ISO 20567-1:2017

Overview

ISO 20567-1:2017 - Paints and varnishes - Determination of stone-chip resistance of coatings - Part 1: Multi-impact testing - defines a laboratory method to evaluate the stone-chip resistance of automobile finishes and other coatings. The standard simulates the impact of small stones by projecting chilled‑iron grit onto coated test panels using a multi‑impact tester and quantifies damage by comparison with pictorial reference standards.

Keywords: ISO 20567-1, stone-chip resistance, multi-impact testing, chilled-iron grit, paint durability, automobile finishes

Key topics and technical requirements

• Test principle: Bombard the coated surface with chilled‑iron grit using compressed air; damage depends on angle, pressure, projectile mass, duration and apparatus design.
• Apparatus: A multi‑impact tester with a vibrating conveyor and grit‑accelerating nozzle capable of projecting 500 g of grit during the test period. Pressure chamber and nozzle geometry are specified to ensure uniform impact.
• Grit specification: Chilled‑iron grit conforming to ISO 11124‑2, with a defined particle size distribution (specified in the standard). Grit is replaced after a maximum of 100 test runs.
• Test methods: Three prescribed test conditions (Methods A, B and C) differing in working pressure, number of projections and duration:
  • Method A: ~100 kPa, two projections of 500 g (short bursts)
  • Method B: ~200 kPa, two projections of 500 g
  • Method C: ~200 kPa, single projection of 500 g (also for post‑exposure testing)
• Specimen preparation and conditioning: Panels prepared per ISO 1514, coating thickness measured per ISO 2808, conditioned at (23 ± 2) °C and (50 ± 5) % RH for at least 16 h (ISO 3270).
• Evaluation and precision: Damage (breakdown/flaking) is assessed visually or by optical imaging against pictorial reference standards (ratings from 0.5 to 5.0). Repeatability r = 0.5 and reproducibility R = 1.0 on the rating scale.
• Ancillary procedures: Removal of loose paint (examples in Annex A) and optional calibration guidance (informative Annex B).

Applications and who uses it

• Automotive OEMs and suppliers evaluating stone-chip resistance of primer/topcoat systems and clearcoats.
• Paint and coating manufacturers developing and validating durable exterior finishes.
• Test laboratories performing comparative quality control, material validation and pre‑production testing.
• R&D teams assessing the effect of coating formulation, layer structure or surface treatments on impact durability.

Related standards

• ISO 20567 series (Part 2 and Part 3 - single‑impact tests)
• ISO 11124‑2, ISO 11125‑2 (grit and particle size)
• ISO 21227‑2 (optical imaging evaluation)
• ISO 1514 (test panels), ISO 2808 (film thickness), ISO 3270 (conditioning), ISO 565 (sieves)

ISO 20567-1 is a practical, standardized approach for simulating stone chipping and comparing coating performance under controlled multi‑impact conditions.