POR-15 Inc.
This stuff is amazing, I was at a navel base last year, in the periscope repair bay and considering these things are in sea water there was not a bit of rust on them, and I said to the guy how come you can keep that rust free and I can't keep my LR rust free, then he showed me a tin of this POR15 primer, he said its all in the primer.
So there you go, tried and tested by HMRN and approved by me.