Metal dissolution and passivation

Metal dissolution is the inverse process to the deposition so its principles can be derived from preceding considerations. It should, however, be borne in mind that the preferred sites for deposition need not be the same as those for the dissolution. This is particularly true if the reactions are far from equilibrium. Therefore, rapid cycling of the potential between the deposition and the dissolution region can lead to a substantial roughening of the electrode surface, which can be used in techniques such as surface-enhanced Raman spectroscopy (see Chapter 15 ), which require a large surface area. 

Often the dissolution of a metal leads to the formation of an oxide film on the electrode surface. These films are usually nonconducting and hinder the further dissolution of the metal, a phenomenon known 

The resulting films can attain thicknesses of the order of a thousand 

Note that the field is the important variable, not the electrode potential. Typically fields of the order of 106 V cm-1 are required to produce a noticeable film growth. 

de Levie, in Advances in Electrochemistry and Electrochemical Engineering, Vol. 13, ed. by H. Gerischer and W. Tobias, Interscience, Wiley, 1985. 

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