How to Store Scuba Cylinders
Cylinders are stored in racks to make it easier to access them, maximize floor space, and to prevent them from tipping over. Ideally, cylinders should be stored at a slight angle in order to direct any moisture or water that may be present in the cylinder to the bottom corner where the cylinder metal is the thickest. This thicker area may take longer to corrode compared to the thinner side walls which would be impacted if the cylinders were lying flat on their sides, where water could spread out causing a long line of corrosion, potentially along the entire length of the cylinder.
So, to increase the longevity of your cylinders, it is preferable to store them at an angle. Regular visual inspections will also catch any water corrosion so that the cylinder may be serviced as needed.