On chrome one can use just plain water and crumpled up aluminium foil to remove rust Basically wet the foil then rub on rusted chrome until shiny. If it's inside, a little salt and veggie oil (or oil of choice) and paper towel or foil could remove rust from cast iron. I used veggie oil because i had a rusted cast iron skillet and it just needed elbow grease. If it's around decals I would yield to those more knowledgeable than I am. So basically listen to J. Miller
lol
There's always this link:
http://www.instructables.com/id/Elec...val-aka-Magic/ I don't know how well it works on sewing machines and how it could damage the paint. I havent tested it out. But if you have little bits and pieces within the machine like the machine arms and pistons that won't be seen then you could try it out on them.