Aircraft Materials, Hardware & Processes
What is the purpose of the thin pure-aluminum surface layer on Alclad 2024 sheet stock?
Answer
To provide corrosion protection for the stronger alloy core
Alclad is a high-strength aluminum alloy (such as 2024) rolled with a thin layer of commercially pure aluminum on each side (roughly 5% of thickness per side). Pure aluminum resists corrosion and is anodic to the core, so it acts as both a physical barrier and a sacrificial (galvanic) coating that protects the corrosion-prone alloy underneath. The cladding slightly reduces overall strength; it is not added for welding or conductivity.
Source: FAA-H-8083-30B, Ch. 7 Aircraft Materials, Hardware & Processes — Aluminum and Aluminum Alloys (Alclad)
Not the answer
- To make the sheet electrically conductive for bonding
- To increase the tensile strength of the base alloy
- To allow the sheet to be gas welded more easily
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