TECHNICAL STANDARD
ISO 4624
Paints and varnishes — Pull-off test for adhesion
ISO
Edition 4 / 2023
Current
WHAT DOES THIS STANDARD COVER?
Specifies pull-off test methods used to assess adhesion behaviour of single coatings or multi-coat paint systems.
WHY IS IT RELEVANT?
Relevant where quantitative pull-off testing forms part of coating inspection, condition assessment or failure investigation. Record failure mode and test conditions where relevant. ISO 4624 and ASTM D4541 are not identical procedures.
KEY INSPECTION CONSIDERATIONS
ISO 4624 specifies pull-off test methods for assessing the adhesion behaviour of a single coating or multi-coat paint system. The method applies tensile loading through bonded dollies and can be used with a range of substrates and coating configurations. The numerical pull-off result should be considered together with the location and nature of the fracture within the test assembly. Failure can occur within a coating layer, between coating layers, at the coating/substrate interface, within the adhesive used to attach the dolly or elsewhere within the test arrangement. Test configuration, substrate, adhesive, coating condition and execution of the test can influence the result.
WHAT THE STANDARD SHOULD NOT BE USED TO ASSUME
ISO 4624 does not establish one universal minimum pull-off value suitable for every protective coating system. Acceptance criteria should be established from the project specification, coating-system requirements or other controlling documentation. The numerical result should not be interpreted without considering the observed fracture or failure location. Results obtained using different test arrangements should not automatically be treated as directly comparable. Pull-off testing can also be destructive and may require appropriate repair of the test location after completion.
PRACTICAL INSPECTION APPLICATION
ISO 4624 may be used where a project requires quantitative assessment of coating pull-off behaviour. The inspector should identify the test location and applicable test configuration and record the measured result together with the observed fracture or failure mode. Coating condition and relevant test details should also be documented so that the result can be properly interpreted. The result should be assessed against the acceptance requirement established for the particular coating system and project rather than against an assumed universal value.
RELATED TECHNICAL STANDARDS
RELATED TECHNICAL TOPICS
pull-off; adhesion; coating failure; testing
RELATED PIL GUIDANCE
ASTM D4541 and ASTM D3359 are both widely referenced when assessing coating adhesion, but they evaluate coating performance in fundamentally different ways. Understanding those differences is important when selecting an appropriate test method, particularly for high-build protective coating systems.
RELATED EXPERTISE
Coating Inspection; Condition Surveys; Testing & Analysis; Technical Consultancy
ABOUT THIS TECHNICAL SUMMARY
Paint Inspection Ltd provides this information to help inspectors, engineers, asset owners and contractors understand the practical relevance of commonly referenced protective coatings standards. This page is PIL technical guidance and does not reproduce or replace the published standard. Users should refer to the current published standard, project specification, coating manufacturer requirements and other applicable contract documents when establishing project requirements or acceptance criteria.
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OFFICIAL STANDARD
PIL technical summaries are intended to explain the inspection relevance of industry standards and do not replace the published document.
STATUS AND SOURCE VERIFICATION
Edition and status checked against the official ISO catalogue in September 2026.