The Study On Diversity Of Bacterial Community In Inner Rust Layer Of Carbon Steel Immersed In Zhonggang Marine Water Of Qingdao And Electrically Active Of Several Bacterial

In this paper, bacteria were, firstly isolated from Q235steel inner rust layer, andthe diversity of these bacteria were studied by further phylogenetic analysis of16SrDNA. Then the effects of two strains of representative strains on the20＃carbonsteel was investigated using electrochemical techniques (the open circuit potential,electrochemical impedance spectroscopy (EIS) and the surface analysises(scanningelectron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS)).52bacteria were isolated from Q235steel inner rust layer, of which48were from2216E medium, one was from the iron-oxidizing bacteria culture medium, three werefrom the manganese-oxidizing bacteria culture medium, and the bacteria from thelatter two kinds of mediums may be potentially corrosive bacteria. The result ofphylogenetic analysis of16S rDNA indicated that there was a high diversity ofbacteria within the Q235steel inner rust layer. These52bacteria couLd be dividedinto3phylotypes: proteobateria, Firmicutes and Bacteroidetes, in whichγ-Proteobacteria was absolutely dominant bacteria, accounted for63.5%of the totalnumber of bacteria, followed by α-proteobacteria, accounting for23.1%.The results of one iron-oxidizing bacteria and one manganese-oxidizing bacteriaby the electrochemical tests and the surface analysises indicated that:1) Between1-24h, the two systems, either with or without IOB, are allaccelerated corrosion of the20＃carbon steel electrodes, and corrosion acceleratingeffect is more obvious in the system with IOB, which indicated that the20＃carbonsteel electrodes suffered double corrosion acceleration by IOB and its medium. Butwith the increase of immersion time, the accelerated corrosion effect on20＃carbon steel weakened from iron oxide bacteria because the electrochemically active of IOBreduced. And the oxide film and the biofilm inhibited the transmission of oxygen tothe electrode surface, which thereby inhibited the corrosion of the electrodes, whileaccelerate corrosion was continued in the IOB-free system.2) In the MOB1-free system, the20＃carbon steel suffered weak corrosionacceleration at first, corrosion inhibition after4h, and then corrosion inhibitionweakened until2days later, while in the MOB1system, the20＃carbon steel sufferedweak corrosion acceleration at first, corrosion acceleration after4h, and then returnedto be suffering corrosion inhibition again2days,later. Compared to the two kinds ofsystems combined with the growth curve of MOB1, it,s found that between4-24hours, the20＃carbon steel suffered accelerated corrosion effect, while, in otherperiods, corrosion inhibition effect, due to the small number and low activity ofbacteria and the existence of the biofilms.