Any mention of patina is usually in reference to our products made of COR-TEN weathering steel. Patina is an important process for COR-TEN. COR-TEN is named for two of its properties corrosion resistance (COR) and tensile strength (TEN).For COR-TEN to become fully corrosion-resistant, it needs to go through a patina process. During this process, the steel changes from a raw metal look (in which the color of the steel is gray) to patina (where the metal turns the color of orange-brown).To patina, the planter needs to be in the elements. This means that COR-TEN weathering steel should only be outdoors, and the planter should not be covered. It is important to note that when the planter is going through the patina process, the metal can bleed onto the surrounding surface.COR-TEN Weathering Steel After Patina Once this change has occurred, the weathering process of COR-TEN is complete. The steel is now resistant to corrosion and is perfect for many outdoor climates. (Note: COR-TEN weathering steel planters need to be at least two kilometers away from large bodies of saltwater, as saltwater can erode this material. I.e., you wouldn’t want to use COR-TEN in a cafe located next to a saltwater beach).If you love the look of COR-TEN weathering steel but do not think the material will work for your needs, we recommend using powder-coated aluminum planters in weathered rust. Aluminum planters are a commercial alternative that mimics the look of COR-TEN weathering steel.