Objective To explore the relationship between bacterial activity and corrosion behavior of hull steel and research influences of concentration of extracellular polymeric substances (EPS) on corrosion. Methods Fourier transform infrared spectroscopy (FT–IR) and ICP-OES such as inductive coupling were used to analyze composition of EPS and content of iron ion. The morphology of corrosion products was analyzed by atomic force microscope (AFM). Results The fitting analysis of electrochemical impendence showed that EPS inhibited corrosion by hindering scattering of dissolved oxygen, the greater the concentration, the better the effect. That is to say, the corrosion speed of specimen in the initial state was inversely proportional to the EPS concentration. Therefore, although its complexation effect could promote anodic dissolution of the specimen, its effect was limited. It was the mainly the EPS which inhibited scattering of dis-solved oxygen. For EPS solution of high concentration, excessive EPS could promote more bonding between functional group of EPS and Fe2+/Fe3+on material surface, as a result, the EPS protective film might become loose and be unable to separate the dissolved oxygen and thus accelerate corrosion of specimen. Conclusion Effects of EPS on corrosion of hull steel is relevant to structure and concentration of EPS. EPS changes from inhibiting corrosion to accelerating corrosion with the increase of concentration.%目的 研究微生物活性与船用钢DH32腐蚀行为之间的关系,并通过胞外分泌物的提取,研究分泌物浓度对材料腐蚀性能的影响.方法 通过傅里叶红外光谱(FT–IR)分析胞外分泌物的组成,通过电感耦合等离子体发射光谱仪(ICP-OES)分析金属离子的含量,并使用用原子力显微镜(AFM)观测去除腐蚀产物后的表面形貌.结果 通过电化学阻抗谱的拟合分析,短期内,EPS 通过阻碍溶解氧的扩散抑制腐蚀速度,EPS浓度越高,效果越好,即实验初期试样腐蚀的速度与EPS浓度成反比.随着时间的延长,EPS浓度低的溶液中,其 EPS 络合金属离子的能力很快达到饱和,所以尽管其络合行为能促进试样的阳极溶解,但影响作用有限,此时起到主要影响的还是 EPS 抑制溶解氧扩散.对于浓度高的 EPS 溶液,其过量的 EPS 会促进EPS的官能团与材料表面更多的Fe2+/Fe3+离子键合,使得沉积的EPS保护层变得疏松失去隔离溶解氧的作用,进而加速试样腐蚀.结论 海洋微生物胞外分泌物对船用钢腐蚀行为的影响与胞外分泌物的结构与浓度有关,随着浓度升高,EPS从抑制腐蚀变为加速腐蚀.
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