What is the service life of Corten steel?

What is the service life of Corten steel?
In most environments/applications, a medium thickness of Corten steel [2.0 mm or 3.0 mm] will achieve a service life of +25 years. To achieve a +40 year service life, the thickness should be increased by 1.0 mm to minimize expected material loss.

If you only need the title and not the details, here are the key points:
Corten Steel is a group of steels with excellent corrosion resistance and tensile strength. Corten steels are also known as "weathering" steels; this is because a protective layer forms on the surface of the steel when exposed to the weather and does not require painting.

The main benefits of Corten steel are
Unique aesthetics. Corten steel develops different shades of bronze, rust and copper, which are the perfect foil for a variety of natural and architectural planting schemes.
Extremely long service life. Unprotected Corten steel wears out material very slowly (0.8 mm in 40 years and 2.0 mm in 120 years in central London).
Low cost. For a life expectancy of more than 10 years, Corten steel offers the best value for money of any sheet metal, mainly because it requires no painting or repainting.
Essentially zero maintenance. Any necessary maintenance is for purely aesthetic reasons, not functional and/or structural ones.