Definition
Sheet steel coated with a lead-tin alloy (typically about 80% lead and 20% tin) to give it corrosion resistance and improved solderability. Terneplate is used in aircraft for fuel tanks and similar applications where the metal must resist attack from fuel and protect against rust.
Plain English
A type of steel sheet that has been coated with a mixture of lead and tin so it doesn't rust and is easy to solder. It's commonly used to make aircraft fuel tanks.
Context Anchor
Seen in aircraft maintenance and materials discussions, especially when identifying or repairing older fuel tanks, oil tanks, or sheet-metal containers.
Derivation
From the French 'terne,' meaning dull or tarnished, referring to the dull gray finish the lead-tin coating gives the steel — unlike the bright, shiny finish of tinplate (steel coated with pure tin). The name itself tells you what it looks like.
Why Pilots Care
Terneplate fuel tanks must be repaired with the correct soldering technique and materials. Using the wrong solder or repair method can compromise the coating, leading to corrosion or fuel leaks.
Intuition Check
Do not assume plate means a thick metal plate here. Terneplate is usually thin sheet steel with a protective coating.
Example Sentence 1
The fuel tank on the older trainer was made of terneplate, so the mechanic used a lead-tin solder to patch the small leak.
Example Sentence 2
Older aircraft often used terneplate because the coating held up well against fuel vapors.