Cor-Ten is also known as Weathering Steel, is a group of steel alloys which were developed to obviate the need of painting and form a stable rust like appearance if exposed to the weather.
The original Cor-Ten received the standard A242 (Cor-Ten "A") from the ASTM International Standard Group. Newer ASTM grades are A588 (Cor-Ten "B") and A606 for the thin sheet. All alloys are in common production and use. Weathering Steel is popular used in outdoor sculptures, such as exterior facades and architectural applications, for its rustic appearance.