Are you leaving water on it? I don't think most of us guys have problems with rust. Just replace the screws if they become bad enough, they're cheap anyways.
I have some rust remover that I bought for my real car and that will removed some slight surface rust as well. But even the cost of the bottle will pay off for tons of replacement screws.
Just don't get the bearings wet. They'll rust fast and you'll need to clean them out again because it will lock them up.