ASTM Committee D01 (Paint and Related Coatings, Materials, and Applications) withdrew D2794 due to:

Failure is defined by the appearance of cracks or delamination in the coating. Because these cracks can sometimes be microscopic, technicians use several methods for confirmation:

Reverse impact, however, is often considered the more rigorous test of adhesion and tensile elongation. By deforming the metal outward, the coating is forced to stretch apart. If the adhesion to the substrate is weak, the coating will delaminate in a circular pattern, a phenomenon known as "crowing’s feet" or radial cracking. This simulates stresses like a stone striking the undercarriage of a vehicle or the deformation of metal sheets during fabrication processes. Together, these two orientations provide a comprehensive profile of a coating's mechanical behavior.

| Factor | Effect | |--------|--------| | | Thicker = less deformation = higher apparent impact resistance. Must be fixed in spec. | | Substrate hardness | Softer metal (e.g., aluminum vs. steel) deforms more, increasing coating strain. | | Film thickness | Thicker films are more prone to cracking under rapid stretch. | | Temperature | Lower temperature increases brittleness. Some specs require low-temp impact (e.g., –20°C). | | Humidity | High humidity can plasticize some coatings, raising impact values. | | Indenter/die wear | Worn edges change stress concentration. Equipment must be verified with reference panels. | | Operator technique | Dropping vs. releasing, panel centering, inspection method. |

The maximum energy at which the coating shows no cracking or detachment (pass). Sometimes reported as the energy at which first failure occurs (critical value).

ASTM D2794 defines two distinct test modes: