Effect of Minor Ce Additions on Corrosion Behavior of Experimental Pipeline Steel

Abstract Minor additions of rare earth elements (REEs) have been shown to improve various steel properties. In particular, Cerium (Ce), as a relatively abundant and inexpensive element, has received attention as a potentially beneficial minor alloying addition for a variety of steel applications, including pipeline materials. The objective of this work is to investigate the effect of Ce on corrosion performance of experimental pipeline steel. Electrochemical corrosion experiments were carried out on steel without and with 0.0057, 0.0164, and 0.0263 wt.% of Ce in 3.5 wt.% NaCl saturated with CO2 at 20 °C. For comparison purposes, X100 carbon steel specimens machined from an experimental pipe with a yield strength of 731 MPa were tested under the same conditions. The electrochemical techniques employed included: potentiodynamic polarization (PDP), linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS). In addition, post-corrosion surface characterization was performed using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The corrosion of base metal without Ce was significantly lower (0.15 mm/y) compared to carbon steel X100 (0.9 mm/yr). The electrochemical results showed that adding Ce accelerates corrosion rates compared to base metal without Ce. No pitting corrosion of tested steel was detected.