充氢时间对S32750超级双相不锈钢在NaCl溶液中腐蚀行为的影响

Effect of Hydrogen Charging Time on the Corrosion Behavior of S32750 Super Duplex Stainless Steel in NaCl Solution

为了考察氢对S32750超级双相不锈钢(SDSS)腐蚀行为的影响,将S32750 SDSS在25℃的1.26mmol/L Na_4P_2O_7+0.5 mol/L H_2SO_4溶液中进行不同时间的电化学充氢。通过开路电位、动电位极化曲线、电化学阻抗曲线和Mott-Schottky曲线表征了充氢后S32750 SDSS在3.5%NaCl溶液中的电化学行为。结果表明:随着充氢时间的延长,S32750 SDSS的自腐蚀电位逐渐负移,自腐蚀电流密度和维钝电流密度区间逐渐增大,击穿电位逐渐降低,Mott-Schottky曲线斜率逐渐减小。这主要是因为材料中增加的氢延缓了钝化膜生成,增加了钝化膜的缺陷浓度,降低了钝化膜的稳定性和完整性,使钝化膜更容易发生破裂和溶解,电极反应速度加快,腐蚀趋势因而增大。

In order to investigate the effect of hydrogen on the corrosion behavior of S32750 super duplex stainless steel(SDSS),the hydrogen was charged for S32750 SDSS through the 1.26 mmol/L Na4P2O7+0.5 mol/L H2SO4 solution for different time at 25℃.The open circuit potential,potentiodynamic polarization curves,electrochemical impedance curves and Mott-Schottky curves were used to characterize the electrochemical behavior of S32750 SDSS after hydrogen charging in 3.5%Na Cl solution.Results showed that the self-corrosion potential of S32750 SDSS gradually shifted negatively with prolonging the hydrogen filling time.The self-corrosion current density and the passivation current density increased gradually,and the breakdown potential gradually decreased as well as the slope of Mott-Schottky curve decreased gradually.This was mainly caused by that the hydrogen increased in the material retarded the formation of the passivation film,which could increase the defect concentration of the passivation film,reduce the stability and integrity of the passivation film,make the passivation film more susceptible to cracking and dissolution,and increase the electrode reaction speed and the corrosion tendency.