1、Designation: G100 89 (Reapproved 2010)1Standard 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 la
2、st revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEClarified the SI unit statement editorially in May 2010.1. Scope1.1 This test method covers a procedure for conductingcyclic ga
3、lvanostaircase polarization (GSCP) to determine rela-tive susceptibility 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 ch
4、eck for ones experimental technique and instrumentation.1.2 The 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 therespo
5、nsibility 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:3D1193 Specification for Reagent WaterG1 Practice for Preparing, Cleaning, and Evaluating Cor
6、ro-sion Test SpecimensG5 Reference Test Method for Making Potentiostatic andPotentiodynamic Anodic Polarization MeasurementsG59 Test Method for Conducting Potentiodynamic Polar-ization Resistance MeasurementsG69 Test Method for Measurement of Corrosion Potentialsof Aluminum Alloys3. Significance and
7、 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 noble this potential, the less susceptible is the alloy toinitiation of localized corrosion. The results of this
8、 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 protection potentials (Eprot)determined by the cyclic GSCP method correlate with theconstant potential corrosion test (im
9、mersion-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 positive than the GSCPEprot, pitting occurred even when the applied potential was lessnegative than Eb.3.2.1 Severe cre
10、vice 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 GSCP agrees with therepassivation potential determined by the scratch potentiostaticmethod (1, 10). Both the scratch
11、 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 Viebeck (3-5) found that the breakdownpotentials (Eb) (galvanodynamic polarization, similar to GSCPbut no kinetic in
12、formation) 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 induction effect which theyobserved by the potentiodynamic technique.3.4 If this test method is followed using
13、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 eightdifferent laboratories that followed the standard procedureusing aluminum alloy 3003-H14 (UNS A93003). Eba
14、nd 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 fluorocarbon. It shouldhave ports for the insertion of a working electrode (1 cm2flat1This test method is under the
15、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 May 1, 2010. Published May 2010. Originallyapproved in 1989. Last previous edition approved in 2004 as G10089(
16、2004). DOI:10.1520/G0100-89R10E01.2The boldface numbers in parentheses refer to 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 informatio
17、n, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.specimen holder (Note 1) is very convenient), two auxiliaryelectrodes, salt bridge for reference electrode, and a ther
18、mom-eter or a thermostat probe for temperature control.The figure inTest Method G5 would be satisfactory, but a flat bottom cell isalso satisfactory provided that all of the essential ports areprovided. (See Ref (9) for details.)NOTE 1These specific recommendations and conditions were fol-lowed to i
19、mprove the interlaboratory 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 recordermay be replaced by a plotter if the current staircase signal isgenerated with the aid of a
20、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 is avail-able. The electrical equipment may be checked in accordancewith the procedure in Prac
21、tice G59.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 ElectrodeFor generating data to be com-pared to the reference data included herein, use type 3003-H14(
22、UNSA93003)A1 in sheet form. Cut 1.55 cm diameter circlesand prepare in accordance 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.
23、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 spectro-graphic supply companies.4.3.3 Reference ElectrodeSaturated calomel (Note 1). Itshould be checked against an
24、other reference which has notbeen exposed to test solutions and they should 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 soluti
25、on 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 replaced once eachday and the bridge tip immersed in this solution when not inuse. Any test solution that does not
26、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. Forexample, transfer 6.000 g reagent grade NaCl to a 2-Lvolumetric flask. Dissolve in ASTM Type IV water (deminer-aliz
27、ed or distilled) and dilute to the mark. (See SpecificationD1193.)5.2 Assemble 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 th
28、e 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 specimen withoutwhipping air bubbles into the solution.5.7 Apply a current staircase signal from 0 to 120 A/cm2using a step he
29、ight 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 (Note 4). In order to differentiate between thesteady-state potential values of the forward scan from those ofthe reverse sc
30、an, it would be helpful to (1) delay the actualreversal of the pen about 12 s after dropping from 120 to100 A/cm2so 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
31、 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 currentdensity given for each transient. The current is selected at the end of each4VYCOR is a trademark of Corning Incorporated, One Ri
32、verfront Plaza,Corning, NY 14831, Code No. 7930 glass.FIG. 1 Schematic Wiring Diagram for GalvanostaircasePolarizationG100 89 (2010)12step (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 whic
33、h is a discrete current value at each end of the lowercurve. In 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.5.8 ExtrapolationExtrapolate the up-step points to zerocurrent to
34、 obtain Eb. Similarly, extrapolate the down-steppoints to obtain Eprot. Fig. 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 duplica
35、te 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 for Eprotand 7.3 mV for Ebin terms of the pooled standard deviation.(See No
36、te 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. 2 and Fig. 3, typicalquasi-stationary galvanostatic polarization plots are obtained.However, the kinetic and noise information derived
37、from thevoltage transients are desirable attributes of GSCP.NOTE 5The standard deviation was derived from:S25(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.The pooled standard deviation was derived from:Spooled!25(i 5 1KJ1i2 J2i!22
38、K(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; polarizationFIG. 2 Cyclic GSCP Curve of 3003 A1 in 3000 ppm NaCl(Taken from Ref 7)FIG. 3 Relat
39、ionship of a Schematic GSCP Curve (lower) to theCurrent Staircase Signal (upper)G100 89 (2010)13REFERENCES(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
40、 Acid as Determinedby Potentiodynamic, Galvanostaircase and the Zap-GalvanostaircaseTechnique,” 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, 1
41、986, p. 32.(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-nique for the Investigation of Localized Corrosion,” Paper #48 at the
42、Electrochemical 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, Hausler, R. H., Editor, NACE, Houston,1988.(8) Hirozawa, S. T., “Corrosion Monitoring by Galvanosta
43、ircase Polariza-tion,” in Electrochemical Techniques for Corrosion Engineering,Baboian, R., Editor, NACE, Houston, 1986.(9) Hirozawa, S. T., “Current Versus Voltage Hysteresis: Effect onElectrometric Monitoring of Corrosion,” Laboratory Corrosion Testsand Standards, ASTM STP 866, Haynes, G. S., and
44、Baboian, R.,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 patent rights asserted in connection with any item mentionedin thi
45、s 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 revision at any time by the responsible technical committee and must be
46、 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 comments will receive careful consideration at a meeting of theresp
47、onsible 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 copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, We
48、st 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).G100 89 (2010)14
