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Potential Oscillations in Cellular Automaton Based Model for Passivation of Metal Surface
Jan Stępień and Janusz Stafiej

Stochastic Cellular Automaton is used to model the corrosion and passivation of metals in electrolytes. The growth of the passive layer is simulated with asynchronous CA implementation for parallel processing on a GPU.

In the present version of our model, the studied system is under galvanostatic control. We assume that the electric potential corresponds one-to-one to the intrinsic corrosion rate. At the same time, the electric current is directly proportional to the observed corrosion rate which is smaller than the intrinsic rate because of passivation. Thus galvanostatic control amounts to adjusting the intrinsic corrosion rate to keep observed corrosion rate constant. In other words, potential is adjusted to fix the current flow to a prescribed value. In the electrochemical experiments, this leads to potential oscillations for certain values of the current. This is related to the fact that for certain range of potentials our system displays negative differential resistivity. Similarly, we observe potential oscillations in our simulations. To our knowledge this is the first time that this peculiar feature of passivating systems is reproduced by a simulation.

Keywords: Corrosion, passivation, diffusion, oscillations, modelling, parallel computing, block-synchronous automata, asynchronous cellular automata, stochastic cellular automata

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