Protective polymer layer

Abstract

The present invention relates to a method of joining polymer coated steel pipes comprising the steps of—providing polymer coated pipe segments with an uncoated length on both ends of the segments; —welding the polymer coated pipe segments together; —applying a curable polymer (A) onto the uncoated length of the welded pipe segments to form an first coating layer; and—applying a polymer composition (B) onto the first coating layer to form a topcoat layer with a thickness of 0.5 to 10 mm, wherein the polymer composition (B) has a melt flow rate MFRof 1.0 to 6.0 g/10 min, determined according to ISO 1133 at a temperature of 190° C. under a load of 2.16 kg, and includes a base resin comprising (B-1) a non-elastomeric polyethylene in an amount of 60 to 85 wt % of the total polymer composition being produced in a process using a single-site catalyst, and (B-2) an elastomer comprising a copolymer of ethylene and at least one polar comonomer, wherein component (B-1) or components (B-1) and (B-2) have been grafted with an acid grafting agent and the use of polymer composition (B) as topcoat layer with a thickness of 0.5 to 10 mm in a coating of coated steel pipe field-joints, a method of coating a steel pipe and the use of polymer composition (B) for the coating of steel pipe joints or steel pipes.