Hot Forged Components Black Spots: Helpful Cleaning Check

Summary for hot forged components black spots Discussion

Hot forged components have black spots that don't get clean and don't plate in an alkaline zinc line, and Sandra Kulkarni asks whether the cause is carbon, die oil, or a need for acid inhibitors after shot blasting. In the only reply, Daniel Montañés does not diagnose the defect directly; instead, he says the first thing to check is whether the parts are degreased before entering the acid and asks for the full tank-by-tank process before zinc plating, including whether electrolytic degreasing is used. His advice implies the problem may be in the cleaning/pre-treatment sequence rather than simply in the forging scale itself. The thread ends without a final root-cause determination, but it points toward reviewing the entire cleaning and activation process to find where the black areas are being missed.