γ_N相在硼酸缓冲溶液中的腐蚀与钝化性能

采用等离子体源渗氮技术在304L奥氏体不锈钢表面制备高氮面心结构的γ_N相层,利用阳极极化曲线和电化学阻抗谱(EIS)研究γ_N相在pH=8.4硼酸缓冲溶液中的腐蚀行为。结果表明:γ_N相的阳极极化曲线呈现出自钝化-过钝化溶解过程,自腐蚀电位Ecorr较原始不锈钢提高了75mV,维钝电流密度Jp降低近一个数量级,耐蚀性能明显提高。与原始不锈钢钝化膜相比,γ_N相钝化膜的EIS容抗弧直径及|Z|值增大,相位角平台变宽,其电荷转移电阻Rct增至1.064×107Ω·cm2,双电层电容Cdl降至65.4μF/cm2,说明γ_N相钝化膜更致密,表现为近电容特性。随着浸泡时间增加,γ_N相钝化膜的Rct稳定在107Ω·cm2量级,具有良好的稳定性。

Corrosion and Passivation Property of the γN Phase in a Boric Acid Buffer Solution

A single high-nitrogen face-centered-cubic phase (γN) layer formed on the plasma source nitrided AISI 316 austenitic stainless steel.The electrochemical corrosion behavior of the γN phase in boric acid buffer solution with a pH 8.4 was studied by anodic polarization and electrochemical impedance spectroscopy (EIS).The results show that the anodic polarization curve of the γN phase presented a typical transition course from spontaneous passivation into passivation-transpassive dissolution process.Compared with the original stainless steel,the E∞orr of the γN phase layer increased 75 mV,the passivation current density deduced one order magnitude.The EIS of the γN phase passive film had a larger diameter of capacitive arc,higher impedance modulus | Z|,and wider phase degree range,compares with the original stainless steel film.Correspondently,the interfacial charge transfer resistanceRct of the γN phase passive film increased to 1.064 × 107 Ω · cm2 and calculated double layer capacitance Cdl decreased to 65.4 μF/cm2.With the immersion time increased,the interfacial charge transfer resistance Rct of the γN phase passive film was stable to a magnitude of 107 Ω · cm2.The high insulation of the γN phase passive film with higher compactness led to an improved corrosion resistance of the original stainless steel.