SIST EN ISO 4628-2:2016 PDF

Overview

EN ISO 4628-2:2016 (ISO 4628-2:2016) is a standardized method for assessing the degree of blistering in paints and varnishes. The standard specifies visual assessment by comparison with pictorial standards that illustrate blister sizes (S2–S5) and quantities (densities 2–5). It is part of the ISO 4628 series for evaluation of coating degradation and is intended for defects produced by ageing and weathering.

Key topics and requirements

• Assessment method: Compare the coating surface with the pictorial standards (Figures and calibration images) to determine blister size and quantity (density). Typical results are reported in the format degree (size), for example 2(S2).
• Pictorial standards: Illustrations are provided for blister sizes 2, 3, 4, 5, each shown at densities 2, 3, 4, 5. A very small blister size (S1) is noted as not visible to normal corrected vision and requires ×10 magnification.
• Lighting and viewing: Assessments must be carried out under suitable illumination as specified by ISO 13076 (normative reference).
• Optical imaging: If an optical imaging system is used, it must be calibrated against the images in Annex A (calibration images).
• Reporting: The test report shall include coating identification, reference to ISO 4628‑2, surface details and location, the blistering rating and affected area (percentage), illumination conditions, anomalies, and date of examination.
• Correlation guidance: Annex B provides information correlating ISO 4628-2 ratings with ASTM D714 blistering ratings, aiding cross-standard comparisons.

Practical applications and users

• Quality control teams in paint and varnish manufacturing for batch acceptance and consistency checks.
• Independent coating test laboratories performing standardized assessments for contracts and certification.
• Specifiers, architects, and asset owners evaluating coating condition on structures subject to weathering (buildings, bridges, marine structures).
• Failure analysis and R&D groups investigating causes of blistering and improving coating formulations.
• Contract inspectors and maintenance planners who need repeatable, comparable records of coating degradation.

Related standards

• ISO 4628-1 - General introduction and designation system for quantity, size and intensity ratings.
• ISO 13076 - Lighting and procedure for visual assessments of coatings (normative for illumination).
• ASTM D714 - Common U.S. standard for blistering; Annex B offers correlation guidance.

Keywords: ISO 4628-2, degree of blistering, paints and varnishes, coating evaluation, pictorial standards, coating defects, ASTM D714, optical imaging calibration.