ASTM_G_200_-_09_2014.pdf

Designation:G20009(Reapproved 2014)Standard Test Method forMeasurement of Oxidation-Reduction Potential(ORP)ofSoil1This standard is issued under the fixed designation G200;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 a procedure and related testequipment for measuring oxidation-reduction potential(ORP)of soil samples removed from the ground.1.2 The procedure in Section 9 is appropriate for field andlaboratory measurements.1.3 Accurate measurement of oxidation-reduction potentialaids in the analysis of soil corrosivity and its impact on buriedmetallic structure corrosion rates.1.4 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.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:2D1498 Test Method for Oxidation-Reduction Potential ofWaterE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodG3 Practice for Conventions Applicable to ElectrochemicalMeasurements in Corrosion TestingG15 Terminology Relating to Corrosion and Corrosion Test-ing(Withdrawn 2010)3G57 Test Method for Field Measurement of Soil ResistivityUsing the Wenner Four-Electrode MethodG187 Test Method for Measurement of Soil ResistivityUsing the Two-Electrode Soil Box Method3.Terminology3.1 The terminology used in this test method,if not specifi-cally defined otherwise,shall be in accordance with Terminol-ogy G15.3.2 Definitions of Terms Specific to This Standard:3.2.1 calibration solution,ncommercially available solu-tion with a stable ORP used for calibrating an ORP measuringsystem(meter and probe).3.2.2 ORPabbreviation for oxidation-reduction potential.3.2.3 ORP electrode(probe),ncommercially availablecombination two-element electrode(probe)specifically de-signed for the measurement of ORP when used in conjunctionwith a compatible ORP meter.3.2.3.1 DiscussionThe combination probe consists of aplatinum electrode and a reference electrode,which are gen-erally silver/silver chloride.For soil measurements,the probemust be sufficiently robust to withstand the rigors of themeasurement.Regardless,the often fragile probe should beused with caution to avoid damage and maintain measurementreliability.3.2.4 ORP meter,ncommercially available electrical me-ter specifically designed for the measurement of ORP withinternal impedance greater than 10.Often,the meter iscapable of measuring ORP and pH when used in conjunctionwith the appropriate electrode.3.2.4.1 DiscussionStandard voltmeters or multimeterswith internal impedances typically less than 10 are notsuitable for soil ORPmeasurements.Pocket style meters wherethe electrode is an integral part of the meter housing are alsonot suitable.3.2.5 oxidation-reduction potential(soil),nelectrical po-tential measurement to determine the tendency of a soil totransfer electrons between its chemical species.It is themeasured potential of an inert metal electrode(generallyplatinum)with respect to a reference electrode such as silver/silver chloride.1This test method is under the jurisdiction of ASTM Committee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G01.10 onCorrosion in Soils.Current edition approved May 1,2014.Published May 2014.Originallyapproved in 2009.Last previous edition approved in 2009 as G200-09.DOI:10.1520/G0200-09R14.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.5.1 DiscussionA soil with a higher,more positivepotential has an increased tendency to acquire electrons and bereduced(aerobic soil conditions).A soil with a lower positiveor negative potential has an increased tendency to lose elec-trons and be oxidized(anaerobic soil conditions).Soiloxidation-reduction potential is typically reported in units ofmillivolts(mV)or volts(1 volt=1000 mV).Sign conventionand reference electrodes conform to Practice G3.3.2.6 redox potential,nsynonym for oxidation-reductionpotential.3.2.7 soil sample,nsample of soil to be tested.Theminimum(typical)sample size is 1