1、Designation:D371885a(Reapproved 2015)Standard Test Method forLow Concentrations of Chromium in Paint by AtomicAbsorption Spectroscopy1This standard is issued under the fixed designation D3718;the number immediately following the designation indicates the year oforiginal adoption or,in the case of re
2、vision,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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method co
3、vers the determination of the contentof chromium(including chromium oxide)in the range between0.005 and 1.0%present in the solids of liquid coatings or indried films obtained from previously coated substrates.Thereis no reason to believe that higher levels could not bedetermined by this test method,
4、provided that appropriatedilutions and adjustments in specimen size and reagent quan-tities are made.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 a
5、ny,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.Specific hazardstatements are given in Section 7.2.Referenced Documents2.1 ASTM Standards:2D11
6、93 Specification for Reagent WaterD2832 Guide for Determining Volatile and Nonvolatile Con-tent of Paint and Related Coatings3.Summary of Test Method3.1 The sample of liquid coating or dried film is preparedfor analysis by dry ashing at 500C followed by digestion withpotassium permanganate and sulfu
7、ric acid in a polytetrafluo-roethylene(PTFE)-lined acid decomposition vessel at anelevated temperature.The chromium in the filtered digestionmixture is determined by atomic absorption spectroscopy.4.Significance and Use4.1 The permissible level of heavy metals in certain coat-ings is specified by go
8、vernmental regulatory agencies.This testmethod provides a fully documented procedure for determininglow concentrations of chromium present in both water-andsolvent-reducible coatings to determine compliance.5.Apparatus5.1 Atomic Absorption Spectrophotometer,consisting of anatomizer and either a sing
9、le-or three-slot burner;gas pressure-regulating and metering devices for nitrous oxide(N2O)andacetylene;a chromium hollow cathode lamp with a regulatedconstant current supply;a monochromator and associatedoptics;a photosensitive detector connected to an electronicamplifier;and a readout device.5.2 M
10、uffle Furnace,maintained at 500 6 10C.5.3 Force-Draft Oven,maintained at 105 6 2C.5.4 Acid Decomposition Vessel,with PTFE digestion cup.35.5 Hot Plate,with variable surface temperature controlover the range from 70 to 200C.5.6 Volumetric Flasks,50,100 and 1000-mL.5.7 Pipets,5,10,15,and 20-mL capacit
11、y.5.8 Filter Paper,ashless,medium filtering 15-cm.5.9 Paint Shaker.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.21 on Chemical Analysis of Paints and Paint Materials.Curre
12、nt edition approved June 1,2015.Published June 2015.Originallyapproved in 1978.Last previous edition approved in 2010 as D3718 85a(2010).DOI:10.1520/D3718-85AR15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of A
13、STMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The sole source of supply of an acid decomposition cup,(Catalog Number4745),known to the committee at this time is the Parr Instrument Co.,211Fifty-third St.,Moline,IL 61265.If you are aware of alternati
14、ve suppliers,pleaseprovide this information to ASTM International Headquarters.Your comments willreceive careful consideration at a meeting of the responsible technical committee,1which you may attend.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.Unit
15、ed States1 5.10 Crucibles,wide form,porcelain,approximately 30-mLcapacity.45.11 Mortar and Pestle.5.12 Paint Draw-Down Bar.6.Reagents6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended thatall reagents shall conform to the specifications
16、of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.5Other grades may beused,provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.6.2 Purity of WaterUnless otherwise indicated,referencesto water shall be understood to mean reagent water conformingto Type II of Specification D1193.6.3 Chromium Standard Stock Solution(1 mg/mL)Dissolve 3.735 g