What's the difference between Corten steel and stainless steel?

Corten steel is an exceptionally strong steel grade that was originally used in the American rail industry.  Due to its rust-coloured finish, it has become popular among architects.

Chromium, Copper, Titanium, Molybdenum, and a few others make stainless steel a highly corrosion-resistant metal alloy. Stainless Steel comes in many grades, but all Stainless Steels contain at least 11% Chromium.

Corten Steel will continue to oxidise until it disappears. The final appearance can take anywhere from 6 months to 2 years depending on the natural elements it is exposed to.

The term 'steel grades' is frequently used when researching steel. Steel's chemical composition is simply described here. For external architectural uses, Grade 304 and Grade 316 are the most common grades.