Solid brass doesn't rust, since it contains no steel/iron, it just tarnishes - another way of saying "discolor" or change appearance - when it comes in contact with various agents.
That's why it's had naval use for centuries.
When "rusted" brass is seen, what is actually seen is the rusting of a non-brass base metal that had been brass plated.
The green "verdigris", seen from brass' prolonged leather contact, is a surface growth.
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