Denny - Jimmie sez it
didn't just sand like any cured paint, and the only black undercoat I know that's bullet proof is EDP .... I've found the same on TF sheet metal and saw no reason to fight it or research what it actually was .... considering the general process of electodeposit really started in the 30's or earlier [tin cans], no tellin what GM used in 52, if it was in fact an "original" door
also alpo is aluminum phosphate I think
Bill
