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

Current oscillations vs time series were measured during iron electrod issolution in sulfuric acid solutions. The load line of the potentiost at was modified by an external resistance connected between the iron w ire electrode and the potentiostat. The complex temporal behavior of t hese time series was diagnosed as deterministic chaos by the (i) recon struction of the strange attractor, (ii) measurement of the Grassberge r-Procaccia dimension (iii) calculation of the first Lyapunov exponent , and (iv) analysis of-the power spectra. In the anodic scan, oscillat ions start and stop with high values of Lyapunov exponent (greater tha n 40 bits/s). For the cathodic scan, the Lyapunov exponent increases a s the potential increases. The calculated dimension varies between 1 a nd 3, for distinct values of potential and external resistances. The v alues of the dimension and the Lyapunov exponent decrease with the inc reasing of the external resistance. The route from periodicity (or qua si-periodicity) to chaos is probably related to the doubling at the pe riod, with typical characteristics of a degenerated Hopf bifurcation.