Spatiotemporal patterns on iron electrodes in sulfuric acid: Experiments and models

Spatiotemporal patterns on electrodissolving iron surfaces are studied under autonomous and forced conditions in experiments and models.; An iron ring has been shown to produce a sequence of patterns in experiments, as a function of applied potential. The ring was undergoing electrodissolution potentiostatically in 1 M H₂SO₄. A polarized light was shined on the surface and the reflected light was directed through a crosspolarizing film. The spatiotemporal patterns produced were recorded and digitized. The patterns illustrate changes in symmetry as spatial and temporal bifurcations take place. Proper orthogonal decomposition is used to determine how these symmetry changes occur.; Several models of active-passive electrodissolution of a metal surface are developed which produce oscillatory behavior and spatiotemporal patterns. The first model has a 2-dimensional electrolyte and simulates a ringlike working electrode with the point-like reference electrode. Simple homogeneous oscillations are transformed into more complex dynamics and then to spatiotemporal chaos by changing the reference electrode position. The second model contains a full 3-dimensional electrolyte. This allows the reference electrode to be placed within the radius of the ring. By changing the conductivity of the electrolyte, antiphase oscillations are turned into rotating waves on the working electrode.; An eight electrode line-array of iron electrodes was used to study the effects of forcing on a set of coupled chaotic oscillators. First a local forcing was applied by controlling the current on one electrode using a sinusoidal forcing function. When the frequency and amplitude of the forcing reached proper values the chaotic signals were converted to periodic signals in a stepwise manner moving away from the forced electrode. Additionally, a global forcing term was added to the applied potential in separate experiments. It also reduced complexity on some electrodes. A model based on the active-passive electrodissolution was used to simulate local and global forcing in a chaotic set of oscillators and also produced periodic behavior on a ring-like electrode.