Pinhole and blister formation during autodeposition coating of active metal objects, particularly galvanized steel, other zinciferous surfaces, and even ordinary steel that has been abraded, scratched, or otherwise strained, can be greatly reduced by exposing the active metal surfaces to a solution containing cystine before using a autodeposition process itself, or by adding cystine to an otherwise conventional autodeposition composition.
Pinhole and blister formation during autodeposition coating of galvanized steel and similar zinciferous surfaces can be greatly reduced by exposing the zinciferous surfaces to a pinhole inhibiting aqueous HF solution containing a suitable additive before using an autodeposition process itself. The most effective additives are boric acid, polyphosphonic acids, and polyethyleneimine.
