ASTM E376-19
(Practice)Standard Practice for Measuring Coating Thickness by Magnetic-Field or Eddy Current (Electromagnetic) Testing Methods
Standard Practice for Measuring Coating Thickness by Magnetic-Field or Eddy Current (Electromagnetic) Testing Methods
SIGNIFICANCE AND USE
4.1 General—Most thickness gauges are not applicable to all combinations of coating-substrate thicknesses and materials. The limitations of a particular instrument are generally delineated by its manufacturer. The substrate material and coating combination to be measured as well as the inherent variations in the substrate and coating shall be reviewed prior to selecting the instrument to be used and the measurement accuracy required.
4.2 Magnetic—Magnetic-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.6
4.3 Eddy Current—Eddy 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.
4.4 Accuracy—The accuracy of a measurement depends on the instrument, the foils, 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, electrical conductivity, and surface roughness.
Note 2: This practice under ideal conditions may allow 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.)
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 (that is, electrically conducting) substrate. The substrate may be ferrous or nonferrous. The coating or plating being measured may be electrically conducting or insulating as well as ferrous or non-ferrous.
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, and B530.
1.3 Units—The 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E376 − 19
Standard Practice for
Measuring Coating Thickness by Magnetic-Field or Eddy
1
Current (Electromagnetic) Testing Methods
This standard is issued under the fixed designation E376; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* 2. Referenced Documents
2
1.1 This practice covers the use of magnetic- and eddy
2.1 ASTM Standards:
current-type thickness instruments (gauges) for nondestructive
B244 Test Method for Measurement of Thickness ofAnodic
thickness measurement of a coating on a metal (that is,
Coatings on Aluminum and of Other Nonconductive
electricallyconducting)substrate.Thesubstratemaybeferrous
Coatings on Nonmagnetic Basis Metals with Eddy-
or nonferrous. The coating or plating being measured may be
Current Instruments
electrically conducting or insulating as well as ferrous or
B499 Test Method for Measurement of Coating Thicknesses
non-ferrous.
by the Magnetic Method: Nonmagnetic Coatings on
Magnetic Basis Metals
1.2 More specific uses of these instruments are covered by
B530 Test Method for Measurement of Coating Thicknesses
Practice D7091 and the following test methods issued by
ASTM: Test Methods B244, B499, and B530. by the Magnetic Method: Electrodeposited Nickel Coat-
ings on Magnetic and Nonmagnetic Substrates
1.3 Units—The values stated in SI units are to be regarded
D7091 Practice for Nondestructive Measurement of Dry
as standard. The values given in parentheses are mathematical
Film Thickness of Nonmagnetic Coatings Applied to
conversions to inch-pound units that are provided for informa-
Ferrous Metals and Nonmagnetic, Nonconductive Coat-
tion only and are not considered standard.
ings Applied to Non-Ferrous Metals
1.4 Measurements made in accordance with this practice
E543 Specification forAgencies Performing Nondestructive
will be in compliance with the requirements of ISO 2178 as
Testing
printed in 1982.
E1316 Terminology for Nondestructive Examinations
3
1.5 This standard does not purport to address all of the
2.2 ASNT Standards:
safety concerns, if any, associated with its use. It is the
SNT-TC-1A Recommended Practice for Personnel Qualifi-
responsibility of the user of this standard to establish appro-
cation and Certification in Nondestructive Testing
priate safety, health, and environmental practices and deter-
ANSI/ASNT-CP-189 Standard for Qualification and Certifi-
mine the applicability of regulatory limitations prior to use.
cation of NDT Personnel
1.6 This international standard was developed in accor-
4
2.3 AIA Standard:
dance with internationally recognized principles on standard-
NAS-410 Certification and Qualification of Nondestructive
ization established in the Decision on Principles for the
Testing Personnel
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
1
This practice is under the jurisdiction of ASTM Committee E07 on Nonde- the ASTM website.
3
structive Testing and is the direct responsibility of Subcommittee E07.07 on AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
Electromagnetic Method. 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
4
Current edition approved May 1, 2019. Published June 2019. Originally Available fromAerospace IndustriesAssociation ofAmerica, Inc. (AIA), 1000
approved in 1989. Last previous edition approved in 2017 as E376 – 17. DOI: WilsonBlvd.,Suite1700,Arlington,VA22209-3928,http://www.aia-aerospace.org.
10.1520/E0376-19. (Replacement standard for MIL-STD-410.)
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
E376 − 19
5
2.4 ISO Standards: ties of the basis metal. For practical purposes, magnetic
ISO 2178 Nonmagnetic Coatings on Magnetic Substrate— variations in low-carbon AISI 1005-1020 steels may be con-
Measurement of Coating Thickness—Magnetic Method sidered to be insignificant. To avoid the influences of seve
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E376 − 17 E376 − 19
Standard Practice for
Measuring Coating Thickness by Magnetic-Field or Eddy
1
Current (Electromagnetic) Testing Methods
This standard is issued under the fixed designation E376; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
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 (i.e. (that is, electrically conducting) substrate. The substrate may be ferrous or nonferrous.
The coating or plating being measured may be electrically conducting or insulating as well as ferrous or non-ferrous.
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, and B530.
1.3 Units—The 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 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
3
2.2 ASNT Standards:
SNT-TC-1A Recommended Practice for Personnel Qualification and Certification in Nondestructive Testing
ANSI/ASNT-CP-189 Standard for Qualification and Certification of NDT Personnel
1
This practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.07 on Electromagnetic
Method.
Current edition approved Nov. 1, 2017May 1, 2019. Published December 2017June 2019. Originally approved in 1989. Last previous edition approved in 20112017 as
E376 – 11.E376 – 17. DOI: 10.1520/E0376-17.10.1520/E0376-19.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
E376 − 19
4
2.3 AIA Standard:
NAS-410 Certification and Qualification of Nondestructive Testing Personnel
5
2.4 InternationalISO Standards:
ISO 2178 Nonmagnetic Coatings on Magnetic Substrate—Measurement of Coating Thickness—Magnetic Method
ISO 9712 Non-destructive Testing—Qualification and Certification of NDT Personnel
NOTE 1—See Appendix X1.
3. Terminology
3.1 Definitions—For definitions of terms relatin
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