Impedance anodic dissolution

The anodic dissolution of zinc [233, 264] was investigated in solution H3BO3 + NH4CI + Na2S04 at pH 4.4 using electrochemical impedance spectroscopy and EQCM. In the same solution, zinc anodic dissolution of different galvanized steel sheets of zinc [265] was studied. The postulated [41, 266] mechanism of Zn oxidation in acidic solution corresponds to two consecutive monoelectronic transfers. 

CN ions. Anodic dissolution of silver electrode in cyanide solutions and also the behavior of Ag at potentials preceding dissolution have been studied applying electrode impedance measurements [381]. At potentials of anodic dissolution, the process was represented by the equivalent circuit with two parallel branches. 

Partial blocking effect was first identified for pure iron in contact with aerated sulphuric acid medium [55]. Corrosion of carbon steel in sodium chloride media clearly showed the porous layer effect (see Section 5.2) [74]. The same effect was found for zinc corrosion in sodium sulphate [75] and the properties of the layer which was demonstrated to be formed of an oxide/hydroxide mixture were further used for building a general kinetic model of anodic dissolution [76], usable for measurement of the corrosion rate from impedance data. 

Electrogravimetric transfer functions Am/A (o>) and AmlAq associated with the electrochemical impedance, A /A/(a>) were determined for the anodic dissolution of Fe in sulfuric acid. This gave the unique possibility of discriminating between the change in mass due to metal dissolution and the relaxation of the film thickness on the basis of their individual frequency responses [35, 36]. 

Derive the Faradaic impedance for the anodic dissolution of copper at low overpotential in a chloride medium where the reactions proceed according to... 

I. E. Vermeir, W. P. Gomes, B. H. Erne, and D. Vanmaekelbergh, "The Anodic Dissolution of InP Studied by the Optoelectrical Impedance Method 2. Interaction between Anodic and Chemical Etching of InP in Iodic Acid Solutions," Electrochimica Acta, 38 (1993) 2569-2575. 

For heavily doped materials, either notp type, the surface is degenerated and the material behaves like a metal electrode, meaning that the charge transfer reaction in the Helmholtz double layer is the rate-determining step. This is supported by the lack of an impedance loop associated with the space charge for the heavily doped materials. Also, for heavily doped n-Si large current in the dark is due to electron injection, which is not characterized by a slope of 60 mV/decade. For p-Si, electron injection into the conduction band may also occur during the anodic dissolution. 

F. Ozanam, J.-N. Chazalviel, A. Radi, and M. Etman, Resonant and nomesonant behavior ofthe anodic dissolution of silicon in fluoride media An impedance study, /. Electrochem. Soc. 139(9), 2491, 1992. 

Ozanam F., Chazalviel J. N., Radi A. and Etman M. (1992), Resonant and non-resonant behavior of the anodic dissolution of silicon in fluoride media—an impedance study , J. Electrochem. Soc. 139, 2491-2501. 

In the context of EMM, the diffusion layer thickness at the anode may be more compared to that in conventional ECM due to absence of high flow rate of the electrolyte. Hence the effect of Warburg impedance is more prominent during anodic dissolution in the microscopic domain. 

A. Metcalfe [1977] The Anodic Dissolution of Silver into Silver Rubidium Iodide-Impedance Measurements, J. Electroanal. Chem. 88, 187-192. 

The adsorption of an inhibitor onto the metal surface slows the rate of corrosion by blocking part of the surface. The extent of inhibition depends on the equilibrium between the dissolved and adsorbed inhibitor species, expressed by the adsorption isotherm. This mechanism which is particularly important in acids will be discussed in the next section. (Sect. 12.4.2). Certain inhibitors promote the spontaneous passivation of a metal and thus drastically reduce the corrosion rate. Oxidizing species such as chromates fall in this category. Buffer agents that maintain a high pH at the metal surface also favor the passive state. Other inhibitors lead to the formation of surface films by precipitation of mineral salts or of weakly soluble organic complexes. These films reduce the ability of oxygen to reach the surface and, in addition, they may impede the anodic dissolution reaction. 

Scholl, H., B. Hofman, J. Kupis et al. 1994. Anodic dissolution of cemented carbides of the type [(WC, M) M = Co, Ni OR Fe] in sulphuric acid solution. Electrochemical impedance spectroscopy. Electrochimica Acta 39-. 115-117. 

Advanced Study of Iron Dissolution by Impedance Techniques Early application of impedance measurement to the anodic dissolution of iron in acidic media demonstrated the inductive character of the iaradic impedances. The reaction scheme initially proposed [13,60] is modified according to ... 

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