1、Designation: D4940 15Standard Test Method forConductimetric Analysis of Water Soluble IonicContamination of Blast Cleaning 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 r
2、evision, 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 assessingblast cleaning abrasives for the presence of
3、conductive-potential, ionic contaminants by determining the total concen-tration of water soluble conductive species using a conductivitytest.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 com
4、parisonamong abrasives of 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 purpo
5、rt 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:2D119
6、3 Specification for Reagent WaterE832 Specification for Laboratory Filter Papers2.2 Other Standard:ISO 11127-6 Preparation of Steel Substrates beforeApplica-tion of Paints and Related Products - Test Methods forNon-Metallic Blast Cleaning Abrasives - Part 6: Determi-nation of Water-Soluble Contamina
7、nts by ConductivityMeasurement32.3 SSPC: The Society for Protective Coatings:4SSPC-AB 1 Mineral and Slag AbrasivesSSPC-AB 2 Cleanliness of Recycled Ferrous Metallic Abra-siveSSPC-AB 3 Ferrous Metallic AbrasiveSSPC-AB 4 Recyclable Encapsulated Abrasive Media3. Summary of Test Method3.1 Abrasive and p
8、ure 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 contaminating the abrasive, is calcu-lated from the c
9、onductance and the cell constant.4. Significance and Use4.1 Abrasive media may contain ionic contamination natu-rally (for example, beach sand), from manufacturing (quench-ing with contaminated water), transportation, storage or use (inthe case of abrasive that is reused). Ionic contamination on the
10、abrasive may transfer to the surface during abrasive blastcleaning, resulting in potential osmotic blistering, acceleratedunderfilm corrosion and premature coating failure.4.2 This test method describes a shop/field procedure forassessing the level of conductive species on an abrasive.4.3 Abrasive s
11、tandards published by SSPC (AB) and ISO11126 provide tolerance levels for water soluble contaminantsof the abrasive.5. Apparatus5.1 Conductivity Bridge and CellAny commercial con-ductivity bridge and conductivity cell typically having a range1This test method is under the jurisdiction of ASTM Commit
12、tee D01 on Paintand Related Coatings, Materials, andApplications and is the direct responsibility ofSubcommittee D01.46 on Industrial Protective Coatings.Current edition approved Dec. 1, 2015. Published December 2015. Originallyapproved in 1989. Last previous edition approved in 2010 as D4940 10. DO
13、I:10.1520/D4940-15.2For 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 standards Document Summary page onthe ASTM website.3Available from American National Standard
14、s Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4Available from Society for Protective Coatings (SSPC), 40 24th St., 6th Floor,Pittsburgh, PA 15222-4656, http:/www.sspc.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19
15、428-2959. United States1of at least 5 mho/cm to 10,000 mho/cm with built-intemperature compensation is satisfactory. A dip-type, pipet-type, or cup-type cell may be used.5.2 Filter Paper, conforming to Specification E832, Type 1,Class C, to keep silt from fouling the surfaces of the conduc-tivity ce
16、ll.NOTE 1ISO 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 abrasiveand the fluid (deionized water) used to extract soluble salts fr
17、om 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 to use in the field. The ASTM method is well suited for usein the fie
18、ld or laboratory.(2) The ISO method reports 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 dif
19、ficult to make direct comparisonsbetween the 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
20、 this test method procedure and those determined 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 correlati
21、on between the two methods wasunity. There 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.Con
22、verting from ISO Reported Units to ASTM Reported 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 Centimeter1mhocm1(1106) 1cm1A MilliSiemen Per Meter1 (MilliSiemen)(m1) =
23、 (1103) 1100 cm1Thus one milliSiemen/m = ten mho/cm.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 the Committee onAnalytical Reagents of the American Chemi
24、cal 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 ofthe determination.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be
25、 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 between the purchaser and the seller. Take two 1-Lsamples of abrasive at random from different pac
26、kages 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 that forshipments of less than 5000 kg, take two samples. Te
27、st 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 Prepare a standard solution such as a 0.0005 Nsolution of
28、 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 cell constant, K25, as follows:K255 Cs/Cm! (1)where:Cm= condu
29、ctance, measured at 25C (see 10.1), mho, andCs= conductivity, 72 mho/cm (from Table 1).NOTE 2In general the cell constant is not greatly affected byvariations in the strength of the KCl solution, but, for greater accuracy,measurements should be made at or near the specific conductivity of thesolutio
30、n 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 usefulfor abrasive testing.9. Procedure9.1 Preparation of a Slur
31、ry 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 stand for 8 min and then stiragain for 1 min.9.1.3 Filter
32、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 Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of
33、 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. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE 1 Specific Conductivities for Potassium Chloride
34、 (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 1529.1.4 Rinse the conductivity cell in reagent water until therinse water is a cleanliness of 5.0 mho/cm or less.9.1.5 Rinse the
35、 conductivity cell two or three times with thefiltrate then determine conductance in accordance with theoperating instructions of the instrument. Use successive por-tions of the sample until a constant value is obtained.10. Calculation10.1 Calculate the specific conductivity of the abrasive asfollow
36、s: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 person checking thecalibration.11.1.2 The temperature from the conductivity
37、 meter.11.1.3 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 method in which three operators in threelaboratori
38、es analyzed, in duplicate, six blast cleaning abrasivescontaining ionic contamination, the within-laboratory coeffi-cient 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-laboratory standarddeviati
39、on 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 operator should be consid
40、eredsuspect 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 the mobility ofvario
41、us 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, high conductivity du
42、eto 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. Keywords13.1 abrasive;
43、 blast cleaning; chloride; conductimetric; con-ductivity; contamination; soluble saltsASTM 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 t
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