Study On Microbial Electroactivity And Its Corrosion Influencing Mechanism

The redox reaction between microorganisms and metals is essentially an electron transfer between metals and microorganisms caused by the metabolic activity of microorganisms.Whether the microorganisms are electrically active or not will have a major impact on the corrosion process.Therefore,it is of great significance to study the electrical activity of microorganisms and their effects on corrosion and to understand the microbial corrosion of metals in depth and explore the anti-corrosion strategy.In this paper,based on the study of the electroactivity of Escherichia coli and Pseudomonas fluorescens,the electrochemical mechanism,surface analysis technique and microbiological method were used to study the mechanism of microbial electroactivity on carbon steel corrosion in reclaimed water.The main conclusions are as follows:（1）The microbial electroactivity of Escherichia coli and Pseudomonas fluorescens was studied by cyclic voltammetry.The results showed that Escherichia coli did not show electrical activity in culture medium and PBS buffer.was false.The reduction peak appeared in Pseudomonas fluorescens,probably due to the yellow pigment they secrete.Escherichia coli and Pseudomonas fluorescens showed no significant changes in their electrical activity under anaerobic conditions.Escherichia coli and Pseudomonas fluorescens can use AQS as an electron shuttle for extracellular electron transport,with good reversibility at 10 ppm concentration.At the same concentration of AQS,the greater the concentration of microorganisms,the more positive the potential and the faster the electron transfer rate.（2）Using AQS as an electron shuttle,the corrosion mechanism of Escherichia coli electroactivity on carbon steel was studied.The results showed that AQS further inhibited the corrosion of carbon steel by E.coli and the average corrosion rate was reduced by 17.24%.The electrons produced by the metabolism of E.coli promoted the conversion of Fe OOH to Fe3O4 under the action of AQS and accelerated the delamination of the corrosion layer.The dense inner corrosion layer of Fe3O4 and bacteria blocked the DO diffusion,and Fe²⁺ played a role of replacing anode in the corrosion of the inner layer.（3）Using AQS as an electron shuttle,the mechanism of the influence of Pseudomonas fluorescens electroactivity on the corrosion of carbon steel was studied.The results showed that AQS furtherly promoted the corrosion of carbon steel by Pseudomonas fluorescens and the average corrosion rate increased by 23%.AQS had strong biological toxicity to Pseudomonas fluorescens.At the same time,the iron carrier secreted by Pseudomonas fluorescens could chelate with iron ions,reducing the amount of Fe²⁺,decreasing the content of Fe3O4,and making the content of Fe3O4 and bacteria.The composition of the corroded inner layer was not dense enough and weakened the anode substitution effect of Fe²⁺.