Naval jelly, among other things is used to impart the sharp flavour to Coca Cola and Pepsi Cola. It is used in other foods and food processing and to adjust the PH of many cosmetic products.
Anyway, it does convert rust into black oxide which may be scrubbed off. It may take more than one application but the oxide itself is a modest rust protector but not necessarily pretty. Wikipedia has a lot more information than this about it. I have never used it but I expect I would. If I was Han Solo I'd probably pet my wookie [Non-text portions of this message have been removed]
