Understanding chipping resistance property of automotive coating

For automotive coatings, chipping resistance is an important coating property.

What is chipping resistance?

By definition, the ability of one or more coats of paint or coating system to resist the removal of any portion of their surface as a result of impacts is called chipping resistance. This is an important mechanical property of a coating applied for automotives. This coating property is important for rail, metro, commercial as well as personal vehicles for durability of the coating.

Expectation of a vehicle owner:

As a vehicle owner nobody likes chipping out of coating from the surfaces generally created in front or back of the vehicles due to stone gravels getting impacted over the coating during the vehicle run over the road. Similarly, for other types of transport vehicles also the owner of the vehicle expects the coatings to resist the stone chips which falls during the vehicles run.

Let us understand the phenomena:

Impact over coating surface by gravels or stones (by bombardment) is a very common phenomenon on roads and rails. Coatings can have good adhesion and hardness but chipping is the real test for damage resistance of the coating for hardness, flexibility and adhesion simultaneously due to impact.

To test the coating in lab for resistance to chipping, road gravels are projected by air blast equipment over the coated specimen at specified temperature. After the impact is done by gravel a tape is applied over coating to remove the loose coating chips and the degree of damage is determined by observation.

Coating formulation perspective:

During coating formulations for automobiles, trains etc. this service requirement is an important property to meet. Due to increased brittleness, decreased flexibility of the coating and probability of reduced adhesion at lower temperature, the coating can show poor chipping resistance. So, testing the coating at lower temperature becomes more important. This testing is done at a specified area over the coated panels as per ASTM D 3170.

Test method reference:

Standard Test Method for Chipping Resistance of Coatings (astm.org)

Contact to understand more: Amatech Innovation

Amatech is a registered trademark of Amatech Innovation.