ISO 4628-5:2022

Overview

ISO 4628-5:2022 - Paints and varnishes: Assessment of degree of flaking - specifies a visual method for assessing the degree of flaking of coatings by comparison with pictorial standards. Part of the ISO 4628 series, this fourth edition (2022) defines a consistent, repeatable system to quantify flaking caused by ageing, weathering or other degradation mechanisms. The standard is intended for use in laboratory and field evaluations of coating performance.

Key topics and requirements

• Assessment method: Visual comparison with illustrated reference figures (Figures 1 and 2) showing typical flaking patterns (non‑directional and directional).
• Degree (quantity) of flaking: Numeric rating 0–5, tied to approximate surface area affected:
  • 0 = 0%, 1 = 0.1%, 2 = 0.3%, 3 = 1%, 4 = 3%, 5 = 15%.
• Dimension (size) of flakes: Numeric rating 0–5 based on the largest dimension of individual flaked areas:
  • 0 = invisible at ×10 magnification, 1 ≤ 1 mm, 2 ≤ 3 mm, 3 ≤ 10 mm, 4 ≤ 30 mm, 5 > 30 mm.
  • If sizes vary, assign the rating corresponding to the largest size sufficiently characteristic of the tested surface.
• Depth/type of flaking: Indicate whether flakes involve the coating layers only (type a) or the entire coating system detached from the substrate (type b).
• Lighting and procedure: Evaluations should be performed under suitable lighting as specified in ISO 13076 to ensure reliable visual judgement.
• Reporting requirements: Test reports must identify the coating, reference ISO 4628-5:2022, specify surface type/size/location, give the numeric results (degree, size, and depth type), state lighting conditions, note deviations from procedure, and record anomalies and date.

Practical applications and users

ISO 4628-5:2022 is practical for:

• Coating manufacturers conducting quality control and formulation assessment.
• Independent test laboratories performing accelerated weathering or outdoor exposure studies.
• Contractors and inspectors documenting in-service coating condition on structures (bridges, buildings, marine assets).
• Asset owners and specifiers verifying warranty claims or comparing coating systems.
• R&D teams tracking degradation modes and failure analysis.

Typical use: inspect a coated area under specified lighting, compare to pictorial standards, record results (e.g., “flaking; degree 3(S2)b”), and include percentage/approximate surface affected.

Related standards

• ISO 4628-1 - General system for designation of quantity and size of defects and intensity of uniform changes.
• ISO 13076 - Lighting and procedure for visual assessments of coatings.

Keywords: ISO 4628-5:2022, degree of flaking, paints and varnishes, coating assessment, visual inspection, flaking evaluation, pictorial standards, coating defects, weathering.