The Study Of Influence Caused By Water Quality Factors On Stainless Steel Material In Reclaimed Water And Corrosion Control

This study was set in the context of circulating cooling water system in thermal power plant.It set Stainless Steel 316L(SS316L)as the research material,set the reclaimed water from Beijing gaobeidian sewage plant as the research water,and set Sulfate Reducing Bacteria(SRB)as the research bacteria.Water analysis chemistry,biochemica method,electrochemical method and surface analysis methods were used in this study.This research conducted water quality analysis and assessment of reclaimed water from four representative power plants(A,B,C,D)in the north.This study investigated the effect of Cl-,Ammonia,SO42-on the electrochemical corrosion of SS316L in 3 times concentrated circulating water.It studied the synergistic effect of HEDP,PBTCA,PESA and PASP,and the effect on corrosion inhibition of SS316L.And the effects of fungicide on the properties and corrosion behavior of SRB biofilm on SS316L surface were also studied.From the perspective of the characteristics of biofilm and corrosion under the film,the corrosion resistance of the drug was judged.In terms of the above studies,the results could provide a basis and data support for the choice of anti-scale and corrosion drug for thermal power plants.The study has achieved the following results:(1)Water quality analysis showed that,the reclaimed water has a problem of scaling,such as CaCO3,BaSO4,Ca3(PO4)2.The content of SO42-exceeded standard,there was a corrosion problem by Cl-and SO42-that can not be ignored;the reclaimed water was rich in organic matter.Furthermore,the content of Ammonia nitrogen exceeds standard,which was conducive to the breeding of microorganisms.(2)Electrochemical studies have shown that,the corrosion effect caused by Cl-on SS316L passivation film was significantly increased when the Cl-concentration was more than 380mg/L in the 3 times concentrated recycled water,which showed a significant increase in the anodic dissolution current density,and the maximum was 2.11?A/cm2.The corrosion effect caused by Ammonia nitrogen on SS316L passivation film was significantly increased when the concentration is more than 15mg/L,and the maximum was up to 1.01 ?A/cm2.The erosion of the 3 times concentrated recycled water on SS316L was effectively alleviated when the content of SO42-reached 520mg/L,at the same time,the value of[Cl-]/[SO42-]was 0.54,the maximum drop of dissolution current density of the anode reached 59.0%.But corrosion was still intensified with the soaking time.(3)Study on mixture of scale and corrosion inhibitor showed the performance of four kinds of scale and corrosion inhibitors ranked as follows:PESA>PBTCA>PASP>HEDP,while The crossion inhibiton performance of four kinds of scale and corrosion inhibitors ranked as follows:PBTCA>PASP>HEDP>PESA.PESA and PBTCA had the best synergistic effect of scale inhibition,at the same time,and the corrosion inhibition.When the concentration ratio was 1:3,the scale inhibition rate reached the maximum,97.8%.When the concentration ratio was 1:3,the crossion inhibition rate reached the maximum,81.2%.(4)The study of effects caused by biocides and scale and corrosion inhibitors on SRB biiofilm components showed that,PBTCA and PESA increased the EPS content of SRB on the SS316L surface by 1.4%and 5.8%respectively.The reduction rates of EPS by isothiazolinone,NaCIO and 1227 were 62.5%,70.3%and 80.6%,respectively.NaCIO had the largest reduction ability of protein,the reduction rate was 70.4%,while 1227 had the largest reduction ability of polysaccharide,the reduction rate was 84.0%.Three kinds of biocides can effectively inhibit the SRB and its biofilm adhesion on the surface of stainless steel.(5)Scale inhibitor and fungicide can change the surface morphology of SS316L surface biofilm.X-ray photoelectron spectroscopy results showed that the content of-NH2 on the SS316L surface reached the lowest after the adding of NaClO,which showed that NaClO had a stronger ability to cut proteins from the perspective of chemical group.The FeCl2 was detected,indicating that NaCIO caused corrosion to SS316L passivation film.1227 can significantly change the C:O ratio in SS316L surface film,it affected the structure of polysaccharide-based carbon oxides.(6)The study of effects caused by scale and corrosion inhibitors and fungicides on the corrosion behavior of SS316L in SRB biofilm showed that,PBTCA can reduce the anodic dissolution current density,while PESA had a weak effect on microbial corrosion.Isothiazolinone,NaCIO and 1227 can effectively inhibit the microbial corrosion of SRB.But,NaCIO made the anodic dissolution current density increase sharply,the breakdown potential was significantly reduced,which caused the futher serious corrosion.1227 causes the breakdown potential to reach a maximum of 1.19 V,which is helpful passivation protection.According to EIS analysis,PBTCA and PESA can increase the biofilm thickness.3 kinds of fungicides can reduce the thickness of biofilm,reduced the surface membrane impedance.NaClO makes the SS316L surface film resistance to a minimum,while there was a higher impedance values with 1227.Five kinds of additives had changed the surface roughness of SS316L.This study determined that the optimal compound scale inhibitor was PBTCA:PESA =1:1.The best biocide is 1227,with the best bactericidal and corrosion inhibition performance.