Control strategies for the improvement of corrosion resistance

The corrosion resistance of a metal surface in contact with an aqueous medi um can, in principle, be improved by imposing conditions that cause the oth erwise chemically active surface to be passivated. In this work, several di fferent control strategies directed toward achieving this end are investiga ted using the two-dimensional Sate model as a prototype for metal passivati on. 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 passivati on. Finally, a third strategy, based on feedback control of the two-dimensi onal model, is shown to result in significantly increased levels of passiva tion, and therefore in correspondingly improved corrosion resistance. (C) 1 999 Elsevier Science S.A. All rights reserved.