Overview
EN ISO 6581:2018 specifies a comparative laboratory method for determining the fastness (resistance) of coloured anodic oxidation coatings on aluminium and its alloys to ultraviolet (UV) light and heat. The test exposes representative specimens to a medium‑pressure mercury arc lamp under controlled conditions and evaluates resulting colour change against standard specimens. The method is intended for comparative, rapid assessment and is not suitable for heat‑sensitive coloured anodic coatings.
Key topics and technical requirements
- Principle: Comparative exposure to a UV/heat source and visual or instrumental assessment of colour change.
- Apparatus: A heat‑resistant, fully enclosed cabinet with specimen holders at equal distances from the lamp; safety interlocks to prevent eye exposure.
- UV source: Medium‑pressure mercury arc lamp with a silica envelope (example: 400 W lamp, 150 mm effective arc length, placed ≈170 mm from specimens is cited). Lamp life and irradiance variation are noted (typ. ~1 000 h recommended life).
- Temperature control: Specimen surface temperature must not exceed 100 °C; cooling or forced air may be required but avoid over‑cooling the lamp.
- Ozone and ventilation: Some lamps produce ozone; if so, forced ventilation and ducting to outside are required to protect operators.
- Specimen preparation: Samples must be taken from a flat, representative surface (not edges). Standard specimen size is greater than 150 mm × 70 mm. When the product cannot be tested directly, representative specimens prepared under identical conditions may be used.
- Limitations: Not suitable for heat‑sensitive coatings; dark‑coloured specimens typically reach higher temperatures and require careful monitoring.
- Test control and reporting: The standard includes provisions for standard control specimens, evaluation, expression of results and required test report content.
Applications and who uses it
EN ISO 6581:2018 is used by:
- Anodizing and surface‑treatment laboratories for quality control and comparative durability testing of coloured anodic coatings.
- Manufacturers and contract anodizers to validate process consistency and product performance.
- Materials engineers, specifiers and compliance teams who need objective data on UV/heat fastness to inform product selection, warranties and specifications.
- Third‑party testing bodies that provide certification or comparative performance data.
Practical value: helps predict comparative colour stability under severe UV/heat exposure, supports process optimization, and provides data for product specifications and customer claims.
Related standards
- ISO 7583 - Terms and definitions for anodizing of aluminium and its alloys (normative reference).
- EN ISO 6581:2018 supersedes EN ISO 6581:2010 (update/addition of specimen information).
