Electroless gold plating using L-cysteine as reducing agent & its deposition mechanism

Electroless gold plating was studied in a solution containing a mercaptosuccinic acid complex, with L-cysteine used as a reducing agent. This process contains no cyanides while operating at a neutral pH. The autocatalytic process produced a smooth, dull-to-lustrous gold film. Even at nickel contamination levels up to 100 ppm, the bath neither decomposed nor developed an indication of turbidity. A study of the deposition mechanism for this bath is also given in this paper.