The Thermo Door & the handle are made entirely from a 3mm thick (0.12in) corten steel sheet.
Corten is a steel alloy that forms a protective layer of rust on its surface. When you order the Thermo Door, you will receive it without any rust. As soon as you place your thermo door outside, where it will be subject to different weather conditions, the rusting process will set in. Depending on where you live, the process of turning from blank to rusty steel can take between a few months up to a year.
The steel is meant to rust in order to form a protective coating. In the first phase of the rusting process, some flakes of rust might come loose, but this will stop after some time and the Thermo Door will get its final look.