The sentence "has become rusty" is correct and usable in written English.
You can use it to describe an object or surface that has corroded due to lack of use or exposure to the elements. For example, "The old bike has become rusty from sitting in the shed all winter."
Nails had become rusty, planks had to be smashed to open the cases.
Surmounting the structure at intervals of about three feet are Y-shaped pieces of metal, on which are strung strands of barbed wire that have become rusty.
This duty is also emphasized by the Management of Health and Safety at Work Regulations 1999, which identify situations where health and safety training is particularly important, e.g when people start work, on exposure to new or increased risks and where existing skills may have become rusty or need updating.
Instead, it has become an archipelago of rusty plants and "hit-and-run" mines, where ore is ripped out as fast as possible for quick profit.
But this year, with the Tea Party making the Constitution sexy again, the holiday (which, for those rusty on their civics, falls on Saturday) has become occasion for battle.
"I'm a little rusty on all the details, but the menu has become a tradition," concedes Stan, who is 71, blue-eyed, and, when he grows out his beard, a dead ringer for a robust Santa Claus.
He was standing in a friend's garage-like studio in Gowanus, inside the huge rusty metal Dumpster that he bought in May — "the largest thing I have ever owned" — and that has become a kind of Dumpster of curiosities, filled with personal and obscure mementos.
He declared that: "Kindness opens up and softens the heart as a oil opens a rusty lock .In recent years, as an economic crisis has ravaged Greece and people search for answers, Paisios has become better known (especially in nationalist and far-right circles) for eschatological prophecies which are ascribed to him, although some people doubt their authenticity.
Within the context of our contemporary moment, however, the metaphysical establishment that Kafka sought to overthrown seems to have become a rusty, dusty old thing.
What has also occurred, said David E. Monn, a prominent event planner, is that party manners have become so rusty from disuse, and guests so generally clueless, that a need has emerged for people like him to train socialites not to eat peas with a knife.
