ASTM_D_7378_-_10.pdf

Designation:D737810Standard Practice forMeasurement of Thickness of Applied Coating Powders toPredict Cured Thickness1This standard is issued under the fixed designation D7378;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 practice describes the thickness measurement ofdry coating powders applied to a variety of rigid substrates.Use of some of these procedures may require repair of thecoating powder.This practice is intended to supplement themanufacturers instructions for the operation of the gages andis not intended to replace them.It includes definitions of keyterms,reference documents,the significance and use of thepractice,and the advantages and limitations of the instruments.1.2 Three procedures are provided for measuring dry coat-ing powder thickness:1.2.1 Procedure AUsing rigid metal notched(comb)gages.1.2.2 Procedure BUsing magnetic or eddy current dryfilm thickness gages.1.2.3 Procedure CUsing non-contact ultrasonic powderthickness instruments.1.3 Coating powders generally diminish in thickness duringthe curing process.Some of these procedures therefore requirea reduction factor be established to predict cured film thicknessof powder coatings.1.4 Procedure A and Procedure B measure the thickness(height or depth)of the applied coating powders in thepre-cured,pre-gelled state.By comparing results to the mea-sured cured powder thickness in the same location,a reductionfactor can be determined and applied to future thicknessmeasurements of the same coating powder.1.5 Procedure C results in a predicted thickness value of thecured state based on a calibration for typical coating powders.If the powder in question is not typical then an adjustment canbe made to align gage readings with the actual cured values asdetermined by other measurement methods.1.6 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.7 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:2D4138 Practices for Measurement of Dry Film Thickness ofProtective Coating Systems by Destructive,Cross-Sectioning MeansD6132 Test Method for Nondestructive Measurement of DryFilm Thickness of Applied Organic Coatings Using anUltrasonic Coating Thickness GageD7091 Practice for Nondestructive Measurement of DryFilm Thickness of Nonmagnetic Coatings Applied toFerrous Metals and Nonmagnetic,Nonconductive Coat-ings Applied to Non-Ferrous Metals3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 accuracy,nthe measure of the magnitude of errorbetween the result of a measurement and the true thickness ofthe item being measured.3.1.2 adjustment,nthe physical act of aligning a gagesthickness readings to match those of a known thickness sample(reduction of bias)in order to improve the accuracy of the gageon a specific surface,within a specific portion of its measure-ment range or to specific operating conditions.3.1.2.1 DiscussionAn adjustment will affect the outcomeof subsequent readings.3.1.3 coating powders,nfinely divided particles of resin,either thermoplastic or thermosetting,generally incorporatingpigments,fillers,and additives and remaining finely dividedduring storage under suitable conditions,which,after fusingand possibly curing,give a continuous film.1This practice is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.51 on Powder Coatings.Current edition approved Dec.1,2010.Published January 2011.Originallyapproved in 2007.Last previous edition approved in 2007 as D7378 07.DOI:10.1520/D7378-10.2For 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 3.1.4 calibration,nthe high-level,controlled and docu-mented process of obtaining measurements on traceable cali-bration standards over the full operating range of the gage,thenmaking the necessary gage adjustments(as required)to correctany out-of-tolerance conditions.3.1.4.1 DiscussionCalibration of coating thickness gagesis performed in a controlled environment using a documentedprocess by the equipment manufacturer,an authorized agent,orby an authorized,trained calibration laboratory.The outcomeof the calibration