Combinatorial electrochemistry on Al-Fe alloys

Area of Science:

• Materials Science
• Electrochemistry
• Surface Chemistry

Background:

• Aluminum-rich aluminum-iron (Al-Fe) alloys are crucial in various industrial applications.
• Understanding their interface chemistry is vital for optimizing material performance and preventing corrosion.
• Combinatorial approaches offer efficient methods for exploring complex material systems.

Purpose of the Study:

• To investigate the interface chemistry of Al-Fe alloys across a range of compositions.
• To quantitatively determine key electrochemical properties as a function of alloy composition.
• To identify and explain any synergistic effects influencing oxide formation.

Main Methods:

• Combinatorial material development using composition spread thin films with linear composition gradients.
• High-throughput microelectrochemistry, including scanning droplet cell (SDC) measurements.
• Anodic oxide formation with intermittent electrochemical impedance spectroscopy (EIS).
• X-ray photoelectron spectroscopy (XPS) for composition and depth profiling.

Main Results:

• Quantitative determination of film formation factor, relative permittivity, and oxide formation onset potential with 0.5 at.% resolution.
• Discovery of an unexpected synergistic effect in Al-Fe alloys between 9 and 12 at.% Fe.
• A significant shift in the onset potential (nearly 1 V) was observed within this narrow composition range.
• XPS analysis supported the findings, indicating local iron accumulation and its role.

Conclusions:

• A synergistic effect in Al-Fe alloys within a specific composition range (9-12 at.% Fe) dramatically influences oxide formation.
• This effect is attributed to local iron accumulation, leading to redox stabilization of space charge layer formation during high-field oxide growth.
• The study demonstrates the power of combining combinatorial material development with high-throughput microelectrochemistry for efficient materials investigation.