ABSTRACT

The traditional cathodic protection (CP) criteria of "-850mV CSE" is no longer effective when pipelines are exposed to alternating current (AC) interference. Unfortunately, the CP criteria for buried pipelines in the presence of AC interference have not reached a consensus so far. In this work, weight loss tests on mild steel in the simulating soil solution of 4 g/L Na2SO4 were conducted to explore the reasonable CP potential for mild steel under AC interference. The experimental results show that the corrosion rates of mild steel under different CP potentials were affected significantly by AC current and the effects depended on the applied CP current density. In addition, AC induced corrosion can be controlled by increasing CP level when AC current density was below 300A·m-2. However, the corrosion of mild steel would be accelerated when the CP potentials were too negative. Finally, a reasonable CP potential range for mild steel in the presence of AC interference was proposed basing on the experimental results.

Keywords:
Subsurface Corrosion, mild steel specimen, ac current density, materials and corrosion, Upstream Oil & Gas, Publication Division, Pipeline Corrosion, well integrity, corrosion rate, current density
Subjects:
Pipelines, Flowlines and Risers, Materials and corrosion, Well Integrity, Subsurface corrosion (tubing, casing, completion equipment, conductor)
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2014. NACE International
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