The ability of Mg2Ge crystals to behave as 'smart release' inhibitors of the aqueous corrosion of Zn-Al-Mg alloys

In-situ scanning vibrating electrode technique and time-lapse microscopy are used to investigate the influence of germanium additions (0.19-1.8 wt.%) on the corrosion performance of zinc-aluminium-magnesium model alloys immersed in 0.17 mol.dm(-3) NaCl. The addition of Ge results in the formation of Mg2Ge and a decrease in the fractional area of eutectic phase. A 58 % decrease in SVET derived mass loss is achieved at 1.8 wt.% Ge. It is proposed that Mg2Ge crystals are anodically attacked and behave as reservoirs of Mg2+ ions. Mg(OH)(2) is precipitated and local electrolyte pH stabilises to values at which the zinc surface is passive.

Automated summary

The addition of germanium reduces corrosion in zinc-aluminium-magnesium alloys by forming Mg2Ge crystals. A 58% decrease in mass loss rate was achieved at high germanium content (1.8 wt.%), indicating that Mg2Ge crystals act as reservoirs for Mg2+ ions.