Gravel Bombardment Test As Per ISO 20567-1

Gravel Bombardment Test as per ISO 20567-1: Ensuring Automotive Coating Durability

Introduction

Automotive coatings play a vital role in protecting vehicles from environmental damage, including stone chipping caused by road debris. The gravel bombardment test, as defined in ISO 20567-1, is a standardized process used to assess the resistance of painted surfaces, clear coats, plastic components, and protective films to stone impacts. By simulating real-world conditions, this test helps manufacturers ensure long-term durability and performance of coatings under extreme conditions.

What is the Gravel Bombardment Test?

The gravel bombardment test evaluates how well a coated surface withstands repeated impacts from gravel, stones, or synthetic particles propelled at high speeds. This simulates conditions such as:

✔ High-speed driving on gravel roads.
✔ Debris kicked up by other vehicles.
✔ Stone impacts during harsh weather conditions.

Why is This Test Important?

✔ Ensures paint durability against stone chips.
✔ Improves coating adhesion for long-term protection.
✔ Helps automotive manufacturers meet OEM quality standards.

ISO 20567-1: Standardized Testing Method

ISO 20567-1 defines a structured process to ensure repeatability and reliability in testing. The test is conducted under controlled conditions to evaluate the chipping resistance of coatings based on severity levels A, B, or C.

Test Setup and Procedure

1. Sample Preparation

The test panel consists of a metal or plastic sheet coated with primer, basecoat, and clearcoat.
The panel is fully cured before testing.

2. Gravel Impact Simulation

A gravelometer machine is used to propel small stones at the test panel.
The stones hit the surface at a specified speed and angle.
The test is performed under static conditions (the panel remains fixed).

3. Severity Levels

ISO 20567-1 allows manufacturers to choose between three severity levels:

Severity A – Low-impact test with fewer stone hits.
Severity B – Medium-impact test simulating real-world conditions.
Severity C – High-intensity bombardment for extreme durability testing.

4. Post-Test Evaluation

After exposure to gravel bombardment, the test panel is assessed for:

✅ Number & size of stone chips under microscopic analysis.
✅ Coating adhesion (using tape tests).
✅ Surface protection efficiency based on coating thickness and material integrity.

Functional Requirement as per ISO 16750-1

After the gravel bombardment test, the functional status of the coating must meet Class C as defined in ISO 16750-1. This ensures that the material remains effective even after experiencing severe chipping or mechanical stress.

Applications in the Automotive Industry

The gravel bombardment test is widely used by automotive manufacturers and suppliers to improve:

🚗 Exterior Paint & Clearcoat Durability – Ensuring resistance to stone chips.
🚗 Plastic Components (Bumpers, Grilles, Trim) – Testing impact durability.
🚗 Headlights & Glass Protection – Evaluating the resistance of transparent materials.
🚗 Underbody Protection – Verifying coatings in high-exposure areas.

Conclusion

The gravel bombardment test (ISO 20567-1) is essential for verifying the stone chip resistance of automotive coatings. By following standardized testing methods, manufacturers can enhance material selection, optimize coating performance, and improve vehicle durability.

FAQ

1. What is the Gravel Bombardment Test?

The Gravel Bombardment Test, as per ISO 20567-1, evaluates the resistance of painted surfaces, clear coats, plastic parts, and protective films to stone chipping by simulating real-world gravel impact conditions.

2. What equipment is used for the test?

A gravelometer is used to propel small stones at high speed and a controlled angle to simulate real-world gravel impacts.

3. What is the functional requirement as per ISO 16750-1?

After testing, the material should meet Class C functional status, ensuring it remains effective despite chipping or mechanical stress.

4. Who should perform the Gravel Bombardment Test?

This test is crucial for automotive manufacturers, coating suppliers, and material testing laboratories to verify coating durability and compliance.

Gravel Bombardment Test As Per ISO 20567-1