Remarkably slow corrosion rate of high-purity Mg microalloyed with 0.05wt% Sc

We report that the corrosion resistance of Mg is significantly improved by adding 0.05wt%Sc.Corrosion rates evaluated from weight loss values after room-temperature immersion in 0.6 M NaCl solution for two weeks were 0.27 and 4.0 mm y^(-1)for the high-purity Mg samples with and without microalloyed 0.05wt%Sc,respectively.The beneficial effect of Sc microalloying on the corrosion resistance of Mg is discussed in connection with Sc-induced microstructural modifications.

A Review of Research on Galvanic Corrosion of Aluminum Alloys

When aluminum alloys are coupled with dissimilar materials,they often act as corrosion anodes and are suscepted to accelerated corrosion.Therefore,deepening our knowledge of such corrosion phenomena,related mechanisms,and elaborating new prediction model is of great theoretical and practical significance.In this paper,such mechanisms are explained from both macroscopic and microscopic points of view by considering several aspects such as the second phase particle type,grain size,and environmental ions.More specifically,different perspectives on such a problem are elaborated,which take into account:the properties of the coupling pair materials,geometrical characteristics,environmental media characteristics,the corrosion regularity of different types of aluminum alloys,the influence of area ratio on anode corrosion current density,the interference of the solution primary ions represented by Cl-and the accompanying ions represented by Al3+.A review is also conducted of the standard test methods used in the study of aluminum alloys galvanic corrosion and of research methods such as the Wire Beam Electrodes Technology(WBE),the Scanning Kelvin Probe Force Microscopy(SKPFM)technology.Finally,three kinds of inhibition technologies are discussed,including the anodic oxidation treatment,the corrosion inhibitor treatment and the coating protection method.

Effects of dynamic recrystallization and strain-induced dynamic precipitation on the corrosion behavior of partially recrystallized Mg-9Al-lZn alloys

The corrosion susceptibility of recrystallized and un-recrystallized grains in equal channel angular pressed(ECAPed)Mg-9Al-lZn(AZ91)alloys immersed in chloride containing media was investigated through immersion testing and an electrochemical microcell technique coupledwith high resolution techniques such as scanning Kelvin probe force microscopy(SKPFM),transmission electron microscopy(TEM),andelectron backscatter diffraction(EBSD).During ECAP,dynamic recrystallization(DRX)and strain-induced dynamic precipitation(SIDP)simultaneously occurred,resulting in a bimodal grain structure of original elongated coarse grains and newly formed equiaxed fine grainswith a large volume fraction ofβ-Mg17Al12 precipitates.Corrosion preferentially initiates and propagates in the DRXed grains,owing tothe greater microchemistry difference between theβ-Mg17Al12 precipitates formed at the DRXed grain boundaries and the adjacentα-Mgmatrix,which induces a strong microgalvanic coupling between these phases.Additionally,the weaker basal texture of the DRXed grainsalso makes these grains more susceptible to electrochemical reactions than the highly textured un-DRXed grains.The influence of dynamicrecrystallization and dynamic precipitation was also studied in ECAPed alloys with differenl levels of deformation strain through corrosion andelectrochemical techniques.Increasing the strain level led to a more uniform corrosion with a shallow penetration depth,lower corrosion ratevalues,and higher protective ability of the oxide film.Furthermore,higher levels of strain resulted in greater hardness values of the ECAPedalloys.The superior corrosion resistance and strength of the ECAPed alloys with increasing strain level was attributed to the combination ofsmaller DRXed grain size,higher DRX ratio,and higher volume fraction of uniformly distributed fineβ-Mg17Al12 precipitates.c 2020 Published by Elsevier B.V.on behalf of Chongqing University.