Overview
EN ISO 20566:2021 (identical to ISO 20566:2020) defines a laboratory test method for assessing the scratch resistance (car‑wash resistance) of organic paint coatings, primarily for the automotive industry. The procedure simulates machine-based car washes using a laboratory-scale rotating brush and synthetic dirt to reproduce realistic washing action. When test parameters are suitably selected, the method can also be applied to protective plastic films and plastic components.
Key topics and technical requirements
- Scope: Test procedure for organic paint coatings and, optionally, plastics under simulated car-wash conditions.
- Apparatus essentials:
- Rotating washing brush: diameter (1000 ± 40) mm, polyethylene bristles (bristle thickness 0.8 ± 0.2 mm, visible length 440 ± 20 mm), rotation speed (127 ± 5) min⁻¹.
- Test panel holder: feed speed (5.0 ± 0.2) m/min with defined movement pattern relative to brush and spray nozzles.
- Spray nozzles: stainless steel, spray angle ~65°, flow (2.2 ± 0.2) L/min at (300 ± 50) kPa; two nozzles alternate against the panel travel direction.
- Container and stirring system for washing suspension; glossmeter per ISO 2813.
- Washing suspension: silica micro‑powder at (1.50 ± 0.05) g per litre water (mean particle size ~24 µm). Continuous stirring is required to avoid settling; suspension may be reused once after thorough remixing.
- Test specimens and sampling: representative sampling per ISO 15528 and preparation per ISO 1513. Test panels must be flat and agreed substrate/size; clearcoats tested over single-shade black basecoat.
- Calibration and verification: apparatus calibration using a reference panel (plastics panel or specific black paint + clearcoat) as described in Annex A.
- Evaluation and reporting: visual and instrumental evaluation (gloss, haze, reflow effect) with precision parameters (repeatability r and reproducibility R) specified in the standard; clause 11 defines required test report content.
- Limitations: brush wear increases test severity over time - method is intended for comparative tests conducted within relatively short runs and with controlled brush life.
Applications
- Comparative laboratory testing of automotive paint systems for car‑wash scratch resistance.
- Quality control and R&D for OEMs, paint formulators, and suppliers.
- Screening of protective plastic films and plastic components for wash‑induced abrasion when test parameters are adapted.
Who should use it
- Automotive manufacturers and suppliers, paint and coatings R&D teams, independent test laboratories, material suppliers, and quality assurance departments.
Related standards
Normative references include ISO 1513, ISO 2813, ISO 4618, ISO 4628-1, ISO 13076, ISO 13803, ISO 15528, and ISO 18314-1, which cover sampling, preparation, gloss/haze measurement, terminology and visual assessment methods.