Definition
Metals that contain iron as their principal element, including iron itself and the various grades of steel. Ferrous metals are typically magnetic and are prone to rust when exposed to moisture and oxygen.
Plain English
Metals that are mostly made of iron, such as steel. They usually attract a magnet and can rust if not protected.
Context Anchor
Seen in aircraft maintenance, materials selection, corrosion control, hardware identification, and repair instructions.
Derivation
From the Latin ferrum, meaning iron. The chemical symbol for iron, Fe, comes from the same root. So 'ferrous' simply means 'of iron' or 'iron-containing,' which makes the category easy to remember.
Why Pilots Care
Knowing whether a part is ferrous matters for corrosion inspection, repair selection, and choosing the right hardware. Ferrous parts rust, respond to magnets, and require different treatment than aluminum or other non-ferrous materials common on aircraft.
Intuition Check
Do not read “ferrous” as just “metal” or “strong metal.” Ferrous specifically means iron-based; many aircraft metals, especially aluminum alloys, are not ferrous.
Example Sentence 1
The mechanic used a small magnet to confirm the bracket was made of a ferrous metal before selecting the correct corrosion treatment.
Example Sentence 2
During the preflight inspection the mechanic noted surface rust on ferrous metals in the landing-gear structure.