ASTM G100-1989(2015) Standard Test Method for Conducting Cyclic Galvanostaircase Polarization《循环电流梯级极化的标准试验方法》.pdf

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1、Designation: G100 89 (Reapproved 2015)Standard Test Method forConducting Cyclic Galvanostaircase Polarization1This standard is issued under the fixed designation G100; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las

2、t 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 for conductingcyclic galvanostaircase polarization (GSCP) to determine rela-tive susc

3、eptibility to localized corrosion (pitting and crevicecorrosion) for aluminum alloy 3003-H14 (UNS A93003) (1).2It may serve as guide for examination of other alloys (2-5).This test method also describes a procedure that can be used asa check for ones experimental technique and instrumentation.1.2 Th

4、e values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 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-pria

5、te safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D1193 Specification for Reagent WaterG1 Practice for Preparing, Cleaning, and Evaluating Corro-sion Test SpecimensG5 Reference Test Method for Making Pote

6、ntiodynamicAnodic Polarization MeasurementsG59 Test Method for Conducting Potentiodynamic Polariza-tion Resistance MeasurementsG69 Test Method for Measurement of Corrosion Potentialsof Aluminum Alloys3. Significance and Use3.1 In this test method, susceptibility to localized corrosionof aluminum is

7、indicated by a protection potential (Eprot)determined by cyclic galvanostaircase polarization (1). Themore noble this potential, the less susceptible is the alloy toinitiation of localized corrosion. The results of this test methodare not intended to correlate in a quantitative manner with therate o

8、f propagation of localized corrosion that one mightobserve in service.3.2 The breakdown (Eb), and protection potentials (Eprot)determined by the cyclic GSCP method correlate with theconstant potential corrosion test (immersion-glassware) resultfor aluminum (1, 6, 7). When the applied potential was m

9、orenegative than the GSCP Eprot, no pit initiation was observed.When the applied potential was more positive than the GSCPEprot, pitting occurred even when the applied potential was lessnegative than Eb.3.2.1 Severe crevice corrosion occurred when the separationof Eband Eprotwas 500 mV or greater an

10、d Eprotwas lessthan 400 mV Vs. SCE (in 100 ppm NaCl) (1, 6, 8). Foraluminum, Eprotdetermined by cyclic GSCP agrees with therepassivation potential determined by the scratch potentiostaticmethod (1, 9). Both the scratch potentiostatic method and theconstant potential technique for determination of Ep

11、rotrequiremuch longer test times and are more involved techniques thanthe GSCP method.3.3 DeBerry and Viebeck (3-5) found that the breakdownpotentials (Eb) (galvanodynamic polarization, similar to GSCPbut no kinetic information) had a good correlation with theinhibition of localized corrosion of 304

12、L stainless steel bysurface active compounds. They attained accuracy and preci-sion by avoiding the strong induction effect which theyobserved by the potentiodynamic technique.3.4 If this test method is followed using the specific alloydiscussed it will provide (GSCP) measurements that willreproduce

13、 data developed at other times in other laboratories.3.5 Eband Eprotobtained are based on the results from eightdifferent laboratories that followed the standard procedureusing aluminum alloy 3003-H14 (UNS A93003). Eband Eprotare included with statistical analysis to indicate the acceptablerange.4.

14、Apparatus4.1 CellThe cell should be constructed of inert materialssuch as borosilicate glass and PTFE fluorocarbon. It shouldhave ports for the insertion of a working electrode (1 cm2flat1This test method is under the jurisdiction of ASTM Committee G01 onCorrosion of Metals and is the direct respons

15、ibility of Subcommittee G01.11 onElectrochemical Measurements in Corrosion Testing.Current edition approved Nov. 1, 2015. Published December 2015. Originallyapproved in 1989. Last previous edition approved in 2010 as G10089(2010)1.DOI: 10.1520/G0100-89R15.2The boldface numbers in parentheses refer t

16、o a list of references at the end ofthis standard.3For 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 A

17、STM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1specimen holder (Note 1) is very convenient), two auxiliaryelectrodes, salt bridge for reference electrode, and a thermom-eter or a thermostat probe for temperature control.The figure inTest Method

18、 G5 would be satisfactory, but a flat bottom cell isalso satisfactory provided that all of the essential ports areprovided. (See Ref (10) for details.)NOTE 1These specific recommendations and conditions were fol-lowed to improve the interlaboratory precision during the round robin forgalvanostaircas

19、e polarization.4.2 Current Staircase Generator and RecorderThe sche-matic diagram of the apparatus is given in Fig. 1. The recordermay be replaced by a plotter if the current staircase signal isgenerated with the aid of a computer. The current staircase maybe generated manually (Note 2) but this is

20、not recommended.The most convenient current staircase generators are found inrecent commercial potentiostats where the software is avail-able. The electrical equipment may be checked in accordancewith the procedure in Practice G59.NOTE 2The current staircase signal was generated manually in theround

21、 robin because automated system or software was not available whenthis project was started.4.3 Electrodes:4.3.1 Working ElectrodeFor generating data to be com-pared to the reference data included herein, use type 3003-H14(UNS A93003) A1 in sheet form. Cut 1.55 cm diameter circlesand prepare in accor

22、dance with Practice G1 using 600-gritdiamond slurry on a flat lapping machine. Install in flatspecimen holder using PTFE gasket (no crevice type) (Note 1)so that 1 cm2is exposed to the test solution. Apply 29 m-g oftorque.4.3.2 Auxiliary ElectrodesGraphite, (ultrafine grade)(Note 3).NOTE 3Coarse gra

23、des of graphite should be avoided because theyabsorb solute impurities. Ultrafine grades are available from spectro-graphic supply companies.4.3.3 Reference ElectrodeSaturated calomel (Note 1). Itshould be checked against another reference which has notbeen exposed to test solutions and they should

24、be within 3 mVof each other. Practice G69 round robin test conducted byG01.11 (unpublished results) indicate that potential differenceshould not exceed 2 or 3 mV. The reference electrode isconnected to the test bridge solution which consists of 75 %saturated KCl, prepared by adding 1 part (by volume

25、) ofdistilled water to 3 parts saturated KCl. When the bridge is inactive use, the bridge solution should be replaced once eachday and the bridge tip immersed in this solution when not inuse. Any test solution that does not deposit films may also beused in the bridge. (The VYCOR4tip should not be al

26、lowed togo to dryness.)4.4 Magnetic Stirrer.5. Procedure5.1 Test solution, 3000 6 30 ppm (0.0513 M) NaCl. Forexample, transfer 6.000 g reagent grade NaCl to a 2-Lvolumetric flask. Dissolve in ASTM Type IV water (deminer-alized or distilled) and dilute to the mark. (See SpecificationD1193.)5.2 Assemb

27、le cell with the electrodes described in Section4. Place the reference bridge probe about 2 probe tip diametersaway from the working electrode.5.3 Fill the cell with the test solution so that the level isabout 25 mm above the working electrode.5.4 Maintain a temperature of 25 6 1C.5.5 Do not deaerat

28、e.5.6 Turn on the magnetic stirrer to a maximum speed thatwill maintain a smooth vortex above the specimen withoutwhipping air bubbles into the solution.5.7 Apply a current staircase signal from 0 to 120 A/cm2using a step height of 20 A/cm2and step duration of 2 min;reverse the current staircase sca

29、n to 0 current. Record thevoltage transients on an X-Y or X-T recorder or plotter asshown in Fig. 2 (Note 4). In order to differentiate between thesteady-state potential values of the forward scan from those ofthe reverse scan, it would be helpful to (1) delay the actualreversal of the pen about 12

30、s after dropping from 120 to100 Acm2so that there will be a separation of about 24 sbetween the forward and reverse steady state points and (2)change the pen color in the reverse scan.NOTE 4Fig. 2 can be elucidated with the help of Fig. 3. The upper4VYCOR is a trademark of Corning Incorporated, One

31、Riverfront Plaza,Corning, NY 14831, Code No. 7930 glass.FIG. 1 Schematic Wiring Diagram for Galvanostaircase Polariza-tionG100 89 (2015)2curve in Fig. 3 shows the current staircase signal applied in 5.7 and thelower curve gives schematic voltage response transients with the currentdensity given for

32、each transient. The current is selected at the end of eachstep (even though current is constant during a step) because the steadystate voltage is obtained at the end of the step. This allows extrapolationto zero current which is a discrete current value at each end of the lowercurve. In Fig. 2, the

33、down-steps are reversed with a slight delay to separateup-step (triangles pointing upward) from the down-step (triangle pointingdownward) steady state voltage.5.8 ExtrapolationExtrapolate the up-step points to zerocurrent to obtain Eb. Similarly, extrapolate the down-steppoints to obtain Eprot. Fig.

34、 2 and Fig. 3 give examples of theseextrapolations.6. Precision and Bias6.1 PrecisionThe precision information is based on dataobtained by the GSCP Task Group with eight laboratoriesparticipating. Each laboratory ran duplicate results on the onetest solution. The mean value for Ebwas 636 mV with ast

35、andard deviation of 15.8 mV. The mean value for Eprotwas 652 mV with a standard deviation of 14.8.6.2 The repeatability of this technique was 3.5 mV for Eprotand 7.3 mV for Ebin terms of the pooled standard deviation.(See Note 5.)6.3 BiasThis procedure has no bias because the values ofEband Eprotcan

36、 be defined only in terms of this method. If thevoltage transients are omitted from Fig. 2 and Fig. 3, typicalquasi-stationary galvanostatic polarization plots are obtained.However, the kinetic and noise information derived from thevoltage transients are desirable attributes of GSCP.NOTE 5The standa

37、rd deviation was derived from:S25(i51NYi2 Y!2N 2 1(1)where:Y = the ithresult,Y= the average of all Yivalues, andN = is the total number of results.The pooled standard deviation was derived from:Spooled!25(i51KJ1i2 J2i!22K(2)where:K = the number of laboratories and J1iand J2iare theduplicate results

38、from the ithlaboratory.7. Keywords7.1 aluminum; corrosion; electrochemical measurement;galvanostaircase; localized corrosion; polarizationFIG. 2 Cyclic GSCP Curve of 3003 A1 in 3000 ppm NaCl(Taken from Ref 8)FIG. 3 Relationship of a Schematic GSCP Curve (lower) to theCurrent Staircase Signal (upper)

39、G100 89 (2015)3REFERENCES(1) Hirozawa, S. T., Journal of Electrochemical Society Vol 130 , 1983, p.1718.(2) Hirozawa, S. T. and Coker, D. E., “Comparison of the ProtectionPotential of Type 430 Stainless Steel in Sulfuric Acid as Determinedby Potentiodynamic, Galvanostaircase and the Zap-Galvanostair

40、caseTechnique,” Paper #262, CORROSION/87.(3) Viebeck, A. and DeBerry, D. W., Journal of Electrochemical Society,Vol 131, 1984, p. 1844.(4) DeBerry, D. W. and Viebeck, A., Journal of the ElectrochemicalSociety, Vol 133, 1986, p. 32.(5) DeBerry, D. W. and Viebeck, A., “Inhibition of Pitting Corrosion

41、ofType 304L Stainless Steel by Surface Active Compounds,” Paper#196, CORROSION/86.(6) Hirozawa, S. T.,“Galvanostaircase Polarization: A Powerful Tech-nique for the Investigation of Localized Corrosion,” Paper #48 at theElectrochemical Society Meeting, Oct., 1982.(7) Hirozawa, S. T.,“Corrosion Monito

42、ring by GalvanostaircasePolarization,” in Electrochemical Techniques for CorrosionEngineering, Baboian, R., Editor, NACE, Houston, 1986.(8) Hirozawa, S. T.,“Study of the Mechanism for the Inhibition ofLocalized Corrosion ofAluminum by Galvanostaircase Polarization,”in Corrosion Inhibition, Hausler,

43、R. H., Editor, NACE, Houston,1988.(9) Rudd, W. J. and Scully, J. C., Corrosion Science, Vol 20, 1980, p. 611.(10) Hirozawa, S. T.,“Current Versus Voltage Hysteresis: Effect onElectrometric Monitoring of Corrosion,” Laboratory Corrosion Testsand Standards, ASTM STP 866, Haynes, G. S., and Baboian, R.

44、,Editors, American Society for Testing and Materials, Philadelphia,1985, p. 108.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the val

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