ASTM D4145-83(2002)
(Test Method)Standard Test Method for Coating Flexibility of Prepainted Sheet
Standard Test Method for Coating Flexibility of Prepainted Sheet
SIGNIFICANCE AND USE
Organic coatings on precoated sheet 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 loss of adhesion to the substrate. This test is a means of evaluating the ability of a coating system to withstand the stresses of fabrication.
The bend direction, whether the axis of bend is across or along the rolling diameter of the metal, and the temperature of the specimen when it is bent affect the results of this test and should be agreed upon between the supplier and the user.2
SCOPE
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 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 information only.
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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D4145–83(Reapproved2002)
Standard Test Method for
Coating Flexibility of Prepainted Sheet
This standard is issued under the fixed designation D4145; 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
1.1 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
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
information only.
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 appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
2. Terminology
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
NOTE 1—The above bends are expanded for clarity. They are actually
been applied; as used in this test method, the T-bend rating is flat against themselves in the test.
FIG. 1 T-Bend Test in Which the Coated Specimen is Bent
the minimum number of thicknesses of metal around which the
Around Itself
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.
resulting in fracture of the coating, exposing the substrate, or
loss of adhesion to the substrate. This test is a means of
3. Summary of Test Method
evaluating the ability of a coating system to withstand the
3.1 Prepainted panels are bent 180° around progressively
stresses of fabrication.
more thicknesses of metal or larger diameter dies, the end point
4.2 The bend direction, whether the axis of bend is across or
being when failures no longer occur. The panels are examined
along the rolling diameter of the metal, and the temperature of
at low magnification (5 to 103) after each bend for fracture of
the specimen when it is bent affect the results of this test and
the coating (cracking) and, for loss of adhesion pickoff, by
should be agreed upon between the supplier and the user.
means of a tape pull-off test.
5. Apparatus
4. Significance and Use
5.1 A means of holding one end of the specimen rigidly
4.1 Organic coatings on precoated sheet are subjected to
while making the bend is needed. A bench vise with smooth
stresses when fabricated into products by roll forming, brake
jaws or with smooth inserts, preferably of a soft metal to avoid
bending, or other deformation processes. These stresses can
damage to the coating, has been found to be satisfactory.
exceed the flexibility or adhesive strength of the coating,
5.2 If the metal is not bent around itself as in Fig. 1, a series
of bending dies with smoothly rounded ends may be used as
guides around which the specimen is bent (Fig. 2).
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and Related Coatings, Materials, andApplications and is the direct responsibility of
Subcommittee D01.53 on Coil Coated Metal.
Current edition approved May 10, 2002. Published May 2002. DOI: 10.1520/ Scotch Brand #610 tape manufactured by 3M Co., St. Paul, MN or equivalent,
D4145-83R02. or as agreed upon between the supplier and the user.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4145–83 (2002)
6.1.3 Continue to bend the specimen until the bent end can
be inserted in the jaws of the vise. Tighten the vise to complete
the 180° bend, which is called an OTbend.Take care to tighten
the vise sufficiently so that the apex of the bend is as flat as can
be reasonably achieved.
6.1.4 Examine the bend using a hand lens or low-power
microscope for cracks in the coating.
6.1.5 Apply pressure-sensitive tape along the bend. Rub
thetapeflat;then,holdingthespecimenfirmly,removethetape
with a rapid movement at an angle of 180° to the bend surface.
Examine the tape for coating removed from the surface of the
specimen (that is, pickoff). In the case of a coated steel
specimen (for example, galvanized steel), examine the tape to
FIG. 2 T-Bend Test Using a Die Around Which the Specimen is
determine whether pickoff is between the organic coating and
Bent
the metallic surface or between the metallic coating and the
base steel.
5.3 Magnifier, capable of 5 to 103 magnification for
6.1.6 Secure the bent end
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.