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Reactivity in confinement is central to a wide range of applications and systems, yet it is notoriously difficult to probe reactions in confined spaces in real time. Using a modified electrochemical surface forces apparatus (EC-SFA) on confined metallic surfaces, we observe in situ nano- to microscale dissolution and pit formation (qualitatively similar to previous observation on nonmetallic surfaces, e.g., silica) in well-defined geometries in environments relevant to corrosion processes. We follow "crevice corrosion" processes in real time in different pH-neutral NaCl solutions and applied surface potentials of nickel (vs. Ag|AgCl electrode in solution) for the mica-nickel confined interface of total area ~0.03 mm². The initial corrosion proceeds as self-catalyzed pitting, visualized by the sudden appearance of circular pits with uniform diameters of 6-7 µm and depth ~2-3 nm. At concentrations above 10 mM NaCl, pitting is initiated at the outer rim of the confined zone, while below 10 mM NaCl, pitting is initiated inside the confined zone. We compare statistical analysis of growth kinetics and shape evolution of individual nanoscale deep pits with estimates from macroscopic experiments to study initial pit growth and propagation. Our data and experimental techniques reveal a mechanism that suggests initial corrosion results in formation of an aggressive interfacial electrolyte that rapidly accelerates pitting, similar to crack initiation and propagation within the confined area. These results support a general mechanism for nanoscale material degradation and dissolution (e.g., crevice corrosion) of polycrystalline nonnoble metals, alloys, and inorganic materials within confined interfaces. [ABSTRACT FROM AUTHOR]

Polymers are widely utilized as protective coatings to prevent metal surfaces from wear, corrosion, or bio-fouling. Yet, stability and adhesive properties of polymer to metal bondings are not fully understood at the molecular level. Here, we measured the interaction forces between a gold electrode surface and amine-functionalized polymers (PEG) using a novel electrochemical surface forces apparatus. We examined the potential dependence of specific amine-gold interactions and measured that the binding strength of amine-gold bonds can range from 0.5 to 40 kBT per binding site, depending on the applied electrochemical potential. Notably, this interaction exhibits a pronounced minimum around the potential of zero charge, where the polymer-gold adhesion is dominated by non-specific interactions between the polymer backbone and electrode surface, consistent with the adhesion of PEG polymers with gold surfaces in the absence of amine functionalization. Further, repulsive hydration interactions were observed to be stronger for amine-terminated PEG compared to non-functionalized PEG, due to increased hydration and presence of counterions in the case of amine-terminated PEG. Our results provide molecular-scale insight into design and optimization of polymer coatings for numerous applications requiring strong, specific binding interactions between polymers and metals (or their native oxides), for example passivating layers in biomedical implants and electronic devices. [ABSTRACT FROM AUTHOR]