Formation of Ag Dendrites During the Electrolytic Migration Between Ag-4Pd Wire Couple in Water Under Bias

The growth of Ag dendrites induced by the Ag ion migration between Ag-4Pd alloy wire couples immersed in pure water under bias was observed, and its failure mode leading to a short circuit was investigated. The experimental results indicated that the time of dendrite contact and short circuit decreased obviously with increases in voltage and wire pitch. In contrast, the formation time of hydrogen bubbles and Ag spikes in the initial stage of water drop tests decreased slightly with increases in applied voltage, leading to drastic increases in the Ag dendrite growth rate at higher voltages. During the electrolytic migration process, the outer surface of the anode wire oxidized into a continuous Ag2O layer with a porous grain structure. In addition, Ag+ ions were reduced to crystallographic Ag2O particles that formed a layer concealing the anode wire. Summarizing the observations of Ag dendrite growth and the Ag2O layer formed on cathode and anode wires, respectively, a reaction mechanism for the electrolytic migration of Ag-4Pd wire couple is proposed.