Effects of DC Stray Current on the Polarization Characteristics of X70 Steel

To investigate polarization characteristics of X70 steel at direct current densities in the 50 similar to 1200 A/m(2) range under anodic and cathodic interferences, electrochemical method was used to test Tafel polarization curves. The critical current density was 180 A/m(2) and equal or above this value the Tafel polarization curves were linear. By fitting these curves, we obtained polarization resistance R-p, which can be used to characterize the polarization characteristics of X70 steel at DC current. R-p decreased with an increase in the DC current density under both cathodic and anodic interferences. Relational between R-p and DC current density was calculated. As the anodic interference current density increased, corrosion potential of X70 steel shifted positively. Opposite behavior is observed in the case of cathodic interference.