Comprehensive anodic dissolution model

The strange anodic polarization behaviors (negative difference effect, lower apparent valence, low anodic dissolution efficiency, low anodic polarization resistance and poor passivity ) are closely associated with the AHE process which is further related to the onset of localized corrosion or pitting . A comprehensive anodic dissolution model can be employed to understand these. 

According to the comprehensive anodic dissolution model, the further anodic reaction (1.32) is a potential-dependent electrochemical process which can become faster at a more positive polarization potential. This means that y will increase and therefore n should also increase as the potential becomes more positive. This prediction has been experimentally verified n starting at 1.2 approached a value of 1.8 after the anodic polarization potential was more positive than -1 V/NHE (Perrault, 1978). Because the hydrogen production reactions in the anodic process cannot fully stop at anodic potentials, n cannot reach its theoretical value of 2, which is also consistent with experimental observation (Perrault, 1978). 

Based on an extensive investigation of the anodic i-V relations, dissolution valence, and PS morphology on a large matrix of silicon substrates, Beale el proposed a rather comprehensive model on the formation of PS. This was the first model that analyzed the i-V characteristics and correlated them with the current conduction mechanisms associated with silicon substrates of different types and doping concentrations. 

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