Our elfa products are not designed to be placed directly in the elements, but it can be placed on a porch, in a garage, or in a tool shed. This particular design cannot be placed upon casters. We do carry elfa drawer units on casters.
You may want to look into our Metro line. It is commercial grade, it can support up to 500 lbs. when placed upon casters, and it is made from an epoxy steel so it is resistant to rust. For more details, please take a look at our product recommendations. You can also call us at 1-800-733-3532 to have a custom solution created for you.