Overview
EN ISO 22557:2020 (identical to ISO 22557:2019) specifies a standardized scratch test using a spring‑loaded pen to determine the resistance of paints and varnishes (coatings) to scratches caused by a loaded stylus. The method covers two options: Method A (point stylus) and Method B (disc stylus). Tests can be performed in the laboratory, in the field, or on curved surfaces. The procedure supports both pass/fail testing (test requirement I) and classification testing (test requirement II).
Key topics and technical requirements
- Test principle: A spring‑loaded hardness pen applies a controlled load (0.5 N to 20 N) while the stylus is moved manually over the coating; resulting damage is assessed visually (with magnifier).
- Apparatus: A hardness pen with removable head piece, pressure spring, slider with a scale in newtons and, where applicable, supporting wheels to avoid head‑piece interference.
- Styli:
- Method A - point styli with spherical tungsten‑carbide inserts: diameters (0.50 ± 0.01) mm, (0.75 ± 0.01) mm, (1.00 ± 0.01) mm.
- Method B - disc styli with polished edge; materials include stainless steel, copper, thermoset, or PMMA.
- Test loads and springs: Exchangeable springs allow different load ranges (common ranges cited: 0.5–3 N, 1.5–10 N, 3–20 N). Lower limits must not be underrun due to spring non‑linearity and friction.
- Specimens and conditioning: Method A can be applied on small specimens (minimum 30 mm × 50 mm). Film thickness and conditioning requirements are referenced.
- Assessment and reporting: Damage assessment methods, precision (repeatability/reproducibility) considerations, and required test report formats are included.
Practical applications
- Evaluating coating scratch resistance during product development and quality control.
- Field or on‑site testing of finished components and curved surfaces (e.g., automotive panels, architectural elements, marine fittings).
- Comparative testing for coating selection, supplier compliance, and failure analysis where surface durability against stylus contact is a concern.
Who should use this standard
- Coatings manufacturers and formulators
- Quality control and test laboratories
- Automotive, aerospace, marine and architectural specifiers
- Product designers and surface engineers
- Standards writers and procurement teams specifying scratch resistance requirements
Related standards
The document references normative standards relevant to sample preparation, measurement and assessment, for example:
Using EN ISO 22557:2020 ensures consistent, comparable scratch testing results across laboratories and suppliers, supporting robust specification and acceptance criteria for coatings and finished surfaces.
