ASTM D4138-94(2001)e1
(Test Method)Standard Test Methods for Measurement of Dry Film Thickness of Protective Coating Systems by Destructive Means
Standard Test Methods for Measurement of Dry Film Thickness of Protective Coating Systems by Destructive Means
SCOPE
1.1 These test methods cover the measurement of dry film thickness of coating films by microscopical observation of precision angular cuts in the coating film. Use of these methods usually requires repair of the coating film.
1.2 Three test methods are provided for measuring dry film thickness of protective coating system:
1.2.1 Test Method A--Using groove cutting instruments.
1.2.2 Test Method B --Using grinding instruments.
1.2.3 Test Method C --Using drill bit instruments.
1.3 The substrate should be sufficiently rigid to prevent deformation of the coating during the cutting process. The surface may be flat or moderately curved (pipes as small as 1 in. (25 mm) in diameter may be measured in the axial direction).
1.4 The range of thickness measurement is 0 to 50 mils (0 to 1.3 mm).
1.5 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.
1.6 This standard does not purport to address all of the safety problems, 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.
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e1
Designation:D4138–94(Reapproved 2001)
Standard Test Methods for
Measurement of Dry Film Thickness of Protective Coating
Systems by Destructive Means
This standard is issued under the fixed designation D 4138; 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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Editorial changes made throughout in June 2001.
1. Scope D 823 Practices for Producing Films of Uniform Thickness
of Paint, Varnish, and Related Products on Test Panels
1.1 These test methods cover the measurement of dry film
D 1005 Test Method for Measurement of Dry-Film Thick-
thickness of coating films by microscopic observation of
ness of Organic Coatings Using Micrometers
precisionangularcutsinthecoatingfilm.Useofthesemethods
D 1186 Test Methods for Nondestructive Measurement of
may require repair of the coating film.
Dry Film Thickness of Nonmagnetic Coatings Applied to
1.2 Three test methods are provided for measuring dry film
a Ferrous Base
thickness of protective coating system:
D 1400 Test Method for Nondestructive Measurement of
1.2.1 Test Method A—Using groove cutting instruments.
DryFilmThicknessofNonconductiveCoatingsAppliedto
1.2.2 Test Method B—Using grinding instruments.
a Nonferrous Metal Base
1.2.3 Test Method C—Using drill bit instruments.
1.3 The substrate should be sufficiently rigid to prevent
3. Summary of Test Methods
deformation of the coating during the cutting process. The
3.1 The three methods are based on measurement of dry
surface may be flat or moderately curved (pipes as small as 1
film thickness by observation of angular cuts in the coating
in. (25 mm) in diameter may be measured in the axial
through a microscope having a built-in reticle with a scale.
direction).
Each method employs different instruments to make the cut in
1.4 Therangeofthicknessmeasurementis0to50mils(0to
the coating.
1.3 mm).
3.2 Test Method A—Uses a carbide tipped wedge to cut a
1.5 The values stated in inch-pound units are to be regarded
grooveinthecoating.Thegrooveiscutatapreciseangletothe
as the standard. The values given in parentheses are for
surface. Three wedge angles are available.
information only.
3.3 Test Method B—Uses a high speed rotary grinding disk
1.6 This standard does not purport to address all of the
or drum type bit to cut partial cylindrical cavities in the
safety concerns, if any, associated with its use. It is the
coating.Axes of the cavities can be oriented at three angles of
responsibility of the user of this standard to establish appro-
inclination to the surface.
priate safety and health practices and determine the applica-
3.4 Test Method C—Uses a specific angle tip drill bit to cut
bility of regulatory limitations prior to use.
a conical cavity in the coating.
2. Referenced Documents
4. Significance and Use
2.1 ASTM Standards:
4.1 The use of these test methods is not necessarily limited
by the type of substrate material as are nondestructive
These test methods are under the jurisdiction of ASTM Committee D01 on magnetic-type means.
Paint and Related Coatings, Materials, and Applications and are the direct
4.2 Individual coats or the overall thickness of a coating
responsibility of Subcommittee D01.23 on Physical Properties of Applied Paint
system can be measured by these methods.
Films.
Current edition approved Feb. 16, 2006. Published March 1994. Originally
published as D 4138 – 82. Last previous edition D 4138 – 88.
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. Withdrawn.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D4138–94 (2001)
(A)
FIG. 2 Geometry of Thickness Measurement
(B)
FIG. 2 Grooves Made by 13,23, and 103 Cutting Tips
(continued)
5.1.3 Illuminated, 50-Power Microscope shall contain a
reticle scaled from 0 to 100 divisions (see Fig. 3). The total
viewing field of the microscope shall be approximately 125
mils (3.18 mm).
NOTE 1—A photomicrographic adapter is available with some micro-
FIG. 1 Tooke Inspection Gage
scopic instruments that allows photographs to be taken through the view
finder.
5.2 Test Specimens:
5. Test Method A—Groove Cutting Instruments
5.2.1 If multiple coats of paint are to be measured, succes-
5.1 Apparatus:
sive contiguous coats should be of contrasting colors to aid
5.1.1 Scribe Cutter and an Illuminated Microscope, with
sharp discrimination of interfaces.
Measuring Reticle. The scribe cutter and illuminated micro-
5.2.2 Generally, test specimens shall be prepared (as test
,
4 5
scope may be combined as a single instrument (see Fig. 1).
panels) or chosen (as sites on a structure) to be representative
The instrument calibration shall be performed by taking
of localized coating thickness and variability.
measurements on applied films of known thickness (see Test
5.2.3 For test panels, if measurement repeatability is desired
Method D 1005).
for a particular paint system, care shall be taken in panel
5.1.2 Tungsten Carbide Cutting Tips shall be designed to
preparation. Coating shall be uniformly applied in accordance
provide a very smooth incision in the paint film at a precise
with Practices D 823. Panels shall be placed in a horizontal
angle to the surface (see Fig. 2). Separate tip designs (angles)
position during drying. Uniform application thickness shall be
shall provide cuts of known slopes such as 1 to 1, 1 to 2, and
verified by another measurement method such asTest Methods
1 to 10. These tips shall be nominally designated 13,23, and
D 1005, D 1186, or D 1400.
103 to indicate the ratio of the lateral measurement to vertical
5.3 Procedure:
depth. The lateral measurement is represented by the reticle
5.3.1 Select a test panel or choose a site for the thickness
markings and the vertical depth is represented by the coating
measurement.
film thickness. Metal guide studs on the gage body shall,
5.3.2 Using an appropriate surface marker of contrasting
together with the cutting tip, form a firm base to ensure that the
color, mark a line on the surface approximately 2-in. long
tip aligns vertically with the painted surface for a precisely
(51-mm) where the thickness measurement will be made.
aligned incision.
5.3.3 Select a cutting tip based on estimated film thickness
as follows:
Thickness Range, Conversion
Tip
mils (µm) Factor
The sole source of supply of the Tooke gage known to the committee at this
time is MicroMetrics, P.O. Box 13804, Atlanta, GA 30324.
13 20 to 50 (500 to 1250) 1.0
If you are aware of alternative suppliers, please provide this information to
23 2 to 20 (50 to 500) 0.5
ASTM International Headquarters. Your comments will receive careful consider-
1 103 0to3(0to75) 0.1
ation at a meeting of the responsible technical committee, which you may attend.
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D4138–94 (2001)
,
5 6
6.1.1 Rotary Tool —A cordless high speed (5000 to
10 000 r/m) rotary grinder.
6.1.2 Grinding Bit—Tungsten carbide cylindrical-shaped
grinding bit placed in a chuck of a microgroover for grinding
through the coating system.
6.1.3 Positioning Block—The positioning block provides
two specific angles with the coated surface for microgroover
grinding through the coating system. The third angle is
accomplished without using the positioning block.
6.1.4 Measuring Microscope—A 50-power illuminated mi-
croscope used in Test MethodAis also used in Test Method B
(see 5.1.3).
6.2 Test Specimens:
6.2.1 See requirements outlined in 5.2.
6.3 Procedure:
6.3.1 Select a t
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