Brass doesn't rust. Tarnished Trombone maybe?
While true, trombones aren't 100% brass. We often have nickel silver hand slides, but there isn't any iron on them either. We do get corrosion on the inner hand slides, though.
Science aside, I remember the first time I was told of the Rusty Trombone. I was quite pleased in that it accurately described an action that was very similar to playing a trombone.