The Pit Cover is made entirely from 3mm-thick (0.12in) Corten steel sheets. Corten is a steel alloy that forms a protective layer of rust on its surface. When you order our Pit Cover, you will receive it without any rust. As soon as you place it on top of the Firepit outside, where it will be subject to different weather conditions, the rusting process will set in on the outside. 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 after a while this will stop and the Pit Cover will get its final look.