304不锈钢在熔融多硫化钠中的高温腐蚀行为研究

Study on High-temperature Corrosion Behavior of 304 Stainless Steel in Molten Sodium Polysulfide

钠硫电池不锈钢集流体材料在熔融多硫化钠中易发生高温腐蚀,影响电池的性能并引发安全问题。本工作采用电化学阻抗谱技术研究了304不锈钢在350℃熔融多硫化钠熔盐中的高温腐蚀行为,结合微观组织分析,探索其高温腐蚀机理。结果表明,304不锈钢的电化学阻抗谱由高频段的容抗弧和低频段的直线组成,呈典型的扩散反应控制。电荷转移电阻较小,介于0.918~2.014Ω·cm^(2)之间,表明不锈钢的腐蚀速率较快。腐蚀产物层主要由外层的FeS_(2)、FeNiS_(2)和内层的Crr_(2)S_(3)组成。在腐蚀过程中,合金表面的产物膜经历生长、溶解与脱落的过程。

The stainless steel current collector of sodium-sulfur batteries is prone to suffer high-temperature corrosion in molten sodium polysulfide,which affects the performance of the battery.In this work,the high-temperature corrosion behavior of 304 stainless steel molten sodium polysulfide molten salt at 350℃was studied by electrochemical impedance spectroscopy(EIS).Combined with microstructure analysis,the high-temperature corrosion mechanism was investigated.Electrochemical impedance spectroscopy of 304 stainless steel corroded in the molten sodium polysulfide is composed of the capacitive arc in the high frequency zone and the straight line in the low frequency zone,which shows a typical diffusion controlled reaction.The charge transfer resistance is between 0.918Ω·cm^(2) and 2.014Ω·cm^(2),indicating that 304 stainless steel is apt to corrode in the molten sodium polysulfide.The corrosion scale is mainly composed of FeS_(2),FeNiS_(2) outer layer,and inner layer Cr_(2)S_(3).During the corrosion process,the product film on the surface of the alloy undergoes growth,dissolution and shedding.