Bare metal treatments

For a clear coating, I'd use Krylon's Crystal Clear - it's an acrylic that won't turn yellow with age/exposure.

It comes in two "flavors" - the normal thickness and one that's triple thickness (often used for artsy/craftsy projects). For something that'd be outdoors I'd go with the thicker version.

The stuff comes in a rattle can and is easy to apply, weatherproof, and fingerprint proof.

I've had good results with steel. Common 2"x6" rectangular tubing, (I'd not make a guess at the alloy), design milled into surface, and filled with brazing rod, the whole thing ground flat, sanded fine, then polished to high mirror-like gloss, finally heated with the brazing torch (fine tip) until the heat colored the surface where I wanted it. (Really neat rainbow-effect, flaring out in sunburst attitude), If you overcook it, just cool it, polish, and go at it again, until you achieve the desired appearance. then immediately (as soon as it cooled) clear-coated with automotive lacquer. (Three coats, polished if you like). Highly durable, especially indoor, and 30 years later, still looks worth remembering the effort to do it.

Flash

1) Coloring/patination - heating alone produces interesting effects - totally unpredictable. To darken steel I use Birchwood Casey's Gun Blue paste - I like it better than the liquid. I have coated steel with copper by just painting it with acidified Copper Sulphate - I am in the process of getting an electro-plating system together. There is always rust! I got a pretty even brown coating by *really* cleaning the sanded steel and applying lemon juice - it happens literally before your eyes. 2) Protection - I have used Future Acrylic Floor coating. It is very resistant and does not discolour (has not so far!). One problem is that it sometimes screws up the patina and you have to know how it is going to react with *your* surface treatment. Advantage is that it dries quickly and is non-toxic.

For everything else I like Penetrol. Note: Unless the ambient temperature is warm, it may take 2 days to dry completely.