What Is Scratch?
The scratch test is a test in which scratch resistance is determined by moving a tip of defined geometry across the surface under a constant or increasing load. The result is expressed as a critical load or scratch visibility.
Purpose of Scratch
The purpose is to determine how much the surface resists visible scratch formation during use, and to assess coating-to-substrate adhesion.
Which Products Is Scratch Applied To?
- Automotive interior and exterior trim surfaces
- Paint and varnish systems
- Hard coatings (PVD, DLC)
- Plastic body parts
- Furniture surfaces
In Which Sectors Is Scratch Used?
Standards Related to Scratch
- ISO 1518-1
- ISO 1518-2
- ASTM D7027
- ISO 20502
- ASTM G171
Scratch Conditions
- Tip geometry
- Spherical or diamond tip of the radius defined in the standard
- Load
- Constant load or progressive (increasing) load
- Scratch speed
- Constant rate per the standard
- Environment
- 23 °C ± 2 °C and 50% ± 5 relative humidity
Equipment for Scratch
- Scratch tester
- Calibrated tips
- Optical microscope or confocal profilometer
- Colour/gloss meter (for appearance assessment)
Sample Requirements for Scratch
- The surface must be clean, fully cured and flat
- Coating thickness must be measured and recorded
- The spacing between scratches must conform to the standard
- Generally at least three scratches are applied
Duration of Scratch
The test is short; together with evaluation and microscopic examination, one specimen takes half a working day.
Scratch Procedure
- 1Coating thickness and initial gloss are measured.
- 2The tip and load setup are adjusted per the standard.
- 3A scratch is applied at the defined speed.
- 4The scratch is examined with a microscope; the critical load is determined.
- 5Change in gloss or colour is measured if required.
Scratch Acceptance Criteria
The acceptance criterion is given in the specification as a minimum critical load, or as the absence of a visible scratch at a specified load. Automotive OEM specifications define their own criteria.
Evaluation of Results
Scratch depth, width and coating delamination are evaluated together. The coating opening through to the substrate is recorded as a separate non-conformity.
Scratch Report
- Standard applied
- Tip geometry, load profile and speed
- Coating system and thickness
- Critical load and scratch dimensions
- Microscopic images
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
- Automotive OEM surface standards
- Paint and coating specifications
Otomotiv Testleri — What Does This Testing Field Cover?
The section below describes the field that the Scratch 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 Scratch
How is a choice made between constant load and increasing load?
Constant load is used when the specification asks whether a scratch occurs at a specific load. Increasing load is preferred to determine the coating's damage-onset threshold (critical load).