Investigation of hydrogen evolution behaviour on corroding magnesium electrodes by electrochemical impedance spectroscopy, real-time hydrogen measurement and optical imaging

摘要

Magnesium alloys are attractive engineering materials for low-weight applications, due to their low density compared to most other alloys, but their use is limited due to comparatively poor corrosion resistance. This is due to the low electrochemical potential for magnesium oxidation, combined with the relatively poor protective properties of the oxide/hydroxide film generated after oxidation. In aqueous environment, corrosion of Mg is sustained by the cathodic reaction of hydrogen evolution that takes place in various forms on the corroding surface. Additionally, unlike most other metals, magnesium exhibits the so called 'negative difference effect', i.e. an increase in the rate of hydrogen evolution with increasing anodic polarization. In order to understand the corrosion behaviour of magnesium, thus, it is essential to understand the details of the hydrogen evolution reaction.