Pull-off adhesion test
A test in which a dolly is bonded to the coating and pulled until something breaks, giving a strength in megapascals and — more usefully — a failure mode. ASTM D4541 and ISO 4624 both require the failure mode to be reported alongside the number.
The number on its own says very little. The same recorded strength means opposite things depending on where the break ran: through the coating itself, or at the interface with the steel.
That is why both standards require the failure mode to be reported. A pull-off value quoted without it is not a result, and a specification that asks only for a minimum strength has asked for half the test.
Sources and references
- StandardASTM D4541-22 — Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion TestersASTM International · accessed August 29, 2026
- StandardISO 4624:2023 — Paints and varnishes — Pull-off test for adhesionInternational Organization for Standardization · accessed August 29, 2026