Until you get a better answer an old trick I've used on old tatty bolts is to use a Brass Wire Brush Drill attachment on them.It removes the corrosion and leaves a nice burnished finish.Then a dab of ACF50 or Clear-Nail-Varnish and they take a long time to corrode again usually.Then they are also quickly kept good.
https://www.ebay.co.uk/itm/6-pack-Br...0AAOSwczlbM9z8
Wear overalls and safety glasses though as the bristles can come off and if left in cloth can scratch and irritate.