Overview
EN ISO 4628-8:2012 (ISO 4628-8:2012) defines a standardized method for assessing delamination and corrosion that develops around a deliberate defect (a scribe or other artificial holiday) on coated test panels or specimens exposed to a corrosive environment. The standard is part of the ISO 4628 series for evaluation of degradation of coatings (paints and varnishes) and focuses on measurement- and calculation-based assessment rather than pictorial rating. It expressly does not cover pitting corrosion or pit depth.
Key topics and requirements
- Scope: Assessment of delamination and corrosion around linear scribes or other artificial defects caused by corrosive exposure (e.g., salt spray or seawater immersion).
- Definitions: Holiday, scribe, circular defect, delaminated area, corroded area.
- Principle: Delamination and corrosion are evaluated separately to give detailed performance information.
- Measurement method:
- Remove loose coating (knife blade, compressed air, adhesive tape or suitable stripper) and rinse with fresh water prior to inspection.
- Measure the width of delamination or corroded area to the nearest 0.5 mm at a minimum of six uniformly distributed points along the scribe or around the defect (fewer points allowed for short scribes with conditions).
- Assessments may be carried out directly after exposure or after a conditioning period (e.g., 24 h at 23 ± 2 °C and 50 ± 5 % RH, per ISO 3270) when agreed.
- Test sample requirements: At least three individual test panels unless otherwise specified.
- Options: Corrosion can be assessed on the coated panel or after stripping the coating; optical image processing may be used as an alternative assessment technique.
- Limitations: Excludes evaluation of pitting/pit depth.
Applications
- Quality control and acceptance testing of coating systems in corrosive environments.
- Performance comparison of paints, varnishes and multilayer coating systems.
- R&D and formulation development for improving adhesion and corrosion resistance.
- Corrosion testing labs and certification bodies implementing standardized salt spray or seawater immersion exposures.
- Specifiers and asset owners writing procurement or maintenance specifications for protective coatings on steel and other substrates.
Who should use this standard
- Coatings manufacturers and formulators
- Independent testing and corrosion laboratories
- Coating system specifiers, inspectors and quality managers
- Corrosion engineers and maintenance planners
Related standards
- ISO 4628 series (Parts 1–7, 10) - other defect assessments (blistering, rusting, cracking, flaking, chalking, filiform corrosion)
- ISO 3270 - conditioning temperatures and humidities
- ISO 9227 - salt spray testing (artificial atmosphere)
- ISO 15711 - seawater immersion testing
Keywords: EN ISO 4628-8:2012, ISO 4628-8:2012, delamination assessment, corrosion around scribe, coatings evaluation, paints and varnishes, scribe testing, salt spray, coated panels.