ASTM_D_1400_-_00.pdf

Designation:D 1400 00Standard Test Method forNondestructive Measurement of Dry Film Thickness ofNonconductive Coatings Applied to a Nonferrous MetalBase1This standard is issued under the fixed designation D 1400;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(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the nondestructive measure-ment of the dry film thickness of electrically nonconductivecoatings applied over a nonferrous metal base using commer-cially available eddy current instruments.This test method isintended to supplement manufacturers instructions for themanual operation of the gages,and is not intended to replacethem.1.2 This test method is not applicable to coatings that willbe readily deformable under the load of the measuring instru-ments,as the instrument probe must be placed directly on thecoating surface to take a reading.1.3 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.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 and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:D 823 Practices for Producing Films of Uniform Thicknessof Paint,Varnish,and Related Products on Test Panels2D 1730 Practices for Preparation of Aluminum andAluminum-Alloy Surfaces for Painting33.Summary of Test Method3.1 Instruments complying with this test method measurecoating thickness by the use of eddy currents.The instrumentmust be placed directly on the coating surface to take a reading.4.Significance and Use4.1 The instrument probe is energized by alternating currentthat induces eddy currents in the metal substrate.The eddycurrents in turn create opposing alternating magnetic fields inthe substrate that modify the electrical characteristics of theprobe coil.The extent of such changes is dependent upon thedistance between the probe and the metal,and the distancebeing shown on the instrument meter as thickness(mils ormicrons)of the intervening coating.5.Apparatus5.1 Eddy Current Thickness Gages,commercially available,suitable to measure coating thickness accurately.5.2 Coating Thickness Standards,with assigned valuestraceable to national standards are available.6.Test Specimens6.1 When this test method is used in the field,the specimenis the coated structure or article on which the dry film thicknessis to be evaluated.6.2 For laboratory use,apply the materials to be tested topanels of similar roughness,shape,thickness,and compositionon which it is desired to determine the thickness.NOTE1Applicable test panel description and surface preparationmethods are given in Practices D 1730.NOTE2Coatings should be applied in accordance with PracticesD 823,or as agreed upon between the purchaser and the seller.7.Verification of Calibration of Apparatus7.1 Different gage manufacturers follow different methodsof calibration or adjustment.Verify calibration according tomanufacturers instructions.7.2 Use a bare section of the substrate after the specifiedsurface preparation method has been accomplished.If anuncoated section of the substrate is not available,an uncoatedtest panel of the same metal type over which the specifiedpreparation has been performed may be used.7.3 Use nonconductive thickness shims to verify calibrationor test blocks bearing calibrated nonconductive coatings thatare traceable to a suitable national standard.7.4 Follow the manufacturers instructions for the specificadjustment of the instrument.7.5 Measure the thickness of a series of calibration stan-dards covering the expected range of coating thickness.Toguard against measuring with an inaccurate gage,recheck thegage at regular intervals.That interval should be set and1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.23 on Physical Properties of Applied Paint Films.Current edition approved Nov.10,2000.Published January 2001.Originallypublished as D 1400 56.Last previous edition D 1400 94.2Annual Book of ASTM Standards,Vol 06.01.3Annual Book of ASTM Standards,Vol 02.05.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.maintained throughout the control process.7.6 If the substrate material to be tested changes in rough-ness,shape,thickness or composition,re-verify calibration andadjust as necessary.8.Procedure8.1 Use the instrument only after it has been calibrated inaccordance with Section 7.8.2 Ensure that the coating is dry prior to use of theinstrument.8.3 Inspect the probe tip and s