What Is Stone Chip?
The stone chip test evaluates the paint system's resistance to gravel and stone impacts, and how far the damage progresses through the layers. The method defined in ISO 20567-1 uses a rig similar to the gravel impact test but differs in its grading approach and repeated-exposure options.
Purpose of Stone Chip
The purpose is to evaluate the paint system's interlayer adhesion and its ability to absorb impact energy, and to identify damage reaching the metal that could lead to corrosion initiation.
Which Products Is Stone Chip Applied To?
- Vehicle body painted surfaces
- Undercarriage protective coatings
- Bumper and exterior plastic-part paints
- Commercial-vehicle cab paints
In Which Sectors Is Stone Chip Used?
Standards Related to Stone Chip
- ISO 20567-1
- VDA 621-427
- SAE J400
- ASTM D3170
Stone Chip Conditions
- Gravel properties
- At the hardness and size distribution defined in the standard
- Pressure and repetition
- At the pressure prescribed by the standard; single- or multi-stage exposure
- Conditioning
- At room temperature or the low temperature specified in the specification
Equipment for Stone Chip
- Stone-chip test machine
- Compressed-air system
- Cooling/conditioning cabinet
- Reference grading cards
- Adhesive tape (for lifting off loose particles)
Sample Requirements for Stone Chip
- Standard-size painted panels or real parts
- Generally at least three specimens
- The paint system description and layer thicknesses must be stated
- Specimens must be fully cured
Duration of Stone Chip
The test is short; if corrosion follow-up is required, specimens are subsequently put through a salt-spray test and the duration extends accordingly.
Stone Chip Procedure
- 1The paint system and film thicknesses are recorded.
- 2The specimen is conditioned.
- 3It is placed in the machine and gravel is sprayed under the defined conditions.
- 4Loose paint particles are lifted off with tape.
- 5The damage is graded by comparison with the reference cards.
- 6If requested, the specimen is put through a corrosion test and reassessed at the end of the period.
Stone Chip Acceptance Criteria
The acceptance criterion is the grade in the OEM specification. If a corrosion test after stone chipping is required, the corrosion spreading from the impact points not exceeding the permitted millimetres is also evaluated.
Evaluation of Results
The size, count and layer reached by the damage are graded. Salt spray is often applied following the stone chip test to examine corrosion spread; this combination gives stronger information about the paint system's real performance.
Stone Chip Report
- Standard applied
- Paint system description and layer thicknesses
- Test conditions
- Grading results
- Layer reached by the damage
- Results, if corrosion follow-up was performed
- Photographs
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- OEM paint and corrosion specifications
Otomotiv Testleri — What Does This Testing Field Cover?
The section below describes the field that the Stone Chip test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Automotive testing shows that a component keeps working under conditions representing the loads it will meet over the life of the vehicle. A vehicle is not a single product but an ENVIRONMENT: vibration, temperature cycling, salt water, stone impact, electrical transients and electromagnetic noise are all present at the same time and for years.
What distinguishes this family is that VEHICLE MANUFACTURER SPECIFICATIONS sit on top of the standards. ISO and SAE publications establish the common ground; but Volkswagen, BMW, Ford, Stellantis, Toyota and Renault define different severity levels, additional tests and different acceptance criteria in their own specifications. For a component, the phrase "complies with automotive standards" is not sufficient on its own; which manufacturer's specification, and which revision of it, must be answered.
The family carries three separate processes together and they are often confused. Homologation covers the type approvals a vehicle needs to enter traffic and runs under state authority. Supplier approval means passing the vehicle manufacturer's own quality and testing requirements and is a commercial relationship. The third is design verification: the engineering team demonstrating that its own design meets its targets.
At component level the test plan is built around the LOCATION OF USE. A module in the engine bay and a module in the boot do not go through the same temperature and vibration profile; a component inside a door and one in the roof console do not see the same water and dust exposure. The ISO 16750 series is the common framework for this location-based approach.
The shift to electric vehicles has reshaped the field. High-voltage safety, insulation coordination, battery safety, charging interface conformity and the electromagnetic behaviour of high-voltage components have been added to the classical automotive test set. In a quiet vehicle, acoustic and vibration expectations have changed too; sounds once masked by the combustion engine are now audible.
The quality system side cannot be separated from testing in this field. A manufacturer under IATF 16949 presents test results in the PPAP file; measurement system analysis, process capability study and the control plan stand around the test report. A single good result is not enough — the process must be shown to be able to repeat it.
Method groups in this field
Environmental and climatic
Temperature cycling, thermal shock, damp heat, salt spray, dust and water ingress (IP), solar radiation. Severity levels vary with the mounting location.
Mechanical
Sine and random vibration, shock, mechanical loads, fastener torque and durability cycles.
Electrical
Supply voltage variations, transients (ISO 7637), reverse polarity, overvoltage, short circuit and sleep current measurements.
EMC
Component emissions (CISPR 25), radiated and conducted immunity (ISO 11452 series), electrostatic discharge (ISO 10605).
Materials and emissions
Odour, fogging and VOC emissions from interior materials; flammability; UV ageing; coating durability and stone impact.
Functional safety and cyber security
Functional safety evidence under ISO 26262 and cyber security engineering under ISO/SAE 21434; these are tied to regulation through UNECE R155 and R156.
Commonly confused in this field
- An automotive report without a specification reference is not accepted in the supply chain; which OEM specification and revision was applied must be stated.
- Type approval and supplier approval are different processes. A component with E-Mark approval is not thereby considered to have passed the OEM's own acceptance tests.
- A result obtained on a prototype does not carry over to series production; PPAP is done with series production parts.
- On the EMC side, measuring emissions alone is incomplete; immunity is a separate body of work and is more critical in a vehicle.
- On electric vehicle components, high-voltage safety is a distinct competence; classical 12 V test infrastructure is not sufficient.
Which decisions these results support
- Supplier component approval and the PPAP file
- UNECE type approval and E-Mark marking
- Design verification and durability evidence
- Root cause analysis of field complaints and warranty returns
- Assessing the impact of a design or supplier change
Related Tests
Frequently Asked Questions About Stone Chip
Which should I choose between ISO 20567-1 and SAE J400?
The customer's specification determines this. European OEMs mostly require ISO 20567-1 and VDA 621-427, while North American OEMs require SAE J400. Since the grading scales differ, results cannot be directly compared.