Answer:

oxidize

Answer	Crossword Clue
OXIDIZE	Become rusty
OXIDIZE	Become rusted
OXIDIZE	Discolor, as banana peels, e.g.

OXIDIZE	Become ash, maybe
OXIDIZE	Get rusty
OXIDIZE	Begin to rust
OXIDIZE	Rust
OXIDIZE	Form rust, say
OXIDIZE	Go from aluminum to alumina, say
OXIDIZE	Rust out
OXIDIZE	Get rusty e.g.