The composition and morphology of anodic films on Al-Mo alloys

Journal Article · Sat Mar 01 04:00:00 EST 1997 · Journal of the Electrochemical Society

DOI:https://doi.org/10.1149/1.1837499· OSTI ID:483781

Crossland, A C; Thompson, G E; Wan, J; Habazaki, H; Skeldon, P; Wood, G C ^[1]; Shimizu, K ^[2]

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1. Univ. of Manchester Inst. of Science and Technology (United Kingdom). Corrosion and Protection Centre
2. Keio Univ., Hiyoshi, Yokohama (Japan). University Chemical Lab.

The growth of barrier-type anodic films on amorphous Al-Mo alloys, containing 16 to 40 atom percent Mo, in borate electrolyte was investigated by analytical transmission electron microscopy, Rutherford backscattering spectroscopy, secondary ion mass spectrometry, and extended x-ray absorption spectroscopy. During growth at 1 and 5 mA/cm{sup 2}, two-layered amorphous oxide films formed at high efficiency by outward migration of cations and inward migration of oxygen ions; the outer layer is composed of units of alumina contaminated by boron species derived from the electrolyte and the inner layer contains units ob both Al{sub 2}O{sub 3} and MoO{sub 3} distributed uniformly at the resolution of the analyses. At 0.1 mA/cm{sup 2}, the films form at reduced faradaic efficiency, which results in a decreased thickness of the outer alumina layer. The two-layered films develop as a consequence of faster migration of Al{sup 3+} ions than Mo{sup 6+} ions within the inner layers of the films. New film material forms at the alloy/film and film/electrolyte interfaces and at the interface between the inner and outer layers. At the alloy/film interface, a thin layer of alloy is highly enriched in molybdenum as a consequence of anodic oxidation. Due to the mechanism of film growth, a high concentration of boron accumulates in a sublayer of film material just above the inner/outer layer interface.

• Sponsoring Organization: USDOE
• OSTI ID: 483781
• Journal Information: Journal of the Electrochemical Society, Journal Name: Journal of the Electrochemical Society Journal Issue: 3 Vol. 144; ISSN 0013-4651; ISSN JESOAN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BASE ALLOYS
ALUMINIUM OXIDES
AMORPHOUS STATE
BORATES
CHEMICAL COMPOSITION
MOLYBDENUM ALLOYS
MOLYBDENUM OXIDES
MORPHOLOGY
PROTECTIVE COATINGS