As an Aircraft Mechanic for many years, and also the mechanic of ALL MY TOYS, I have seen two products through the years which stand out because of how well and consistently they work. One is " Mouse-Milk", that liquid which given it time to work, loosens rusted threads like majic !!! The other one is "Corrosion-X", that blue oil-protectant which works wonderfully protecting metals from corroding, and also works as a shining liquid to shine metal or plastic parts and keep`em glossy. Try them, they are a bit expensive because they are approved for Aircraft use, but they are worth the extra bucks.