| In recent years, with the technology of magnetic treatment has been widely used in the fields of such as sterilization and bacteriostasis gradually, especially its role of killing the microorganism in the bio-film, it has attracted widespread attention in the food and medical industries. In the areas of oil and gas, the problems of metal corrosion caused by sulfate-reducing bacteria (SRB) is one of the mainly difficulties that need to be solved urgently. So this kind of technology has many advantages in order to decrease the problems of the environment pollution and high cost brought by much dosage of chemicals. Moreover, according to the fact that the electrochemical reaction during metals being corroded can be effected by a electromagnetic field, the mechanism of the microbiologically-influenced corrosion behavior of Q235steel and304stainless steel (304SS) under the action of a magnetic field (MF) has been studied in this paper, which can provide theoretical basis for the applying of magnetic treatment in the fields of anticorrosion.The means of surface analysis techniques and electrochemical techniques were used to investigate the corrosion behavior of both Q235steel and304SS in the absence and presence of a magnetic field, and the results obtained were as follows:the activities of SRB and the growth rate both decreased after being exposed to the magnetic field of which the strength was only less than lOmT. Moreover, the bacteria could mutate and the mutated SRB with no flagellum existed in the form of bacillus. The results also showed that the magnetic field could reduce the colony forming units just by inhibiting the growth not killing them.As for the Q235steel, a kind of metal inclining to be magnetized, it has been found out that both the structure and compositions of the corrosion products on the surface existed obviously differences between those with and without a MF after being immersed in the SRB-containing medium for14days. Compared to the products of the control group with mainly iron sulfides, the experimental one were chiefly iron oxides which could effectively inhibit the MIC by forming a compact bio-film with high adhesion to the surface of electrode.However, as one kind of material that couldn’t be magnetized easily, the304SS could keep its surface still bright markedly distinct from the Q235steel of which the surface had been totally covered by black products through macroscopic observation, which proved that SRB had less absorption above the304SS than above the Q235steel. The results also showed that304SS inclined to pitting corrosion in the environment of mass propagation of SRB, mainly because the sulfur ion produced by metabolism could combine with iron to form iron sulfides which could promote corrosion process. For the experimental group, as the growth of SRB was restrained because of the presence of MF, the transformation of oxidation on the surface of304SS into iron sulfides became slower and the products magnetized made the bio-film compact pretending the harmful ions from destroying the passive film, the corrosion of304SS was reduced obviously.The corrosion weight-loss of this two kinds of metals indicated that the corrosion rate decreased with the exposure of a magnetic field, the electrochemical impedance spectroscopy and polarization results revealed that the forming of the bio-film on the Q235steel surface lagged and the corrosion mainly occurred during the early immersion period. Moreover, the anode and cathode process were both influenced to some extent and the corrosion was not controlled until there was a uniform and compact bio-film formed. Yet the corrosion of304SS was reduced chiefly through the cathode reaction being inhibited. |
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