I purchased a bunch of Swagelok fittings for my brew rig but they are covered with gray tarnish. They are mostly 316 SS, but a couple Parker A-lok fittings are 304. I don't want to scrub these by hand and have tried soaking in oxyclean which removed the dust on them. Is there something I can soakk them in to remove this? Preferably stuff not too nasty and perhaps found locally; maybe that's too much to ask for.