steel wool 
noun [mass noun]
Fine strands of steel matted together into a mass, used as an abrasive: sand lightly with fine steel wool and dust off thoroughly...
- Periodically, warm mineral oil should be applied with an absorbent cloth or very fine steel wool to the surface and edges.
- Rub greasy spots with a mild or moderate abrasive, such as fine steel wool, and a dish detergent until they disappear.
- If necessary, gently sand away stubborn rust on pruners and loppers with fine steel wool; use medium-grit sandpaper on larger tools.