Damaged antique cast iron

My mother over Christmas leave passed off an old piece to my husband and myself. It's my great-grandmother's dutch oven. It was a wedding present from her grandmother who recieved it new from her husband on their first anniversary. Needless to say it's ancient LOL My aunt had it stored in her tack room of her barn and it's rusted and the bottom of the inside is white. I know I'll have to reseason it but how can I get the rust and old seasoning off without damaging the piece itself?