Raw finish with gun blue?
Not a huge fan of raw finishes myself but some people seem to want them. I've heard that corrosion under the clearcoat is an issue because of the lack of a primer.
Has anyone tried selenious acid, followed by clear coat? This is the stuff known as "gun blue" that is supposed to form one of the other iron oxides that isn't rust (magnetite I think) which makes a protective layer a bit like mill scale. You then usually put a bit of oil on it which is supposed to kind of soak in to the surface but I was thinking clearcoat instead.
Maybe I'll try on a couple of offcuts and leave them out in the British winter for a bit.