ASTM D2794 evaluates the resistance of organic coatings to the effects of rapid deformation (impact). This test provides a method for determining the effect of such deformation by rapidly deforming a coating film and its substrate. The number of inch-pounds or kilogram-meters necessary to produce cracking is termed impact resistance.
Coatings over material substrates are exposed to damaging impacts throughout their use in different services and during the manufacturing of articles. ASTM 2794 test provides a method for determining the effect of such deformation by rapidly deforming a coating film and its substrate. The number of inch-pounds (kilogram-meters) necessary to produce cracking is termed impact resistance. This test is quite useful for determining impact resistance along with predicting the performance of organic coatings and their capability to withstand cracking caused by such impacts.
For ASTM D2794, the organics coatings are applied to appropriate thin metal panels. Then, standard weight is dropped from a distance to strike an indenter, after the coatings have cured, which helps to deform the substrate and the coating. The indentation might be of any type, either an extrusion or an intrusion. Gradually, the distance is increased, and then the weight is dropped. The point at which the failure occurs is determined. Paint films fail typically due to cracking. So, the better visualization of the cracking is done by using a magnifier such as a pinhole detector or copper sulfate solution on steel.
For the testing, uniform coating of the material to 24-gauge (0.025 inches or 0.63 mm) steel panels are treated with a conversion coating as stated by procedure A of ASTM D609. At least four coated panels are required for the test. The coating is applied as specified by ASTM D823. Also, the thickness of the dry coatings should be determined as per ASTM D1186.
The following things for each coating tested are reported: the inch-pounds at the impact failure endpoint, the diameter of the punch used, the thickness of coating and substrate, and the atmospheric conditions required for the coated panels for conditioning and testing.