ASTM_D_6810_-_13.pdf

Designation:D681013Standard Test Method forMeasurement of Hindered Phenolic Antioxidant Content inNon-Zinc Turbine Oils by Linear Sweep Voltammetry1This standard is issued under the fixed designation D6810;the number immediately following the designation 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.Scope*1.1 This test method covers the voltammetric determinationof hindered phenol antioxidants in new or in-service non-zincturbine oils in concentrations from 0.0075 weight%up toconcentrations found in new oils by measuring the amount ofcurrent flow at a specified voltage in the produced voltammo-gram.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 This standard 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 ASTM Standards:2D1193 Specification for Reagent WaterD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4378 Practice for In-Service Monitoring of Mineral Tur-bine Oils for Steam,Gas,and Combined Cycle TurbinesD6224 Practice for In-Service Monitoring of Lubricating Oilfor Auxiliary Power Plant EquipmentD6447 Test Method for Hydroperoxide Number of AviationTurbine Fuels by Voltammetric AnalysisD6971 Test Method for Measurement of Hindered Phenolicand Aromatic Amine Antioxidant Content in Non-zincTurbine Oils by Linear Sweep Voltammetry3.Summary of Test Method3.1 A measured quantity of sample is dispensed into a vialcontaining a measured quantity of alcohol-based electrolytesolution and containing a layer of sand.When the vial isshaken,the hindered phenol antioxidants and other solutionsoluble oil components present in the sample are extracted intothe solution and the remaining droplets suspended in thesolution are agglomerated by the sand.The sand/dropletsuspension is allowed to settle out and the hindered phenolantioxidants dissolved in the solution are quantified by volta-mmetric analysis.The results are calculated and reported asweight percent of antioxidant or as millimoles(mmol)ofantioxidant per litre of sample for prepared and fresh oils andas a percent remaining antioxidant for used oils.3.2 Voltammetric analysis is a technique that applieselectro-analytic methods when a sample 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 electrodes.The cell consists of a fluidcontainer into which is mounted a small,easily polarizedworking electrode,and a large nonpolarizable reference elec-trode.The reference electrode should be massive relative to theworking electrode so that its behavior remains essentiallyconstant with the passage of small current;that is,it remainsunpolarized during the analysis period.Additional electrodes,auxiliary electrodes,can be added to the electrode system toeliminate the effects of resistive drop for high resistancesolutions.In performing a voltammetric analysis,the potentialacross the electrodes is varied linearly with time,and theresulting current is recorded as a function of the potential.Asthe increasing voltage is applied to the prepared sample withinthe cell,the various additive species under investigation withinthe oil are caused to electrochemically oxidize.The datarecorded 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.Initially,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,the1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.09.0C on Oxidation of Turbine Oils.Current edition approved May 1,2013.Published May 2013.Originallyapproved in 2002.Last previous edition approved in 2007 as D6810-07.DOI:10.1520/D6810-13.2For 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.Unite