Subject：First-Principles Investigations of Corrosion Mechanisms ofLightweight Metals

Speaker：A.P. Liang Qi 

Emcee：Prof. Yang Yang 

Time：9:00 am, 11th June,2021

Place:  Voov meeting :185724438;code:341902

Abstract： 

A significant challenge forapplications of lightweight metals and alloys (such as Mg and Al alloys) istheir poor corrosion resistance under service conditions. Here I present twoexamples of first-principles investigations of corrosion mechanisms of Mg andAl. The first example is to design Mg alloys with built-in corrosionresistance. Corrosion can result from the coupling of anodic dissolution of Mgand cathodic reduction of water on impurities such as Fe-rich second-phaseparticles. Experiments show that small quantities of Arsenic (As) or Germanium(Ge) can inhibit Mg corrosion, possibly slowing the hydrogen evolution reaction(HER) as the cathodic reaction on Fe surfaces. We designed thermodynamic andHER criteria and used high-throughput first-principles computations to search apool of 68 elements. Our computational results predict that As and Ge are thebest two alloying elements according to their ability to reduce the HER rate,in qualitative accord with recent experiments. The second example is tounderstand the chloride (Cl)-induced initiation mechanism of localizedcorrosion of Al alloys by investigating the interactions between Cl andhydroxylated α–Al2O3 surfaces under aqueouselectrochemical conditions. The results suggest a Cl anion can only bestabilized on these surfaces by substituting a surface hydroxyl (OH) group.This substitution is thermodynamically favorable at sites on surfaceterminations of grain boundaries (GBs) in bicrystal configurations but notfavorable at sites on single-crystal surfaces. The adsorbed Cl significantlyincreases the thermodynamic driving force for Al cation dissolution fromalumina surfaces to initiate localized corrosion.

References for the second talk:

1.Mingfei Zhang, Louis G. Hector, YangGuo, Ming Liu, Liang Qi, First-principles search for alloying elements thatincrease corrosion resistance of Mg with second-phase particles of transition metalimpurities, Computational Materials Science, 165 (2019) 154-166,

2.Sundar,A.,Chen,G.&Qi,L.Substitutional adsorptions of chloride at grainboundary sites on hydroxylated alumina surfaces initialize localized corrosion.npj Mater Degrad 5(2021)18.