1、Designation: D 4940 98 (Reapproved 2003)Standard Test Method forConductimetric Analysis of Water Soluble IonicContamination of Blasting Abrasives1This standard is issued under the fixed designation D 4940; the number immediately following the designation indicates the year oforiginal adoption or, in
2、 the case of revision, the year of last 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 describes a procedure for rapid evalu-ation of abrasives for the
3、presence of ionic contamination bydetermining the total concentration of water soluble ioniccontaminants by means of a conductivity test.1.2 This test method does not identify the ionic speciespresent nor provide quantitative results on each species.1.3 This test method is based on a volume comparis
4、onamong abrasives of similar sizes. A volume comparison ismore closely related to surface area of the abrasives than is aweight comparison.1.4 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
5、 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 1193 Specification for Reagent Water2E 832 Specification for Laboratory Filter Papers32.2 Other Standard:ISO 11127-6 Preparation of
6、Steel Substrates before Appli-cation of Paints and Related Products - Test Methods forNon-Metallic Blast Cleaning Abrasives - Part 6: Determi-nation of Water-Soluble Contaminants by ConductivityMeasurement42.3 SSPC: The Society for Protective CoatingsSSPC-AB 1 “Specification for Mineral and Slag Abr
7、asives53. Summary of Test Method3.1 Abrasive and pure water are combined into a slurry thatis stirred to leach the soluble salts from the abrasive. Thisslurry is filtered and conductance of the filtrate is measured.The conductivity, which is related to the concentration ofsoluble ionic materials con
8、taminating the abrasive surface, iscalculated from the conductance and the cell constant.4. Significance and Use4.1 By-product abrasives manufactured from slags that areair cooled or quenched with pure water, normally contain lowconcentrations of ionic materials, as do mined mineral abra-sives. Howe
9、ver, slags quenched with seawater or other con-taminated water, contain high amounts of ionic material asdoes seashore sand. This contamination of the abrasive cantransfer to the steel surfaces being blasted, where it mayaccelerate corrosion. This test is useful in establishing thecleanliness of the
10、 abrasive at the jobsite.4.2 This test method provides a value that indicates theconcentration of total water soluble ions based on theirelectrolytic mobility. Thus, it provides an indication of ioniccorrosion potential.NOTE 1A typical value of conductivity for a high level of contami-nation is 500
11、mho/cm. A typical value for a low level of contaminationis 50 mho/cm.5. Apparatus5.1 Conductivity Bridge and CellAny commercial con-ductivity bridge and conductivity cell having a range of at least5 mho/cm to 1 000 000 mho/cm and temperature compen-sation capability is satisfactory. Either a dip-typ
12、e, pipet-type, orcup-type cell may be used. A means of adjusting for tempera-ture or controlling the temperature is essential. While someinstruments have an adjustment to compensate for temperature,one means is to use a 25C constant temperature bath. Anothermethod is to stir the solution with a clea
13、n thermometer whilethe vessel is warmed or cooled by an external source.NOTE 2ISO 11127-6 is another method for assessing the level ofsoluble salt contamination present in an abrasive. It differs from this testmethod in two major areas:(1) The ISO method uses a weight to volume ratio between the abr
14、asiveand the fluid (deionized water) used to extract soluble salts from theabrasive. The ASTM method allows a user to measure a loose packedvolume of abrasive and mix that abrasive with an equal volume of reagentwater. The ISO method is well suited to use in a laboratory setting but ispoorly suited
15、to use in the field. The ASTM method is well suited for usein the field or laboratory.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.46 on Industrial Protective Coatings.C
16、urrent edition approved January 10, 2003. Published March 2003. Originallyapproved in 1989. Last previous edition approved in 1998 as D 4940 - 98.2Annual Book of ASTM Standards, Vol 11.01.3Annual Book of ASTM Standards, Vol 14.04.4Available from American National Standards Institute, 13th Floor, 11
17、W. 42ndSt., New York, NY 10036.5Available from SSPC: The Society for Protective Coatings, 40 24th St.,Pittsburgh, PA 15222.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.(2) The ISO method reports the effect of the level of extracte
18、d salts interms of milliSiemens/m, whereas this test method uses mho/cm. TheISO method uses strict SI units, this test method reports using SIcompliant units.Method to Method Comparison:The reader is warned that it is difficult to make direct comparisonsbetween the results of these two different met
19、hods of analysis.Weight/Volume versus Volume/Volume Method Considerations:In the ASTM Method the weight of the abrasive is not known; thismakes it impossible to assess the ratio between conductivity valuesdetermined using this test method procedure and those determined usingthe ISO 11127-6 procedure
20、.Comparisons Between Reported Units for Each Method:An independent study by SSPC showed that the relative order ofextracted salts using each type of procedure on abrasive materials wasidentical. The ranked order correlation between the two methods wasunity. There was no direct correlation possible b
21、etween numerical resultsobtained and reported by the two different methods. Abrasives thatshowed qualifying extracted salts using the ISO Procedure also showedqualifying extracted salt levels as specified in SSPC-AB 1.Converting from ISO Reported Units to ASTM Reported Units:Converting from one unit
22、 base to another is not useful as the twomethods differ in process. The conversion factor from mho/cm tomilliSiemens/m is as follows:A Micro Mho Per Centimetre1mhocm1(1 3 106) V1cm1A MilliSiemen Per Metre1 (MilliSiemen)(m1)=(13103) V1100 cm1Thus one milliSiemen/m = ten mho/cm.5.2 Filter Paper, confo
23、rming to Specification E 832, Type1, Class C, to keep silt from fouling the surfaces of theconductivity cell.6. Reagents and Materials6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of
24、the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.6Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.6.2 Purity of Wat
25、erUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Type IV of Specification D 1193.6.3 Potassium Chloride (KCl or 0.02 N KCl solution).7. Sampling7.1 Sampling shall be as follows unless otherwise agreedupon between the purchaser and the seller. Ta
26、ke two 1-Lsamples of abrasive at random from different packages of eachlot, batch, days pack, or other unit of production in theshipment. When no markings distinguishing between units ofproduction appear, take samples from the different packages inthe ratio of two samples for each 5000 kg, except th
27、at forshipments of less than 5000 kg, take two samples. Test thesamples separately.8. Calibration and Standardization8.1 Determination of Cell Constant:8.1.1 The conductivity cell will come with a predeterminedconstant. This constant should be checked periodically, onemethod being as follows:8.1.1.1
28、 Prepare a standard solution such as a 0.0005 Nsolution of KCl by diluting a 0.02 N KCl solution with wateror by dissolving 0.0372 g of KCl (weighed after heating for 1h at 105C) in water, followed by dilution to 1 L. Cool andmeasure the conductance at 25C as described in Section 9.Calculate the cel
29、l constant, K25, as follows:K255 Cs/Cm!(1)where:Cm= conductance, measured at 25C (see 10.1), mho,andCs= conductivity, 72 mho/cm (from Table 1).NOTE 3In general the cell constant is not greatly affected by varia-tions in the strength of the KCl solution, but, for greater accuracy,measurements should
30、be made at or near the specific conductivity of thesolution to be measured and at values that use the middle range of thescale of the conductivity bridge, using the same multiplier tap.8.1.2 Table 1 gives values of specific conductivities forcorresponding KCl solution concentrations which are useful
31、for abrasive testing.9. Procedure9.1 Preparation of a Slurry Filtrate:9.1.1 Rinse beakers, stirring rods, and funnels with reagentwater until tests show the rinse water has a conductivity of 5.0mho/cm or less.9.1.2 Add 300 mL of water to 300 mL of abrasive and stirfor 1 min with a stirring rod. Let
32、stand for 8 min and then stiragain for 1 min.9.1.3 Filter sufficient supernatant liquid for tests, discardingthe first 10 mL of the filtrate. The amount of supernatant liquidfiltered shall be sufficient to cover the cell.9.1.4 Rinse the conductivity cell in reagent water until therinse water is a cl
33、eanliness of 5.0 mho/cm or less.9.1.5 Rinse the conductivity cell two or three times with thefiltrate then determine conductance at 25C in accordance withthe operating instructions of the instrument. Use successiveportions of the sample until a constant value is obtained.6Reagent Chemicals, American
34、 Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.
35、S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE 1 Specific Conductivities for Potassium Chloride (KCl)Concentrations at 25CNormalityHeated, Dry KCl/ReagentWater Solution, g/LKCl Conductivity,mho/cm0.0005 0.0373 720.001 0.0746 1470.005 0.3728 7180.01 0.7455 1414D 4940 98 (2003)210. Calcu
36、lation10.1 Calculate the specific conductivity of the abrasive asfollows:Cs5 Cm3 K25(2)11. Report11.1 Report the following information:11.1.1 The calibration value of the cell constant (both asmeasured and as predetermined and supplied with the conduc-tivity cell), the date, and the name of the pers
37、on checking thecalibration.11.1.2 The material, date, readings, and mean in mho/cmalong with name of person conducting the tests and identifi-cation of the apparatus.12. Precision and Bias712.1 PrecisionOn the basis of five replicate interlabora-tory tests of this test method in which three operator
38、s in threelaboratories analyzed, in duplicate, six blasting abrasivescontaining ionogenic contamination, the within-laboratory co-efficient of variation (after rejecting results from one set ofreplicate tests as outliers), was found to be 1.7 % with 20degrees of freedom (df) and the between-laborato
39、ry standarddeviation coefficient of variation was found to be 7.4 % with 15df. Based on these coefficients, the following criteria should beused for judging the acceptability of results at the 95 %confidence level:12.1.1 RepeatabilityTwo results, each the mean of tworuns obtained by the same operato
40、r should be consideredsuspect if they differ by more than 5 % relative.12.1.2 ReproducibilityTwo results, each the mean of tworuns, obtained by operators in different laboratories should beconsidered suspect if they differ by more than 22 % relative.12.2 Bias:12.2.1 Bias can be present because of th
41、e mobility ofvarious ions. The hydrogen ion has a much greater mobilitythan the hydroxyl ion or other ions so that at low pHs theconductivity will be relatively higher than at high pHs for thesame ionic concentration. However, the bias introduced by thisfactor is in the proper direction. That is, hi
42、gh conductivity dueto a lower pH of the contamination would normally indicategreater corrosion potential.12.2.2 A bias may be introduced by extraneous contamina-tion or from reduced sensitivity of instruments for low levels ofcontamination in the range of conductivity between 0 and 30mho/cm.13. Keyw
43、ords13.1 abrasive; analysis; blasting; chloride; conductimetric;conductivity; contamination; interlaboratory testing; iono-genic; precision; salts.; steel surfacesASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this s
44、tandard. 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 re
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46、ible 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
47、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).7Supporting data available fromASTM International Headquarters. Request RR:D01-1061.D 4940 98 (2003)3
