Effect of microstructure on passive film formation and breakdown on al alloys. Final report, 15 December 1988-14 December 1992

Technical Report · Mon May 31 04:00:00 EDT 1993

OSTI ID:6471375

Kruger, J; Wagner, J W; Lillard, R S; Streinz, C C

Two in situ techniques, dynamic imaging microellipsometry (DIM) and local impedance spectroscopy (LEIS), were developed and applied to a study of the effect of microstructure on passive film formation and breakdown on Al-Ta alloys. DIM acquires ellipsometric data (thickness and optical constants of the films on surfaces) at a spatial resolution of ca. 20 micrometers using a radiometric full-field imaging approach. LEIS is an electrochemical impedance technique that generates local a.c. impedance data by measuring a.c. solution current densities very near the microstructural features of an electrode surface. The DIM technique was used to look at passive film formation at (a) the Al3Ta precipitate (b) the dealloyed zone adjacent to the precipitate and (c) the solid solution phase that is present in Al-Ta alloys. The DIM technique observed different film thicknesses and optical constants for the films that form on these phases at potentials in the passive regions. The LEIS technique was used to study the precipitate and the region surrounding it under conditions where passive film breakdown occurs. Using these techniques, insight was obtained into the passive film formation and breakdown processes that control localized corrosion.

• Research Organization: Johns Hopkins Univ., Baltimore, MD (United States)
• OSTI ID: 6471375
• Report Number(s): AD-A-265339/2/XAB; CNN: N00014-89-J-1180
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360104 -- Metals & Alloys-- Physical Properties
ALLOYS
ALUMINIUM ALLOYS
CHEMICAL REACTIONS
CORROSION
ELLIPSOMETRY
FILMS
IMPEDANCE
INTERMETALLIC COMPOUNDS
MEASURING METHODS
MICROSTRUCTURE
OPTICAL PROPERTIES
PHASE STUDIES
PHYSICAL PROPERTIES
PRECIPITATION
RESOLUTION
SEPARATION PROCESSES
SPATIAL RESOLUTION
SPECTROSCOPY
SURFACES
TANTALUM ALLOYS