Control strategies for the improvement of corrosion resistance

The corrosion resistance of a metal surface in contact with an aqueous medium can, in principle, be improved by imposing conditions that cause the otherwise chemically active surface to be passivated. In this work, several different control strategies directed toward achieving this end are investigated using the two-dimensional Sato model as a prototype for metal passivation. First, the classic linear feedback theory is applied and is shown quite generally to be unusable in the sense of achieving complete passivation of a chemically active surface. Then, extension of the model by addition of a third state variable is shown to be capable of yielding complete passivation. Finally, a third strategy, based on feedback control of the two-dimensional model, is shown to result in significantly increased levels of passivation, and therefore in correspondingly improved corrosion resistance.