Rust-proofing metals

Hi everyone! I’m experimenting with sanding a variety of metals and
then seeing how the surface holds up after time passes. They all seem
to do pretty well but I noticed one of the sliver-colored metals (I
think it’s tin) rusts pretty quickly.

What sort of light coating could be applied to the surface of the
metal to prevent rusting but allow the sanded metal to keep as much
of it’s original “scuffed” appearance?

Thanks so much!
Warmly,
Raphael