Overview
ISO 22557:2019 - Paints and varnishes: Scratch test using a spring-loaded pen - specifies a standardized manual method to determine a coating’s resistance to scratches introduced by a loaded stylus. The test is performed with either a point stylus (Method A) or a disc stylus (Method B) using a spring-loaded hardness pen with test loads from 0.5 N to 20 N. ISO 22557:2019 supports both simple pass/fail evaluation (test requirement I) and a classification procedure with varied loads (test requirement II), and is suitable for field testing and curved surfaces.
Key topics and requirements
- Test principle: A hand-held loaded stylus is moved over the coating; damage is examined visually (magnifier) and classified.
- Methods:
- Method A (point stylus): spherical tungsten-carbide inserts, diameters 0.50, 0.75 or 1.00 mm; can be used on small specimens (min. 30 mm × 50 mm).
- Method B (disc stylus): polished discs made of stainless steel, copper, thermoset (phenolic), or PMMA for different application purposes; minimum specimen area 50 mm × 150 mm.
- Apparatus: Spring-loaded hardness pen with exchangeable springs and head pieces; supporting wheels recommended to avoid unintended damage from head piece.
- Test loads and ranges: 0.5 N to 20 N, with common graduated ranges (e.g., 0.5–3 N, 1.5–10 N, 3–20 N).
- Procedure requirements:
- Conditioning: (23 ± 2) °C, (50 ± 5) % RH for ≥16 h unless otherwise agreed.
- Speeds: ~10 mm/s (Method A) over ≥10 mm; ~100 mm/s (Method B) over ≥100 mm.
- Spacing: min. 10 mm from specimen edge; 5 mm between adjacent tracks.
- Assessment: Visual evaluation per ISO 13076; damage criteria include first visible scratch, tangible deformation, or cracking.
- Test types: Triplicate testing for pass/fail; iterative loading for classification to determine lowest load causing damage.
Applications and users
- Who uses it: Coating manufacturers, quality control labs, R&D teams, specification writers, and field inspectors in automotive, industrial, architectural and consumer coatings sectors.
- Why use it: To assess scratch resistance, compare formulations or substrates, verify compliance with product specifications, and support claims about mar resistance or metal marking resistance.
- Practical value: Portable test suitable for lab and on-site evaluation, applicable to flat and curved surfaces, and helpful for both pass/fail acceptance testing and quantitative ranking of coatings.
Related standards
- ISO 2808 (film thickness), ISO 13076 (lighting and visual assessment), ISO 4618 (terms and definitions), ISO 868 (Shore hardness for PMMA), ISO 14526-1 (phenolic materials). These referenced standards are used for specimen prep, assessment conditions, and material identification.
Keywords: ISO 22557:2019, scratch test, spring-loaded pen, paint and varnish testing, coating scratch resistance, point stylus, disc stylus, pass/fail test, classification test.
