The influence of tungsten alloying additions on the passivity of aluminium

Journal Article · Thu Oct 31 23:00:00 EST 1991 · Journal of the Electrochemical Society; (United States)

DOI:https://doi.org/10.1149/1.2085404· OSTI ID:7068638

Shaw, B A ^[1]; Davis, G D; Fritz, T L; Rees, B J ^[2]; Moshier, W C ^[3]

---

1. Pennsylvania State Univ., Dept. of Engineering Science and Mechanics, University Park, PA (US)
2. Martin Marietta Lab., Baltimore, MD (US)
3. Martin Marietta Space Systems, Denver, CO (US)

Transition metals such as Mo, W, Ta, Cr, and W can be used to significantly enhance the localized corrosion resistance of Al. Since these elements exhibit very low solubilities in aluminum, a nonequilibrium alloying method, such as sputter deposition, must be used to produce single-phase alloys. The addition of approximately 9 atom percent W to Al can shift its pitting potential in the positive direction as much as 2600 mV. Heat-treatment of these nonequilibrium alloys results in the precipitation of a second phase that is detrimental, but not catastrophic, to corrosion performance. Surface analysis of the Al-W passive film formed as a function of applied anodic potential reveals that it remains thin throughout the polarization sequence and contains very little oxidized solute, regardless of the applied potential. The oxidized W present in the film is in the form of WO{sub 2} and WO{sub 3} (or WO{sup {minus}2}{sub 4}). The results of this paper reveal that the electrostatic-repulsion or oxidized-solute barrier-layer mechanisms are not responsible for the dramatic enhancement in the passivity of Al with the addition of W. Instead, the small amount of oxidized W in the passive film may interact synergistically with the hydrated aluminum oxide structure to form a more protective film.

• OSTI ID: 7068638
• Journal Information: Journal of the Electrochemical Society; (United States), Journal Name: Journal of the Electrochemical Society; (United States) Vol. 138:11; ISSN JESOA; ISSN 0013-4651
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400 -- Electrochemistry
ALLOYS
ALUMINIUM
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHROMIUM
COATINGS
CORROSION
CORROSION RESISTANCE
CORROSION RESISTANT ALLOYS
ELECTROCHEMICAL CORROSION
ELEMENTS
HEAT TREATMENTS
METALS
MOLYBDENUM
PASSIVATION
PROTECTIVE COATINGS
REDOX POTENTIAL
SPUTTERING
TANTALUM
TRANSITION ELEMENTS
TUNGSTEN ADDITIONS
TUNGSTEN ALLOYS