In the ASTM D2794 falling-weight test, a rounded indenter is dropped from increasing heights and the result is reported in inch-pounds. Direct impact hits the coated face; reverse impact hits the back so the coating stretches over the dome, which is far more severe. Many powders are specified to pass 160 inch-pounds. Failure at low values points to undercure, overbake or poor pretreatment.
Reverse impact cracked at 40 inch-pounds, that's undercure, bump the oven and pull another panel.
Also heard as
- reverse impact
- direct impact
- falling weight test
Related terms
Undercure
A film that did not get enough time at temperature to crosslink fully, so it looks fine but performs poorly.
Overbake
Cure that went too hot or too long, causing yellowing, gloss loss and brittle film.
Cross-hatch adhesion
An adhesion test that cuts a grid through the film, pulls tape over it and rates how much coating comes off.
Pencil hardness
A scratch test that rates film hardness by the hardest pencil lead that will not gouge it.