1、Designation: D4940 10Standard Test Method forConductimetric Analysis of Water Soluble IonicContamination of Blasting Abrasives1This standard is issued under the fixed designation D4940; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio
2、n, 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 describes a procedure for rapid evalu-ation of abrasives for the presence of ionic con
3、tamination 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 comparisonamong abrasives of
4、similar sizes. A volume comparison ismore closely related to surface area of the abrasives than is aweight comparison.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesa
5、fety 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:2D1193 Specification for Reagen
6、t WaterE832 Specification for Laboratory Filter Papers2.2 Other Standard:ISO 11127-6 Preparation of 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 ConductivityMeasur
7、ement32.3 SSPC: The Society for Protective CoatingsSSPC-AB 1 Specification for Mineral and Slag Abrasives43. 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 filtrat
8、e is measured.The conductivity, which is related to the concentration ofsoluble ionic materials contaminating 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
9、 water, normally contain lowconcentrations of ionic materials, as do mined mineral abra-sives. However, 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 b
10、lasted, where it mayaccelerate corrosion. This test is useful in establishing thecleanliness of the 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 ionicc
11、orrosion potential.NOTE 1A typical value of conductivity for a high level of contami-nation is 500 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 typically having a rangeof at
12、least 5 mho/cm to 10 000 mho/cm is satisfactory. Eithera dip-type, pipet-type, or cup-type cell may be used. A meansof adjusting for temperature or controlling the temperature isessential. While some instruments have an adjustment tocompensate for temperature (automatic temperature compen-sation), o
13、ne means is to use a 25C constant temperature bath.Another method is to stir the solution with a clean thermometerwhile the vessel is warmed or cooled by an external source.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and
14、 is the direct responsibility ofSubcommittee D01.46 on Industrial Protective Coatings.Current edition approved June 1, 2010. Published June 2010. Originallyapproved in 1989. Last previous edition approved in 2003 as D4940 - 98 (2003).DOI: 10.1520/D4940-10.2For referenced ASTM standards, visit the AS
15、TM 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.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 1003
16、6, http:/www.ansi.org.4Available from Society for Protective Coatings (SSPC), 40 24th St., 6th Floor,Pittsburgh, PA 15222-4656, http:/www.sspc.org1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.NOTE 2ISO 11127-6 is another method for
17、 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 abrasiveand the fluid (deionized water) used to extract soluble salts from theabrasive. The ASTM method allows a u
18、ser 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 to use in the field. The ASTM method is well suited for usein the field or laboratory.(2) The ISO method report
19、s the effect of the level of extracted 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 t
20、he results of these two different methods 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 dete
21、rmined usingthe ISO 11127-6 procedure.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
22、 was no direct correlation possible between 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 Re
23、ported Units:Converting from one unit 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
24、 = ten mho/cm.5.2 Filter Paper, conforming to Specification E832, Type 1,Class C, to keep silt from fouling the surfaces of the conduc-tivity cell.6. Reagents and Materials6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reag
25、ents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.5Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy
26、 ofthe determination.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Type IV of Specification D1193.6.3 Potassium Chloride (KCl or 0.02 N KCl solution).7. Sampling7.1 Sampling shall be as follows unless otherwise agreedupon bet
27、ween the purchaser and the seller. Take 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 tw
28、o samples for each 5000 kg, except that 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 periodicall
29、y, onemethod being as follows:8.1.1.1 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 des
30、cribed in Section 9.Calculate the cell 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
31、greater accuracy,measurements should 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 sol
32、ution concentrations which are usefulfor 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 st
33、irfor 1 min with a stirring rod. Let 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.5Reagent Chemicals, American Chemical Soci
34、ety 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.S. Pharmacopei
35、al 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 1414D4940 1029.1.4 Rinse the conductivity ce
36、ll in reagent water until therinse water is a cleanliness 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 constan
37、t value is obtained.10. Calculation10.1 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 d
38、ate, and the name of the person 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 Bias612.1 PrecisionOn the basis of five replicate interlabora-tory tests of this test m
39、ethod in which three operators 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
40、(df) and the between-laboratory 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
41、 obtained by the same operator 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
42、 can be present because of the 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
43、proper direction. That is, high 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 be
44、tween 0 and 30mho/cm.13. Keywords13.1 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 wit
45、h 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 techn
46、ical 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 considerati
47、on 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 Har
48、bor 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).6Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D01-1061.D4940 103
