Anodic dissolution passivity domain

The principle of this mechanism is based on the fact that conductive (p-doped) coatings could provide anodic galvanic protection to the metal substrate and act as an oxidizer to maintain the metal in the passive domain. This mechanism can lead to passivation of the exposed metal surface at small defects in the passive layer. A considerable number of reports have been made claiming the formation of passive films at the exposed site, with subsequent inhibition of further metal dissolution [129]. 

It is usual to consider that various classes of anodic mechanisms exist depending on the range of potential with respect to the passivity domain. Active dissolution taking place at potentials preceding the passivation on a film-free surface is of major importance for the homogeneous corrosion in weakly oxidizing media such as acidic solutions of stable anions (e.g. sulfuric, perchloric, phosphoric, hydrochloric). Localized corrosion in pits, crevices, cracks, etc. is also assirmed to proceed through active dissolution stabilized at passive potentials by ohmic drops and/or local chemistry. 

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