Stone Throwing Devices

ISO 20567-1 / SAE J400 / ASTM 3170

In the automotive industry, multi-layer paint coatings are applied to vehicle bodies for protection purposes. Materials such as sand, road stones, and other debris can damage these coatings, causing individual layers to peel off or the entire coating to separate from the substrate.

The stone chip resistance of the tested coating is evaluated by exposing it to numerous small sharp-edged particles in a short period. The test involves the controlled air blast of standard road gravel onto an appropriate test panel. The test apparatus is designed as a stone chip tester, which includes road gravel, a test panel holder, and a stone impact mechanism based on air pressure.

At the end of the test, the resistance of single-layer or multi-layer coatings to multiple mechanical impacts is determined.

The extent of the damage will depend not only on the angle but also on the pressure level, the mass of the stones, the duration of the bombardment, and the design of the test apparatus. The size of the damage is determined by comparing it to pictorial reference standards.

To operate this device, you must have the following systems:

• • Air compressor (providing 6-8 bar or 8-12 bar pressure)

SAE J400 / ASTM 3170

The test is designed to replicate the effect of gravel or other media striking the exposed paint or coated surfaces of an automobile. The specific purpose of the test is to evaluate organic surface coatings or systems on flat test panels; however, such tests may be extended to finished parts or other types of materials.