A tank for pressurized gas such as hydrogen, comprises a paste sealant, a sealing envelope, and a base comprising a recess accommodating a neck. A substantially annular external cavity is between a convex surfaces of the neck and a concave surfaces of the recess A substantially annular inner cavity is between a concave surface of the neck and a convex surface of the recess. The paste sealant occupies the annular external and annular inner cavities uniformly and thus ensures the mechanical strength and the gas seal between the sealing envelope and the base. The sealing envelope comprises a body and a neck on the surfaces of which at least two angularly equidistant protrusions extend radially.