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Open‐circuit potentials were measured for freshly immersed metal surfaces and for metal surfaces renewed abrasively (scraped‐off) in situ in aqueous electrolytes. Electrode materials included Au, Ag, Cu, Pt, Ga, In, Bi, and Sn and the electrolytes included alkali halides and alkali sulfates in acid, neutral, and alkaline solutions. The fresh‐surface potentials for Au, Ga, In, Bi, and Sn were approximately the same following either immersion or scraping in solution and yielded the potential of zero charge at certain pH conditions. For Ag, Cu, and Pt the immersion potentials were several hundred millivolts more positive than the scrape potentials. This is attributed to the presence of adsorbed oxygen on these metals at the instant of immersing them in solution. For Ag, Cu, and Pt the scrape potentials are interpreted as the potential of zero charge for the bare metal while the immersion potentials reflect a superimposed dipolar effect or faradaic reduction of the oxygen.
Clark et al. (Tue,) studied this question.