Abstract
Bacillus widely exists in wet natural environment such as soil, water and air, and is often studied as one of representative microorganisms for microbiologically influenced corrosion(MIC) research. In this paper, the growth curve of Bacillus subtilis isolated from marine environment was determined by turbidimetry and its effect on corrosion behavior of 10MnNiCrCu steel was studied by open circuit potential, AC impedance, polarization curve and scanning electron microscopy(SEM). The results showed that with the change of the growth curve of Bacillus subtilis(BS), the open circuit potential(Eocp) shifted positively and then negatively, and the charge transfer resistance shown by AC impedance was much lower than that of the sterile system, increasing first and then decreasing. The polarization curves showed that the corrosion current density in BS medium was obviously higher than that in sterile system. The corrosion morphology observation showed that although a biofilm by BS developed on the steel surface, the localized corrosion of 10MnNiCrCu steel was aggravated due to the acidness of the metabolite itself and the biofilm with access for electrolyte ions.
Highlights
Bacillus widely exists in wet natural environment such as soil, water and air, and is often studied as one of representative microorganisms for microbiologically influenced corrosion(MIC) research
Enzymes, coenzymes and other metabolic intermediates were produced[15,16], the bacteria were in a lag phase
Sufficient material base was provided for the growth of microorganisms in this period, the external environment was in the best state, and the bacteria grew fast
Summary
Bacillus widely exists in wet natural environment such as soil, water and air, and is often studied as one of representative microorganisms for microbiologically influenced corrosion(MIC) research. The growth curve of Bacillus subtilis isolated from marine environment was determined by turbidimetry and its effect on corrosion behavior of 10MnNiCrCu steel was studied by open circuit potential, AC impedance, polarization curve and scanning electron microscopy(SEM). Research showed that EPS produced by Bacillus was the main component of the biofilm formed on the metal surface and provided the biologically active compound which affected the corrosion process[9]. It was confirmed that the reason for the increase of corrosion of cold rolled steel in the presence of B. subtilis C2 was the organic acid produced in the metabolic activity of BS in earlier stage, which accelerated the corrosion. By comparing the effect of biofilm on metal corrosion on metal surface, we can understand the important role of biofilm in metal corrosion process more clearly
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