Lloyd, I use Meguiars Cleaner Wax on my cans. Once over for cleaning, (I do not let this dry), then a wax layer that I let dry. Try to clean the tops up some using the same method and if really rusty, use aluminum foil on it. At least it leaves a nice "patina". I would NOT use a clear coat.

You may want to invest in a de-humidifyer for your garage. I don't think the dryer cold air we have here in Tn affects the cans like the hot muggy summer season with 100% humidity. I have air in my shop but only use the de-humidifyer in summer months as it's a lot cheaper to run.