ASTM G61-1986(2003)e1 Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements for Localized Corrosion Susceptibility of Iron- Nickel- or Cobalt-Based A.pdf
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1、Designation: G 61 86 (Reapproved 2003)e1Standard Test Method forConducting Cyclic Potentiodynamic PolarizationMeasurements for Localized Corrosion Susceptibility ofIron-, Nickel-, or Cobalt-Based Alloys1This standard is issued under the fixed designation G 61; the number immediately following the de
2、signation indicates the year of originaladoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEAdjunct references were corrected edi
3、torially in April 2006.1. Scope1.1 This test method covers a procedure for conductingcyclic potentiodynamic polarization measurements to deter-mine relative susceptibility to localized corrosion (pitting andcrevice corrosion) for iron-, nickel-, or cobalt-based alloys in achloride environment. This
4、test method also describes anexperimental procedure which can be used to check onesexperimental technique and instrumentation.1.2 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 ap
5、pro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterG3 Practice for ConventionsApplicable to ElectrochemicalMeasurements in Corrosion TestingG5 Reference Test M
6、ethod for Making Potentiostatic andPotentiodynamic Anodic Polarization Measurements2.2 ASTM Adjuncts:Standard Samples (set of two)33. Significance and Use3.1 An indication of the susceptibility to initiation of local-ized corrosion in this test method is given by the potential atwhich the anodic cur
7、rent increases rapidly. The more noble thispotential, obtained at a fixed scan rate in this test, the lesssusceptible is the alloy to initiation of localized corrosion. Theresults of this test are not intended to correlate in a quantitativemanner with the rate of propagation that one might observe i
8、nservice when localized corrosion occurs.3.2 In general, once initiated, localized corrosion can propa-gate at some potential more electropositive than that at whichthe hysteresis loop is completed. In this test method, thepotential at which the hysteresis loop is completed is deter-mined at a fixed
9、 scan rate. In these cases, the more electrop-ositive the potential at which the hysteresis loop is completedthe less likely it is that localized corrosion will occur.3.3 If followed, this test method will provide cyclic poten-tiodynamic anodic polarization measurements that will repro-duce data dev
10、eloped at other times in other laboratories usingthis test method for the two specified alloys discussed in 3.4.The procedure is used for iron-, nickel-, or cobalt-based alloysin a chloride environment.3.4 A standard potentiodynamic polarization plot is in-cluded. These reference data are based on t
11、he results from fivedifferent laboratories that followed the standard procedure,using specific alloys of Type 304 stainless steel, UNS S30400and Alloy C-276, UNS N10276.3Curves are included whichhave been constructed using statistical analysis to indicate theacceptable range of polarization curves.3
12、.5 The availability of a standard test method, standardmaterial, and standard plots should make it easy for aninvestigator to check his techniques to evaluate susceptibilityto localized corrosion.4. Apparatus4.1 The polarization cell should be similar to the onedescribed in Practice G5. Other polari
13、zation cells may beequally suitable.4.1.1 The cell should have a capacity of about 1 L andshould have suitable necks or seals to permit the introductionof electrodes, gas inlet and outlet tubes, and a thermometer.The Luggin probe-salt bridge separates the bulk solution from1This test method is under
14、 the jurisdiction of ASTM Committee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G01.11 onElectrochemical Measurements in Corrosion Testing.Current edition approved October 1, 2003. Published October 2003. Originallyapproved in 1986. Last previous edition approved in 19
15、98 as G 61 86 (1998).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.3Available from ASTM International Headq
16、uarters. Order Adjunct No.ADJG0061. Original adjunct produced before 1995.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the saturated calomel reference electrode. The probe tip shouldbe adjustable so that it can be brought into clo
17、se proximity withthe working electrode.4.2 Specimen Holder:4.2.1 Specimens should be mounted in a suitable holderdesigned for flat strip, exposing 1 cm2to the test solution (Fig.1). Such specimen holders have been described in the litera-ture.4It is important that the circular TFE-fluorocarbon gaske
18、tbe drilled and machined flat in order to minimize crevices.4.3 Potentiostat (Note 1)A potentiostat that will maintainan electrode potential within 1 mV of a preset value over awide range of applied currents should be used. For the type andsize of standard specimen supplied, the potentiostat shouldh
19、ave a potential range of 1.0 to +1.6 V and an anodic currentoutput range of 1.0 to 105A. Most commercial potentiostatsmeet the specific requirements for these types of measure-ments.NOTE 1These instrumental requirements are based upon values typi-cal of the instruments in the five laboratories that
20、have provided the dataused in determining the standard polarization plot.4.4 Potential-Measuring Instruments (Note 1)Thepotential-measuring circuit should have a high input imped-ance on the order of 1011to 1014V to minimize current drawnfrom the system during measurements. Instruments shouldhave su
21、fficient sensitivity and accuracy to detect a change inpotential of 61 mV, usually included in commercial poten-tiostats. An output as a voltage is preferred for recordingpurposes.4.5 Current-Measuring Instruments (Note 1)An instru-ment that is capable of measuring a current accurately to within1 %
22、of the absolute value over a current range between 1.0 and105Ashould be used. Many commercial units have a build-ininstrument with an output as a voltage, which is preferred forrecording purposes. For the purpose of the present test alogarithmic output is desirable.4.6 Anodic Polarization CircuitAsc
23、anning potentiostat isused for potentiodynamic measurements. Potential and currentare plotted continuously using an X-Y recorder and a logarith-mic converter (contained in the potentiostat or incorporatedinto the circuit) for the current. Commercially available unitsare suitable.4.7 Electrodes:4.7.1
24、 The standard Type 304 stainless steel (UNS S30400)and Alloy C-276 (UNS N10276) should be machined into flat0.625-in. (14-mm) diameter disks. The chemical compositionsof the alloys used in the round robin are listed in Table 1.4.7.2 Counter ElectrodesThe counter electrodes may beprepared as describe
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