METHOD FOR PREVENTING GALVANIC CORROSION OF PIPE AND ITS INSULATING PIPE

摘要

PURPOSE:To prevent the galvanic corrosion and crevice corrosion from being caused when pipes of different kinds are joined in an oil well, etc. CONSTITUTION:A low-corrosion-resistance pipe 1 and a high-corrosion-resistance pipe 2 are screw-joined directly or through a coupling 3. Insulating films 4 and 5 are formed on the inner and outer faces of the pipe 1 over a length L of =40mm from the pipe end. Insulating films 6 and 7 are also formed on the coupling 3 over a length L of =40mm from the pipe end. Insulating films 8 and 9 are formed on the inner and outer faces of the pipe 2 over a length L of =40mm from the pipe end in the same way as the pipe 1. The thickness of the insulating films is controlled to =0.4mum and the resistivity in a 5% NaCl soln. at ordinary temp. to =106OMEGAcm. The similar film is formed, as required, on the screw part for forming a crevice between the joining boundaries A and B of the screw parts on the inner and outer faces.