I have tried vinegar unsuccessfully. I've used Pecard Leather oil on my other scabbards and while it does not dissolve the crud it acts as a slurry to carry it out while I gently rotate the swivel. I've been working on five scabbards and this one is a bad actor and will not rotate at all. I've tried to break the corrosion by shielding the brass US rosette with leather and using a pair of pliers to no avail; any more force would probably break the leather. Regards, H.T.