Galvanostatic oxide growth

For galvanostatic oxide growth (log i = const) the E field has to be constant resulting immediately in the proportionality ... 

Data on anion incorporation into a growing porous oxide were obtained Fukuda and Fukushima.165,166 Their study was the first to demonstrate a correlation between the kinetics of accumulation of oxalate165 or sulfate166 anions and the change of porous oxide growth stages. The results of galvanostatic and potentiostatic... 

Figure 31. Correlation of the kinetics of oxide growth with kinetics of sulfate incorporation into the oxide during galvanostatic (a) and potentio-static (b) anodization of A1 in Ff2S04 solutions.166...

To achieve anodic film growth, two methods are widely used (i) application of a constant current (galvanostatic oxidation), (ii) application of an anodic potential (potentiostatic oxidation). 

The chemical reaction mechanism of electropolymerization can be described as follows. The first step in course of the oxidative electropolymerization is the formation of cation radicals. The further fate of this highly reactive species depends on the experimental conditions (composition of the solution, temperature, potential or the rate of the potential change, galvanostatic current density, material of the electrode, state of the electrode surface, etc.). In favorable case the next step is a dimerization reaction, and then stepwise chain growth proceeds via association of radical ions (RR-route) or that of cation radical with a neutral monomer (RS-route). There might even be parallel dimerization reactions leading to different products or to the polymer of a disordered structure. The inactive ions present in the solution may play a pivotal role in the stabilization of the radical ions. Potential cycling is usually more efficient than the potentiostatic method, i.e., at least a partial reduction... 

Fig. 9.26 - Galvanostatic (constant current) transients for the growth of the anodic oxide film on a titanium electrode in 1.0moldm H2SO4. The current densities in mA cm are (1) 0.06, (2) 0.12, (3) 0.60, (4) 1.2, and (e) 6.0. Note that the potential is displayed against charge (i.e. / X f) rather than against time. The increase in slope of the transients with current density therefore corresponds to an increase of the electric field. (Data taken from J. F. McAIeer PhD Thesis, University of Southampton, 1980).

Harris, L. B. and Damjanovic, A. 1975. Initial anodic growth of oxide film on platinum in 2NH2SO4 under galvanostatic, potentiostatic, and potentiodynamic conditions The question of mechanism. 122, 593-600. 

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