再生水生物膜作用下Q235B钢的电化学腐蚀特性研究

Electrochemical Corrosion Behavior of Q235B Carbon Steel Induced by Iron-oxidizing Bacteria and Sulfate Reducing Bacteria Biofilm Inreclaimed Water

采用微生物计数法(MPN)、扫描电镜(SEM)、电化学测试技术探究了再生水环境中铁细菌和硫酸盐还原菌生物膜对Q235B钢的电化学腐蚀机理。结果表明,铁细菌(IOB)和硫酸盐还原菌(SRB)生物膜在整个实验过程中抑制了Q235B钢腐蚀过程的发生,然而具体的腐蚀机理随着细菌生长周期的变化而不同;与无菌体系相比,前20 d,Q235B钢电极表面的铁细菌和硫酸盐还原菌及其新陈代谢产物与腐蚀产物络合在一起的混合膜层的物理阻隔作用要比单纯Fe的腐蚀产物要大,使得其在有菌体系中腐蚀电位正移,腐蚀电流密度降低,阻抗值较大,腐蚀过程被抑制;20 d后,由于新陈代谢产物的粘性较大导致无局部腐蚀产物脱落现象,且处于衰亡期的SRB的阴极去极化作用减弱,进而使得阴极Tafel斜率βc较大,电荷转移电阻仍高于无菌体系的值,腐蚀过程继续被抑制。

Corrosion behavior of Q235B carbon steel in the presence of iron-oxidizing bacteria （lOB） and sulfate reducing bacteria （SRB） biofilm in reclaimed water was studied by means of most probable number （MPN） method, scanning electron microscopy （SEM） and electrochemical testing technology. Re- sults showed that： the simultaneous existence of iron-oxidizing bacteria and sulfate reducing bacteria bio- film could inhibit the corrosion process throughout the experiment course, while the corrosion mecha- nisms varied with the bacteria growth cycle. In contrast to the corrosion products of the steel formed in sterile water, the mixed film composed of iron-oxidizing bacteria and sulfate reducing bacteria, their me- tabolites and the corrosion products on the steel formed in the reclaimed water exhibits greater blocking effect, which induced the positive shift of open circuit potential, increase in corrosion current density, high- er impedance value and suppress of corrosion process in the initial 20 d of immersion. After 20 d, the cor- rosion products suffered from spallation due to the large viscosity of the metabolites and the cathodic de-polarization effect of SRB was weakened due to the decay of them, which all make the cathode Tafel slope /3, larger and the charge transfer resistance higher than their counter parts in the sterile water, therefore, the corrosion process continues to be inhibited.