Electrochemical Oscillatory Behaviors Of Aluminum In H₂SO₄-NaCl Solutions

Aluminum and its alloys have been extensively used in aerospace, automobile manufacturing industry, construction, electronic industry, equipment production and other civilian areas due to their satisfactory features such as light weight, high strength and good mechanical properties. With the development of science and new technology, the requirement of comprehensive performance for materials is of increasing demand. Aluminum, however, are easy to be corrupted due to the unstable chemical properties. Therefore, it is of great significance to study aluminum's behaviors and mechanism of oscillations. Researches about aluminum electrochemical oscillations behavior in the process anodes dissolution can deepen understanding of the corrosion mechanism of aluminum and make contributions to development of nonlinear science.Oscillatory electrodissolution of Al in H₂SO₄ and H₂SO₄-NaCl solutions are investigated separately. Results indicate that current oscillations could occur obviously in a relatively low temperature (30℃) when NaCl is added to H₂SO₄ solution. For further study, the effects of the applied potential, the concentration of H₂SO₄ and NaCl on the current oscillations are explored respectively. Experimental results reveal that the induce time (ti) and average cycle (tp) decrease gradually with the increasing of electrode potential. In addition, the electrode potential affects reaction coefficient (k) with index form increasing, which leads to enlargement of average amplitude (â–³i) at the same time. More H+ are obtained with the increasing of H₂SO₄ concentration, which accelerates the oxidation film dissolution resulting in the rise of ti and tp, while, bringing downâ–³i. As oxidation film dissolution was accelerated with the increasing of Cl-, ti decline gradually and tp rise by depress. Besides, as the quantity of reaction electron raise up, current density comes to expansion, this ultimately enlargesâ–³i gradually.Based on the results above, dynamic analysis and simulation of current oscillation for Aluminum in H₂SO₄-NaCl system were undertaken. It involves two stage, nonlinear steps analysis and electrochemical coupling factors studying, then, a electrode process dynamic model was proposed. Regimes of dynamic behavior in the parametric plane were obtained with reference to linear stability theorem and bifurcation analysis. Meanwhile, constant potential current oscillations is modified as stable limit cycle oscillations. According to the analysis above, the concentration oscillation curve, the current oscillation curve and the power spectra are calculated respectively, and theoretical results are in accordance satisfactorily with experimental observation reported in this paper. We can conclude that the theoretical study of isoamplitude electrochemical oscillations for such electrode process can be integrated into Hopf bifurcation analysis framework, providing profoundly understanding for the mechanism of oscillations of Aluminum from new nonlinear dynamic angle.