The Effect And Mechanism Of Corrosion Inhibitor In Circulating Cooling Water On Corrosion Of Iron Bacteria

With the continuous increase of the requirements for the concentration ratio of the circulating cooling water that supplements the reclaimed water in large-scale power plants,it undoubtedly increases the growth of microorganisms and the risk of microorganisms corroding the metal pipe network.Therefore,in this study,through experiments,the growth and composition changes of the common corrosion inhibitor hydroxyethylidene diphosphonic acid?HEDP?/water-soluble imidazoline on the surface of carbon steel steel iron bacteria?IB?biofilm,electrochemical corrosion behavior,iron The research on the adhesion characteristics of bacteria and the effect of compound conversion,put forward the mechanism of the corrosion inhibitor HEDP/water-soluble imidazoline on the corrosion of iron bacteria.Compared with the IB condition,the thickness of the biofilm was reduced by about 56%when the HEDP+IB condition was corroded for 7 days.The distribution of IB bacteria and EPS in the corrosion layer was more dense,and the depth distribution of the biofilm was earlier.The structure of IB-EPS-IB is formed;the content of IB bacteria in the biofilm within15 days of corrosion is 6.00×10⁶³.60×10⁸ cfu/ml,which is 1.5 orders of magnitude higher than the IB working condition,and the EPS content in the biofilm.It also increased by 0.2².6 mg/cm²,indicating that HEDP promotes the growth of IB bacteria and the secretion of EPS.The water-soluble imidazoline+IB working condition was 7 days corroded by carbon steel,the thickness of the biofilm was reduced by about 20%,and the amount of IB bacteria in the biofilm within 15 days of corrosion was 1.00×10⁵⁸.20×10⁵ cfu/ml,and the amount of iron bacteria decreased by 1² orders of magnitude;EPS secretion decreased by 0.8¹.8mg/cm²,and the ratio of polysaccharide to protein content in EPS increased to PS/PN=5.2⁷.3,that is,water-soluble imidazoline has an inhibitory effect on the activity of IB bacteria,while mainly inhibiting Protein secretion in EPS.Compared with the IB condition,after adding the corrosion inhibitor HEDP/imidazoline,the corrosion current density was significantly reduced,the polarization resistance was significantly increased,and the impedance increased,indicating that the corrosion inhibitor HEDP and imidazoline both inhibited the corrosion of the carbon steel surface.;Corrosion current density decreased by 83.6%and 57.3%relative to IB operating conditions when corroded for 15 days,indicating that both corrosion inhibitors have inhibitory effects on microbial corrosion,and HEDP has better corrosion inhibition than water-soluble imidazoline.The results of the AFM adhesion test showed that after dipping the corrosion inhibitors HEDP and imidazoline on the surface of the carbon steel,the percentage of adhesion drop was 51.9%and 43.1%,respectively,indicating that the corrosion inhibitors HEDP and imidazoline were formed on the surface of the carbon steel.The corrosion inhibitor film inhibited the adhesion of IB bacteria.The chemical composition analysis results of surface corrosion products and biofilms by XPS show that:compared with the IB condition,the HEDP+IB condition,the Fe mass fraction decreases;the C mass fraction increases,and the increase value is greater than that of the C contained in the corrosion inhibitor adsorption.The mass fraction indicates that part of HEDP as a nutrient promotes the growth of IB bacteria and inhibits the dissolution of Fe?II?.The percentage of C used for the growth of IB bacteria is 14.2%⁴5.5%;the content of FeOOH increases within 3d¹5d of corrosion 33.6%⁴3.4%,the formation of non-magnetite Fe₃O₄,indicating that the corrosion inhibitor HEDP accelerates its metabolic effect of converting Fe?II?to FeOOH by promoting the metabolism of IB bacteria,while its excellent film-forming ability suppresses anorexia.The growth of aerobic bacteria such as iron reducing bacteria?IRB?is not conducive to the production of Fe₃O₄.Compared with the IB condition,the mass fraction of C in the imidazoline+IB condition decreases,the mass fraction of Fe increases,and the proportion of FeOOH peak decreases by 1.02².09%,and the proportion of Fe₂O₃ peak increases by 2.09⁶.69%,The proportion of Fe₃O₄ peak decreased by 2.75⁴.96%.That is,water-soluble imidazoline inhibits the metabolic effect of IB bacteria converting Fe?II?to FeOOH.