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|Type:||Artigo de periódico|
|Title:||Wettability Effect On Stability And Breakdown Of Anodic Films On Iron And Aluminum Electrodes|
|Abstract:||Wettability of iron and aluminum electrodes at both hydrogen and oxygen evolution potentials was determined with a Wilhelmy-type apparatus, in which the pull exerted by the electrolyte solution on the electrode was measured at each switching of the electrode potential for a periodically reversed step potential. Bare iron electrodes have a different wettability than those in which metal is coated with oxide. The wettability of the coatings and their adhesion to metal are dependent on the dissolved oxygen concentration. On the other hand, the wettability of the passivating coating generated on iron by previous immersion in HNO3 is greater than that of the metal; as a result, the coating adheres to metal, and this accounts for its passivating ability. For aluminum electrodes, wetting properties were determined and are quite different from those of iron electrodes. On these electrodes, there is always present an oxide coating even after prolonged evolution of hydrogen. Oxygen-evolving aluminum surfaces are more wettable than the oxide coating present during hydrogen evolution, and oxygen does not affect their wettability. These results show that there is a dependence between anodic film stability and its wettability, as compared to that of the adjacent-to-the-metal coating; moreover, wettability gradients at the passivating layer are harmful to oxide film stability. © 1989 American Chemical Society.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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