渗滤液对碳钢腐蚀过程的影响研究

Research of three leachates' corrosion property to carbon steel

渗滤液腐蚀是降低垃圾收运/处置设施运行寿命的重要原因,据此研究了3种渗滤液(焚烧厂、堆肥厂和老龄渗滤液)对常用设备材料——碳钢的腐蚀性能,选用电化学阻抗谱(EIS)、腐蚀速率和渗滤液常规指标,探讨了不同渗滤液的腐蚀性能和腐蚀机理。结果表明,焚烧厂渗滤液腐蚀性能最强,对碳钢的初始腐蚀速率最大,为5.79mm/a,而堆肥厂和老龄渗滤液则分别为4.84、0.09mm/a。随时间的延长,渗滤液的EIS图中,焚烧厂渗滤液等效电路从R(Q(RW))向R(QR)周期性转换,扩散阻抗(W)从1.23×10^(-3) S·s0.5/cm^2先降为极小值,经过120h接触后又上升到369.00×10^(-3) S·s0.5/cm^2,说明其腐蚀过程由初始电化学步骤和扩散步骤共同控制向只受电化学步骤控制周期性变化;堆肥厂渗滤液的等效电路始终为R(Q(RW)),W最大值达到20.04×10^(-3)S·s0.5/cm^2。不同特性渗滤液的腐蚀机理有一定的差别,需采用不同的防腐措施以延长设备使用寿命。

The corrosion property was the main factor influencing the service life of MSW collection and disposal facilities.The corrosion behaviors of carbon steel in three typical leachates,namely the leachate from a incineration plant,a composting plant and an old landfill,had been continuously investigated using the electrochemical impedance spectra of carbon steel.Results showed that leachate from the incineration plant had most serious pollutants.The fastest corrosion rates of the leachates from the incineration plant,the composting plant and the old landfill were 5.79,4.84,0.09 mm/a.Electrochemical impedance spectroscopy（EIS）and the fitted equivalent circuit showed that the fitted equivalent circuit of leachate from the incineration plant changed from R（Q（RW））to R（QR）,as the diffusion impedance W varied from 1.23×10^（-3） S·s0.5/cm^2 to minimum value,then increased to 369.00×10^（-3） S·s0.5/cm^2.The corrosion control process shift from the electrochemical step and diffusion step in the initial stage to the electrochemical step control finally,which performed certain cyclical.The fitted equivalent circuit of leachate from the composting plant belonged to R（Q（RW））under the whole test period,and the largest W values reached 20.04×10^（-3） S·s0.5/cm^2.The reaction principles of different leachates were different that it should be taken relevant actions to prolong service life of the equipment.