ASTM_D_7527_-_10.pdf

Designation:D752710Standard Test Method forMeasurement of Antioxidant Content in Lubricating Greasesby Linear Sweep Voltammetry1This standard is issued under the fixed designation D7527;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.Scope1.1 This test method covers the voltammetric determinationof antioxidants in new or in-service lubricating greases inconcentrations from 0.0075 weight percent up to concentra-tions found in new greases by measuring the amount of currentflow at a specified voltage in the produced voltammogram.1.2 This test method is intended to monitor the antioxidantcontent in lubricating greases;it cannot be applied for lubri-cating greases that do not contain antioxidants.1.3 This test method is designed to allow the user to monitorthe antioxidant depletion rate of in-service greases through itslife cycle as part of condition monitoring programs.This testmethod is performed in order to collect and trend early signs ofdeteriorating lubricant grease,and it may be used as a guide forthe direction of any required maintenance activities.This willensure a safe,reliable,and cost-effective operation of themonitored plant equipment.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 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:2D942 Test Method for Oxidation Stability of LubricatingGreases by the Oxygen Pressure Vessel MethodD1193 Specification for Reagent WaterD5483 Test Method for Oxidation Induction Time of Lubri-cating Greases by Pressure Differential Scanning Calorim-etryD6810 Test Method for Measurement of Hindered PhenolicAntioxidant Content in Non-Zinc Turbine Oils by LinearSweep VoltammetryD6971 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 weighed into a vialcontaining a measured quantity of acetone based electrolytesolution and containing a layer of sand.When the vial isshaken,the dissolved antioxidants and other solution solubleoil components present in the sample are extracted into thesolution,and the remaining droplets suspended in the solutionare agglomerated by the sand.The sand/droplet suspension isallowed to settle out,and the antioxidants dissolved in thesolution are quantified by voltammetric analysis.NOTE1Voltages are listed with respect to reference electrode.Thevoltammograms shown in Figs.1 and 2 were obtained with a platinumreference electrode and a voltage scan rate of 0.1 V/s.4.Significance and Use4.1 The quantitative determination of antioxidants in newgreases measures the amount of the chemical compounds thatwere added to the base oil as protection against greaseoxidation.For in-service oil greases,the voltammetric testmethod measures the amount of original(individual)antioxi-dants remaining after grease oxidation have reduced its con-centration.Before making final judgment on the remaininguseful life of the in-service grease,which might result in thereplacement of the grease reservoir,it is advised to performadditional analytical techniques,such as Test Method D942and D5483,which may be used to measure the remainingoxidative life of the used grease.4.1.1 This test method is applicable to mineral oil-based andsynthetic oil-based greases,based on all type of appliedthickeners.This test method is applicable to greases containingat least one type of antioxidant.The presence of other types ofadditives like corrosion inhibitors or metal deactivators will notinterfere with this test method.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.G0.07 on Research Techniques.Current edition approved May 1,2010.Published June 2010.DOI:10.1520/D7527-10.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.2 When a voltammetric analysis is obtained using aneutral acetone test solution for a grease inhibited with atypical synergistic mixture of hindered phenol and aromaticamine antioxidants,there is an increase in the voltammogramcurrent between 8 to