Process of electroless deposition of zinc and lead on aluminum in electrolyte melt by contact exchange method

The mechanism of electroless deposition of lead and zinc and their codeposition on an aluminum substrate in a chloride electrolyte melt at temperatures below the melting point of aluminum has been studied. It is shown that lead forms a dense thick (up to 60 μm) porousless layer on aluminum during the contact exchange, whereas zinc coatings are not more than 30 μm thick and have a number of pores a few nm to 1 μm in diameter penetrating to the aluminum substrate. When lead and zinc are deposited simultaneously, the whole aluminum surface is covered with a two-phase coating lead precipitates as round spots with zinc between them; areas with deposited lead are free of zinc and vice versa.