XCarb^® Indaten^® weathering steel selected for world class architectural collaboration

13 November 2025

ArcelorMittal has collaborated with renowned furniture design and manufacturing company Vitra to construct the recently opened “Doshi Retreat”, a new multi-sensory sculptural experience, in Weil am Rhein, Germany.

The retreat has been created as part of the Vitra Campus, a unique site developed by the legendary Swiss furniture design company, Vitra, that showcases architecture from some of the most respected architects internationally, including Frank Gehry, Zaha Hadid, Tadao Ando, and Herzog & de Meuron. It was designed by Balkrishna Vithaldas Doshi, one of the pioneers of modern architecture in India, and was his first project outside India and his last project before he died in 2023. He was awarded the prestigious Pritzker Architecture Prize in 2018. His granddaughter Khushnu Panthaki Hoof and her husband Sönke Hoof took on the responsibility of completing the retreat project with Vitra Chairman Emeritus Rolf Fehlbaum, which has finally come to fruition in 2025.

The intertwining paths of the design seen from above © Vitra, photos: Julien Lanoo

Weathering steel plays a key role in the construction involving a central, high walled, enclosed Gong Room and a series of intertwining paths, and ArcelorMittal’s Indaten^® corten structural steel was selected for its excellent corrosion resistance, sustainability and appealing aesthetics. Indaten^® develops an attractive ‘natural’ patina that evolves over time gradually deepening into a distinctive rich dark brown hue which matures with age.

The design is based on technically challenging, curving three-dimensional steel forms. The intricate forming and shaping operations were carried out by a specialised supplier for shipyards in Germany, the only one able to form the 3-dimensional shapes from Doshi’s original design. The largest steel plate section is 8 metres by 2.5 metres and with some of the path borders extending to 10 metres in length. The 3D designs were fabricated through cold forming techniques, using high strength portal presses and bending and rolling machines.

153 tonnes of XCarb^® recycled and renewably produced heavy plate steel was supplied from ArcelorMittal’s Gijon plant in Spain, together with 13 tonnes of beams from the Differdange plant in Luxembourg - the XCarb^® recycled and renewably produced steel has a carbon footprint of circa 65% lower than conventional steel produced in a traditional blast furnace, and the energy used is certified 100% renewable electricity.

ArcelorMittal undertook specific development and testing processes to produce the weathering steel grade in its low emission XCarb^® version. These efforts mark a significant step forward in combining architectural ambition with sustainability goals.

“I am excited that ArcelorMittal has been able, together with Vitra, to support the realisation of the first work of the great Indian architect BV Doshi outside of India.” said Aditya Mittal, CEO of ArcelorMittal. “The Doshi Retreat now takes its place at the Vitra Campus alongside works by Frank Gehry, Zaha Hadid, Tadao Ando, and Herzog & de Meuron. Using ArcelorMittal’s XCarb^® recycled and renewably produced steel, the Doshi Retreat shows once again that steel can be art.”

Given the principles of Hindu philosophy behind the retreat, the parties involved in the project were all keen to incorporate low carbon-emissions steel and sustainability into the project, and the supply of XCarb^® steel from Gijon and Differdange enabled this.

“This has been a challenging and exciting collaboration with Vitra,” said Denis Parein, Sales and Marketing director ArcelorMittal Heavy plates Europe, “and we have been delighted to work so closely with them. The Vitra Campus is a centre for iconic architecture and materials from around the world, and we are delighted to be able to showcase our low emission XCarb^® steel in such a worthy project.”

The “Doshi Retreat” is open to the public from October 25^th, 2025.