Rust away
Definition 1 of 1
Pro Tip 1/3Neglect Implies
Using 'rust away' suggests something was ignored or not maintained properly over time. 
Without regular cleaning, the pipe will just rust away.
Pro Tip 2/3Time Passage
'Rust away' indicates a gradual process, not something that happens instantly. 
The garden tools were allowed to rust away over years of disuse.
Pro Tip 3/3Irreversible Change
The phrase often conveys that the rusting damage can't be undone. 
The bridge's supports rusted away, and it eventually collapsed.