Aug 22, 2018 · COR-TEN® Steel will continue to patina over time into a darker mocha looking metal instead of the bright yellow-orange that it originally started with. The image below shows the aging/patina process of COR-TEN™ Steel starting from left to right(0.5 Months, 1.5 Months, 6 Months, 2 Years, 5 Years, 22 Years, 40 Years).