The developed patina finish protects the steel from additional corrosion and exhibits surface rust for design purposes only! The Corten Steel Raised Garden Planter arrives in their raw unrusted state and will rust with natural exposure to the weather. Usage:Outdoor only; Made from corten steel, only develops surface rust, will never rust through; Deep planting base for both large and small plantsCorten steel planter EtsyCorten Steel Planters, Raised bed Corten Steel Planter boxes. DIY Corten 96" L x 48" W x 20" H Planter Bed, no bottom, Assembly Required. Custom sizes are our specialty. Custom Made Planter Box. Corten Steel Planters, Raised bed Corten Steel Planter boxes.