In a study of electroless indium plating with titanium trichloride as a reducing agent, indium film was directly deposited onto Pd-catalyzed aluminum substrate at a rate of 1.56mg·cm-2
, and it was possible to continue plating by renewing the bath at 30-minute intervals.
The optimum bath composition was 0.08M indium trichloride, 0.32M trisodium citrate, 0.20M NTA, and 0.04M titanium trichloride. The recommended plating conditions were pH10.0 and 80°C. It was seen that further addition of EDTA to stabilize the bath greatly delayed plating.
Indium alloy plating was also investigated. Binary alloy films of indium were electrolessly plated from indium baths to which various metal salts were added for alloying. Alloy films of Ni-In, Pb-In, As-In, Fe-In, and Sn-In were formed, but Co, Zn, Al, Bi, Sb and Cu were not co-deposited with indium.