The Effect of Plastic Deformation on the Corrosion Susceptibility of Casing and Tubing Steels in Synthetic Formation Water and Sweet Environment

The aim of this work is to investigate the effect of plastic deformation on the corrosion susceptibility of casing and tubing steels; i.e., K-55 and P-110. The steels were cold-rolled to obtain a reduction in thickness of 10%, 20% and 30%, and tested in synthetic formation water purged with CO2 gas. The corrosion behavior and the evolution of interfacial layers were investigated using linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). Corrosion products morphologies, structures and compositions were evaluated using field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectroscopy (EDS). The results show that when the amount of cold work increased, K-55 steel exhibited an increased corrosion rate, and P-110 steel showed a decreased corrosion rate when compared to the as received values. The mechanisms are characterized based on the impedance response that shows a one-time constant for K-55 steel and two time-constants for P-110 steel which was attributed to different scale developments. The induced plastic deformation enhanced the corrosion rate and altered the evolution of the covering layers with time.