How to say "rust" in Japanese

• 錆さびJLPT N2approx.Common
  nounThe noun for rust itself: the reddish-brown coating that forms on iron or steel, as in rust on a bicycle or a gate. This is the word for rust as a thing you see or wipe off.
  この車くるまは錆さびに強つよい。↗

  This car is resistant to rust.
• 錆びるさびるJLPT N2approx.Common
  ichidan verb, intransitive verbThe verb for when metal rusts or becomes rusty: a blade, a fence, or a car part rusts over time when exposed to moisture. Use this where English uses 'rust' as a verb.
  雨あめの中なかに放置ほうちしておくと自転車じてんしゃはさびるでしょう。↗

  A bicycle will rust if you leave it in the rain.
• 腐食ふしょくCommon
  noun, suru verb, transitive verb, intransitive verbReally means corrosion — the gradual eating-away of metal by chemical action — and also etching. Its 'rust' sense is marginal: for ordinary rust on iron, 錆 is the word you want, while this fits technical discussion of corrosion.
  ほら、錆さびで金属きんぞくがどんどん腐食ふしょくしているよ。↗

  Hey, rust is eating away the metal.

Use 錆 for rust as a thing, 「錆びる」 for the action of becoming rusty, and 腐食 when you mean corrosion in its broader sense — its 'rust' sense is secondary, so it is seldom the everyday choice.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 錆さびrust
• 錆びるさびるto rust
• ラストrust
• 錆色さびいろrust (colour)
• 赤錆びるあかさびるto rust
• 金錆かなさびrust
• さび菌さびきんrust (fungus)
• さび病さびびょう(plant) rust
• 腐食ふしょくcorrosion
• 錆び付くさびつくto rust