Connection device for a fuel tank

A connection device for a fuel tank, wherein the connection device comprises a weld-on nipple (1) and a line (2) in fluid communication with the weld-on nipple (1), wherein the weld-on nipple (1) and the line (2) are made of plastic, wherein the weld-on nipple (1) has an inner barrier layer (3) for hydrocarbons embedded in the plastic, wherein the barrier layer (3) extends along the weld-on nipple (1), and a method for manufacturing such a connection device.