Corten steel is alloy which allows the weathering effect of rust to take effect without damaging the structural integrity of the material. There is no need to treat the metal to preserve the effect and the result is a striking orange patina which is becoming ever more popular. The most common designs are squares and circle because they are easy to make out of sheet material and weld together. With my designs I create them from a fibre reinforced concrete in a red base colour and then surface treat them to give a very similar effect to corten steel. The benefit is that you end up with a much more interesting shape to house your planting and it will much much more of a statement than a standard box pot. To create my designs in real steel would be extremely hard so with an Adam Christopher planter you get the best of both worlds, an interesting shape and striking finish.