POLYOLEFIN-COATED STEEL PIPE HAVING HIGH RESISTANCE TO THERMAL OXIDATIVE DEGRADATION AND HIGH WEATHERABILITY AND A PROCESS FOR MANUFACTURING THE SAME

摘要

In a polyolefin-coated steel pipe having an epoxy primer layer, a maleic anhydride-modified polyolefin layer and a polyolefin layer formed one upon another on the external surface of a steel pipe, the maleic anhydride-modified polyolefin layer contains at least three kinds of specific antioxidants, and the polyolefin layer contains those antioxidants, a specific light stabilizer and a specific inorganic pigment. A process for manufacturing it is also disclosed. The polyolefin-coated steel pipe has both a high level of resistance to deterioration by thermal oxidation and a high level of weatherability. Both of the maleic anhydride-modified polyolefin layer and the polyolefin layer are preferably of an ethylene-propylene block copolymer.