TECHNICAL STANDARD
ISO 4628-5
Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity and size of defects, and of intensity of uniform changes in appearance — Part 5: Assessment of degree of flaking
ISO
2022
Current
WHAT DOES THIS STANDARD COVER?
ISO 4628-5 specifies a method for assessing the degree of flaking of coatings using the designation system and reference approach of the ISO 4628 series.
WHY IS IT RELEVANT?
Provides a recognised method for recording coating flaking during condition surveys and failure investigations. Flaking can provide important evidence about deterioration and coating integrity, but the observed classification should not automatically be interpreted as identifying the underlying cause.
KEY INSPECTION CONSIDERATIONS
The standard addresses assessment of the degree of flaking of coatings. Flaking involves visible separation or loss of coating and can occur at different interfaces within a coating system. The quantity and size of affected areas should be recorded consistently, together with the apparent level at which separation has occurred where this can be determined.
WHAT THE STANDARD SHOULD NOT BE USED TO ASSUME
Classification of flaking does not establish why the coating has separated. Separation may occur at the substrate, between coating layers or cohesively within a layer, and visual assessment alone may not establish the underlying mechanism. A flaking assessment should not be treated as a quantitative adhesion-strength measurement. Adhesion testing should be considered separately where required.
PRACTICAL INSPECTION APPLICATION
Inspectors can record locations of flaking, the applicable assessment, apparent separation level and representative photographs. Where the cause or maintenance significance needs to be established, the assessment can be supplemented by coating identification, adhesion testing, substrate examination and review of coating history.
RELATED TECHNICAL STANDARDS
RELATED TECHNICAL TOPICS
Condition Assessment Flaking Delamination Coating Defects 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.
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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.