Overview
EN ISO 4628-5:2022 / ISO 4628-5:2022 specifies a visual method for the assessment of flaking (degree of flaking) in paints and varnishes. The standard defines how to assess the quantity, size and depth of flaked areas by comparison with pictorial standards. It is part of the ISO 4628 series that provides a unified system for designating the quantity and size of coating defects and intensity of uniform appearance changes caused by ageing, weathering or other degradation.
Key topics and technical requirements
- Assessment method: Compare the coating under test with pictorial standards (Figures 1 and 2) showing flaking without preferential direction and with preferential direction.
- Quantity (density) rating: Numeric scale 0–5 based on percentage of flaked area:
- 0 = 0%
- 1 = 0.1%
- 2 = 0.3%
- 3 = 1%
- 4 = 3%
- 5 = 15%
- Size rating: Numeric scale 0–5 for largest dimension of exposed areas:
- 0 = not visible under ×10 magnification
- 1 = up to 1 mm
- 2 = up to 3 mm
- 3 = up to 10 mm
- 4 = up to 30 mm
- 5 = larger than 30 mm
- Depth of flaking: Indicate failure level where possible:
- Type a = coat(s) flaking from an underlying coat
- Type b = whole coating system flaking from the substrate
- Illumination: Assess under good lighting as specified in ISO 13076 (lighting and procedure for visual assessments).
- Reporting: Results expressed numerically and, if needed, amplified in words. Example format: “flaking; degree of flaking 3(S2)b” (quantity 3, size 2, whole system flaking - type b).
- Test report must include: coating identification, reference to ISO 4628-5:2022, surface area, assessment result, illumination, deviations, anomalies and date.
Practical applications
- Quality control and production - routine inspection of batches and acceptance testing of painted components.
- Weathering and ageing studies - evaluation after accelerated or natural exposure to compare formulations.
- Field inspections & maintenance - condition surveys for buildings, infrastructure, bridges and marine structures.
- Warranty and claims - objective, repeatable basis for assessing coating failure severity.
- Research & development - comparing anti-flaking performance of formulations or pretreatments.
Who should use this standard
- Coating manufacturers and formulators
- Independent testing laboratories and QC departments
- Corrosion and coatings inspectors, specifiers and asset owners
- Architects, civil/structural engineers and maintenance planners
Related standards
- ISO 4628-1 - general introduction and designation system for defects and appearance changes
- ISO 13076 - lighting and procedure for visual assessments of coatings
Keywords: ISO 4628-5, EN ISO 4628-5:2022, paints and varnishes, degree of flaking, flaking assessment, pictorial standards, coating degradation, visual assessment.
