Effect of Crystal Orientation on the Anodic Polarization and Passivity of Zinc

Abstract

Potentiostatic polarization measurements on exposed (0001), (1010), and (1120) faces of single crystals and on polycrystalline zinc were made in aqueous solutions of sodium hydroxide. Crystal orientation was observed to have a well defined effect on anodic polarization with overvoltages for active dissolution increasing with increasing density of crystal planar packing. Potentials for passivation were equal for (0001) and (1010) crystal specimens, which were both noble to potentials for (1120) specimens.

The Anodic Dissolution and Passivation of Zinc in Concentrated Potassium Hydroxide Solutions

“…In solutions saturated with zincate in the potential range --1.0 < U < 0.2v with respect to a mercury-mercuric oxide electrode, the direct dissolution reaction Zn ~ Zn + + + 2e- [10] was suggested to occur to a large extent in addition to the chemical dissolution of zinc oxide ZnO + 2OH-q-H20"-> (Zn(OH)4)-- [11] The independence of current on potential at U less than 0.2v was attributed to the limiting rate of diffusion of zinc atoms through the oxide layer. Ashton and Hepworth established that the rate of dissolution of zinc single crystals in 0.5M NaOH in the active region decreases slightly at constant potential with an increase in the planar packing density (29). This latter quantity increases in the order (0001) < (10~0) < (1120) for zinc and other hexagonal close-packed metals.…”

Corrosion electrochemistry of magnesium (Mg) and its alloys

“…with its surface energy (Abayarathna et al, 1991;Ashton and Hepworth, 1968;Buck and Henry, 1957;Konig and Davepon, 2001;Weininger and Breiter, 1963) which is somewhat associated with the atomic density of a given crystal plane. For example, the lowest index plane (0001) has a significantly higher atomic density than (hki0) planes, thus it has the lowest surface energy and as such should be dissolved slower than the other surfaces (Liu et al, 2008) (refer to Fig.…”

Theoretical and experimental study of the interaction of O2 and H2O with metallic zinc—discussion of the initial step of oxide formation

“…As reported by several authors [28,[31][32][33][34], water interacts most strongly with the zinc sites available on the (001) and (100) faces and more weakly with the oxygen sites on the (001) and (100) faces, forming Zn oxyhydroxides. A few studies on the effect of crystallographic orientation on corrosion resistance of Zn have previously been reported [35,36].…”