ASTM_D_8331_-_D_8331M_-_20.pdf

Designation:D8331/D8331M20Standard Test Method forMeasurement of Film Thickness of Thin-Film Coatings byNon-Destructive Means Using Ruggedized OpticalInterference1This standard is issued under the fixed designation D8331/D8331M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method encompasses measuring the film thick-ness of a coil coated organic coating layer.Operators can usethis method in process during the coating application or in alaboratory setting.1.2 This test method does not specify the expected filmthickness/test results for a coating,nor the specific“recipe”fileneeded to measure a coating.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system are not necessarily exact equivalents;therefore,toensure conformance with the standard,each system shall beused independently of the other,and values from the twosystems shall not be combined.1.4 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Terminology2.1 producer,nprimary manufacturer of the coil coatedmaterial,that is,the coil coater,from which parts are fabri-cated.2.2 recipe,na combination of specified settings in theRuggedized Optical Interference(ROI)measurement systemwhich is used by the instrument to interpret the reflectanceinformation gathered during a reading and provide an output ina specified unit of film thickness measurement.2.3 ruggedized optical interference(ROI),na term used todistinguish this instrument that is suitable for use in anindustrial environment from other optical interference devicesthat are only suitable for use in a laboratory environment.2.4 supplier,nthe organization or person contracted tosupply the coil coated material who may or may not be theproducer(that is,coil coater,service center,or other seller).2.5 user,nthe person or organization that makes use of thecoil coated product.3.Summary of Test Method3.1 An instrument is used to measure either a single paintlayer,like a primer,or the total film thickness of a multi-layerorganic coil coating system through a non-contact,non-destructive,ruggedized optical interference(ROI)method.3.2 It is recommended that this system only be used todetermine total system thickness if the optical propertiesbetween multiple layers are similar(for example,topcoat overprimer).Individual layers may be able to be distinguished if theoptical properties vary enough(for example,clear over pig-mented layer).4.Significance and Use4.1 Coating film thickness plays a critical role in theperformance of the final product.This includes physicalproperties(abrasion/scratch resistance,color,gloss),chemicalproperties(solvent resistance),corrosion resistance,and long-term durability(color change,chalk,fade).4.2 The non-destructive measurement system based on rug-gedized optical interference transforms signal outputs in coat-ing film thickness using digital formulas(or“recipes”)whichare reproducible from one instrument to another.4.3 The ROI measurement unit takes a significant number ofmeasurements which can be read in a determined period oftime and each of these data points is recorded and reportable.4.4 Due to the number of variables that can affect filmthickness during application and the number of variables thatmust be set in the measurement unit while determining a1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.53 on Coil Coated Metal.Current edition approved Aug.1,2020.Published September 2020.DOI:10.1520/D8331_D8331M-20.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1recipe,it is important for the producer and the user to agreeupon recipe settings depending on the coating system.5.Interferences5.1 Probe setup is o