Effect Of External Factors On The Current Oscillations Of Zinc In Sodium Hydroxide Solutions

Zinc metal has been extensively used in many industrial fields owing to their satisfactory features such as low equilibrium potential, good reversibility, high specific energy, low cost, non-polluting, abundant resources. Zinc, however, are easy to be corrupted due to the unstable chemical properties,especially in alkaline solution. Therefore, it is of great significance to study zinc’s behaviors and mechanism of oscillations. Researches about zinc electrochemical oscillations behavior in the process anodes dissolution can deepen understanding of the corrosion mechanism of zinc and make contributions to development of nonlinear science.In this paper, cyclic voltammetry and potentiostatic methods have been applied to study the impact of the potential, external resistance, temperature, additive, agitation on the oscillatory behavior of zinc in Na OH solution, combined with the power spectrum analysis and phase space reconstruction analyzing the current-time series. Experimental results indicate that amplitude(Δi) increase gradually with the increase of the applied potential, while average period and induce time(ti) initially decreases and then increases. Adding a external resistance(Rex) in series with the working electrode, upon the Rex increased, the amplitude of the oscillations decreased gradually, while ti and tp increased. Besides, the oscillation waveform undergone significant changes. What’s more, mixed-mode oscillations are displayed when the Rex is large enough. In addition, the morphology of the Zn electrode surface during the current oscillation has been evaluated using sanning electron microscopy. It reveals that the current oscillation is related with the dissolution and passivation of the film on the Zn electrode. The resistance of the film on the electrode surface has been testing by electrochemical impedance spectroscopy and its result suggests that an important role in the coupling between the external resistance and electrochemical system. For further study, the effects of temperature and agitation on the current oscillations are explored. Results indicate that Δi increases with the increase of temperature while ti and tp decrease. When a small amount of Cl- solution is injected at the electrode interface, the periodic current oscillation restores to its original pattern quickly. The current oscillation disappears by stirring the solution that suggests oscillatory behavior is related with diffusion steps.Based on the results above, dynamic analysis and simulation of current oscillation for Zn in Na OH system were undertaken. It involves two stage, nonlinear steps analysis and electrochemical coupling factors studying. Then, the current oscillation mechanism are discussed and a electrode process dynamic model was proposed by simplified the reaction process. 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 simulated with appropriate parameters. According to the analysis above, the concentration oscillation curve, the current oscillation curve are calculated respectively, and theoretical results are in accordance satisfactorily with experimental observation reported in this paper. In the engineering applications, choosing a higher electrode potential or a lower temperature can reduce the corrosion of the metal zinc effectively.