Contribution of the oxygen reduction reaction to the electrochemical cathodic partial reaction for Mg-Al-Ca solid solutions

Markus FeltenSiyuan ZhangRasa ChangiziChristina ScheuMark BrunsMichael StreblSannakaisa VirtanenDaniela Zander

Markus FeltenSiyuan ZhangRasa Changizi ...+4 Daniela Zander

Mar 2023

摘要

The electrochemical corrosion rate of Magnesium (Mg) and Mg alloys depends onthe stability of the formed surface layer. Based on the Mg substrate, the oxidestructure comprises a dense MgO/Mg(OH)2 mixture underneath a porous plate-likeMg(OH)2 layer. While the kinetics of the anodic partial reaction has beenmainly attributed to MgO, recent studies showed an effect of the Mg(OH)2 layerthickness on the cathodic partial reaction. A thinner Mg(OH)2 layer has beenassociated with a higher kinetics of the oxygen reduction rate. In the presentstudy, the proposed mechanism has been further investigated via in siturespirometric measurements with Mg-Al-Ca solid solution in electrolytes withdifferent pH values (pH = 8-13). The results indicate an additional effectbased on the structure of the surface layer in the passive state of Mgcorrosion. Furthermore, two different Al enriched interlayers at the Mg/MgO-and MgO/Mg(OH)2 interfaces were observed and discussed in terms of theirthermodynamic stability under alkaline immersion conditions.

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