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The mechanisms of dezincification of single phase alpha and beta brasses were studied using X-ray diffraction, electron microprobe, metallographic, atomic absorption, and electrochemical techniques. The two mechanisms of dezincification which had been previously reported, (1) dissolution of both alloy constituents followed by redeposition of the more noble species, and (2) the selective removal of the less noble constituent, were found to be operative under certain conditions of potential and pH for both alpha and beta brasses. An electrochemical explanation of the circumstances under which dealloying can be expected to occur was developed based on the use of Pourbaix Diagrams.

Work by previous investigators has shown that BaTiO, films can be synthesized from solution over temperature ranges from 80°C to greater than 200°C. In the present work, electrically insulating crystalline films of BaTiO, have been electrochemically deposited on titanium substrates at temperatures as low as 55°C. Auger spectroscopic analyses with depth profiling indicate that a titanium oxide layer whose thickness is governed by current density acts as a precursor to BaTiO,. Formation of BaTiO, is found to be favored only in highly alkaline solutions. This is consistent with the phase stability reported for the Ba-Ti-C0,-H,O system at 25°C. Lower processing temperatures (55°C) favor the formation of thick, electrically resistive, and wellcrystallized BaTiO, films, apparently due to increased oxygen solubility in the electrolyte solution. Films produced at 100°C are much thinner and are electrically conductive due to fissures and pores in their microstructure. Initial studies on the effect of current density indicate the formation of thinner and porous films with thicker titanium oxide intermediate layers.

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