What kind of metal drums are used to store Hydrochloric Acid?
We might as well consult the experts, namely storage tank manufacturers.  This site describes several types of storage tanks, none of them metal except for rubber-lined steel, in which (we hope) the rubber keeps the acid out of contact with the steel.  Rubber lining of steel is often used in processes such as acid rinsing tanks where the steel is needed for structural purposes, but for a storage tank as such the referenced site renders cross-linked polyethylene better.