1.1 This test method covers a procedure for evaluating the pull-off strength (commonly
referred to as adhesion) of a coating system from metal substrates. Pull-off strength
of coatings from concrete is described in Test Method D7234. This test offers two
test protocols. Protocol 1 (test to fracture) determines the greatest perpendicular
force (in tension) that a surface area can bear before a plug of material is detached.
Protocol 2 (pass/fail) determines if the coated surface remains intact at a defined
load criteria. Fracture will occur along the weakest plane within the system comprised
of the test fixture, glue, coating system, and substrate, and will be exposed by the
fracture surface. This test method maximizes tensile stress as compared to the shear
stress applied by other methods, such as scratch or knife adhesion, and results may
not be comparable.
NOTE 1— The procedure in this standard was developed for metal substrates, but may be appropriate
for other rigid substrates such as plastic and wood. Factors such as loading rate
and flexibility of the substrate must be addressed by the user/specifier.
NOTE 2— The procedure in this standard was developed for use on flat surfaces. The results
could have greater variability with lower values and averages for surfaces other than
flat.