First of all, clean and wash the items using first water, then fine steel wool soaked in oil, which you use to remove dirt or encrustation. Then observe the surface of the object.
If it has been damaged by rust, put the object in the water for a few hours, and then clean up all traces of rust using a brass brush, in order to scrape off any rusty residue. Later you can lubricate the artifacts, using the appropriate products, which are easily available on the market.
If over time you note that the object is particularly badly ruined, in addition to cleaning you can cover it with suitable coatings, which allow the iron to remain exposed to the elements without being ruined.