The bottom of API Std 650 carbon steel storage tanks

Protection of Plates during Shipping and Storage
Plates shall be adequately protected during shipping and storage to avoid damage to API Std 650 carbon steel storage tanks material plate surfaces and edges from handling (scratches, gouge marks, etc.) and from environmental conditions (corrosion, pitting, etc.).
Plates shall be protected from moisture or stored in inclined position to prevent water from collecting and standing on surface.

Oil, Gas, Chemical, Water, and Bio-Fuel storage. Maximum of the most common welded steel tanks used in industry are designed following API 650. Tanks typically found in Refinery API Std 650 carbon steel storage tanks tank farms, Terminals, Pipelines, and other process facilities use these tanks.

Natural ventilation loss: the main cause of natural ventilation loss is that the API Std 650 carbon steel storage tanks is not tightly sealed. This is usually due to corrosion perforation on the top of the oil tank, or there is a height difference between the two orifices. The air tightness of the mixture in the API Std 650 carbon steel storage tanks is higher than that of the air, which causes the mixture gas in the tank to be discharged into the atmosphere from the lower hole, and the external air flows into the tank from the high hole, resulting in natural ventilation loss.