The Atmospheric Sulfidation of Copper Single Crystals

Abstract
The oxidation of copper single crystals is known to proceed at different rates on different crystal faces. To determine whether this behavior extends to subsequent atmospheric sulfidation as well, we have exposed polycrystalline copper and (100), (110), and (111) single crystals of copper to low concentrations of hydrogen sulfide in high humidity air. For short exposures, all of the single crystals sulfidize much more slowly than does polycrystalline copper. In each case, is the predominant sulfur species formed. As with oxide formation on copper single crystals, there is a slight tendency for the (111) face to be the most inert. For long exposures, the sulfide film on the single‐crystal samples increases to become essentially equal to that on polycrystalline copper. We envision a corrosion process initially controlled by grain boundary diffusion (and thus the degree of crystallinity of the underlying oxide), followed by a transition to a regime in which the diffusion of copper ions through limits the growth of the corrosion film.

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