Aluminum cylinders unlike steel cylinders don't rust, they oxidize. The oxidization of aluminum forms a protective coat that hinders the continuation of corrosion making aluminum cylinders less likely to be condemned due to excessive corrosion. When shipped the tanks valves will be removed and the tank will require re-inspection before being filled. Note: All Catalina cylinders are nitrox ready and meet certificated specifications of the US Department of Transportation (DOT) with DOT-3AL specification and Transport Canada Safety and Security (TC) with TC-3ALM specifications.