Magnesium (Mg) is an attractive material for a transportation industry because it has low density and good mechanical properties. However, a high reactivity of Mg in an aqueous solution limits its wider usage in the industry. It was reported that the rate of hydrogen evolution reaction on Mg is increased with noble potential from the open circuit potential. This phenomenon is termed the Negative Difference Effect (NDE) ^1-5.

In order to investigate the anodic dissolution of Mg, we developed a pH sensing channel flow double electrode (CFDE). The CFDE is one of the hydrodynamic method for analysis of anodic dissolution of metals and alloys ^6-10. In this method, the metallic ions dissolved from the working electrode (WE) can be detected by arranging a detecting electrode (DE) downstream of the WE. In the present study, the Mg and tungsten (W) were used as the WE and DE. Because the hydroxide ions generated due to the anodic dissolution of Mg flow to the W, pH can be estimated from the measurement of the open circuit potential of W. In addition, a video recording of Mg surface was performed during measurement in the developed system ¹⁰. The hydrogen evolution of Mg during anodic dissolution was discussed with results of pH changes and an in-situ surface observation.

References

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