Surface treatment effect on the low temperature hydriding behavior of Mg 2Ni

Abstract

The effects on the hydriding behavior, long term storability in air and microstructure of Mg 2Ni alloy resulting from surface treatments using (1) HCl acid (HCl-treatment), (2) F-containing solution after HCl etching (HCl + F-treatment) were determined and compared with those due to (3) F-treatment alone. Both the treatments (1) and (2) could clean up the originally contaminated surface as F-treatment did. HCl leached some pure Mg phase from the eutectic structure of the Mg-rich Mg 2Ni alloy. This resulted in an increase of specific surface area and led Mg 2Ni to partially hydride under very moderate temperature and pressure conditions. HCl-treatment alone could not form a fluorinated surface structure as F-treatment did. Instead of this, some magnesium hydroxide was formed. The fluorinated surface formed by F-treatment provided strong protection from surface contamination by long term air exposure.