Aye Tim,
Rub over with a wire brush to get rid of the flaky stuff, degrease with Jizer and then a rub down with a thinners soaked rag. Now brush paint with a smooth hammerite colour of your choice. Maybe red if it is for the small USSR machine!
After all it is a decorative utilitarean approach for a utilitarean machine.
If the utilitarean approach "full stop" is required, then do nothing apart from clagging the rim with a good dose of 150W steam cylinder lubricating oil, warmed over your waste oil stove to a brushing consistency. Once hardened this stuff is only pervious to warm paraffin and Jizer attack or a steam cleaner.
The latter technique should rapidly produce a "designer chic patina"
after a few outings on NI dairy cow/tractor travelled highways and bi-ways at this time of year!
Batten down the hatches for 'Babs' and have a grand festive, Bill