Corrosion Behavior of Super 13Cr Tubing Steel in Cl^- Solution and Electrochemical Characteristics of Corrosion Film on Its Surface

Immersion corrosion tests in NaCl solutions with different NaCl mass fractions (5%-35%) were conducted on super 13Cr tubing steel at room temperature. Corrosion morphology, corrosion rate, corrosion products of the steel and electrochemical characteristics of its surface corrosion film were studied. The results show that the tested steel had relatively good corrosion resistance in NaCl solution. The corrosion resistance decreased with increasing mass fraction of NaCl and the decline was obvious when the NaCl mass fraction increased over 25%. With increasing NaCl mass fraction, the corrosion form changed from local corrosion to general corrosion. The corrosion products were composed of Fe₃O₄,and the corrosion film was loose and not dense. The polarization curves of the corrosion film had a passivation zone, indicating that the film had passivation characteristics. The electrode process in the low-frequency zone was diffusion control, and that in the high-frequency zone was charge transfer control. The impedance of the corrosion film was determined by a time constant.