An old or unused thing that has become weak or imperfect because of age is called "rusty".
When something's been sitting around for too long, it can get rusty. If your bike's been locked up outside for months and you finally take it out, the chain might be all rusty and creaky. This means the metal has oxidized and started to break down. But being rusty isn't always a bad thing - some people even like old, rusty tools because they have character. Sometimes "rusty" is used more loosely to mean something's a bit outdated or not as good as it used to be. For example, if you watched an old TV show from the 80s and thought it was cheesy, you might say it's "a little rusty."
Marked or corroded by rust.
