Effects of temperature and voltage on the growth process of electrochemical migration (ECM) for screen-printed silver wiring electrodes were investigated using electrochemical impedance spectroscopy.The reaction resistances for the anode and cathode decreased along with the decrease of temperature during the initial growth of a silver dendrite on the cathode surface. However, no change in the reaction resistance for the anode with temperature was observed immediately before short-circuiting of the silver wiring electrodes because the rate-determining step of the anodic reaction changed with dendrite growth from the charge transfer reaction of silver dissolution to the diffusion of the silver ion. Growth processes can be classified as four stages according to the time variation of the reaction resistances and solution resistance for voltages lower than 0.7 V.
An electronic balance was used to investigate the time-variation of the amount of hydrogen gas evolved during anodic dissolution of iron corresponding to electric charges of 5.0 C at 20 mA/cm2 current density. The electrodes were made of commercial type iron of 99.5% purity. The corrosive solutions were a chloride-sulfate mixed bath of pH 8.0(0.5 M NH4Cl - 0.5 M Na2SO4 - 0.1 M H3BO3 - 0.1 M Na2B4O7). Use of an electronic balance enabled in situ measurements of the buoyancy attributable to the hydrogen gas bubble formed during the pitting corrosion of the iron. Measurements also elucidated the induction period from the beginning of electrolysis until hydrogen gas formation. The results indicate that a strongly corrosive solution formed progressively in the pits brought about chemical dissolution of iron followed by hydrogen gas evolution.