Chip Resistance of Coatings
(Gravelometer)
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ASTM D3170
SAE J400
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Scope:
The Gravelometer is designed to evaluate the resistance of surface coatings (paint, clear coats, metallic plating, etc.) to chipping caused by the impacts of gravel or other flying objects. The primary usage of this test is to simulate the effects of the impact of gravel or other debris on automotive parts.
Test Procedure:
The test sample is mounted in the back of the Gravelometer, and air pressure is used to project 1 pint (approximately 300 pieces) of gravel at the sample. The test sample is then removed an gently wiped off with a clean cloth. Tape is then applied to the entire tested surface. Removal of the tape then pulls off any loose fragments of the coating. The appearance of the tested sample is then compared to standard transparencies supplied by SAE to determine the chipping ratings. Visual examination can also be used to describe where in the coating/substrate system that the failure has been induced.
Specimen size:
A coated 4 inch by 12 inch panel - SAE recommends 3 replicates.
Data:
Chipping Ratings consist of one or more letter-number combinations. The letter designates the chip sizes being counted, and the number designates the number of chips of that size. For example B6 indicates 10-24 chips 1 to 3 mm in size.
Point of Failure describes the coating layer where the primary failures are occurring - for example P/T indicates that the point of failure is between the primer and the top coat.
Equipment Used:
Q-Panel Q-G-R Gravelometer
Water-worn road gravel from Q-Panel
SAE J400 Chipping Standards
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