Susceptibility of rare-earth-magnesium alloys to micro-galvanic corrosion

Four commercially produced rare-earth-magnesium alloys, as-cast ZE41, sand-cast WE43-T6, and wrought WE43-T6 and WE54-T6, were studied by scanning Kelvin probe force microscopy (SKPFM) in order to evaluate the role of their micro-constituent phases on potential galvanic interactions. Such interactions were then examined by immersion of the alloys in 3.5 wt% NaCl solution. The results confirmed that SKPFM was a powerful tool to determine the corrosion mechanism of magnesium alloys, where the intensity of the corrosion attack depended on the relative Volta potential differences of the micro-constituents, as well as their amounts, compositions and distributions within the alloys.

Research highlights
► SKPFM provided information about galvanic interactions existing in Mg alloys.
► Galvanic interactions depended on the Volta potential differences of the alloy constituents.
► The Volta potential differences of the constituents depended on their composition.
► The as-cast ZE41 alloy presented strong galvanic corrosion.
► No evidence of galvanic corrosion by RE-containing phases was observed in WEXX alloys.