The tribo‐ellipsometric technique allows one to distinguish between film growth and other reactions that occur after removal of a film from a metal surface in a given environment. This technique was used to study the relationship between repassivation kinetics and stress corrosion cracking (SCC) susceptibility for Ti 8A1‐1M0‐1V alloy. In these studies the effect of the rate of film growth on the amount of metal dissolution which occurs during the repassivation process was investigated by comparing the repassivation transient behavior in a
1.0N normalNaCl
solution, where cracks have been found to propagate, to that in a
1.0N NaNO3
solution where SCC susceptibility has never been detected. Film growth kinetics in both solutions were consistent with a Fleischmann‐Thirsk mechanism of oxide patch nucleation and two‐dimensional growth, although the film growth rate was significantly slower in the
1.0N normalNaCl
solution. Low film growth rate led to an increase in metal dissolution in a solution where crack propagation velocities have been measured, but at an apparent rate slower than necessary to propagate such cracks by metal dissolution alone.
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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