Someone (can't remember who) has previously recommended Rustins metal lacquer.
http://www.rustins.eu/Details.asp?ProductID=811
Roger
Edit: Note that they (Rustins) recommend it for brass, copper, bronze, and silver, with no mention of MS at all. It would be interesting to know why MS is omitted. Maybe they simply expect any steel product to have a protective coating already applied.
Edited By Roger Head on 06/08/2016 10:19:12