1、Designation: G217 16Standard Guide forCorrosion Monitoring in Laboratories and Plants withCoupled Multielectrode Array Sensor Method1This standard is issued under the fixed designation G217; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, 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 outlines the procedure for conducting corro-sion monitoring in laboratories and plants
3、by use of the coupledmultielectrode array sensor (CMAS) technique.1.2 For plant applications, this technique can be used toassess the instantaneous non-uniform corrosion rate, includinglocalized corrosion rate, on a continuous basis, without re-moval of the monitoring probes, from the plant.1.3 For
4、laboratory applications, this technique can be usedto study the effects of various testing conditions and inhibitorson non-uniform corrosion, including pitting corrosion andcrevice corrosion.1.4 UnitsThe values stated in SI units are to be regardedas the standard. No other units of measurement are i
5、ncluded inthis 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 prio
6、r to use.2. Referenced Documents2.1 ASTM Standards:2G1 Practice for Preparing, Cleaning, and Evaluating Corro-sion Test SpecimensG4 Guide for Conducting Corrosion Tests in Field Applica-tionsG16 Guide for Applying Statistics to Analysis of CorrosionDataG46 Guide for Examination and Evaluation of Pit
7、ting Cor-rosionG48 Test Methods for Pitting and Crevice Corrosion Resis-tance of Stainless Steels and Related Alloys by Use ofFerric Chloride SolutionG96 Guide for Online Monitoring of Corrosion in PlantEquipment (Electrical and Electrochemical Methods)G102 Practice for Calculation of Corrosion Rate
8、s and Re-lated Information from Electrochemical MeasurementsG193 Terminology and Acronyms Relating to CorrosionG199 Guide for Electrochemical Noise Measurement3. Terminology3.1 DefinitionsThe terminology used herein, if not spe-cifically defined otherwise, shall be in accordance with Termi-nology G1
9、93. Definitions provided herein and not given inTerminology G193 are limited only to this guide.3.2 Definitions of Terms Specific to This Standard:3.2.1 coupled multielectrode array sensor, CMAS,ndevice with multiple working electrodes that are coupledthrough an external circuit such that all the el
10、ectrodes operateat the same electrode potential to simulate the electrochemicalbehavior of a single-piece metal.3.2.2 non-uniform corrosion, ncorrosion that occurs atvarious rates across the metal surface, with some locationsexhibiting higher anodic rates while others have higher ca-thodic rates, th
11、ereby requiring that the electron transfer occursbetween these sites within the metal.3.2.2.1 DiscussionNon-uniform corrosion includes bothlocalized corrosion and uneven general corrosion (1).3Non-uniform corrosion also includes the type of general corrosionthat produces even surfaces at the end of
12、a large time interval,but uneven surfaces during small time intervals.3.2.3 uneven general corrosion, ncorrosion that occursover the whole exposed surface or a large area at different rates.3.2.3.1 DiscussionIn this guide, general corrosion is fur-ther divided into even general corrosion, or uniform
13、 corrosion,which is defined as the corrosion that proceeds at exactly thesame rate over the surface of a material (see TerminologyG193) and uneven general corrosion. Uneven general corro-sion is defined as the general corrosion that produces uneven1This guide is under the jurisdiction of ASTM Commit
14、tee G01 on Corrosion ofMetals and is the direct responsibility of Subcommittee G01.11 on ElectrochemicalMeasurements in Corrosion Testing.Current edition approved Nov. 1, 2016. Published November 2016. DOI:10.1520/G0217-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orconta
15、ct ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to a list of references at the end ofthis standard.Copyright ASTM International, 100 Barr Harbo
16、r Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1surface or wave-like surface on a metal that has an even surfacebefore the corrosion (2, 3).3.2.4 zero-voltage ammeter, ZVA, ndevice that imposes anegligibly low voltage drop when inserted into a circuit formeasurement of current.
17、3.2.4.1 DiscussionThe ZVA defined in this guide alsomeets the definition of the zero-resistance ammeter (ZRA) inGuide G199. A typical ZRA is built with inverting operationalamplifiers to limit the voltage drop in the current-measuringcircuit to a low value. Both ZRA and a simple device formedwith a
18、shunt resistor and a voltmeter can be used as a ZVA aslong as they do not impose a significant voltage drop (0.94 0.93 0.19 0.22 0.56(Iain/Icorr)C6 % 7 % 81 % 78 % 44 %Corrosion ModeLocalized corrosionNon-uniform generalcorrosionUniform corrosion Uniform corrosion Uniform corrosionAIainThese values
19、were derived with the Tafel extrapolation method and they are the upper bounds of the Iainvalues.BIcorrCorrosion current on most anodic electrode (Icorr= Iaex+ Iain).CIain/IcorrEffect of internal current.G217 169A2. ZERO-VOLTAGE AMMETER (ZVA) AND ZERO-RESISTANCE AMMETER (ZRA)A2.1 Definitions of ZVA
20、and ZRAIn 3.2.4,aZVAisdefined as a device that imposes a negligibly low voltage dropwhen inserted into a circuit for measurement of current. Thisdefinition is essentially the same as the definition of ZRA inGuide G199electronic device used to measure current with-out imposing a significant IR drop b
21、y maintaining close to 0-Vpotential difference between the inputs.A2.2 The commonly accepted concept for ZRA is that it isbuilt with an operational amplifier (Op-Amp) as shown in Fig.A2.1 and its input resistance is zero when it is used as anammeter. If Op-Amp is ideal, the potential at the invertin
22、gterminal (VpVn) is zero and the ratio of the input voltage dropto the measured current is zero.A2.3 In reality, Op-Amps are not ideal and do have inputvoltage. For example, every Op-Amps has an input offsetvoltage (VOS) which is defined as the small differential voltagethat must be applied to the i
23、nput of an Op-Amp (VpVn)toproduce zero output (Vout). As a matter of fact, the input offsetvoltage is one of the most important parameters that arereported in manufacturers product specification sheets. Theinput offset voltage of general-purpose Op-Amps usuallyvaries between -0.5 mV and +0.5 mV, but
24、 may be as large as62 mV. When general-purpose Op-Amps are used to build aZRA, the input voltage must be the input offset voltage whenthe readout of the ZRA is zero. In addition, the input offsetvoltage may drift with time. Commercial potentiostats mayimpose an input voltage between -1 mv and +1 mV
25、when usedas a ZRA according to some manufacturers specifications.While the change of electrode potential caused by a ZRA thathas an input voltage of 1 mV is often negligibly small, thevoltage-to-current ratio corresponds to this small input voltageis astonishingly high when the input current is smal
26、l. Forexample, when the input current is 1 nA, which is a typicalvalue of the coupling current in a CMAS probe, the voltage-to-current ratio is actually 500 000 ohm when the input voltageis 0.5 mV.A2.4 By comparing the definitions of ZVA and ZRA inA2.1, the ZRA can be used as the ZVA and many resear
27、chershave used the ZRA in their work with the coupled multielec-trode systems. The device built with a simple shunt resistor anda voltmeter has also been used by many researchers in theirwork with CMAS probes. With the shunt-resistor approach, thevoltmeter is used to measure the small voltage drop a
28、cross theshunt resistor to derive the current. As long as the voltage dropacross the shunt resistor is negligibly low (less than 0.5 mV forexample), the device built with a shunt resistor can be used asthe ZVA for the CMAS systems.A2.5 Even though a real-world ZRA may have a voltage-to-current ratio
29、 as high as 500 000 ohms, an ideal ZRA doeshave a zero voltage-to-current ratio. It is understandable to callthe current-measuring device built with the Op-Amps a ZRA.However, it is not appropriate to call the current-measuringdevice built with the shunt resistors a ZRA because the valuesof the shun
30、t resistors can never be zero. To avoid the confusion,the devices used for the measurement of the currents in CMASprobes have been called ZVA (1) because both ZRA and thedevice built with a simple shunt resistor can provide the samefunction. This guide defines all devices that can be used forCMAS pr
31、obes as ZVA. The term ZVA applies to both the ZRAand the device built with shunt resistors as long as such devicesdo not impose a significant voltage drop in the measuringcircuit.FIG. A2.1 Basic Circuit of a Zero-Resistance Ammeter for the Measurement of Current Without Imposing a Significant IR Dro
32、p by Main-taining Close to 0-V Potential Difference Between the InputsG217 1610REFERENCES(1) Yang, L., Chiang, K. T., Shukla, P. K., and Shiratori, N., “InternalCurrent Effects on Localized Corrosion Rate Measurements UsingCoupled Multielectrode Array Sensors,” Corrosion, Vol 66, 2010, p.115005.(2)
33、Champion, F. A., J. Inst. Met., Vol 69, 1943, pp. 4766.(3) Greene, N. D., and Fontana, M. G., Corrosion, Vol 15, 1959, pp.25t31t.(4) Sun, X. and Yang, L., “Real-Time Monitoring of Localized andGeneral Corrosion Rates in Drinking Water Utilizing Coupled Mul-tielectrode Array Sensors,” CORROSION/2006,
34、 Paper No. 06094,Houston, TX, NACE, 2006.(5) Yang, L., “Multielectrode Systems,” in Techniques for CorrosionMonitoring, L. Yang, Ed., Woodhead Publishing, Cambridge, UnitedKingdom, 2008, Chap. 8.(6) Fei, Z., Kelly, R. G., and Hudson, J. L., “Spatiotemporal Patterns onElectrode Arrays,” J. Phys. Chem
35、., Vol 100, 1996, pp. 1898618991.(7) Tan, Y. J., “Monitoring Localized Corrosion Processes and EstimatingLocalized Corrosion Rates Using a Wire-beam Electrode,” Corrosion,Vol 54, No. 5, 1998, pp. 403413.(8) Yang, L., Sridhar, N., Pensado, O., and Dunn, D., “An In-situGalvanically Coupled Multi-Elect
36、rode Array Sensor for LocalizedCorrosion,” Corrosion, Vol 58, 2002, p. 1004.(9) Yang, L., Sun, X., and Barnes, R., “Coupled Multielectrode ArraySensor with Coated, Fingered Electrodes for Corrosion Monitoring inOil-Water Mixtures and Gas Systems Containing Hydrogen Sulfide,”CORROSION/2014, Paper No.
37、 06094, Houston, TX, NACE, 2014.(10) Hinds, G. and Turnbull, A., “Novel Multi-electrode Test Method forEvaluating Inhibition of Underdeposit Corrosion. Part 1: SweetConditions,” Corrosion, Vol 66, No. 4, 2010, p. 046001.(11) Cong, H., Bocher, F., Budiansky, N. D., Hurley, M. F., and Scully, J.R., “U
38、se of Coupled Multi-Electrode Arrays to Advance the Under-standing of Selected Corrosion Phenomena,” Journal of ASTMInternational, Vol 4, No. 10, Paper ID JAI101248, 2007.(12) Yang, B., Marinho, F. J., and Gershun, A. V., “New ElectrochemicalMethods for the Evaluation of Localized Corrosion in Engin
39、eCoolants,” Journal of ASTM International, Vol 4, No. 1, 2007.(13) Colbert, R., and Reich, R., “Corrosion Monitoring of a Water BasedRolling Facility with Coupled Multielectrode Array Sensors and theCorrelations with Other Process Variables: Conductivity, pH,Temperature, Dissolved Oxygen and Corrosi
40、on Potential,”CORROSION/2008, Paper 08295, Houston, TX, NACE, 2008.(14) Yang, L., Sridhar, N., Brossia, C. S., and Dunn, D. S., “Evaluation ofthe Coupled Multielectrode Array Sensor as a Real Time CorrosionMonitor,” Corrosion Science, Vol 47, 2005, pp. 17941809.(15) Chiang, K. T., and Yang, L., “Hig
41、h-Temperature ElectrochemicalSensor for Online Corrosion Monitoring,” Corrosion, Vol 66, 2010,p. 095002.(16) Yang, L., “Effect of Voltage between Electrodes of a CoupledMultielectrode Array Sensor on Corrosion Rate Measurement,”CORROSION/2016, Paper No. 7911, Houston, TX, NACE, 2016.(17) Southwell,
42、C. R., Hummer, C. W., Jr., and Alexander, A. L.,“Corrosion of Metals in Tropical Environments, Part 7Copper andCopperAlloysSixteen YearsExposure,” NRL Report 6452, NavalResearch Laboratory, Washington, DC, 1966, p. 4.(18) Dorsey, et al, CORROSION/2002, Paper No. 02009, Houston, TX,NACE, 2002, p. 14.
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