ASTM D6132-13(2022)

Standard Test Method for Nondestructive Measurement of Dry Film Thickness of Applied Organic Coatings Using an Ultrasonic Coating Thickness Gage

SIGNIFICANCE AND USE
5.1 Many coating properties are markedly affected by the film thickness of the dry film such as adhesion, flexibility, wear, durability, chemical resistance, and hardness. To be able to compare results obtained by different operators, it is essential to measure film thickness carefully.  
5.2 Most protective and high performance coatings are applied to meet a requirement or a specification for the dry-film thickness of each coat, or for the complete system, or both. Coatings must be applied within certain minimum and maximum thickness tolerances in order that they can fulfill their intended function. In addition to potential performance deficiencies, it is uneconomical to apply more material than necessary when coating large areas such as floors and walls.  
5.3 Low readings may occur occasionally on coatings with rough surfaces. The instrument may allow a user adjustment to prevent this.  
5.4 This test method may not be applicable to measure organic coating thickness on all substrates. The instrument's ability to detect a distinct interface between the coating and the substrate may be impeded if the coating and the substrate are of similar composition, density or attenuation or if the coating is non-homogeneous. Verify operation on a known thickness of the coating/substrate combination if these circumstances are thought to exist.  
5.5 Multilayered coatings have many interfaces and the instrument will measure to the interface separating the two most acoustically different materials. Some instruments have the ability to detect and measure the individual layer thicknesses in a multi-layer system.  
5.6 The use of this test method is not necessarily limited by the type of substrate material.
SCOPE
1.1 This test method describes the use of ultrasonic film thickness gages to measure accurately and nondestructively the dry film thickness of organic coatings applied over a substrate of dissimilar material. Measurements may be made on field structures, on commercially manufactured products, or on laboratory test specimens. These types of gages can accurately measure the dry film thickness of organic coatings on a variety of substrates such as concrete, wood, wallboard, plastic, fiber composites and metal.  
1.2 This test method is not applicable to coatings that will be readily deformable under load of the measuring instrument as the instrument probe is placed directly on the coating surface to take a reading.  
1.3 The effective range of instruments using the principle of ultrasonics is limited by gage design. A thickness range of 8 μm to 7.60 mm (0.3 to 300 mils) has been demonstrated.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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.

General Information

• Status: Published
• Publication Date: 31-May-2022
• ICS: 25.220.60 - Organic coatings
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.23 - Physical Properties of Applied Paint Films

Relations

• Refers: ASTM D1005-95(2020) - Standard Test Method for Measurement of Dry-Film Thickness of Organic Coatings Using Micrometers
• Effective Date: 01-Jun-2020
• Refers: ASTM D823-17 - Standard Practices for Producing Films of Uniform Thickness of Paint, Varnish, and Related Products on Test Panels
• Effective Date: 01-Dec-2017
• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E177-13 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2013
• Refers: ASTM D823-95(2012) - Standard Practices for Producing Films of Uniform Thickness of Paint, Varnish, and Related Products on Test Panels
• Effective Date: 01-Nov-2012
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM E177-10 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Oct-2010
• Refers: ASTM E177-08 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Oct-2008
• Refers: ASTM E691-08 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Oct-2008
• Refers: ASTM D1005-95(2007) - Standard Test Method for Measurement of Dry-Film Thickness of Organic Coatings Using Micrometers
• Effective Date: 01-Nov-2007
• Refers: ASTM D4138-07a - Standard Practices for Measurement of Dry Film Thickness of Protective Coating Systems by Destructive, Cross-Sectioning Means
• Effective Date: 01-Jul-2007
• Refers: ASTM D823-95(2007) - Standard Practices for Producing Films of Uniform Thickness of Paint, Varnish, and Related Products on Test Panels
• Effective Date: 01-Jun-2007
• Refers: ASTM D4138-07 - Standard Practices for Measurement of Dry Film Thickness of Protective Coating Systems by Destructive, Cross-Sectioning Means
• Effective Date: 01-Feb-2007
• Refers: ASTM E177-06b - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 15-Nov-2006

Overview

ASTM D6132-13(2022) is the internationally recognized standard test method for the nondestructive measurement of dry film thickness of applied organic coatings using an ultrasonic coating thickness gage. Developed by ASTM International, this standard defines a reliable and accurate process for determining the thickness of dry organic coatings on a variety of substrates, including concrete, wood, wallboard, plastic, fiber composites, and metals. The method enables field measurements, quality control in manufacturing, and laboratory testing without damaging the coating or substrate.

Consistent and accurate measurement of dry film thickness is critical, as it directly affects essential coating properties such as adhesion, flexibility, wear resistance, durability, chemical resistance, and hardness. This standard is widely adopted to ensure coatings are applied within specified minimum and maximum thicknesses, optimizing performance and material use.

Key Topics

• Scope of Application

  • Designed for nondestructive thickness measurement of organic coatings on substrates of dissimilar material.
  • Applicable to field structures, commercial products, and laboratory specimens.
  • Suitable substrates include concrete, wood, wallboard, plastics, fiber composites, and metals.

• Measurement Principles

  • Utilizes an ultrasonic pulse emitted through the coating, which is reflected by the substrate and received by the probe.
  • The transit time of the ultrasonic pulse is used to calculate dry film thickness.
  • A couplant (water, gel, oil) is typically required to ensure sonic transmission between probe and surface.

• Instrument Calibration and Verification

  • Calibration is performed using traceable standards and is normally handled by authorized laboratories or manufacturers.
  • Regular verification with known standards is necessary before use, following manufacturer guidelines.
  • Adjustment may be needed for coatings with specific acoustic properties.

• Limitations and Considerations

  • Not suitable for coatings that deform under probe pressure.
  • Instrument accuracy may decrease if coating and substrate have similar acoustic properties or if the coating is non-homogeneous.
  • The method is most accurate for distinct layers and may only measure to the interface with the greatest acoustic variation in multilayer systems.

Applications

Adherence to ASTM D6132-13(2022) is crucial in diverse industries where protective and performance coatings are applied:

• Quality Control and Manufacturing
  Ensures coatings meet specified thickness tolerances on products such as construction panels, machinery, automotive parts, and consumer goods.

• Field Inspection
  Verifies coating application on infrastructure, pipelines, floors, walls, and architectural structures, both during and after installation.

• Laboratory Testing
  Assists researchers and product developers in evaluating coating systems, optimizing formulations, and confirming performance standards.

• Asset Maintenance and Management
  Enables nondestructive monitoring of in-service coatings, supporting maintenance planning and extending asset lifespans.

By utilizing ultrasonic coating thickness gages as described in ASTM D6132-13(2022), organizations can improve coating process efficiency, reduce material waste, and ensure regulatory and client specification compliance.

Related Standards

For effective implementation and complementary practices, ASTM D6132-13(2022) references and aligns with several other standards:

• ASTM D823: Practices for producing films of uniform thickness of paint and related products.
• ASTM D1005: Test method for measurement of dry-film thickness of organic coatings using micrometers.
• ASTM D4138: Practices for measurement of dry film thickness of protective coating systems by destructive, cross-sectioning means.
• SSPC-PA 2: Procedure for determining conformance to dry film thickness requirements.
• SSPC-PA 9: Measurement of dry organic coating thickness on cementitious substrates using ultrasonic gages.
• ASME B46.1: Surface texture (surface roughness, waviness, and lay).
• ASTM E177: Practice for use of the terms precision and bias in ASTM test methods.

Keywords: ultrasonic coating thickness gage, dry film thickness measurement, organic coatings, nondestructive testing, ASTM D6132, paint thickness standard, coating thickness testing, quality control, calibration, field inspection.

By following ASTM D6132-13(2022), industry professionals gain a standardized, efficient approach to dry film thickness measurement, enhancing the durability, safety, and performance of coated products and structures.

Standards Content (Sample)

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: D6132 − 13 (Reapproved 2022)
Standard Test Method for
Nondestructive Measurement of Dry Film Thickness of
Applied Organic Coatings Using an Ultrasonic Coating
Thickness Gage
This standard is issued under the fixed designation D6132; 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.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method describes the use of ultrasonic film
D823 Practices for Producing Films of Uniform Thickness
thicknessgagestomeasureaccuratelyandnondestructivelythe
of Paint, Coatings and Related Products on Test Panels
dry film thickness of organic coatings applied over a substrate
D1005 Test Method for Measurement of Dry-Film Thick-
of dissimilar material. Measurements may be made on field
ness of Organic Coatings Using Micrometers
structures, on commercially manufactured products, or on
D4138 Practices for Measurement of Dry Film Thickness of
laboratory test specimens. These types of gages can accurately
Protective Coating Systems by Destructive, Cross-
measure the dry film thickness of organic coatings on a variety
Sectioning Means
of substrates such as concrete, wood, wallboard, plastic, fiber
E177 Practice for Use of the Terms Precision and Bias in
composites and metal.
ASTM Test Methods
1.2 This test method is not applicable to coatings that will
E691 Practice for Conducting an Interlaboratory Study to
be readily deformable under load of the measuring instrument
Determine the Precision of a Test Method
astheinstrumentprobeisplaceddirectlyonthecoatingsurface
2.2 SSPC—The Society for Protective Coatings Standards:
to take a reading.
PA 2 Procedure for Determining Conformance to Dry Coat-
ing Thickness Requirements
1.3 The effective range of instruments using the principle of
PA 9 Measurement of Dry Organic Coating Thickness on
ultrasonicsislimitedbygagedesign.Athicknessrangeof8µm
Cementitious Substrates Using Ultrasonic Gages
to 7.60 mm (0.3 to 300 mils) has been demonstrated.
2.3 ASME—The American Society of Mechanical Engi-
1.4 The values stated in SI units are to be regarded as
neers:
standard. No other units of measurement are included in this
B46.1 Surface Texture (Surface Roughness, Waviness, and
standard.
Lay)
1.5 This standard does not purport to address all of the
3. Terminology
safety concerns, if any, associated with its use. It is the
3.1 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.1.1 accuracy, n—the measure of the magnitude of error
priate safety, health, and environmental practices and deter-
between the result of a measurement and the true thickness of
mine the applicability of regulatory limitations prior to use.
the item being measured.
1.6 This international standard was developed in accor-
3.1.1.1 Discussion—An accuracy statement predicts the
dance with internationally recognized principles on standard-
abilityofacoatingthicknessgagetomeasurethetruethickness
ization established in the Decision on Principles for the
of a coating to be measured. Accuracy statements provide the
Development of International Standards, Guides and Recom-
performance capability across the full functional measurement
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
This test method is under the jurisdiction of ASTM Committee D01 on Paint the ASTM website.
and Related Coatings, Materials, andApplications and is the direct responsibility of Available from Society for Protective Coatings (SSPC), 800 Trumbull Dr.,
Subcommittee D01.23 on Physical Properties of Applied Paint Films. Pittsburgh, PA 15205, http://www.sspc.org.
CurrenteditionapprovedJune1,2022.PublishedJuly2022.Originallyapproved Available from American Society of Mechanical Engineers (ASME), ASME
in 1997. Last previously edition approved in 2017 as D6132 – 13 (2017). DOI: International Headquarters, Two Park Ave., New York, NY 10016-5990, http://
10.1520/D6132-13R22. www.asme.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6132 − 13 (2022)
range of the gage. Accuracy statements frequently include a intended application, used to adjust and/or verify the accuracy
fixed portion that remains constant across the measurement ofanultrasoniccoatingthicknessmeasuringgageforaspecific
range,plusavariableportionthatisrelatedtothemeasurement project.
result for a particular thickness. 3.1.13.1 Discussion—A coated reference sample may or
may not have thickness values traceable to a National Metrol-
3.1.2 adjustment, n—the physical act of aligning a gage’s
ogy Institution. However, the reference sample should be
thickness readings to match those of a known thickness sample
marked with the stated value and the degree of accuracy. The
(removal of bias), in order to improve the accuracy of the gage
coating thickness of the sample should be equal to or slightly
on a specific coating.
greater than the user’s coating thickness measurement require-
3.1.2.1 Discussion—An adjustment will affect the outcome
ment and the coating material must have the same acoustic
of subsequent readings.
velocity and attenuation as the coating to be measured.
3.1.3 calibration, n—the high-level, controlled and docu-
3.1.14 substrate, n—the base material, the type of surface,
mented process of obtaining measurements on traceable cali-
or the component that is being coated.
brationstandardsoverthefulloperatingrangeofthegage,then
3.1.15 verification of accuracy, n—obtaining measurements
makingthenecessarygagemodification(asrequired)tocorrect
any out-of-tolerance conditions. on coating thickness standards, comprising of at least one
thicknessvalueclosetotheexpectedcoatingthickness,priorto
3.1.3.1 Discussion—Calibration of coating thickness gages
gage use for the purpose of determining the ability of the
is typically performed by the equipment manufacturer, their
coating thickness gage to produce thickness results within the
authorized agent, or by an accredited calibration laboratory in
gage manufacturer’s stated accuracy.
a controlled environment using a documented process. The
outcomeofthecalibrationprocessistorestore/realignthegage
4. Summary of Test Method
to meet/exceed the manufacturer’s stated accuracy.
3.1.4 certification, n—documentation of the state of condi- 4.1 Instruments complying with this test method measure
tion of the gage, which can (but not required by definition) be thickness by emitting an ultrasonic pulse into the coating that
accompanied by corrective action (such as adjustment or is reflected back from the substrate to the probe. The travel
calibration, or both, or the replacement of components) neces- time is converted into a thickness reading. The instrument’s
sary to correct any out-of-tolerance conditions. probe must be placed directly on the coating surface to take a
reading.
3.1.5 coating thickness standard, n—coated metal plates, or
uncoated shims of flat sheet, with assigned values traceable to
4.2 After verifying accuracy on a known coated part of the
a National Metrology Institution.
object or material of the same kind, the instrument probe is
coupled with the coated specimen, after proper cure and
3.1.6 couplant, n—a substance such as water, oil, grease, or
conditioning according to the coating manufacturer’s instruc-
paste used to avoid the retarding of sound transmission by air
tions.
between the transducer and the test piece during ultrasonic
examination.
4.3 It should be recognized that the accuracy of the mea-
surements can be influenced when:
3.1.7 dry film thickness, n—the thickness of a coating (or
4.3.1 The coated object to be measured is not planar with
coating layers) as measured from the surface of the substrate.
respect to the transducer face at the point of measurement,
3.1.8 gage (gauge), n—an instrument for measuring
4.3.2 Coating density is not uniform, and
quantity, or an instrument for testing.
4.3.3 The substrate peak-to-valley surface profile of the
3.1.8.1 Discussion—In this test method, the term “gage”
coated specimen exceeds the coating thickness.
refers to an instrument for quantifying coating thickness.
NOTE 1—The height of surface profile can be determined in accordance
3.1.9 manufacturer’s specifications, n—a statement or set of
with ASME B46.1.
statements that describes the performance characteristics of the
gage under a given set of conditions.
5. Significance and Use
3.1.9.1 Discussion—Manufacturer’s specifications typically
5.1 Many coating properties are markedly affected by the
include the range of measurement, accuracy statement, oper-
film thickness of the dry film such as adhesion, flexibility,
atingtemperaturerange,powersource,dimensionsandweight,
wear, durability, chemical resistance, and hardness. To be able
and conformance to industry standards.
to compare results obtained by different operators, it is essen-
3.1.10 measurement (reading), n—the value obtained when
tial to measure film thickness carefully.
placing the probe of a thickness gage in contact with a surface.
5.2 Most protective and high performance coatings are
3.1.11 micrometer (micron), n—one one-thousandth of a
appliedtomeetarequirementoraspecificationforthedry-film
milimetre (0.001 mm); 25.4 microns = 1 mil.
thickness of each coat, or for the complete system, or both.
3.1.12 mil, n—a U.S. term referring to the imperial unit of
Coatings must be applied within certain minimum and maxi-
measure of one one-thousandth of an inch (0.001 in.) referred
mum thickness tolerances in order that they can fulfill their
to elsewhere in the world as “one thou;” 1 mil = 25.4 microns.
intended function. In addition to potential performance
3.1.13 reference sample, n—a specimen, coated with a deficiencies, it is uneconomical to apply more material than
material that is as close as possible in composition to the necessary when coating large areas such as floors and walls.
D6132 − 13 (2022)
5.3 Low readings may occur occasionally on coatings with coating thickness standards and, if necessary, any deficiencies
rough surfaces.The instrument may allow a user adjustment to found shall be corrected. The probe should also be examined
prevent this. for cleanliness and excessive wear before verifying the accu-
racy and before obtaining coating thickness measurements.
5.4 This test method may not be applicable to measure
8.2.1 If gage readings obtained during verification are
organic coating thickness on all substrates. The instrument’s
outside the combined accuracy of the coating thickness stan-
ability to detect a distinct interface between the coating and the
dard and the manufacturer’s stated gage accuracy, the gage
substrate may be impeded if the coating and the substrate are
should b
...