Mason jar lids and rings often rust if they aren’t stored in a dry environment. If your jar with metal lids is rusted, it is recommended that you don’t use them for canning.
However, you can always use it for your DIY mason jar lid crafts or freeze jams and jellies.
If your canning jar rings or bands are rusted from the outside, you can reuse them after cleaning.
Take a soft cloth and soak it in white vinegar. Rub the cloth vigorously to remove the rust from the lids and rings.
Alternatively, you can soak the lids and rings in white vinegar for a few hours. Then, take a cloth and clean the Mason jar lids and rings.