I had to replace the plastic hopper on my Uniflow powder measure because I left Power Pistol in it for two nights. It etched the entire surface everywhere powder was in contact in it. FWIW, the hoppers are very easily replaced. The new one tapped right into place using a 2X4 as a block.
Some powders are worse than others about etching. My oldest 550 that I load 45 acp on has had 231 left in it overnight quite a few times and while it did darken the plastic it is not bad enough to warrant replacement.