Aircraft Materials, Hardware & Processes
Why must 2017 (D) and 2024 (DD) solid rivets be kept in a refrigerator ('icebox') after solution heat treatment and driven within a limited time?
Answer
Cold storage retards age hardening so the rivets stay soft enough to drive
After solution heat treatment, 2017 and 2024 rivets begin to age-harden at room temperature and would become too hard to drive without cracking. Storing them at or below freezing greatly slows that age hardening (hence 'ice box' rivets); once removed they must be driven within a set time — roughly 1 hour for D/2017 and only about 10-20 minutes for DD/2024. Refrigeration does not harden them, and its purpose is neither corrosion control nor a momentary cold-ductility effect.
Source: FAA-H-8083-30B, Ch. 7 Aircraft Materials, Hardware & Processes — Solid Rivets / Heat Treatment of Rivets
Not the answer
- The aluminum is ductile only while it is actually cold
- Refrigeration permanently hardens the rivets so they hold better
- Cold storage removes moisture that would corrode the rivet holes
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