再生水水质因素对铸铁管道的腐蚀研究

Influence of Water Quality on Corrosion of Cast Iron Pipe in Reclaimed Water

基于再生水管道(无内衬球墨铸铁管)腐蚀模拟实验装置,选取pH、总硬度、SO42-和Cl-等开展多水质因素腐蚀实验,采用电化学测试方法和挂片失重法,研究了再生水管道的瞬时腐蚀速率、平均腐蚀速率与腐蚀垢层阻抗特性的变化规律。结果表明,电化学测试所得瞬时腐蚀速率、挂片失重法所得平均腐蚀速率与腐蚀垢层阻抗变化规律具有一致性。正交试验结果表明,水质因素对球墨铸铁管腐蚀影响程度排序为:pH>总硬度>SO42->Cl-;偏酸性、低硬度的水体更易造成管道腐蚀,且水体低pH对管道腐蚀最为明显;偏碱性的水体在减少管壁腐蚀的同时,促进管道形成管垢保护管壁;阴离子浓度越高,垢层扩散阻抗值越小,垢层越不稳定。

In view of the complexity of the corrosion for reclaimed water pipe,the corrosion behavior of coupons of reclaimed water pipe(ductile iron pipe without lining)in collected reclaimed waters with varying pH,total hardness,SO42--and Cl--content was characterized by means of weight loss measurement,potentiodynamic polarization measurement and electrochemical impedance spectroscopy.The results indicated that:the instantaneous corrosion rate obtained by electrochemical test and the average corrosion rate obtained by weight loss method of the coupons are consistent with the variation of corrosion scale resistance.The orthogonal experimental results show that the effect degree of water parameters on corrosivity of reclaim waters may be ranked corresponding to the following order:pH>total hardness>SO42->Cl-.The slightly acidic water with low hardness was apt to cause corrosion of the pipeline coupon,and the water of low pH value presented the most obvious effect on the corrosion of the pipeline coupon.The alkalescent water could promote the formation of scales on the pipeline coupons so that to act as a protective scale for the substrate.However,the higher the anion concentration of waters,the smaller the diffusion impedance of the scale,and the more unstable the scale.