# ASTM G180-13

Designation: G180 − 13Standard Test Method forCorrosion Inhibiting Admixtures for Steel in Concrete byPolarization Resistance in Cementitious Slurries1This standard is issued under the fixed designation G180; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, 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 test method covers a procedure for determining theeffects of chemical admixtures on the corrosion of metals inconcrete. This test method can be used to evaluate materialsintended to inhibit chloride-induced corrosion of steel inconcrete. It can also be used to evaluate the corrosivity ofadmixtures by themselves or in a chloride environment. Thistest is not applicable for emulsions.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 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 Documents2.1 ASTM Standards:2C150 Specification for Portland CementC670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsD632 Specification for Sodium ChlorideE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodG3 Practice for Conventions Applicable to ElectrochemicalMeasurements in Corrosion TestingG5 Reference Test Method for Making PotentiodynamicAnodic Polarization MeasurementsG59 Test Method for Conducting Potentiodynamic Polariza-tion Resistance MeasurementsG193 Terminology and Acronyms Relating to Corrosion3. Terminology3.1 Definitions—For definitions of terms used in this prac-tice see Terminology G193.4. Significance and Use4.1 This test method provides a means for assessingcorrosion-inhibiting concrete admixtures.4.2 This test method is useful for development of admix-tures intended to reduce corrosion of reinforcing steel inconcrete.4.3 This test method is useful in determining the corrosivityof admixtures toward steel reinforcing if the admixture sampleis compared to a control without admixtures.4.4 Good performance, a reduction in corrosion rate versuschloride alone by at least one order of magnitude in this test, isa strong indication that an admixture is a corrosion inhibitor.However, poor performance requires additional testing todetermine if the admixture improves corrosion resistance.4.5 This test method shall not be used to predict perfor-mance in the field.4.6 The filtering process makes this test not suitable for theevaluation of emulsions.5. Apparatus5.1 The test cell as described in Test Method G5.5.2 Potentiostat, as described in Test Method G5, capable ofvarying potential at a constant scan rate and measuring theresulting current.5.3 A method of recording the varying potential and result-ing current is needed.5.4 Electrode holder such as described in Fig. 3 of TestMethod G5.5.5 Electrodes:5.5.1 Working electrode, prepared from a 12.7 mm length of9.5 mm diameter rod stock. Carbon steel C1215 should beused.NOTE 1—If specimen forms are used other than those called for by thistest method, for example flat sheet specimens, care should be taken not tointroduce crevices which can lead to erroneous results.1This test method is under the jurisdiction of ASTM Committee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G01.14 onCorrosion of Metals in Construction Materials.Current edition approved May 1, 2013. Published May 2013. Originallyapproved in 2004. Last previous edition approved in 2007 as G180 – 07. DOI:10.1520/G0180-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.6 Auxiliary Electrodes—Two graphite rods or platinized-niobium or platinum mesh.5.7 Reference Electrodes—A saturated calomel electrodewith a controlled rate of leakage (about 3 µL/h) is recom-mended.6. Reagents and Materials6.1 Type I/II cement (C3A content between 6 and 10 %),according to Specification C150.6.2 Filter paper with 1.1 µm retention.6.3 PTFE stir bars.6.4 Carbon steel C1215 samples, cylindrical in shape, with5.1 cm2exposed area.36.5 Sodium chloride, reagent grade, according to Specifica-tion D632.6.6 Calcium hydroxide, reagent grade.6.7 Admixtures to be tested.6.8 Carbon dioxide free compressed air.47. Experimental Procedure7.1 Prepare a cement slurry consisting of 1000 g of waterand 200 g cement. Mix thoroughly, stir for 60 min and filter.NOTE 2—An admixture should be added at a quantity consistent with itsaddition rate in concrete. Water measured at 35 to 965 mL is equivalent to5 L/m3in concrete. If other dosages are desired, proportion them based onthis ratio.7.2 Filter, and add 4 g/Lcalcium hydroxide and stir a further30 min.7.3 Setup a standard electrochemical cell according to TestMethod G5 and fill it with 900 mL of filtered slurry solution.Purge the cell with carbon dioxide free air.Air flow rate shouldbe at least 300 cc/min.7.4 Degrease the metal sample by cleaning ultrasonically inhexane for 2 min. If an ultrasonic bath is not available, soak thesamples in hexane and wipe dry. Make sure the sample isthoroughly dried before mounting it on the electrode holder.7.5 While purging the cell with carbon dioxide free air,precondition the electrode in the solution for 24 h.7.5.1 Add NaCl to the solution obtained in 7.3 (having beenpurged for 24 h with CO2-free air), to obtain a 0.5 or a 1Msolution, and continue to stir and purge for a further 4 h. After4 h, stop stirring and continue purging for a another 20 h.NOTE 3—The multi-laboratory test was run at the two different chloridelevels to develop the precision statement. The higher chloride level wouldbe representative of a more severe exposure.7.5.2 Measure the open circuit potential.7.5.3 Measure the polarization resistance (Rp) by recordingthe potentiodynamic polarization curve at a scan rate of0.167 mV/s, from –20 mV to +20 mV versus open circuitpotential.7.5.4 Plot the polarization resistance curve as a linearpotential-current density plot as shown in Practice G3.7.5.5 Determine the polarization resistance Rp, as the tan-gent of the curve at i = 0, as described in Test Method G59. Thecorrosion rate is expressed as 1/Rpin µS/cm2.NOTE 4—An example of a polarization resistance curve is given in Fig.X1.4.8. Interpretation of Results8.1 An admixture is behaving as a corrosion inhibitor in thistest method if the average log10(1/Rp) value is 1.0 or less thanthat of the chloride only average.8.2 If the admixture does not reduce average 1/Rpby anorder of magnitude another test method is needed to determineif it is an inhibitor.8.3 An admixture that increases average 1/Rpby an order ofmagnitude over a slurry without chloride or inhibitor iscorrosive.NOTE 5—The change in log10(1/Rp) by 1.0 is an order of magnitudechange in 1/Rp. Log values are useful in comparing corrosion rates sincerates from different specimens or conditions can differ by orders ofmagnitude making a linear scale less useful.9. Report9.1 Report the following information:9.1.1 Value of the open circuit potential (OCP) versus SCE,and9.1.2 Corrosion rate given by 1/Rpin µS/cm2.10. Precision and Bias510.1 Based on the pooled estimates of precision, the follow-ing statement of precision and bias can be made:10.1.1 Interlaboratory Test Program—An interlaboratorystudy of a pore solution test for corrosion inhibiting admixturesfor steel reinforcement in concrete was conducted in 2001.Each of six laboratories tested two randomly drawn samples ofeach of four materials (two sodium chloride solutions, 0.5Mand 1.0M, each with and without 35 mL/L of a solutioncontaining 30 % calcium nitrite). Practice E691 was followedfor the design and analysis of the study.10.1.2 Single-Operator Precision—The single operatorstandard deviation of the logarithm to the base 10 of a singletest result is 0.36. Therefore, log10(1/Rp) values of two properlyconducted tests by the same operator should not differ by morethan 1.0.10.1.3 Interlaboratory Precision—The interlaboratory stan-dard deviation of the logarithm to the base 10 of a single testresult is 0.44. Therefore, log10(1/Rp) values of two properlyconducted tests in different laboratories should not differ bymore than 1.24.3The sole source of supply of the apparatus known to the committee at this timeis Metal Samples,AL, sample type P/N410. If you are aware of alternative suppliers,please provide this information to ASTM International Headquarters. Your com-ments will receive careful consideration at a meeting of the responsible technicalcommittee,1which you may attend.4ACO2free air gas generator (typically used for FT-IR equipment) can be used.5Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:G01-1021.G180 − 132NOTE 6—These numbers represent, respectively, the (1s) and (2ds)limits as described in Practice C670.10.2 Bias—Since there is no accepted reference materialsuitable for determining the bias in this test method, nostatement on bias is made.11. Keywords11.1 admixtures; cement; corrosion inhibitors; slurry; solu-tionAPPENDIX(Nonmandatory Information)X1. PRECISION CALCULATIONSX1.1 Information on the precision of the results obtained bythis test method was derived from an interlaboratory test withtwo samples for each molarity tested, per laboratory. Sixlaboratories participated in the study. Statistical analysis of thedata was performed using Practice E691 Interlaboratory DataAnalysis Software. Results are shown in the attached Table Afor 1/Rpmeasurements. Values of repeatability (Sr, r), andreproducibility (SR, R) are for the logarithm (base 10) of 1/Rp,where Sr, r, SR, and R are defined as follows:Sr= repeatability standard deviation [log(µS/cm2] (1s),r = 95 % repeatability limit within a laboratory [log(µS/cm2] (2ds),SR= reproducibility standard deviation [log(µS/cm2] (1s),andR = 95 % reproducibility limit between laboratories[log(µS/cm2] (2ds).X1.2 This study meets the minimum requirements for de-termining precision prescribed in Practice E691 in terms of thenumber of laboratories, materials and determinations (seeTable X1.1).X1.3 Fig. X1.1 is a graph of r and R versus average [log10(1/Rp) + 1]. Because the ASTM data analysis software does notaccept negative numbers, a value of 1 was added to everylog10(1/Rp) value. Adding a constant to all values does notchange the standard deviation estimates. It does, however,change the calculated averages. In Table X1.1, the averagevalues were corrected by subtracting 1 from the softwareoutput. In Fig. X1.1, the average values were not corrected.There is no indication that precision varies systematically withaverage level. Therefore, pooled estimates of precision weredetermined which should be valid over the range of 1/Rpencompassed in the interlaboratory study.X1.4 The consistency statistics for log10(1/Rp) by laboratoryand by material, are shown in Figs. X1.2 and X1.3, respec-tively. The h statistic examines consistency of test results fromlaboratory to laboratory. The k statistic examines consistencyof within-laboratory precision from laboratory to laboratory. Inthese plots, the horizontal lines are the critical values for h andk at the 0.5 % statistical significance level. There are a coupleof excursions beyond the critical values for h or k in each plot,but there are no consistent patterns of concern in the plots.Therefore, the data appear consistent for purposes of thisanalysis.X1.5 Fig. X1.4 is an example of a polarization resistancecurve.TABLE X1.1 Statistical Analysis of Corrosion Potential DataPractice E691 Interlaboratory Data Analysis SoftwareThe number of laboratories, materials, and determinations in this study DOESmeet the minimum requirements for determining precision prescribed in Prac-tice E691:ThisStudyPractice E691MinimumLaboratories 6 6Materials 4 3Determinations 2 2Precision Statement for Test MethodPrecision and Reproducibility of Log10(1/Rp) for Each MaterialPrecision, characterized by repeatability (Sr, r) and reproducibility (SR, R) hasbeen determined for the materials to be:Material Average SrSRrR(All dimensions are Log10(µS/cm2)0.5M NaCl 1.65 0.38 0.59 1.05 1.640.5M NaCl + Ca(NO2)20.42 0.34 0.40 0.95 1.111.0M NaCl 1.66 0.17 0.23 0.49 0.661.0M NaCl + Ca(NO2)20.49 0.43 0.43 1.20 1.20Precision and Reproducibility of Log10(1/Rp) Pooled Over All MaterialsAverage SrSRrR(All dimensions are Log10(µS/cm2)1.06 0.36 0.44 1.00 1.24where:Sr= repeatability standard deviationr = 95 % repeatability limit (within laboratory)SR= reproducibility standard deviationR = 95 % reproducibility limit (between laboratories)G180 − 133FIG. X1.1 r and R versus Material AveragesAnalysis: Log10(1/Rp)+1G180 − 134FIG. X1.2 Consistency Statistics by LaboratoryAnalysis: Log10(1/Rp)+1FIG. X1.3 Consistency Statistics by MaterialAnalysis: Log10(1/Rp)+1G180 − 135ASTM 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 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 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 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 copyrighted 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 service@astm.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/).FIG. X1.4 Polarization Resistance CurveG180 − 136