices for taking voltage drops into consideration and preventing incorrect data from being collected and used, and procedures for testing for electrical continuity between USTs and other metallic equipment. The use of CP coupons to determine the adequacy
25、 of CP is described in Appendix A (Nonmandatory). 1.2 The provisions of this test method shall be applied by personnel who have acquired, by education and related practical experience, knowledge of the principles of CP of UST systems. Such individuals, at a minimum, must either be NACE International
26、 certified CP Testers, NACE International CP Specialists, or individuals qualified by professional education and related practical experience. 1.3 A given test technique may be ineffective or only partially effective. Conditions that may cause this to occur include elevated temperatures, disbonded d
27、ielectric or thermally insulating coatings, shielding, bacterial attack, and unusual contaminants in the electrolyte. 1.4 Deviation from this test method may be warranted in specific situations if corrosion control personnel can demonstrate that adequate CP has been achieved. _ Section 2: Definition
28、s(1) Anode: The electrode of an electrochemical cell at which oxidation occurs. (Electrons flow away from the anode in the external circuit. It is usually the electrode where corrosion occurs and metal ions enter solution.) Cable: A bound or sheathed group of insulated conductors. Cathode: The elect
29、rode of an electrochemical cell at which reduction is the principal reaction. (Electrons flow toward the cathode in the external circuit.) Cathodic Polarization: (1) The change of electrode potential caused by a cathodic current flowing across the electrode/electrolyte interface; (2) a forced active
30、 (negative) shift in electrode potential. (See Polarization.) Cathodic Protection: A technique to reduce the corrosion rate of a metal surface by making that surface the cathode of an electrochemical cell. Coating: (1) A liquid, liquefiable, or mastic composition that, after application to a surface
31、, is converted into a solid protective, decorative, or functional adherent film; (2) (in a more general sense) a thin layer of solid material on a surface that provides improved protective, decorative, or functional properties. Conductor: A bare or insulated material suitable for carrying electric c
32、urrent. Contact Resistance: The resistance in the measurement circuit present in the interface between a reference electrode and an electrolyte. Corrosion: The deterioration of a material, usually a metal, that results from a chemical or electrochemical reaction with its environment. Corrosion Poten
33、tial (Ecorr): The potential of a corroding surface in an electrolyte measured under open-circuit conditions relative to a reference electrode. (Also known as Electrochemical Corrosion Potential, Free Corrosion Potential, and Open-Circuit Potential.) (1) Definitions in this section reflect common usa
34、ge among practicing corrosion control personnel and apply specifically to how terms are used in this standard. As much as possible, these definitions are in accordance with those in NACE/ASTM G 193 (latest revision).2 TM0101-2012 2 NACE International CP Coupon: A metal sample representing the UST at
35、 the test site, used for CP testing, and having a chemical composition approximating that of the UST. The CP coupon size should be small to avoid excessive current drain on the CP system. CP Criterion: A standard for assessment of the effectiveness of a CP system. Electrical Isolation: The condition
36、 of being electrically separated from other metallic structures or the environment. Electrode: A material that conducts electrons, is 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
37、in an electrolyte as measured against a reference electrode. (The electrode potential does not include any resistance losses in potential in either the electrolyte or the external circuit. It represents the reversible work to move a unit of charge from the electrode surface through the electrolyte t
38、o the reference electrode.) Electrolyte: A chemical substance containing ions that migrate in an electric field. For the purposes of this standard, electrolyte refers to the soil or liquid adjacent to and in contact with a buried or submerged metallic UST system, including the moisture and other che
39、micals contained therein. Foreign Structure: Any metallic structure that is not intended as a part of a system under cathodic protection. Galvanic Anode: A metal that provides sacrificial protection to another metal that is more noble when electrically coupled in an electrolyte. This type of anode i
40、s the electron source in one type of cathodic protection. Groundbed: One or more anodes installed below the earths surface for the purpose of supplying cathodic protection current. Holiday: A discontinuity in a protective coating that exposes unprotected surface to the environment. Impressed Current
41、: 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: The polarized half-cell potential of an electrode taken immediately after the cathodic protection current is st
42、opped, which closely approximates the potential without IR drop (i.e., the polarized potential) when the current was on. Interference: Any electrical disturbance on a metallic structure as a result of stray current. Off or On: A condition whereby cathodic protection current is either turned off or o
43、n. Polarization: The change from the corrosion potential as a result of current flow across the electrode/electrolyte interface. Polarized Potential: (1) (general use) the potential across the electrode/electrolyte interface that is the sum of the corrosion potential and the applied polarization; (2
44、) (cathodic protection use) the potential across the structure/electrolyte interface that is the sum of the corrosion potential and the cathodic polarization. Potential Gradient: A change in the potential with respect to distance, expressed in millivolts per unit of distance. Potentiometer: A device
45、 for the measurement of an electromotive force by comparison with a known potential difference. Protection Potential: The most noble potential at which pitting or crevice corrosion, or both, will not propagate in a specific environment. Reference Electrode: An electrode having a stable and reproduci
46、ble potential, which is used in the measurement of other electrode potentials. Remote Earth: A location on the earth far enough from the affected structure that the soil potential gradients associated with currents entering the earth from the affected structure are insignificant. Shielding: (1) Prot
47、ecting; protective cover against mechanical damage. (2) Preventing or diverting cathodic protection current from its natural path. Stray Current: Current flowing through paths other than the intended circuit. TM0101-2012 NACE International 3 Structure: Tanks, piping, and associated equipment that ma
48、y/may not be under the influence of a cathodic protection system. Structure-to-Electrolyte Potential: The potential difference between the surface of a buried or submerged metallic structure and the electrolyte that is measured with reference to an electrode in contact with the electrolyte. Test Lead: A wire or cable attached to a structure for connection of a test instrument to make cathodic protection potential or current measurements. Undergro
