As a follow-up to the 1989 symposium presentation on Cadmium Free Gold Brazing Alloys, information on indium toxicity, experimental vaporization tests, and industrial exposures to indium fumes were presented. Additionally, the formation of indium cyanide surface corrosion after exposures of solder formulations to chemical “bombing” treatments was discussed. Results indicate negligible vaporization of molten indium upon exposure to air. Industrial exposure evaluations of airborne concentrations around soldering and melting operations confirm this behavior. Indium toxicity data contains minimal references to workplace exposure situations. The formation of an indium cyanide corrosion layer on 10K yellow gold solder containing 2.5% indium was confirmed through cyanide assay and scanning electron microscope surface analysis. The potential for workplace exposure to indium cyanide dusts during abrasive polishing was considered minimal due to the limited quantity of reaction product formed during cyanide chemical “bombing” operations.

Author: Greg Normandeau