Local alkalinisation

This leads to an excess of hydroxyl OH ions, and thus to local alkalinisation. As a result, after two full periods, the metal surface will be alkaline, dissolving the natural oxide film... 

Alkalinisation of local anaesthetic solution with sodium bicarbonate (NaHC03) increases the pH of the solution to a value near its pKa. This results in an increased proportion of unionised drug available for neural penetration and thereby reduces the onset time. Carbonation is a term used to describe the acidification of a local anaesthetic solution with carbon dioxide. Following injection, the carbon dioxide diffuses into the axoplasm causing a decrease in the pH. This results in a higher proportion of ionised drug within the cell. In theory this should enhance the Na-i- channel block but in practice the results are disappointing. 

Figure 4. Electrical and chemical aspects of the galvanic coupling for a localized corrosion site in a real metallic microstructure. Acidification is related to the anodic dissolution and alkalinisation is associated to the surrounding cathodic reaction.

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