一级反渗透淡化海水对输水管材的腐蚀性研究

Corrosion of Metal Pipe Used in Reverse Osmosis Desalination

研究了某电厂一级反渗透淡化海水对输送管道的腐蚀,通过冲刷腐蚀试验、电化学测量方法、并结合扫描电镜(SEM)、三维视频显微镜方法评价20钢和球墨铸铁在一级反渗透淡化海水中的腐蚀行为,并对试验过程中水质参数的变化趋势进行监测。结果表明,经过45天的冲刷腐蚀,20钢的平均腐蚀速率大于0.1 mm·a-1,耐蚀性在6级水平,球墨铸铁的腐蚀速率约为0.1 mm·a-1,两者的腐蚀速率均随冲刷时间的延长而有所降低,两种金属表面均呈现宏观上相对均匀的腐蚀形貌,没有明显的点蚀发生。电化学测试结果显示,随着冲刷时间延长,两种金属的自腐蚀电流密度呈降低趋势,电荷转移电阻变化不大。试验过程中,介质的p H值和溶解氧含量呈不规律变化,但由于腐蚀产物溶入等影响因素,介质的盐度和电导率增加。

The corrosion of pipeline delivering the reverse osmosis permeate of seawater in one power plant was investigated. Ero- sion -corrosion test and electrochemical test were made and scanning electron microscopy（SEM） and three -dimensional video microscope were adopted to study the corrosion behavior rules of 20 steel and ductile iron in reverse osmosis permeate of seawa- ter. The change of water quality parameters was also checked and recorded during the tests. The results indicated that after 45 days of erosion-corrosion, the corrosion rate of 20 steel was higher than 0. 1 mm · a-1 （the sixth level of corrosion resistance） while the corrosion rate of ductile iron was about 0. 1 mm · a-1. The corrosion rates of two metals were decreased with the in- crease of erosion time. From a macro perspective, the corrosion morphologies of two metals were relatively uniform without obvi- ous pitting. The results of electrochemical tests showed that with the erosion going on, the corrosion current density of the two metals decreased while the change of charge - transfer resistance was not obvious. The medium values of pH and dissolved oxy- gen contents changed irregularly while the medium values of salinity and conductivity increased with dissolution of corrosion products in the medium.