Overview
EN ISO 4628-3:2024 - Paints and varnishes - Evaluation of quantity and size of defects, and of intensity of uniform changes in appearance - Part 3: Assessment of degree of rusting (ISO 4628-3:2024) specifies standardized visual methods to assess rust on coated surfaces. It covers organic coatings and duplex systems (metallic coating plus an organic topcoat) and uses pictorial standards to estimate the extent of corrosion. The assessment provides an estimation of the corroded area on specimens (edges excluded) and distinguishes between red rust (ferrous corrosion) and white rust (non‑ferrous corrosion).
Key Topics
- Scope and purpose
- Visual assessment of the degree of rusting on painted and varnished surfaces and duplex systems.
- Two assessment methods
- Method 1: Comparison with pictorial standards (Ri for red rust, WRi for white rust).
- Method 2: Estimation of the corroded area in percent (R% and WR%).
- Definitions and terms
- Clear definitions for red rust, white rust and rust traces; rust traces (bleeding contamination) are excluded from degree ratings.
- Reporting and results
- Guidance on expression of results and required information in the test report, including which assessment method was used.
- Annexes
- Calibration images (pictorial standards), an example panel after NSS salt spray testing (ISO 9227), and correlation with other rating systems (e.g., ASTM).
- Normative references
- ISO 4618 (vocabulary) and ISO 13076 (lighting and visual assessment procedure) are referenced for consistent terminology and viewing conditions.
Applications
EN ISO 4628-3:2024 is used by:
- Coating manufacturers for product development and quality control.
- Independent test laboratories conducting corrosion and durability evaluations.
- Specifiers and asset owners (infrastructure, marine, industrial) for acceptance criteria and maintenance planning.
- Corrosion engineers and inspectors performing visual inspections after weathering, salt spray (NSS) tests, or field exposure.
Practical uses include conformity testing, comparative performance trials, service-life assessment, and contractual acceptance of coatings.
Related Standards
- ISO 4628 series (general system for defects and changes in appearance)
- ISO 4618 - Paints and varnishes: Vocabulary
- ISO 13076 - Lighting and procedure for visual assessments of coatings
- ISO 9227 - NSS salt spray test (example panel in Annex B)
- Correlation provided with ASTM D610 series for cross-reference with other rust-rating systems
EN ISO 4628-3:2024 supports consistent, repeatable visual rust assessment using pictorial standards and percent-area estimation, helping stakeholders apply objective criteria for coating performance and corrosion evaluation.
