Sealing corten steel with polyurethane or a product called Everbrite can enhance its durability. After applying, the finish will be darker than dry rust, but will look similar to rust sprayed with water or oil
Corten steel A shows full strength and stiffness (yield strength, modulus of elasticity) up to 540°C. This limit is set at 425°C for Corten steel B and 400°C for carbon steel. Corten steel is also used for outdoor stoves due to its higher heat-resistant properties.
If you live in a dry climate, a periodic mist of water will accelerate the oxidation process. In a matter of minutes, vinegar will give the planter the rust look.