Shipping containers are constructed with alloy and weathering steel that forms a layer of oxidation for protection. However, rust may still occur without the proper maintenance and care. Steel can only slow down the rate of corrosion. Anytime you place a container in a wet area, you'll likely battle with rust. However, there are high-quality coatings that will cover up the metal and stage off rust for a while. They won't last you forever, but they should last for many years.