Research On The Corrosion Law Of The Bacteria And Disinfector To The Tank Material Of The Secondary Water Supply System

With the advancement of urbanization in our country, more and more tallbuilding stands in the city. It is not realistic for us to supply water only on municipalpipe network, so a growing number of secondary water supply system is established.However, the water quality of the secondary water supply is increasingly serious,user tap water quality is far from standard. Like the municipal pipe network, theproblem of metal corrosion is also happen. Microbial corrosion played an importantrole, and iron bacteria and sulfate reducing bacteria are the main factors that causecorrosion. It is common to see the problems of colour, turbidity, odor and blockagein water supply system caused by corrosion. Researching the microbial corrosion ofthe secondary water supply system is good for us to solve the corrosion problemsand improve water quality.This paper mainly studies the corrosion of stainless steel from three hands whatare the laws of microbial growth, the laws of corrosion and corrosion factors. In thetank of the simulation secondary water supply system, we research the rule of themicrobial growth in different factors, such as different material and different waterdepth. There are three kinds of material what are stainless steel, cast iron, glass fiberreinforced plastic and two water depth what are the top and down. Results showedthat in the same conditions the number of pre unit area coupon is: cast iron＞FRP＞stainless steel. The surface biofilm exists obviously different in spatial distributionwith the depth increase. We can also see that the microbial growth cycle is60d, after20d it starts living long logarithmic phase and40d began to decline. After thesurvival of the fittest, in the second cycle period per unit area of stainless steel reachto about105magnitude.Through the electrochemical test （polarization curve and ac impedance, etc.）and surface analysis techniques （SEM, EDS, etc.）, we research the corrosiondynamic mechanism of304stainless steel. Results showed that the corrosionpotential of304SS decreases faster with the of microbial quantity increase;corrosion rate was positively correlation with the number of microbe, the increasedamount of biofilm accelerated the corrosion rate.In different factors include disinfectants, concentrations and the types ofstainless steel to research the corrosion. We can see that in the early soaked thehigher the concentration of disinfectant form the passivation membrane quickly,when the passivation membrane damaged, the higher one corrode faster. Thecorrosion rate of Cl₂is greater rapidly than ClO₂,201SS is faster than304SS.Nomatter in what kind of disinfectant, the201SS surface passivation membrane form faster than304SS.