ASTM_G_199_-_09_2014.pdf

Designation:G19909(Reapproved 2014)Standard Guide forElectrochemical Noise Measurement1This standard is issued under the fixed designation G199;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 guide covers the procedure for conducting onlinecorrosion monitoring of metals by the use of the electrochemi-cal noise technique.Within the limitations described,thistechnique can be used to detect localized corrosion activity andto estimate corrosion rate on a continuous basis withoutremoval of the monitoring probes from the plant or experimen-tal cell.1.2 This guide presents briefly some generally acceptedmethods of analyses that are useful in the interpretation ofcorrosion test results.1.3 This guide does not cover detailed calculations andmethods;rather it covers a range of approaches that have foundapplication in corrosion testing.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:2G1 Practice for Preparing,Cleaning,and Evaluating Corro-sion Test SpecimensG3 Practice for Conventions Applicable to ElectrochemicalMeasurements in Corrosion TestingG4 Guide for Conducting Corrosion Tests in Field Applica-tionsG5 Reference Test Method for Making PotentiodynamicAnodic Polarization MeasurementsG15 Terminology Relating to Corrosion and Corrosion Test-ing(Withdrawn 2010)3G16 Guide for Applying Statistics to Analysis of CorrosionDataG31 Guide for Laboratory Immersion Corrosion Testing ofMetalsG46 Guide for Examination and Evaluation of Pitting Cor-rosionG59 Test Method for Conducting Potentiodynamic Polariza-tion Resistance MeasurementsG61 Test Method for Conducting Cyclic PotentiodynamicPolarization Measurements for Localized Corrosion Sus-ceptibility of Iron-,Nickel-,or Cobalt-Based AlloysG96 Guide for Online Monitoring of Corrosion in PlantEquipment(Electrical and Electrochemical Methods)G102 Practice for Calculation of Corrosion Rates and Re-lated Information from Electrochemical MeasurementsG106 Practice for Verification of Algorithm and Equipmentfor Electrochemical Impedance Measurements3.Terminology3.1 DefinitionsThe terminology used herein,if not spe-cifically defined otherwise,shall be in accordance with Termi-nology G15.Definitions provided herein and not given inTerminology G15 are limited only to this guide.3.2 Definitions of Terms Specific to This Standard:3.2.1 coupling current,nmeasured current flowing be-tween two electrodes in an electrolyte coupled by an externalcircuit.3.2.2 current measuring device,ndevice that is capable ofmeasuring the current flow across the electrode/electrolyteinterface or the coupling current of a pair of electrodes,usuallya zero resistance ammeter(ZRA)or current-to-voltage con-verter.3.2.3 electrochemicalcurrentnoisemeasurement,nelectrochemical noise measurement using an electrochemi-cal current signal.3.2.4 electrochemicalnoisemeasurement(ENM),ntechnique involving the acquisition and analysis of electro-chemical current and potential signals.1This guide is under the jurisdiction of ASTM Committee G01 on Corrosion ofMetals and is the direct responsibility of Subcommittee G01.11 on ElectrochemicalMeasurements in Corrosion Testing.Current edition approved May 1,2014.Published May 2014.Originallyapproved in 2009.Last previous edition approved in 2009 as G199-09.DOI:10.1520/G0199-09R14.2For 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 electrochemicalpotentialnoisemeasurement,nelectrochemical noise measurement using an electrochemi-cal potential signal.3.2.6 Fourier transform,ntransformation of a time do-main signal into the frequency domain.3.2.7 galvanostat,ndevice used for automatically main-taining a controlled current between two electrodes.3.2.8 noise impedance,|Zn|,nratio of the amplitudeof potential noise to current noise,in the frequency domain,ata specified frequency.3.2.9 noise resistance,Rn,nstandard deviation ofpotential noise divided by the standard deviation of currentnoise.3.2.10 pit indicator,nstandard deviation of current noisedivided by the mean o