1、 Standard Test Method Evaluating the Accuracy of Field-Grade Reference Electrodes 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 respect preclude anyone, whether he or she
2、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 implication or otherwise, to manufacture,
3、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 interpreted as a restriction on the use of
4、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 the interpretation or use of this standard b
5、y 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 volunteers. Users of this NACE International standa
6、rd 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 health and safety problems or environ
7、mental 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 protection practices, in consultation with app
8、ropriate 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 CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revised or withdrawn at any time in accordance with N
9、ACE 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 cautioned to obtain the late
10、st 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 +1 281-228-6200). Approved 2013-0
11、1-08 NACE International 1440 South Creek Drive Houston, Texas 77084-4906 +1 281-228-6200 ISBN 1-57590-261-3 2013, NACE International NACE TM0113-2013 Item No. 21265 TM0113-2013 NACE International i _ Foreword This standard describes a test method for evaluating the accuracy of field-grade reference
12、electrodes used for obtaining field measurement of structure-to-electrolyte potentials. The test method described in this standard is a relatively quick, simple, and inexpensive way to evaluate the accuracy of a field-grade reference electrode. The test method measures the potential difference betwe
13、en the field-grade electrode and a master reference electrode. Field-grade reference electrodes are subject to contamination from repeated exposure to electrolytes of varying chemical composition. Contamination can alter the open-circuit potential of the field-grade reference electrode and thus alte
14、r the accuracy of structure-to-electrolyte potential measurements in the field. This standard test method is intended for use by consultants, suppliers, and users of cathodic protection systems to ensure the accuracy of field-grade reference electrodes. This standard was prepared Task Group (TG) 436
15、, “Electrodes, Field-Grade: Test Methods,” which is administered by Specific Technology Group (STG) 62, “Corrosion Monitoring and MeasurementScience and Engineering Applications,” and sponsored by STG 05, “Cathodic/Anodic Protection,” STG 30, “Oil and Gas ProductionCathodic Protection,” and STG 35,
16、“Pipelines, Tanks, and Well Casings.” It is published by NACE International under the auspices of STG 62. 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 shall and must are used to s
17、tate 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. _ TM0113-2013 ii NACE International _ Standard Test Method Evaluating the Accuracy of Fi
18、eld-Grade Reference Electrodes Contents 1: General: 1 2: Definitions 1 3: Test Equipment and Test Solution .1 4: Test Procedure 2 References 5 Bibliography .5 FIGURES Figure 1: Electrodes in test solution in nonmetallic container .3 Figure 2: Electrode tips pressed into sponge thoroughly soaked with
19、 test solution. .4 _ TM0113-2013 NACE International 1 _ Section 1: General 1.1 This standard describes a test method for evaluating the accuracy of copper/copper sulfate and silver/silver chloride reference electrodes used in the field for measurement of structure-to-electrolyte potentials. 1.2 This
20、 standard does not apply to the evaluation of reference electrodes used in laboratory work. 1.3 This standard should be used in conjunction with the practices described in the latest revision of NACE Standard TM01011 and NACE Standard TM0497,2 when appropriate. _ Section 2: Definitions Reference Ele
21、ctrode: An electrode having a stable and reproducible potential, which is used in the measurement of other electrode potentials. Structure-to-Electrolyte Potential: The potential difference between the surface of a buried or submerged metallic structure and the electrolyte that is measured with refe
22、rence to an electrode in contact with the electrolyte. Master Reference Electrode: An electrode of known accuracy that is used in the evaluation of the accuracy of reference electrodes used in field work. Open Silver/Silver Chloride Electrode: An electrode in which the Ag/AgCl element is in direct c
23、ontact with the surrounding electrolyte; these electrodes are usually used in full-strength seawater. _ Section 3: Test Equipment and Test Solution 3.1 The intent of the following procedure is to establish a low-resistance conductive (ionic) path, free of junction potentials, between the Master Elec
24、trode and the the field-grade reference electrode to be tested. Experience has shown that the following test arrangement will accomplish this. Deviations from the arrangement in Section 3 and the procedure in Section 4 are allowed provided that they do not affect the test results. 3.2 Test Equipment
25、 3.2.1 The test equipment used to evaluate the accuracy of the field-grade reference electrode shall be as follows: 3.2.1.1 Voltmeter with a minimum of 10 M of input resistance and appropriate lead wires. 3.2.1.2 A suitably sized nonmetallic container. 3.2.1.3 A sponge large enough to contact both e
26、lectrodes simultaneously (optional). 3.2.1.4 Field-grade reference electrode to be evaluated in this test. 3.2.1.5 Master reference electrode, which shall be a new or newly rebuilt reference electrode that is the same type as the test reference electrode. 3.2.1.5.1 The electrolyte type and concentra
27、tion of the master reference electrode shall be the same as the test reference electrode. 3.2.1.5.2 Newly rebuilt reference electrodes shall be rebuilt in accordance with the manufacturers published instructions. TM0113-2013 2 NACE International 3.3 Test Solution 3.3.1 Test solution shall be of the
28、same chemical composition as the electrolyte in the master reference electrode, but may be of lower concentration. 3.3.2 When the accuracy of an open silver/silver chloride reference electrode is being evaluated, the test solution shall be synthetic seawater. Synthetic seawater can be prepared by ad
29、ding 35 g of sea salt to 1 L of distilled water. Sea salt is available from most grocery stores. _ Section 4: Test Procedure 4.1 Allow sufficient time for the master reference electrode, the field-grade reference electrode, and the test solution to come to approximately the same temperature before t
30、he test is performed. 4.2 Turn the voltmeter on and set to the appropriate direct current (DC) voltage range. 4.3 Add a sufficient quantity of test solution to the nonmetallic containera level of approximately 25 to 50 mm (1 to 2 in) of test solutionto completely immerse the porous plugs of the mast
31、er reference electrode and the test reference electrode. Alternatively, thoroughly soak the sponge with test solution. 4.4 Remove plastic caps from ends of the master reference electrode and the test reference electrode and insert the porous plugs of both electrodes into the test solution in the non
32、metallic container, as shown in Figure 1, or press the electrode tips into the sponge, as shown in Figure 2. 4.5 Connect the voltmeter negative lead wire to the master reference electrode and connect the positive lead wire to the test reference electrode, as shown in Figures 1 and 2. 4.6 Record the
33、reading to the nearest millivolt (mV), including polarity. TM0113-2013 NACE International 3 Figure 1: Electrodes in test solution in nonmetallic container. In this figure, “V in.” is the positive terminal, and “Com” is the negative terminal. Voltmeter TM0113-2013 4 NACE International Figure 2: Elect
34、rode tips pressed into sponge thoroughly soaked with test solution. In this figure, “V in.” is the positive terminal, and “Com” is the negative terminal. Voltmeter TM0113-2013 NACE International 5 _ References 1. NACE Standard TM0101 (latest revision), “Measurement Techniques Related to Criteria for
35、 Cathodic Protection on Underground or Submerged Metallic Tank Systems” (Houston, TX: NACE). 2. NACE Standard TM0497 (latest revision), “Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Piping Systems” (Houston, TX: NACE). _ Bibliography Ives, D
36、.J.G., and G.J. Janz. Reference Electrodes, Theory and Practice. New York, NY: Academic Press, 1961. Out of print; reprinted with permission by NACE International, Houston, TX, 1996. Peterson, M.H., and R.E. Groover. “Tests Indicate the Ag/AgCl Electrode Is Ideal Reference Cell in Sea Water.” Materi
37、als Protection and Performance 11, 5 (1972): pp. 1922. Ansuini, F.J. and J.R. Dimond. “Factors Affecting the Accuracy of Reference Electrodes.” Materials Performance, 33, 11 (1994): pp. 1417. Dimond, J.R. and F.J. Ansuini, F.J. “Potential Measurement Errors.” Materials Performance 44, 9 (2005): pp. 2225. Parks, R.M. “A Guide to Understanding Reference Electrode Readings.” Materials Performance 48, 9 (2009): pp. 3236. TM0113-2013 NACE International ISBN 1-57590-261-3
