Corrosive

As the name suggests, a corrosive atmosphere eats away at matter. The type and speed of the erosion varies, but the most common use of this term describes atmospheres capable of dissolving most matter. A typical corrosive atmosphere deals anywhere from 1 acid damage per minute up to 10d6 acid damage per round to creatures and objects within. Certain metals and treated materials may be immune to the specific atmosphere of a planet, and often the corrosion can be mitigated with dutiful preparation.