Contemporary Materials III−1 (2012)
Contemporary Materials, III−1 (2012) Page 1 of 12
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UNEXPECTED PRESENCE OF SOLUTE-FREE ZONES AT METAL-WATER INTERFACES
B. Chai, A. G. Mahtani, G. H. Pollack
Department of Bioengineering, Box 355061, University of Washington, Seattle, WA 98195
Abstract
Solute–free zones, termed “exclusion zones” are routinely seen next to hydrophilic surfaces in aqueous solution. Here we report similar zones next to various metals. The largest, approximately 200 µm in width, was found adjacent to zinc. Other reactive metals, including aluminum, tin, lead, and tungsten exhibited distinct but smaller exclusion zones, while precious metals such as platinum and gold did not produce any. Electrical potential measurements showed positive potentials within the exclusion zones, while pH measurements revealed an abundance of OH- groups in the aqueous regions beyond the exclusion zones. A correspondence was found between exclusion-zone size and the respective metal’s position within the galvanic series. The presence of these interfacial exclusion zones is unexpected, and may shed new light on electrochemical processes taking place at metal interfaces.
Keywords: metals, aqueous solution, oxidation, metal-water interfaces, charge separation, exclusion zones.
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