I rcently got 30 Sten mags, for my Oly 9mm upper conversion, from Tapco during their $9.95 for 6 mags with a carrying pouch deal.
The mags that showed up were completely covered in cosmoline, had no obvious damage, but also little to no finish remaining.
I had some PermaSilk left from doing a bunch of AR mags so I thought I'd give it a shot, despite hearing issues of the PermaSilk not bonding well to the steel Sten mag bodies.
To clean the Sten mags they were soaked overnight in a bucket of kerosene (melts the cosmolime), then rinsed with WD40. After that they were disassembled, and completely scrubbed down with hot water and dish detergent.
To make sure there was no remaining cosmoline or moisture trapped under the welded piece, the mags were then baked in a 350 degree oven for 1 hour.
The mags were then removed from the oven, rubbed down with paper towels, and, while still hot, hung up for spraying.
The PermaSilk was sprayed as per its directions, allowed to dry as per the directions, then the magazines were baked in a 300 degree oven for 90 minutes.
Upon removal from the oven the magazines were allowed to cool to the point where they could be handled, then rubbed down again with paper towels to remove any excess PermaSilk.
Springs and followers were inspected for any signs of damage, then cleaned in hot water and detergent, dried then lightly oiled.
The magazines were then reassembled.
Repeated insertions into the firearm have left no marks on the refinished mags. Cycling a magazine or three worth of dummy 9mm rounds has not affected the finish. Tuesday I'll take the 6 mags I did today to the range and run at least a full mag of ammo through each of them, but it initially looks like the PermaSilk refinish will work.