Aerated corrosion behavior of API-X100 pipelies steel at high temperature - Electrochemical ivestigation

The aim of this experimental work is to provide an insight to the main electrochemical perspectives related to carbon dioxide corrosion behavior of API-X100 pipeline steel at high temperatures. The corrosion performance is investigated in laboratory conditions simulating the extensive dissolution of carbon dioxide in water cuts at the early stages of transmission where considerable amounts of oxygen is entrapped. Open Circuit Potentials (OCP), potentiodynamic polarization, as well as Electrochemical Impedance Spectroscopy are all utilized in the electrochemical analysis. The tests are performed in 0.05, 0.1, 0.5, and 1 mol/L bicarbonate solutions containing 3 wt% NaCl at 40, 60, and 80^oC in conditions facilitating good oxygen diffusivity. OCP values were mainly influenced by the cathodic reduction of oxygen and water and got nobler with increased bicarbonate content. Additionally, corrosion rates increased generally with temperature showing sole anodic peaks before the extensive dissolution. The equivalent circuits proposed for the electrochemical systems encountered achieved very good agreement with the experimental results as well as with the polarization characteristics.