Don't store your bike over the winter under a cover outdoors if you can avoid it. I did this with a previous bike once, it was enough to learn to never do it again. It will rust as covers trap moisture and blowing snow will get up under the cover. I do use a cover over my bike to store it for the winter in a garage, but only to keep the dust off. If you are forced to store it outdoors under a cover or in a damp location spray the bike down (frame, engine, bolts, chain, brake disks, etc.) with fogging/misting oil first. It will make a mess but you can clean it off in the spring. Bikes do not use the same anti corrosive primers as cars and rust and corrode extremely readily.