The hydrogen evolution of pure magnesium in different electrolytes.

The hydrogen gas evolution from the corroding magnesium (Mg) arises not only from the bare Mg surface but also from the Mg(OH)2 oxide layer as well. In fact, the presence of Mg(OH)2 oxide layer also doubled the rate of hydrogen gas evolution. In this work, a conventional hydrogen gas collection using volumetric method has been applied to observe the effect of sodium chloride (NaCl) on hydrogen evolution of Mg. Cathodic polarization and scanning electron microscopic (SEM) tests had been done in the same solution to confirm the observations. These observations demonstrate that, even though the initial surface of Mg had been fully covered by Mg(OH)2 oxide layer, the abundant hydrogen gas still can be released from the corroded surface. In addition, the double increases of hydrogen evolution rate (HER) during free corrosion in 7.0% NaCl can be seen as compared to distilled water. [ABSTRACT FROM AUTHOR]