PERIODIC BEHAVIOR IN THE IRON SULFURIC-ACID SYSTEM

Potentiostatic current oscillations observed during the anodic dissolution of an iron electrode in a sulfuric acid electrolyte are considered. This behavior has been experimentally characterized with respect to its potential dependence. A new mechanism has been developed that is consistent with observed behaviors and trends. This mechanism combines previously developed ideas concerning periodic behavior and passivation of iron with a new interpretation of precipitated salt-film behavior. The salt film is taken to be nonporous, serving as both a necessary precursor to oxide passivation as well as an effective passivating species itself. The mechanism is well corroborated by results from a mathematical model which also highlights the necessity of salt-film precipitation for the development of periodic behavior. Additionally, the issue of coherence is explicitly considered.