1、Designation: D 6971 09An American National StandardStandard Test Method forMeasurement of Hindered Phenolic and Aromatic AmineAntioxidant Content in Non-zinc Turbine Oils by LinearSweep Voltammetry1This standard is issued under the fixed designation D 6971; the number immediately following the desig
2、nation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the vol
3、tammetric determinationof hindered phenol and aromatic amine antioxidants in new orin-service type non-zinc turbine oils in concentrations from0.0075 mass % up to concentrations found in new oils bymeasuring the amount of current flow at a specified voltage inthe produced voltammogram.1.2 This stand
4、ard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 AS
5、TM Standards:2D 1193 Specification for Reagent WaterD 2272 Test Method for Oxidation Stability of Steam Tur-bine Oils by Rotating Pressure VesselD 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 4378 Practice for In-Service Monitoring of Mineral Tur-bine Oils for Steam and Gas
6、TurbinesD 6224 Practice for In-Service Monitoring of LubricatingOil for Auxiliary Power Plant EquipmentD 6810 Test Method for Measurement of Hindered Phe-nolic Antioxidant Content in Non-Zinc Turbine Oils byLinear Sweep Voltammetry2.2 ISO Standards:3ISO 6743 Part 4, Lubricants, Industrial Oils, and
7、RelatedProducts3. Summary of Test Method3.1 A measured quantity of sample is dispensed into a vialcontaining a measured quantity of acetone based electrolytetest solution and a layer of sand. When the vial is shaken, thehindered phenol and aromatic amine antioxidants and other testsolution soluble o
8、il components present in the sample areextracted into the test solution and the remaining dropletssuspended in the test solution are agglomerated by the sand.The sand/droplet suspension is allowed to settle out and thehindered phenol and aromatic amine antioxidants dissolved inthe test solution are
9、quantified by voltammetric analysis. Theresults are calculated and reported as mass % of antioxidant oras millimoles (mmol) of antioxidant per litre of sample forprepared and fresh oils and as a percent remaining antioxidantfor in-service oils.3.2 Voltammetric analysis is a technique that appliesele
10、ctro-analytic methods wherein a sample to be analyzed ismixed with an electrolyte and a test solution, and placed withinan electrolytic cell. Data is obtained by measuring the currentpassing through the cell as a function of the potential applied,and test results are based upon current, voltage, and
11、 timerelationships at the cell electrodes. The cell consists of a fluidcontainer into which is mounted a small, easily polarized,working electrode, and a large, non-polarizable, referenceelectrode. The reference electrode should be massive relativeto the working electrode so that its behavior remain
12、s essentiallyconstant with the passage of small current; that is, it remainsunpolarized during the analysis period. Additional electrodes,such as auxiliary electrodes, can be added to the electrodesystem to eliminate the effects of resistive drop for highresistance test solutions. In performing a vo
13、ltammetric analy-sis, the potential across the electrodes is varied linearly withtime, and the resulting current is recorded as a function of thepotential. As the increasing voltage is applied to the preparedsample within the cell, the various additive species underinvestigation within the oil are c
14、aused to electrochemically1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.09.0C on Oxidation of Turbine Oils.Current edition approved June 1, 2009. Published June 2009. Originallyapproved in 200
15、4. Last previous edition approved in 2004 as D 697104.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Availa
16、ble from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.oxidize. The data recorded during this oxidation reaction canthen
17、 be used to determine the remaining useful life of the oiltype. A typical current-potential curve produced during thepractice of the voltammetric test can be seen by reference toFig. 1. Initially the applied potential produces an electrochemi-cal reaction having a rate so slow that virtually no curr
18、ent flowsthrough the cell. As the voltage is increased, as shown in Fig.1, the electro-active species (for example, substituted phenols)begin to oxidize at the working electrode surface, producing ananodic rise in the current. As the potential is further increased,the decrease in the electro-active
19、species concentration at theelectrode surface and the exponential increase of the oxidationrate lead to a maximum in the current-potential curve shown inFig. 1.4. Significance and Use4.1 The quantitative determination of hindered phenol andaromatic amine antioxidants in a new turbine oil measures th
20、eamount of these compounds that has been added to the oil asprotection against oxidation. Beside phenols, turbine oils canbe formulated with other antioxidants such as amines whichcan extend the oil life. In in-service oil, the determinationmeasures the amount of original (hindered phenol and aromat
21、icamine) antioxidants remaining after oxidation has reduced itsinitial concentration. This test method is not designed orintended to detect all of the antioxidant intermediates formedduring the thermal and oxidative stressing of the oils, which arerecognized as having some contribution to the remain
22、ing usefullife of the in-service oil. Nor does it measure the overallstability of an oil, which is determined by the total contributionof all species present. Before making final judgment on theremaining useful life of the in-service oil, which might result inthe replacement of the oil reservoir, it
23、 is advised to performadditional analytical techniques (as in accordance with TestMethods D 6224 and D 4378; see also Test Method D 2272),having the capability of measuring remaining oxidative life ofthe in-service oil.4.1.1 This test method is applicable to non-zinc type ofturbine oils as defined b
24、y ISO 6743 Part 4, Table 1. Theseare refined mineral oils containing rust and oxidationinhibitors, but not antiwear additives.4.2 The test is also suitable for manufacturing control andspecification acceptance.4.3 When a voltammetric analysis is obtained for a turbineoil inhibited with a typical syn
25、ergistic mixture of hinderedphenol and aromatic amine antioxidants, there is an increase inthe current of the produced voltammogram between 8 to 12 s(or 0.8 to 1.2 V applied voltage) (see Note 1) for the aromaticamines, and an increase in the current of the producedvoltammogram between 13 and 16 s (
26、or 1.3 to 1.6 V appliedvoltage) (see Note 1) for the hindered phenols in the neutralacetone test solution (Fig. 1: x-axis1s=0.1V).Hinderedphenol antioxidants detected by voltammetric analysis include,but are not limited to, 2,6-di-tert-butyl-4-methylphenol; 2,6-di-tert-butylphenol; and 4,4-Methylene
27、bis (2,6-di-tert-butylphenol). Aromatic amine antioxidants detected by volta-mmetric analysis include, but are not limited to, phenyl alphanaphthylamines, and alkylated diphenylamines.NOTE 1Voltages listed with respect to reference electrode. Thevoltammograms shown in Figs. 1 and 2 were obtained wit
28、h a platinumreference electrode and a voltage scan rate of 0.1 V/s.4.4 For turbine oil containing only aromatic amines asantioxidants, there will only be an increase in the current of theproduced voltammogram between 8 to 12 seconds (or 0.8 toNOTEx-axis = time (seconds) and y-axis is current (arbitr
29、ary units). Top line in Fig. 1 is voltammogram of a fresh R2,6-di-tert-butylphenol; alkylated diphenylamine; aromatic amine antioxi-dant; hindered phenol antioxidant; in-service oils; linear sweepvoltammetry; non-zinc turbine oils; phenyl alpha naphthy-lamine; turbine oilASTM International takes no
30、position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsi
31、bility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to
32、 ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the addr
33、ess shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).6Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D02-1548.D6971096
