Abstract

For pipelines running across cold regions; soil temperature at the depth of buried pipeline would be sub-zero. However, whether the -0.85VCSE protection potential criteria or a more positive one was applicable for this situation was still an issue. In this paper, the electrochemical behavior of X80 steel in sub-zero NS4 solutions (a usually used soil simulation solution with 0.483g/L NaHCO3, 0.122g/L KCl, 0.181 g/L CaCl2·2H2O, 0.131g/L MgSO4·2H2O) at different temperature (with ethylene glycol added to avoid freezing) was studied by EIS and polarization curve using a Pt wire as reference electrode. The results showed that with the temperature decreasing, the polarization resistance increased and the corrosion current decreased, which was the same as the common experience. A polarization potential less negative than -0.85VCSE in the sub-zero experimental environment would be adequate to reduce the general corrosion rate to less than 0.025mm/yr as required in NACE standard and 0.01mm/yr as required in ISO standard.

Keywords:
pipeline corrosion, well integrity, materials and corrosion, reference electrode, subsurface corrosion, platinum wire, publication division, electrochemical impedance spectroscopy, different temperature, pt wire
Subjects:
Pipelines, Flowlines and Risers, Materials and corrosion, Well Integrity, Subsurface corrosion (tubing, casing, completion equipment, conductor)
This content is only available via PDF.
2015. NACE International
You can access this article if you purchase or spend a download.