Tank process for plating aluminum substrates including porous aluminum castings

Abstract

An improved tank process for plating aluminum substrates which is especially advantageous for plating porous aluminum castings and, blister-free plated aluminum substrates produced thereby, characterized in that the aluminum piece parts are: (i) emulsion cleaned in a room temperature alkaline cleaner; (ii) immersed in a room temperature dilute acid, inorganic, fluoride salt solution to dissolve heavy oxides and surface silicon while minimizing etching and intergranular attack of the aluminum substrate such, for example, as a porous cast aluminum substrate; (iii) immersed in a room temperature dilute zincate bath for applying a relatively thin zinc protective coating, preferably utilizing a double zincate immersion process with an intermediate prolonged (1-3 min.) nitric acid soak to reduce the zincate deposition rate and to thereby provide improved zincate adhesion; (iv) plated with a non-porous strike applied directly on the zincate protective coating--e.g., by electroplating or by electroless plating methods such, for example, as by immersion in a bath of nickle-hypophosphite material maintained at a temperature of approximately 190.degree. F.; and (v), immersed in a metal plating bath such, for example, as a tin plating bath--preferably, a low pH, room temperature acid tin bath--so as to apply a blister-free electrically conductive surface on the porous aluminum casting.

Dependencies are inferred from the claim text.