Evolution of the Chemistry of Passive Films of Sputter-Deposited, Supersaturated Al Alloys
Abstract
Aluminum and conventional aluminum alloys are readily susceptible to localized attack in chloride containing environments. Recently, under funding from the Office of Naval Research, we have investigated the passivity and corrosion behavior of several super-saturated aluminum alloys formed by co- sputter deposition. In this report, we show that several of these alloys exhibit superior resistance to localized attack in eletro-chemical polarization measurements and salt-fog tests. X-ray photoelectron spectroscopy was used to examine the surface chemistry of the passive film as a function of applied potential for A1,A1-Ta, and A1-Zr alloys. We find that the passive film that forms on each alloy becomes enriched in oxidized solute as the specimen is anodically polarized. In general, the oxidized solute protects the substrate by restricting the ingress of chloride and oxygen and thereby preventing or reducing localized attack and film growth, respectively. Of the solutes examined to date, Ta is the most effective in this regard; the passive film on A1-Ta alloys remains thin and protective at the most noble potentials. Breakdown occurs only as the potential drop across the film becomes great enough to allow the transport of chlorides. Tantalum, Zirconium.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1989
- Accession Number
- ADA204742
Entities
People
- D. R. Black
- G. D. Davis
- G. G. Long
- G. O. Cote
- T. L. Fritz
- W. C. Moshier
Organizations
- Martin Marietta