Not every residence offers outdoor storage options, and that can make finding a home for your ladder or stepstool a little tricky. As with any item, it is always preferred to store covered or away from exposure to the elements, but if up against the house or under a carport are what you have to work with, the materials can offer some insight into the best option.
Cosco ladders and stepstools will either be made of aluminum or powder-coated steel. Aluminum will perform better when left outdoors, but generally speaking, neither of these materials will rust. Powder coating is most vulnerable in the crevices or if the coating were to chip or become scratched. If this occurs, rust can become a concern; there are several touch up options available online or at your local hardware store.