The sheet is oiled. Oil must be removed for the plate to corrode. Corten sheets and expanded metal available in the e-shop are supplied in their as-manufactured condition (grey-silver steel without surface patination). The patination of Corten can be accelerated by applying a vinegar solution to the surface or by exposing the sheet to outdoor weather conditions, where natural patination will gradually occur. Please note that the patination process may cause “staining” of the surrounding areas where the Corten sheet is installed, until the surface patination stabilises. It is recommended to install the sheet or expanded metal only after the patination process has been completed.