TECHNICAL STANDARD
ISO 4628-4
Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity and size of defects, and of intensity of uniform changes in appearance — Part 4: Assessment of degree of cracking
ISO
2016
Current
WHAT DOES THIS STANDARD COVER?
ISO 4628-4 specifies a method for assessing the degree of cracking of coatings by comparison with recognised pictorial standards.
WHY IS IT RELEVANT?
Provides a consistent method for recording coating cracking during condition assessment and failure investigation. The resulting classification describes the observed deterioration but does not, by itself, establish why the coating has cracked.
KEY INSPECTION CONSIDERATIONS
The standard addresses assessment of the degree of cracking in coatings, including the quantity and size of observed cracking. Cracking can occur within one or more coating layers. Distribution, severity and location should be recorded consistently.
WHAT THE STANDARD SHOULD NOT BE USED TO ASSUME
Identification of cracking does not by itself establish the deterioration mechanism. Possible contributing factors can include ageing, film build, movement, embrittlement, incompatibility or application-related factors, but visual classification alone cannot establish root cause. The maintenance significance of cracking should be considered alongside the wider coating condition.
PRACTICAL INSPECTION APPLICATION
Inspectors can record cracking locations, the applicable assessment and representative photographs during condition surveys or failure investigations. Different forms or severities of cracking should be distinguished where relevant. Further investigation may be necessary to determine the cause and effect on the protective coating system.
RELATED TECHNICAL STANDARDS
RELATED TECHNICAL TOPICS
Condition Assessment Cracking Coating Cracking Coating Deterioration Failure Investigation
RELATED PIL GUIDANCE
A pre-condition coating survey brings visual inspection, testing, sampling and access planning together to support evidence-based maintenance decisions.
A structured approach to investigating protective coating failure through evidence, testing, sampling and project-record review.
RELATED EXPERTISE
Condition Surveys Coating Inspection 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.
PIL TECHNICAL ASSISTANT
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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
Standard number, edition, title and current publication status checked against the official ISO catalogue in September 2026.