Corrosion behavior of API 5L X-60 pipeline steel exposed to near-neutral pH soil simulating solution

Steel gas pipelines are exposed externally to damage by surface corrosion and cracking phenomena. They are the main deterioration mechanism under coating failure and cathodic protection (CP) that can reduce the structural integrity of buried gas transmission pipelines where the soil aggressiveness and bacterial activity appear. Corrosion phenomenon is accentuated by the soil parameters influence such resistivity, pH, temperature, moisture content and chemical composition of electrolytes contained in the soil. Soil parameters influence on pipeline steel corrosion behaviour exposed in near-neutral pH soil simulating solution has been investigated by potentiodynamic polarisation and EIS method. Results showed that the steel corrosion increases, corrosion current density increases with temperature in the range from 20 to 60 degrees C. The associated activation energy has been determined. Impedance curves showed that the charge transfer resistance (R-t) increases with increasing immersion duration. Parameters such as corrosion current density (I-corr), polarization resistance (R-p), and soil resistivity (p) can serve as the parameters for evaluation of soil corrosivity.