Standard Test Method for
Coating Flexibility of Prepainted Sheet1
This standard is issued under the fixed designation D 4145; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of the 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.
1.1 This test method describes a procedure for determining
the flexibility and adhesion of organic coatings (paints) on
metallic substrates that are deformed by bending when the
the sheet is fabricated into building panels or other products.
1.2 The metal substrate must be capable of passing this test
without fracturing and with no excessive grain development.
1.3 The values stated in inch-pound units are to be regarded
as the standard. The values given in parentheses are for
1.4 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.
2.1 Definitions of Terms Specific to This Standard:
2.1.1 T-bend—a description of the severity of a bend in
terms of the thickness (T) of the sheet to which the coating has
been applied; as used in this test method, the T-bend rating is
the minimum number of thicknesses of metal around which the
coated sheet is bent (Fig. 1), or if bent around a die, the number
of thicknesses of metal equivalent to the diameter of the die to
achieve no fracture or removal of the coating.
3. Summary of Test Method
3.1 Prepainted panels are bent 180° around progressively
more thicknesses of metal or larger diameter die, the endpoint
being when failures no longer occur. The panels are examined
at low magnification (5 to 103) after each bend for fracture of
the coating (cracking) and, for loss of adhesion pickoff, by
means of a tape pull-off test.
4. Significance and Use
4.1 Organic coatings on the precoated sheets are subjected to
stresses when fabricated into products by roll forming, brake
bending, or other deformation processes. These stresses can
exceed the flexibility or adhesive strength of the coating,
resulting in fracture of the coating, exposing the substrate, or
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