| abstract |
ALUMINUM AND ALUMINUM ALLOYS ARE SUBJECTED TO A PREPLATING TREATMENT WHICH CONDITIONS THE SURFACES OF THESE METALS FOR RECEIVING ELECTROLESSLY DEPOSITED NICKEL PLATING DIRECTLY THEREON. A CLEAN ALUMINOUS SURFACE IS PREPARED FOR ELECTROLESS PLATING BY ETCHING IN AN ALKALINE SOLUTION AND THEN PICKLING IN AN ACIDIC SOLUTION CONTAINING CHLORIDE IONS. AN ALKALINE SOLUTION CONTAINING HYPOPHOSPHITE IONS IS EMPLOYED TO ACTIVATE THE ALUMINOUS SURFACE WHICH IS THEN PROVIDED WITH A THIN ELECTROLESS NICKEL STRIKE COAT BY IMMERSION IN AN AMMONICAL SOLUTION CONTAINING NICKEL IONS, HYPOPHOSPHITE IONS, AND A CHELATING AGENT. AFTER THE ELCTROLESS STRIKE COAT IS APPLIED, THE ALUMINOUS SURFACE IS PROVIDED WITH A PLATING OF ELECTRLESS NICKEL IN A CONVENTIONAL, ESSENTALLY HALOGEN-FREE BATH. |