Influence of Nd and Y additions on the corrosion behaviour of extruded Mg-Zn-Zr alloys

Abstract

To improve the corrosion resistance of wrought magnesium alloys through rare earth (RE) additions, the corrosion behaviour of Mg-5Zn-0.3Zr-xNd (x=0, 1, and 2; wt%) and Mg-5Zn-0.3Zr-2Nd-yY (y=0.5 and 1; wt%) alloys in a 5wt% NaCl solution was investigated using immersion test and electrochemical measurements. The results of immersion test show that Mg-5Zn-0.3Zr-2Nd alloy exhibits the best corrosion resistance among the tested alloys. Electrochemical measurements show that secondary phases in RE-containing Mg-5Zn-0.3Zr alloys behave as less noble cathodes in micro-galvanic corrosion and suppress the cathodic process. The additions of Nd and Y into Mg-5Zn-0.3Zr alloy also improve the compactness of the corrosion product film and are beneficial to the corrosion resistance.

Understanding the corrosion behaviour of the magnesium alloys EV31A, WE43B, and ZE41A

“…A decrease in the corrosion rates of Mg alloys alloyed with RE elements was also reported by Nam et al, Liu et al, and Chang et al Nam et al studied the influence of alloying with up to 1 wt% mischmetal (MM; of composition 50 wt% Ce, 25 wt% La, 20 wt% Nd, and 5 wt% Pr) on the corrosion behaviour of Mg–5Al using electrochemical testing in 0.06 wt% NaCl solution, and reported that increasing the MM content in Mg–5Al increased (a) the pitting potential, (b) the charge transfer resistance implying a decreased corrosion rate, and (c) the film resistance. The authors attributed this decrease in corrosion rate to grain size reduction of the α matrix, and the precipitation of a high density of more continuous Al–MM compounds.…”

The Influence of Microstructure on the Corrosion of Magnesium Alloy ZEK100

“…38 In the ZEK100, Zr and Nd together are added as grain refiners with the general claim that Zr has a negative effect on corrosion, while Nd reduces the cathodic activity of the phase which hosts it. 39 In the presence of chloride, both Mg-Zn-Nd and Zr, particles were located in the corroded region with Zr particles containing Fe appearing to be the dominant microgalvanically coupled cathodes. By initiating corrosion in pure water, it was possible to limit the extent of corrosion damage due to microgalvanic coupling to the vicinity of the coupled cathodes.…”

The Corrosion Performance and Mechanical Properties of Mg-Zn Based Alloys—A Review

“…By optimizing the content of Zn (Mg3Zn0.6Zr, in wt.%) in Mg-Zn-Zr alloy, the corrosion rate of Mg-Zn-Zr alloy can be comparable to that of WE43 alloy, which exhibits good corrosion behavior relative to AZ31, AZ91, and LAE42 alloys [125,127]. The further addition of Y and/or neodymium (Nd) into Mg-Zn-Zr alloys results in the precipitation of less noble T-phase and/or W-phase, and leads to the formation of more a compact corrosion product layer with higher corrosion resistance [128,129]. It is quite often observed for Mg alloys that the protective film is denser when the overall corrosion rate is low.…”