Corrosion resistance of newly developed inside coated materials in sour environments

A research program was conducted by a joint research group. New coating technologies were applied to oil country tubular goods to improve their corrosion resistance. Six types of coating facilities for 0.5 m long pipes were constructed as candidate process. Chemical vapor deposition (CVD), physical vapor deposition (PVD), plasma transferred arc hard facing (PTH), polymer coating, low pressure plasma spraying (LPPS) and laser remelting of LPPS were selected. By CVD and PVD process, TiN was mainly coated. High Ni alloy was coated by LPPS and PTH process. Tetrafluoroethylene-perfluoroalkylether polymer alloy (PFA) was coated by polymer coating process. Corrosion resistance of coated pipes and connections was evaluated under dynamic condition (flow rate was 40 m/sec) at 200--230 C in simulated sour environments. Only pipes manufactured by PTH process showed corrosion resistance at 230 C. According to the above results, a facility manufacturing 5 m long pipe using PTH process was constructed. Tube size is 89.9 mm OD and 76 mm ID for all process. A high Ni alloy (15% Cr-16% Mo-5% Fe-2%Co-4% W) was coated by PTH process and its thickness was 0.8 - 1.0 mm. Corrosion test was conducted under a dynamic flowing condition. No corrosion attack was observed onmore » the coated surface of long pipe after the corrosion test. The manufacturing procedure of FM process is established and its corrosion resistance is excellent.« less