Translation guide
The English word "rust" can refer to the reddish-brown coating on iron, the plant disease, or the color. This guide focuses on the most common meaning: the corrosion of iron. Japanese has several words for rust, with 錆 (さび) being the most general and common.
To refer to the reddish-brown flaky coating that forms on iron or steel when it oxidizes.
The most common and general word for rust. Can be used for rust on any metal object, but primarily iron/steel.
The bicycle chain is rusty.
This knife is resistant to rust.
Literally 'red rust', refers specifically to the common red rust (iron(III) oxide). Often used in technical contexts or to distinguish from other types of rust.
Red rust forms on the surface of iron.
Literally 'black rust', refers to black iron oxide (magnetite) that can form a protective layer. Used in technical or craft contexts (e.g., knife making).
Black rust protects the iron.
To refer to a group of fungal diseases that cause rust-colored spots on plant leaves and stems.
To describe the color resembling rust, a reddish-brown or orange-brown.
To express the process of metal becoming rusty.
Intransitive verb: to rust, to become rusty. Used when the subject itself rusts.
Iron rusts when it gets wet.
This bicycle has already rusted.
Transitive verb: to cause to rust, to let rust. Used when someone/something causes rusting.
Humidity causes iron to rust.
Literally 'rust attaches'. A common phrase meaning to get rusty. Often used for tools or skills.
If you don't use it, the kitchen knife will get rusty.
To express that a skill or ability has declined due to lack of practice, similar to 'getting rusty' in English.
Literally 'one's arm becomes dull'. A common idiom meaning one's skills have become rusty. Not directly using the word 'rust', but the natural equivalent.
I haven't practiced for a while, so my skills have gotten rusty.
Literally 'one's intuition becomes dull'. Used when one's sense or instinct for something has become rusty.
Literally 'to become rusty'. Can be used figuratively for skills, but less common than 鈍る. Sounds more literal/metaphorical.
While 錆 can technically refer to corrosion on other metals, it is most strongly associated with iron. For aluminum or copper, you might use 腐食 (ふしょく, corrosion) or specific terms like 緑青 (ろくしょう, verdigris on copper). In casual speech, 錆 is often understood for any metal, but be aware of the nuance.
錆びる is the everyday word for rusting (iron oxidation). 腐食する is a more technical term for corrosion in general, including chemical corrosion of various materials. Use 錆びる for common rust, 腐食する for scientific/engineering contexts.
After a long break, my work instincts got rusty.
My English has gotten rusty.