Overview
ISO 20567-3:2012 - Paints and varnishes - Determination of stone‑chip resistance of coatings - Part 3: Single‑impact test with a free‑flying impact body specifies a laboratory method for evaluating how coatings resist damage from single stone impacts. The standard defines the test principle, apparatus, calibration, specimen preparation, test conditions and reporting requirements to simulate stone‑chipping on vehicle finishes and other coated substrates.
Key topics and technical requirements
- Test principle: A single, free‑flying impact body (hardened steel ball) is accelerated by compressed air and projected onto a coated test panel. Damage is quantified by the area of coating removed or delaminated.
- Impact body: Hardened steel ball, nominal diameter 2 mm, mass 0.033 g (ISO 3290‑1); each ball is used once.
- Impact conditions: Speed (250 ± 10) km/h [(69.4 ± 2.8) m/s] at an angle (2.0 ± 0.5)° to the normal. Preferred test temperatures: 23 ± 2 °C, 0 ± 2 °C, and −20 ± 2 °C.
- Test panels: Steel panels 200 × 100 mm, thickness 0.7–1.0 mm; surface preparation and coating application per paint manufacturer and ISO 1514/ISO 1513.
- Conditioning: Panels conditioned at least 16 h at (23 ± 2) °C, (50 ± 5) % RH before testing.
- Replicates: At least five impacts on each of two panels.
- Damage evaluation: Remove loose coating (e.g., nitrogen jet at 40 bar, adhesive tape or mechanical under microscope), then measure total damaged area (mm²) using magnification ×5–×10 or optical imaging; round to nearest whole number.
- Calibration & precision: Annex A details calibration using an aluminium plate and measuring microscope (×50–×100). Typical repeatability r ≈ 5%, reproducibility R ≈ 10% (relative).
Applications and users
- Primary application: Simulating and comparing stone‑chip resistance of automotive topcoats, primers and multi‑layer systems.
- Who uses it: Automotive OEMs, coating manufacturers, independent test laboratories, quality assurance teams, and R&D groups formulating chip‑resistant coatings.
- Practical value: Enables standardized comparison of formulations, process changes and substrate pretreatments; supports product specifications, supplier qualification and failure analysis.
Related standards
Normative and complementary references in ISO 20567‑3 include:
Using ISO 20567‑3:2012 helps ensure reproducible stone‑chip testing and meaningful comparisons across coatings and laboratories.
Open preview (PDF)Paints and varnishes — Determination of stone-chip resistance of coatings — Part 3: Single-impact test with a free-flying impact body