Tank and method of fabrication

A tank vessel of predetermined length having a cylindrical body and a at least one domed tank end member, said tank being capable of resisting outward expansion thereof under the pneumatic forces of a pressurized gas present therein comprising an elongated cylindrical tank body having a support structure member therein for supporting the walls of said tank body, a domed tank end member in contact with the body of said tank end with the support structure member, said tank end forming a cylindrical butt joint with said cylindrical tank body, the rim of the support structure member overlapping and supporting the butt joint between the tank dome and the tank cylinder body, all three members being simultaneously jointed by utilization of a friction stir welding .process in a three-body joint so that the support structure member acts as a rigid backing support for the domed cylinder circumferential butt joint, and subsequently acts as an integral part of the load-carrying pressure vessel of the finished tank, thereby resisting outward expansion of the tank under the pneumatic forces of the pressurized gas in the tank.