Thermoplastic element for protection against corrosion in the thermofusion coupling of a thermoplastic tube

A method of joining a thermoplastic tube and a corrosion-protecting element in a thermofused splice of the thermoplastic tube and a thermoplastic connection, comprising:

• providing the thermoplastic tube comprising an inner radial thermoplastic layer, an outer radial thermoplastic layer, and an intermediate radial metal layer disposed between the inner radial thermoplastic layer and the outer radial thermoplastic layer, an end of the thermoplastic tube being expanded to form a socket mouth;
• providing the corrosion-protecting element comprising a thermoplastic sleeve having an axially extending portion and a radially projecting portion joined with the axially extending portion by a radial step, the axially extending portion dimensioned to be housed within the socket mouth;
• providing a female thermofusion nozzle and a male thermofusion nozzle;
• heating the corrosion-protecting element by inserting the axially extending portion of the corrosion-protecting element into the female nozzle and activating the female nozzle;
• heating the thermoplastic tube by inserting the male nozzle into the socket mouth of the thermoplastic tube and activating the male nozzle;
• removing the axially extending portion from the female nozzle and removing the male nozzle from the socket mouth;
• attaching the corrosion protecting element to thermoplastic tube by inserting the axially extending portion into the socket mouth;
• and
• joining a tubular thermoplastic connection element to the thermoplastic tube with the corrosion-protecting element interposed therebetween, wherein joining the tubular thermoplastic connection element to the thermoplastic tube comprises heating the corrosion-protecting element by inserting the radially projecting portion into a second female thermofusion nozzle, activating the second female nozzle, removing the radially projecting portion from the second female nozzle, and attaching the thermoplastic connection element by inserting the radially projecting portion into the tubular connection element and wherein the corrosion-protecting element further comprises an auxiliary ring that spatially extends around the axially extending portion of the protection element by way of a collar and is joined thereto by a thin intermediate wall.