1、Designation: G 100 89 (Reapproved 2004)Standard Test Method forConducting Cyclic Galvanostaircase Polarization1This standard is issued under the fixed designation G 100; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 s
3、usceptibility to localized corrosion (pitting and crevicecorrosion) for aluminum alloy 3003-H14 (UNS A93003) (1).2It may serve as guide for examination of other alloys (25).This test method also describes a procedure that can be used asa check for ones experimental technique and instrumentation.1.2
4、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 Docum
5、ents2.1 ASTM Standards:3D 1193 Specification for Reagent WaterG 1 Practice for Preparing, Cleaning, and Evaluating Cor-rosion Test SpecimensG 5 Reference Test Method for Making Potentiostatic andPotentiodynamic Anodic Polarization MeasurementsG 59 Practice for Conducting Potentiodynamic Polarization
6、Resistance MeasurementsG 69 Practice for Measurement of Corrosion Potentials ofAluminum Alloys3. Significance and Use3.1 In this test method, susceptibility to localized corrosionof aluminum is indicated by a protection potential (Eprot)determined by cyclic galvanostaircase polarization (1). Themore
7、 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 of propagation of localized corrosion that one mightobserve in service.3.2 The breakdown (Eb), and protecti
8、on potentials (Eprot)determined by the cyclic GSCP method correlate with theconstant potential corrosion test (immersion-glassware) resultfor aluminum (1, 6, 8). When the applied potential was morenegative than the GSCP Eprot, no pit initiation was observed.When the applied potential was more positi
9、ve 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 and Eprotwas lessthan 400 mV Vs. SCE (in 100 ppm NaCl) (1, 6, 7). Foraluminum, Eprotdetermined by cyclic GSC
10、P agrees with therepassivation potential determined by the scratch potentiostaticmethod (1, 10). Both the scratch potentiostatic method and theconstant potential technique for determination of Eprotrequiremuch longer test times and are more involved techniques thanthe GSCP method.3.3 DeBerry and Vie
11、beck (35) found that the breakdownpotentials (Eb) (galvanodynamic polarization, similar to GSCPbut no kinetic information) had a good correlation with theinhibition of localized corrosion of 304L stainless steel bysurface active compounds. They attained accuracy and preci-sion by avoiding the strong
12、 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 data developed at other times in other laboratories.3.5 Eband Eprotobtained are based on the results from
13、 eightdifferent laboratories that followed the standard procedureusing aluminum alloy 3003-H14 (UNS A93003). Eband Eprotare included with statistical analysis to indicate the acceptablerange.4. Apparatus4.1 CellThe cell should be constructed of inert materialssuch as borosilicate glass and PTFE fluo
14、rocarbon. It shouldhave ports for the insertion of a working electrode (1 cm2flatspecimen 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 in1This test method is under the j
15、urisdiction of ASTM Committee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G1.11 onElectrochemical Measurements in Corrosion Testing.Current edition approved Nov 1, 2004. Published November 2004. Originallyapproved in 1989. Last previous edition approved in 1999 as G 10
16、0 1999).2The boldface numbers in parentheses refer to the list of references at the end ofthis test method.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 stand
17、ards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Test Method G 5 would be satisfactory, but a flat bottom cell isalso satisfactory provided that all of the essential ports areprovided. (Se
18、e Ref (9) for details.)NOTE 1These specific recommendations and conditions were fol-lowed to improve the inter-laboratory precision during the round robin forgalvanostaircase polarization.4.2 Current Staircase Generator and RecorderThe sche-matic diagram of the apparatus is given in Fig. 1. The reco
19、rdermay 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 not recommended.The most convenient current staircase generators are found inrecent commercial potentiostats where the software
20、 is avail-able. The electrical equipment may be checked in accordancewith the procedure in Practice G 59.NOTE 2The current staircase signal was generated manually in theround robin because automated system or software was not available whenthis project was started.4.3 Electrodes:4.3.1 Working Electr
21、odeFor 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 accordance with Practice G 1 using 600-gritdiamond slurry on a flat lapping machine. Install in flatspecimen holder using PTFE gask
22、et (no crevice type) (Note 1)so that 1 cm2is exposed to the test solution. Apply 28.8 m-g(40 in.-oz) of torque.4.3.2 Auxiliary ElectrodesGraphite, (ultrafine grade)(Note 3).NOTE 3Coarse grades of graphite should be avoided because theyabsorb solute impurities. Ultrafine grades are available from spe
23、ctro-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 be within 3 mVof each other. Practice G 69 round robin test conducted byG01.11 (unpublished results) indicate t
24、hat 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) ofdistilled water to 3 parts saturated KCl. When the bridge is inactive use, the bridge solution should be r
25、eplaced 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 allowed togo to dryness.)4.4 Magnetic Stirrer.5. Procedure5.1 Test solution, 3000 6 30 ppm (0.0513 M) NaCl. Fore
26、xample, 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 SpecificationD 1193.)5.2 Assemble cell with the electrodes described in Section4. Place the reference bridge probe about 2 probe tip diamete
27、rsaway from the working electrode.5.3 Fill the cell with the test solution so that the level isabout 25 mm (1 in.) above the working electrode.5.4 Maintain a temperature of 25 6 1C.5.5 Do not deaerate.5.6 Turn on the magnetic stirrer to a maximum speed thatwill maintain a smooth vortex above the spe
28、cimen 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 scan to 0 current. Record thevoltage transients on an X-Y or X-T recorder or plotter asshown in Fig. 2 (
29、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 s after dropping from 120 to 100A/cm2so that there will be a separation of about 24 s betweenthe forw
30、ard and reverse steady state points and (2) change thepen color in the reverse scan.NOTE 4Fig. 2 can be elucidated with the help of Fig. 3. The uppercurve in Fig. 3 shows the current staircase signal applied in 5.7 and thelower curve gives schematic voltage response transients with the currentdensit
31、y given for 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
32、Fig. 2, the down-steps are reversed with a slight delay to separateup-step (triangles pointing upward) from the down-step (triangle pointingdownward) steady state voltage.4VYCOR is a trademark of Owen Corning, Code No. 7930 glass.FIG. 1 Schematic Wiring Diagram for GalvanostaircasePolarizationG 100
33、89 (2004)25.8 ExtrapolationExtrapolate the up-step points to zerocurrent to obtain Eb. Similarly, extrapolate the down-steppoints to obtain Eprot. Fig. 3 and Fig. 2 give examples of theseextrapolations.6. Precision and Bias56.1 PrecisionThe precision information is based on dataobtained by the GSCP
34、Task Group with eight laboratoriesparticipating. Each laboratory ran duplicate results on the onetest solution. The mean value for Ebwas 636 mV with astandard 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
35、 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 be defined only in terms of this method. If thevoltage transients are omitted from Fig. 3 and Fig. 2, typicalquasi-stationary galvanostatic polariz
36、ation plots are obtained.However, the kinetic and noise information derived from thevoltage transients are desirable attributes of GSCP.NOTE 5The standard deviation was derived fromS25(i 5 1NYi2 Y!2N 2 1(1)where:Y = the ithresult,Y= the average of all Yivalues, andN = is the total number of results.
37、The pooled standard deviation was derived fromSpooled!25(i 5 1KJ1i2 J2i!22K(2)where:K = the number of laboratories and J1iand J2iare theduplicate results from the ithlaboratory.7. Keywords7.1 aluminum; corrosion; electrochemical measurement;galvanostaircase; localized corrosion; polarization5The res
38、ults of the round robin are available from ASTM headquarters.FIG. 2 Cyclic GSCP Curve of 3003 A1 in 3000 ppm NaCl(Taken from Ref. 7)G 100 89 (2004)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 Protect
39、ionPotential of Type 430 Stainless Steel in Sulfuric Acid as Determinedby Potentiodynamic, Galvanostaircase and the Zap-GalvanostaircaseTechnique,” Paper #262, CORROSION/87. In publication.(3) Viebeck, A. and DeBerry, D. W., Journal of Electrochemical SocietyVol 131, p. 1844 (1984).(4) DeBerry, D. W
40、. and Viebeck, A., Journal of the ElectrochemicalSociety Vol 133, p. 32 (1986).(5) DeBerry, D. W. and Viebeck, A., “Inhibition of Pitting Corrosion ofType 304L Stainless Steel by Surface Active Compounds,” Paper#196, CORROSION/86.(6) Hirozawa, S. T., “Galvanostaircase Polarization: A Powerful Tech-n
41、ique for the Investigation of Localized Corrosion,” Paper #48 at theElectrochemical Society Meeting, Oct., 1982.(7) Hirozawa, S. T., “Study of the Mechanism for the Inhibition ofLocalized Corrosion of Aluminum by Galvanostaircase Polarization,”in Corrosion Inhibition, R. H. Hausler, Editor, NACE, Ho
42、uston, 1988.(8) Hirozawa, S. T., “Corrosion Monitoring by Galvanostaircase Polariza-tion,” in Electrochemical Techniques for Corrosion Engineering,R.Baboian, Editor, NACE, Houston, 1986.(9) Hirozawa, S. T., “Current Versus Voltage Hysteresis: Effect onElectrometric Monitoring of Corrosion,” Laborato
43、ry Corrosion Testsand Standards, ASTM STP 866, G. S. Haynes and R. Baboian, Editors,American Society for Testing and Materials, Philadelphia, 1985, p.108.(10) Rudd, W. J. and Scully, J. C., Corrosion Science, Vol 20, 1980, p. 611.ASTM International takes no position respecting the validity of any pa
44、tent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revisio
45、n at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your com
46、ments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyright
47、ed by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).FIG. 3 Relationship of a Schematic GSCP Curve (lower) to the Current Staircase Signal (upper)G 100 89 (2004)4
