Cathodic cycling effects in the oxide films formed on zirconium alloys type AB2

The passive behavior of ZrNi alloys near the rest potential is studied through in situ voltammetry, ellipsometry, and microscopic observation.A significant oxide layer growth is observed in aqueous 1 M KOH during the application of different potential programs currently used in the activation processes of the alloy.The understanding of both the alloy activation process and the hydrogen absorption process is important in the strategies employed for the design of electrodes for nickel metal hydride batteries.The kinetics of the oxide layer formation, under potential cycling in the cathodic region related to the rest potential, plays a significant role in the activation process of metal alloy.Cathodic potential cycling increases the thickness and decreases the compactness of the passive oxide layer.The protonation of the oxide decreases the barrier effect and makes the anodic polarization more effective.Potential cycling gives rise to increasing surface oxidation, hydrogen absorption and hydride formation, and produces the consequent fragmentation of the material mainly through grain limits (J.Solid State Eletrochem. in press)