ASTM_D_6580_-_00_2009.pdf

Designation:D658000(Reapproved 2009)Standard Test Method forThe Determination of Metallic Zinc Content in Both ZincDust Pigment and in Cured Films of Zinc-Rich Coatings1This standard is issued under the fixed designation D6580;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 the determination by differentialscanning calorimetry of the metallic zinc content of bothzinc-dust pigment,and of dried films of zinc-rich coatings.This test method is applicable to both inorganic and organiczinc-rich coatings1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.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:2D521 Test Methods for Chemical Analysis of Zinc Dust(Metallic Zinc Powder)E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Summary of Test Method3.1 Samples of either zinc-dust pigment or of cured films ofzinc-rich coatings are ground in a mortar and pestle,thencarefully weighed into standard differential scanning calorim-etry(DSC)sample pans.The pans are then crimped shut,andanalyzed in a differential scanning calorimeter in a singledynamic heating step,ranging from 370 to 435C at 10C permin,under a nitrogen purge.The percent metallic zinc in thesample is determined by measuring the energy associated withthe endothermic peak near 419C caused by the melting of themetallic zinc,and comparing this value to the heat of fusion ofpure zinc.4.Significance and Use4.1 This test method is useful for determining the amount ofmetallic zinc in zinc dust pigment,and also in dried films ofboth inorganic and organic zinc-rich coatings.Test MethodsD521 is an appropriate method for analyzing zinc dust,but hasshortcomings when applied to samples of cured coatings.5.Interferences5.1 An increase or decrease in heating rate from thosespecified may slightly alter the results.However,the variationwould be expected to be minimal,so long as the zinc referencestandard and the samples are subjected to the same heatingrate.5.2 Daily calibration of the calorimeter with high purity zincfoil results in improved results.Reagent grade zinc granules orzinc powder are of insufficient purity to properly calibrate theinstrument.Furthermore,the high purity-zinc foil should onlybe used one time as a calibration standard.WarningUsingthe same piece of foil more than once can result in inaccurateresults,due to oxidation of the zinc at the high temperatures inthe calorimeter,coupled with the alloying effects of zinc withthe aluminum sample pans.5.3 Important steps in achieving accurate and reproducibleresults are very gentle tapping of the pan in order to distributethe sample evenly over the bottom of the pan,and carefulplacement of the pan lid to avoid expulsion of the fine powderduring crimping.NOTE1Round-robin testing has shown no evidence that pyrolysis ofthe binder interferes with the measurement of the heat of fusion.Eitherpyrolysis does not occur,occurs during stabilization of the instrumentprior to the scan,or is negligible due to the small amount of binder presentin such coatings.If there is reason to suspect interference from the binder,the analyst may wish to test a blank sample of binder(with no zincpigment)to ensure that there is no effect on heat flow measurements.6.Apparatus6.1 Differential Scanning Calorimeter,either of the heatflux or power compensation type,capable of heating rates up to1This 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.Current edition approved June 1,2009.Published June 2009.Originallyapproved in 2000.Last previous edition approved in 2005 as D6580 00(2005).DOI:10.1520/D6580-00R09.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 at least 10 6 1C/min and of automatic recording of differencein heat input between the sample and a reference material,tothe required sensitivity and precision.6.2 Sample Pans Aluminum or other metal pans of highthermal conductivity are appropriate.A method or instrumentfo