1、Designation: D 6971 04An 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the vo
3、ltammetric determinationof hindered phenol and aromatic amine antioxidants in new orused type non-zinc turbine oils in concentrations from 0.0075mass % up to concentrations found in new oils by measuringthe amount of current flow at a specified voltage in theproduced voltammogram.1.2 This standard d
4、oes 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 ASTM St
5、andards:2D 1193 Specification for Reagent WaterD 2272 Test Method for Oxidation Stability of Steam Tur-bine Engine 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 Ga
6、s 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 HL Turbine Oils by LinearSweep Voltammetry2.2 ISO Standards:3ISO 6743 Part 4, Lubricants, Industrial Oils, and Rela
7、tedProducts3. Summary of Test Method3.1 A measured quantity of sample is dispensed into a vialcontaining a measured quantity of acetone based electrolytesolution and a layer of sand. When the vial is shaken, thehindered phenol and aromatic amine antioxidants and othersolution soluble oil components
8、present in the sample areextracted into the solution and the remaining droplets sus-pended in the solution are agglomerated by the sand. Thesand/droplet suspension is allowed to settle out and thehindered phenol and aromatic amine antioxidants dissolved inthe solution are quantified by voltammetric
9、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 used oils.3.2 Voltammetric analysis is a technique that applieselectro-analytic methods wherein a s
10、ample to be analyzed ismixed with an electrolyte and a solvent, and placed within anelectrolytic 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 timerelationships at the cell electrod
11、es. 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 remains essentiallyconstant with the passage
12、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 solutions. In performing a voltammetric analysis, thepotential across the
13、 electrodes is varied linearly with time, andthe resulting current is recorded as a function of the potential.As the increasing voltage is applied to the prepared samplewithin the cell, the various additive species under investigationwithin the oil are caused to electrochemically oxidize. The datare
14、corded during this oxidation reaction can then be used todetermine the remaining useful life of the oil type. A typicalcurrent-potential curve produced during the practice of thevoltammetric test can be seen by reference to Fig. 1. Initially1This test method is under the jurisdiction of ASTM Committ
15、ee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.09 on Oxidation.Current edition approved July 1, 2004. Published July 2004.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annu
16、al Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken
17、, PA 19428-2959, United States.the applied potential produces an electrochemical reactionhaving a rate so slow that virtually no current flows through thecell. As the voltage is increased, as shown in Fig. 1, theelectro-active species (for example, substituted phenols) beginto oxidize at the working
18、 electrode surface, producing ananodic rise in the current. As the potential is further increased,the decrease in the electro-active 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. Sign
19、ificance and Use4.1 The quantitative determination of hindered phenol andaromatic amine antioxidants in a new turbine oil measures theamount of these compounds that has been added to the oil asprotection against oxidation. Beside phenols, turbine oils canbe formulated with other antioxidants such as
20、 amines whichcan extend the oil life. In used oil, the determination measuresthe amount of original (hindered phenol and aromatic amine)antioxidants remaining after oxidation has reduced its initialconcentration. This test method is not designed or intended todetect all of the antioxidant intermedia
21、tes formed during thethermal and oxidative stressing of the oils, which are recog-nized as having some contribution to the remaining useful lifeof the used or in-service oil. Nor does it measure the overallstability of an oil, which is determined by the total contributionof all species present. Befo
22、re making final judgment on theremaining useful life of the used oil, which might result in thereplacement of the oil reservoir, it 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 measur
23、ing remaining oxidative life ofthe used oil.4.1.1 This test method is applicable to non-zinc type ofturbine oils as defined by ISO 6743 Part 4, Table 1. These arerefined mineral oils containing rust and oxidation inhibitors,but not antiwear additives.4.2 The test is also suitable for manufacturing c
24、ontrol andspecification acceptance.4.3 When a voltammetric analysis is obtained for a turbineoil inhibited with a typical synergistic 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 v
25、oltage)4for the aromatic amines, andan increase in the current of the produced voltammogrambetween 13 and 16 s (or 1.3 to 1.6 V applied voltage)4for thehindered phenols in the neutral acetone solution (Fig. 1: x-axis1 s = 0.1 V). Hindered phenol antioxidants detected byvoltammetric analysis include,
26、 but are not limited to, 2,6-di-tert-butyl-4-methylphenol; 2,6-di-tert-butylphenol; and 4,4-Methylenebis (2,6-di-tert-butylphenol). Aromatic amine anti-oxidants detected by voltammetric analysis include, but are notlimited to, phenyl alpha naphthylamines, and alkylated diphe-nylamines.4.4 For turbin
27、e 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 to1.2 V applied voltage)4for the aromatic amines, by using theneutral acetone test solution (first peak in Fig. 1).4.5 For turbine oils cont
28、aining only hindered phenolicantioxidants, it is preferable to use a basic alcohol solution4Voltages listed with respect to reference electrode. The voltammograms shownin Figs. 1 and 2 were obtained with a platinum reference electrode and a voltagescan rate of 0.1 V/s.NOTEx-axis = time (seconds) and
29、 y-axis is current (arbitrary units). Top line in Fig. 1 is voltammogram of a fresh R 2,6-di-tert-butylphenol; alkylated diphenylamine; aromatic amine antioxi-dant; hindered phenol antioxidant; linear sweep voltammetry;phenyl alpha naphthylamine; turbine oilASTM International takes no position respe
30、cting 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 responsibility.This st
31、andard 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 ASTM Internat
32、ional 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 address shown belo
33、w.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).10Supporting data have been filed at ASTM Headquarters and is available asRound Robin Research Report ASTM D02-1548.D6971046
