An Evaluation of the Resistance to Electrolysis of Metals for Use in Biostimulation Microprobes

Electrolysis measurements have been made on electrodes of platinum, stainless steel, tungsten, iridium, palladium, rhodium, rhenium, gold, tantalum, titanium, zirconium, and some conducting oxides of the tungsten bronze family. Electrodes were immersed in physiologic saline solution and subjected to biphasic rectangular current pulses of various current densities at 50 pps, 24 hours per day for periods up to nine months. Weight loss was recorded at intervals during this time. We conclude that iridium,rhodium, platinum and palladium are extremely resistant to electrolysis under these conditions and electrolysis under 5¿ thick, made of such materials should have lifetimes on the order of decades. Gold is somewhat poorer but probably acceptable; all the other materials tested, including tungsten and stainless steel, are unacceptable as chronic microelectrode materials.