The technology concerns 3-layer coating pipes with diameters ranging from 1/2" to 80" in compliance with DIN 30670 and UNI 9099 requirements. Steel pipes can be coated either by using an annular coextrusion die-head for applying the adehsive and the polyethylene (for small diameters pipes 1/2" to 24") or by applying separately the adhesive and the polyethylene by two different extrusion heads (for big diameters pipes 18" to 80" ).