Get rid of rust...
- 3M Clean-n-Strip XT (purple) are great at getting a bright Sa2.5
finish with a cheap cordless drill
- Combine use with Loctite white milky stuff (goes black) to get into
pores to help neutralise what you can't get to

Zinc protection...
- Galvafroid - pure zinc so truly protects, £25 per tin that weighs
like a neutron star, rubs off, requires blackfriars galvanising primer
before painting
- Dinitrol - Lower zinc so lesser protection, more abrasion
resistance, easier to spray-prime & paint

It comes down to how rusted and what final finish.

Frost's Restoration do 3M clean-n-strip discs and etch sprays if just
surface corrosion, then primer (fill in imperfections), paint,
polishing compound and wax after a few weeks.

Zinga (think that is right) is an improvement on Galvafroid, but the
best is 2pk (or lesser 1pk) zinc epoxy primer at £30-55. Colleague
used 1pk zinc epoxy primer on a windscreen surround that had been
wrecked years earlier by an windscreen removal tool in the hands of an
idiot main dealer. No rust progression (or leaks) after several years,
he also saturated the underside of the windscreen trim with 3M 08509
non-setting black butyl goo in a cartridge for a belt-n-braces backup.