Autocatalytic Deposition of Gold‐Copper Alloys

A wide range of Au—Cu alloys was deposited from alkaline electroless solutions containing KAu(CN) sub 2 , cupric ions complexed with EDTA and formaldehyde as reducing agent. Using electrochemical measurements it was shown that in the presence of cyanide ions the oxidation of formaldehyde, which provides the electrons for the Au-ion reduction, can only occur on a Cu-containing surface. The kinetics of the electroless deposition reaction are described and discussed in terms of the electrochemical results. X-ray diffraction measurements showed that only homogeneous mixed crystals of Au and Cu are obtained with a single lattice constant for each composition. 10 ref.—AA