CHAOTIC BEHAVIOR OF CURRENT OSCILLATIONS DURING IRON ELECTRODISSOLUTION IN SULFURIC-ACID

Current oscillations vs time series were measured during iron electrodissolution in sulfuric acid solutions. The load line of the potentiostat was modified by an external resistance connected between the iron wire electrode and the potentiostat. The complex temporal behavior of these time series was diagnosed as deterministic chaos by the (i) reconstruction of the strange attractor, (ii) measurement of the Grassberger-Procaccia dimension (iii) calculation of the first Lyapunov exponent, and (iv) analysis of-the power spectra. In the anodic scan, oscillations start and stop with high values of Lyapunov exponent (greater than 40 bits/s). For the cathodic scan, the Lyapunov exponent increases as the potential increases. The calculated dimension varies between 1 and 3, for distinct values of potential and external resistances. The values of the dimension and the Lyapunov exponent decrease with the increasing of the external resistance. The route from periodicity (or quasi-periodicity) to chaos is probably related to the doubling at the period, with typical characteristics of a degenerated Hopf bifurcation.9948174031740