Process for plating adherent co-deposit of aluminum, zinc, and tin onto metallic substrates, and apparatus

Abstract

A co-deposit of aluminum, zinc and tin can be deposited onto metallic substrates including small metal parts, and the co-deposit is strongly adherent to the substrate and exhibits improved corrosion resistant properties. The co-deposits are plated onto metallic substrates by a process which comprises the steps of a. preparing the substrate to receive the co-deposit, b. forming a slurry comprising a soluble source of stannous ions, impact media, and aluminum and zinc in particulate form in a liquid medium maintained at a pH below about 4, c. mechanically impacting the slurry against the surface of the metallic substrate in a plating container to plate a co-deposit of tin, aluminum and zinc on a metal surface, d. renewing the stannous ions, aluminum and zinc in the slurry while maintaining the pH of the slurry below about 4 throughout the plating process until a co-deposit of the desired thickness is obtained. The invention also includes metallic substrates plated with the co-deposit of aluminum, zinc, and tin in accordance with the process of the present invention as well as slurry compositions which are useful in plating such co-deposits on metal substrates. The invention also includes metal fasteners plated with said co-deposits in contact with aluminum articles to be fastened. An improved apparatus also is described and claimed for carrying out the process of the invention.

Dependencies are inferred from the claim text.