Specific factors characterizing corrosion behavior

In alkaline solutions of pH 10.45, Mg tends to passivate in alkaline solutions at pH 10.45, and at more alkaline pH sueh as 13 (O.IM NaOH) a truly passive behaviour is expected (Fig. 2.5). An average eurrent density of a few p,A/cm is observed in the passive region at a relatively high sean rate 1 mV/s. 

5 Potentiodynamic polarization characteristics of magnesium as a function of solution pH in de-aerated 0.1 M NaOH solution with scan rate 1 mV/s (Mitrovic-Scepanovic and Brigham, 1990). 

Theoretical schematic approach to active-passive behavior 

Mitrovic-Scepanovic and Brigham (1990) considered a schematic and theoretical approach for the dissolution of magnesium in de-aerated alkaline solution at pH 13. In this approach the divalent state dissolution has been considered the dissolution of magnesium in the monovalent state accompanied by the oxidation-reduction reaction of hydrogen ions leading to the negative difference effect on the anodic curve and the formation and stability of magnesium hydride at this pH are not considered. 

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