Bronze doesn’t rust, but it can certainly tarnish if not cared for properly. The tarnish – sometimes called patina – results from a chemical reaction between the metals in the alloy and acids. Acids from the air, pollution, or even in the skin can cause the metal to tarnish, leaving behind an unattractive patina. Chlorine exposure also causes damaging corrosive tarnish known as bronze disease that will eventually pit and destroy the metal.