I don't know about aluminum but I have a pair of 870s that have no finish at all on them.
They are just bare steel, I wipe them like I would a blued gun and they have not rusted.
One of them has been without a finish for almost 3 years the other for about 2.
I keep meaning to get HHB to parkerize them but just never quite get around to it.
Most of the parts that are jewelled are either stainless or hard chromed so you don't have to worry about it. The only triggers I've jewelled were 1911 (including my own) and I've never had a problem with them turning. I do use a little renaissance wax on the parts I jewell though,it really brightens them up and I imagine it helps preserve the look of the alloy parts.