市政再生水对铸铁材料的腐蚀特性研究

Corrosion of Cast Iron in Reclaimed Municipal Wastewater

以我国北方某市政再生水厂的出水为研究对象,采用失重法和电化学测试法研究了该再生水对铸铁材料的腐蚀特性,同时考察了初始pH值和含盐量对腐蚀的影响效应。失重法和电化学测试结果均表明,该再生水对铸铁材料的腐蚀速率随时间的延长而逐渐降低,并最终趋于稳定。用失重法比较再生水和自来水对铸铁的腐蚀情况,发现在初期再生水的腐蚀速率大于自来水,但随着时间的延长,二者腐蚀速率的差异逐渐缩小。电化学测试结果表明,铸铁在再生水中能形成抑制腐蚀的保护层。当pH值为6.5～8.2时,铸铁在再生水中的腐蚀速率随pH值的升高而降低。经纯水稀释后的再生水对铸铁的腐蚀速率有增加的趋势,表明仅以含盐量和Larson指数等来评价再生水的腐蚀性是不可靠的。

The corrosivity of the effluent from a reclaimed municipal wastewater plant in Northern China on cast iron was studied by using weight loss method and electrochemical test method. The effects of initial pH and salt content on the corrosion rate were investigated. Both weight loss method and electro- chemical test method show that the corrosion rate of cast iron in reclaimed wastewater is decreased with time and finally reaches relative stabilization. Comparison of this reclaimed wastewater with tap water by weight loss method indicates that the corrosion rate in the reclaimed water is higher than that in tap water, but their difference is reduced with time. The electrochemical test indicates that a corrosion protective layer can be developed on cast iron surface in the reclaimed wastewater. The corrosion rate of cast iron in reclaimed wastewater is decreased with the increase of pH within the range of 6.5 to 8.2. However, dilution of reclaimed wastewater can increase the corrosion rate of cast iron, which indicates that using salt content and Larson Index to evaluate the corrosivity of reclaimed wastewater is not reliable.