Effect of Hydrogen on Corrosion Behavior of S32750 Super Duplex Stainless Steel

Electrochemical behaviors and critical pitting temperature (CPT) of S32750 super duplex stainless steel (SDSS) in 3.5% NaCl solution with various hydrogen charging current densities (HCCD) were investigated by using open-circuit potential (OCP) curves, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), Mott-Schottky curves, and the potentiostatic polarization curves electrochemical measurements methods. Results showed that the open-circuit potential and self-corrosion potential gradually shift negatively, the passivity current density increases, pitting corrosion potential and self-corrosion potential decreases with the increase of the hydrogen charging current density from 10 mA·cm -2 to 100 mA·cm -2 . Slope of the Mott-Schottky curves and the CPT gradually decreases as HCCD increased. As compared with the blank specimen, it is indicated that hydrogen leads to the delay of the passivation film formation and the reduction of the stability and integrity of the passivation film. The passivation film is more prone to cracking and dissolution, therefore, the corrosion of S32750 SDSS is more likely to occur after the hydrogen is charged.