ASTM E376 - 11

    Standard Practice for Measuring Coating Thickness by Magnetic-Field or Eddy-Current (Electromagnetic) Testing Methods

    Active Standard ASTM E376 | Developed by Subcommittee: E07.07

    Book of Standards Volume: 03.03


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    ASTM E376

    Significance and Use

    GeneralNo presently available thickness gauge is applicable to all combinations of coating-substrate thicknesses and materials. The limitations of a particular instrument are generally delineated by its manufacturer.

    MagneticMagnetic-type gauges measure either magnetic attraction between a magnet and a coating or its substrate, or reluctance of a magnetic flux path passing through the coating and substrate. These gauges are designed to measure thickness of a nonmagnetic coating on a magnetic substrate. Some of them will also measure thickness of nickel coatings on a magnetic or nonmagnetic substrate.

    Eddy CurrentEddy-current-type thickness gauges are electronic instruments that measure variations in impedance of an eddy-current inducing coil caused by coating thickness variations. They can only be used if the electrical conductivity of the coating differs significantly from that of the substrate.

    AccuracyThe accuracy of a measurement depends on the instrument, its calibration and standardization, and its operating conditions. The accuracy is also affected by the interferences listed in Section 5, such as part geometry (curvature), magnetic permeability, and surface roughness.

    Note 2—This practice allows the coating thickness to be determined within ±10 % of its true thickness or to within ±2.5 μm (or ±0.0001-in.), whichever is the greater. (See exceptions in Appendix X2.)

    1. Scope

    1.1 This practice covers the use of magnetic- and eddy-current-type thickness instruments (gauges) for nondestructive thickness measurement of a coating on a metal substrate.

    1.2 More specific uses of these instruments are covered by Practice D7091 and the following test methods issued by ASTM: Test Methods B244, B499, B530, and G12.

    1.3 UnitsThe values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.

    1.4 Measurements made in accordance with this practice will be in compliance with the requirements of ISO 2178 as printed in 1982.

    1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    B244 Test Method for Measurement of Thickness of Anodic Coatings on Aluminum and of Other Nonconductive Coatings on Nonmagnetic Basis Metals with Eddy-Current Instruments

    B499 Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings on Magnetic Basis Metals

    B530 Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Electrodeposited Nickel Coatings on Magnetic and Nonmagnetic Substrates

    D7091 Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to Ferrous Metals and Nonmagnetic, Nonconductive Coatings Applied to Non-Ferrous Metals

    E543 Specification for Agencies Performing Nondestructive Testing

    E1316 Terminology for Nondestructive Examinations

    G12 Test Method for Nondestructive Measurement of Film Thickness of Pipeline Coatings on Steel

    AIA Standard

    NAS-410 Certification and Qualification of Nondestructive Testing Personnel Available from Aerospace Industries Association of America, Inc. (AIA), 1000 Wilson Blvd., Suite 1700, Arlington, VA 22209-3928, http://www.aia-aerospace.org. (Replacement standard for MIL-STD-410.)

    ASNT Standards

    ANSI/ASNT-CP-189 Standard for Qualification and Certification of NDT Personnel

    International Standard

    ISO2178 Nonmagnetic Coatings on Magnetic Substrate--Measurement of Coating Thickness--MagneticMethod Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.


    ICS Code

    ICS Number Code 17.040.20 (Properties of surfaces)

    UNSPSC Code

    UNSPSC Code 41111801(Eddy current examination equipment)


    DOI: 10.1520/E0376-11

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