Evidence of the Enrichment of Transition Metal Elements on Corroding Magnesium Surfaces Using Rutherford Backscattering Spectrometry

The increasing rate of hydrogen evolving from magnesium (Mg) surfaces under anodic polarization was characterized through simultaneous hydrogen volume collection, mass loss, potentiostatic and potentiodynamic polarization, and inductively coupled plasma optical emission spectroscopy (ICP-OES). This is distinct from the literature in that all four techniques are not often performed in the same test. Results indicate Mg dissolves as Mg2+ with anodically induced increases in hydrogen evolution rates due to increases in the water reduction reaction rate. In order to contribute to a mechanistic understanding of the cause for anodically induced increases in hydrogen evolution, quantitative surface spectroscopy for accurate chemical analyses of the Mg surface subject to dissolution was carried out via post exposure Rutherford Backscattering Spectrometry. Surface enrichment of transition elements other than Mg were confirmed, which provides a foundation for understanding the origin of enhanced hydrogen evolution. The selection of this technique was necessitated by limitations of near surface analysis by more conventional methods.