Hello mimipo60, to get a mirror effect on metal parts, I often advise to first prepare your surface well and then polish your piece in several stages: first with a coarser polishing, then medium and finally a fine polishing (there are pastes, discs and brushes for each type of polishing). This gives a mirror effect to your piece. And to be sure that this finish lasts over time, you can apply a specific protector for metals.

But given the shape of your piece, perhaps galvanizing is more suitable to be sure that the finish is uniform on all surfaces of your piece. And you can always polish your piece in advance.