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采用扫描电镜(SEM)、红外光谱(IR)、X射线衍射(XRD)及电化学方法研究了碳钢在海水及海水淡化一级反渗透(RO)产水中锈层形态及其电化学特性.结果表明,碳钢在两种水体中形成的锈层在结构、成分及功能上具有显著差异,导致其腐蚀情况截然不同.海水淡化一级RO产水中,腐蚀产物γ-FeOOH的还原电位高于碳钢自腐蚀电位,易被还原成Fe3O4,使锈层形成Fe3O4内层及γ-FeOOH外层的双层结构.外锈层很薄,无阻碍氧扩散作用,且因γ-FeOOH的还原加快了腐蚀反应.Fe3O4内层具有良好导电性及Fe2+传递性,使氧还原反应从金属表面转移至内锈层表面进行;同时因其大阴极作用,显著促进了氧还原过程.由于锈层的上述作用,碳钢在一级RO产水中的腐蚀得到了极大加速,其腐蚀速率最终由溶液至内锈层之间的氧极限扩散电流密度决定.防腐方法应能抑制腐蚀产物γ-FeOOH的还原.
The morphology and electrochemical properties of rust layer of carbon steel in primary reverse osmosis (RO) water production of seawater and seawater desalination were studied by scanning electron microscope (SEM), infrared spectroscopy (IR), X-ray diffraction (XRD) and electrochemical methods. The results show that the rust layer formed by carbon steel in the two kinds of water has significant differences in structure, composition and function, resulting in very different corrosion conditions. The desorption potential of γ-FeOOH in desalination primary RO water is higher than The corrosion potential of carbon steel is easily reduced to Fe3O4 so that the rust layer forms a double-layer structure of the inner layer of Fe3O4 and the outer layer of γ-FeOOH. The outer layer of rust is very thin and does not hinder the oxygen diffusion and accelerates the reduction of γ-FeOOH The corrosion reaction.Fe3O4 inner layer has good conductivity and Fe2 + transmissibility, the oxygen reduction reaction from the metal surface to the surface of the rust layer carried out at the same time due to its large cathode, significantly promote the oxygen reduction process.As the rust layer of the above , The corrosion rate of carbon steel in the first-stage RO production has been greatly accelerated, and its corrosion rate is finally determined by the oxygen diffusion current density between the solution and the inner rust layer. The anticorrosive method should be able to restrain the reduction of the corrosion product γ-FeOOH .