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.
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
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.
The range of thickness measurement is 0 to 3.5 mils (0 to 89
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.
Measurements may be made on coil-coated sheet, certain formed
products, or on test panels.
The values stated in SI units are to be regarded as the
standard. The values given in parentheses are for information
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.