对相钢在流动中性含砂氯化物中的磨损腐蚀

研究了双相钢在流动含砂的3．5％NaCl溶液中的磨损腐蚀规律，测定、分析了流动体系中的电化学阻抗谱，揭示了双相钢磨损腐蚀过程中电化学的作用及其机制。结果表明，腐蚀曜 磨损腐蚀过程中起主要作用，流体力学因素只是加速了腐蚀电化学过程，阻抗谱在低频区出现一直线段和低频收缩现象。分别是双相钢在磨损腐蚀过程中电极处于自钝化状态，并受离子在钝化膜中的扩散、迁移过程控制和电极表面局部遭受破坏的特征，对于流动体系中电化学阻抗谱的分析，曹氏阻抗理论同样适用。

ESOSION CORROSION OF DUPLEX STAINLESS STEEL IN FLOWING NEUTRAL CHLORIDE CONTAINING SAND

The erosion corrosion behavior of duplex stainless steel in flowing 3.5% NaCl solution containing sand was studied. The electrochemical impedance spectroscopy (EIS) of electrode in flowing media has been measured and analyzed to clearly understand the electrochemical mechanism in erosion corrosion of duplex stainless steel. The results show that there is a critical flow velocity above which the erosion corrosion rate increases markedly. Electrochemical factors play a dominant role in the erosion corrosion of duplex stainless steel, while the hydrodynamic factor only accelerates the electrochemical process. The EIS of duplex stainless steel takes the shape of capacitive loop in high frequency region and a straight line in low frequency region when the flow velocity is below the critical value. Once now velocity is above the critical Value, the EIS of duplex stainless steel appears as a single capacitive loop with contraction of Nyquist plot in low frequency region, the diameter of which is much small. Thus, the erosion corrosion of duplex stainless steel is wholly controlled by anodic passivation and that the diffusion of ions in passivation film is a speed-controlled step when the flow velocity is below the critical value. Serious localized corrosion occurs on the surface of duplex stainless steel when the flow velocity is above the critical value. Cao's EIS theory can be equally and accurately used to analyze the EIS of electrode in flowing media.