red rust
Refers specifically to the reddish-brown rust that forms on iron or steel.
古い鉄橋に赤錆が浮いていた。
Red rust had appeared on the old iron bridge.
赤錆を落とすにはサンドペーパーが要る
You need sandpaper to remove red rust.
Black rust, a different type of iron oxide. 赤錆 is the more common red variety.
Standard kanji spelling.
Mixed kana spelling, common in everyday writing.
Search-only katakana form.
Search-only variant using a rare kanji for rust.
Compound of 赤 (red) and 錆 (rust).