Iron ion control in lead coating bath

Claim 1

IN A METHOD OF FORMING A LEAD COATING ON A FERROUS ARTICLE WHEREIN SUCH ARTICLE IS IMMERSED IN A BATH COMPRISING A WATER SOLUTION OF A LEAD SALT OF AN ALIPHATIC POLY-BASIC HYDROXY ACID HAVING A PH OF FROM ABOUT 4.5 TO ABOUT 6.5, A LEAD ION CONCENTRATION OF FROM ABOUT 3 TO ABOUT 50 GRAMS PER LITER, A SOLUBILIZING AGENT FOR SUCH LEAD ION CAPABLE OF FORMING A SOLUBLE COMPLEX THEREWITH, AND AN OPERATING TEMPERATURE OF FROM ABOUT 70*F. TO BOILING FOR A TIME SUFFICIENT TO DEPOSIT AN APPRECIABLE LEAD COATING ON SUCH ARTICLE BY A CHEMICAL DISPLACEMENT REACTION, THE METHOD OF PROLONGING THE EFFECTIVENESS OF SUCH BATH WHICH COMPRISES OXIDIZING FERROUS IRON WHICH ENTERS SUCH BATH AS A RESULT OF SUCH DISPLACEMENT REACTION TO THE FERRIC STATE, AND PRECIPITATING THE FERRIC IRON FROM SOLUTION BY REACTION WITH A SALT SELECTED FROM THE CLASS CONSISTING OF THE AMMONIUM AND ALKALI METAL FLUORIDES AND BIFLUORIDES.