ASTM D5796-03(2010)
(Test Method)Standard Test Method for Measurement of Dry Film Thickness of Thin Film Coil-Coated Systems by Destructive Means Using a Boring Device
Standard Test Method for Measurement of Dry Film Thickness of Thin Film Coil-Coated Systems by Destructive Means Using a Boring Device
SIGNIFICANCE AND USE
Measurement of dry film thickness of organic coatings by physically cutting through the film and optically observing and measuring the thickness offers the advantage of direct measurement as compared with nondestructive means.
Constituent coating layers of an overall thickness of a coating system can usually be measured individually by this test method, provide adhesion between each layer is sufficient. (However, this can be difficult in cases where the primer, topcoat, or multiple coating layers have the same, or very similar, appearance.)
SCOPE
1.1 This test method covers the measurement of dry film thickness (DFT) of coating films by microscopic observation of a precision-cut, shallow-angle crater bored into the coating film. This crater reveals cross sectional layers appearing as rings, whose width is proportional to the depth of the coating layer(s) and allows for direct calculation of dry film thickness.
1.1.1 The Apparatus, Procedure, and Precision and Bias discussions include Method A and Method B. Method A involves the use of an optical measurement apparatus which is no longer commercially available, but remains a valid method of dry film measurement. Method B is a software driven measurement procedure that supersedes Method A.
1.2 The substrate may be any rigid, metallic material, such as cold-rolled steel, hot-dipped galvanized steel, aluminum, etc. The substrate must be planar with the exception of substrates exhibiting “coil set,” which may be held level by the use of the clamping tool on the drilling device.
Note 1—Variations in the surface profile of the substrate may result in misrepresentative organic coating thickness readings. This condition may exist over substrates such as hot-dipped, coated steel sheet. This is true of all “precision cut” methods that are used to determine dry film thickness of organic coatings. This is why several measurements across the strip may be useful if substrate surface profile is suspect.
1.3 The range of thickness measurement is 0 to 3.5 mils (0 to 89 μm).
Note 2—For DFT measurements of films greater than 3.5 mils (89μm), but less than 63 mils (1600 μm), a 45° borer may be used in accordance with this test method, with the exception of 6.8, where the micrometer reading would provide a direct read-out, and division by ten would be unnecessary per 4.3.1 Method A.
1.4 Measurements may be made on coil-coated sheet, certain formed products, or on test panels.
1.5 The values stated in SI 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 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.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D5796–03(Reapproved2010)
Standard Test Method for
Measurement of Dry Film Thickness of Thin-Film Coil-
Coated Systems by Destructive Means Using a Boring
Device
This standard is issued under the fixed designation D5796; 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 1.5 The values stated in SI units are to be regarded as the
standard. The values given in parentheses are for information
1.1 This test method covers the measurement of dry film
only.
thickness(DFT)ofcoatingfilmsbymicroscopicobservationof
1.6 This standard does not purport to address all of the
a precision-cut, shallow-angle crater bored into the coating
safety concerns, if any, associated with its use. It is the
film. This crater reveals cross sectional layers appearing as
responsibility of the user of this standard to establish appro-
rings, whose width is proportional to the depth of the coating
priate safety and health practices and determine the applica-
layer(s) and allows for direct calculation of dry film thickness.
bility of regulatory limitations prior to use.
1.1.1 The Apparatus, Procedure, and Precision and Bias
discussions include Method A and Method B. Method A
2. Referenced Documents
involves the use of an optical measurement apparatus which is
2.1 ASTM Standards:
no longer commercially available, but remains a valid method
D3794 Guide for Testing Coil Coatings
of dry film measurement. Method B is a software driven
measurement procedure that supersedes Method A.
3. Significance and Use
1.2 The substrate may be any rigid, metallic material, such
3.1 Measurement of dry film thickness of organic coatings
as cold-rolled steel, hot-dipped galvanized steel, aluminum,
by physically cutting through the film and optically observing
etc. The substrate must be planar with the exception of
and measuring the thickness offers the advantage of direct
substrates exhibiting “coil set,” which may be held level by the
measurement as compared with nondestructive means.
use of the clamping tool on the drilling device.
3.2 Constituent coating layers of an overall thickness of a
NOTE 1—Variations in the surface profile of the substrate may result in
coating system can usually be measured individually by this
misrepresentative organic coating thickness readings. This condition may
test method, provide adhesion between each layer is sufficient.
exist over substrates such as hot-dipped, coated steel sheet. This is true of
(However, this can be difficult in cases where the primer,
all “precision cut” methods that are used to determine dry film thickness
topcoat, or multiple coating layers have the same, or very
of organic coatings. This is why several measurements across the strip
similar, appearance.)
may be useful if substrate surface profile is suspect.
1.3 The range of thickness measurement is 0 to 3.5 mils (0
4. Apparatus
to 89 µm).
4.1 Dry Film Thickness Device, It is an apparatus consist-
NOTE 2—For DFTmeasurements of films greater than 3.5 mils (89µm),
ing of either a manual or automated carbide-tipped drill that
but less than 63 mils (1600 µm), a 45° borer may be used in accordance
raises and lowers the boring tip perpendicular to the surface to
with this test method, with the exception of 6.8, where the micrometer
reading would provide a direct read-out, and division by ten would be
unnecessary per 4.3.1 Method A.
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
1.4 Measurements may be made on coil-coated sheet, cer-
Standards volume information, refer to the standard’s Document Summary page on
tain formed products, or on test panels.
the ASTM website.
Withdrawn. The last approved version of this historical standard is referenced
on www.astm.org.
1 4
This test method is under the jurisdiction of ASTM Committee D01 on Paint The sole source of supply of the dry film thickness device known to the
and Related Coatings, Materials, andApplications and is the direct responsibility of committee at this time is DJH Designs, 2366Wyecroft Rd., Unit D4, Oakville, Ont.,
Subcommittee D01.53 on Coil Coated Metal. Canada L6L 6M1. If you are aware of alternative suppliers, please provide this
CurrenteditionapprovedJune1,2010.PublishedJuly2010.Originallyapproved information to ASTM International Headquarters. Your comments will receive
in 1995. Last previous edition approved in 2003 as D5796 – 03. DOI: 10.1520/ careful consideration at a meeting of the responsible technical committee, which
D5796-03R10. you may attend.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5796–03 (2010)
5.3 If test panels are to be laboratory prepared, this should
be done using accepted industry practices, in accordance with
Guide D3794.
6. Procedure
6.1 Select a test panel or choose a site for thickness
NOTE 1—Thedrawingisnottoscale.Itisforillustrationpurposesonly.
measurement.
NOTE 2—u = 5° 42’ 389 7
6.2 Using an appropriate surface marker of contrasting
Tan u = A/B = 0.1
color,markalineonthesurfaceabout25-mmlongand12-mm
A = 0.1B
wide. In most cases, the use of a marker is not necessary, but
FIG. 1 Typical Crater Formed by Boring Device
for certain colors, usually whites, its use may be desirable.
Depending upon the coating and the type of marker used, it is
be tested, a cleaning brush, a marking device (optional), and a
possible for the marker to be absorbed into the coating, up to
video imaging system, which is attached to a microscope that
0.2-mils (5-µm) deep. This effect can make it difficult to
views the crater formed by the boring device.
determine the position of the top edge of the crater. External
4.2 Carbide Borer Bit, The configuration is designed to
fluorescent lighting may be positioned to enhance the image
provide a very smooth circular incision in the paint film at a
and eliminate the need for a marker. The use of a marker,
precise angle to the surface (see Fig. 1).
lighting, or marker and lighting shall be agreed upon between
4.3 Optical Magnification:
the user and customer.
4.3.1 Method A, Video Camera—It is attached to an illumi-
6.3 Place the test panel on the borer stage (align the marked
nated microscope and conveys the image onto a closed-circuit
line,ifrequired)sothatitispositionedunderthebit.Clampthe
television (CCTV) monitor, so that it is an easy matter to line
panel into place.
up the cross-hair on the enlarged image. This very effectively
6.4 With a small brush, clean debris from the borer bit, the
minimizes error or lack of consistency on the part of the
“depth stop surface,” and the surface of the test panel. Debris
operator in lining up the cross-hair.
in these areas will result in a shallower and smaller crater, with
4.3.2 Method B, Computer Monitor—It is attached to a
consequently inaccurate results.
microscope with external lighting and conveys the image via
6.5 Adjust the depth control wheel so that the carbide borer
software onto a computer monitor. The monitor and software
bit just penetrates the metallic substrate, to avoid undue wear
enlarge the image for viewing and measuring, while the
on the borer tip. This can only be done by trial and error due
computerretainsthepictureasanimagefile,iftheuserdesires.
to substrate thickness variation.
4.4 Microscope—The measurement is performed by first
6.6 Iftheboringdeviceisautomated,followtheinstructions
boring a shallow-angle crater of known configuration through
in 6.6.1; if the boring device is manually operated, follow the
the coating(s) film into the substrate. The microscope facili-
instructions in 6.6.2.
tates viewing and measuring the crater.
6.6.1 Automated Boring Device—Push the button to acti-
4.5 Theinstrumentiscalibratedbytakingmeasurementson
vate boring device. Do not make a second stroke into the same
a standard, which is traceable to a national standards institu-
crater; do not allow the borer head to penetrate a previously
tion. Calibration is a procedure that is done during setup and
tested crater.
will require recalibration if changes are made to the micro-
6.6.2 Manual Boring Device—Move the borer head down
scope, boring device, or the camera system. Calibration veri-
in a smooth, slow action to its full travel position, then
fication should be done at intervals agreed upon between the
immediately return it to its full rest position. Do not allow the
user and the consumer, but no less often than indicated by the
borer head to rest in the “down” position; ragged edges or
manufacturer of the measuring device.
smeared coating may result, rendering accurate film measure-
ment more difficult. Do not make a second stroke into the same
5. Test Specimens
crater;
...
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