Experimental Research On Corrosion Of Three Types Of Stainless Steel Water Supply Pipes

More than 90% of our country's water supply systems use metal pipes,but metal pipes are prone to corrosion in the water environment for a long time,and the corrosion products produced when entering the water body will cause secondary pollution of drinking water and cause a series of water quality safety issues;The subject is 304,304 L and 316 L stainless steels that can be used as water supply pipes and have the highest market utilization rate stipulated in "Thin-walled Stainless Steel Pipe Technology"(GB/T 29038—2012).By simulating the actual water supply pipe network,the influence of the corrosion law of stainless steel pipes on the quality of water supply is studied by means of water quality analysis,electrochemistry,surface analysis,etc.,and the static immersion test method is used to explore The influence of iron bacteria and residual chlorine concentration on the corrosion of stainless steel.The main research results are as follows:(1)Dynamic Corrosion Simulation Test of Stainless Steel Pipe: Through the cyclic biofilm reactor(Biofilm Annular Reactor,BAR)and magnetic stirrer device simulation dynamic test,the experiment has been running for 120 days,and the water quality indicators such as pH,TDS,turbidity,metal ion concentration,total organic carbon,etc.are basically far lower than "Sanitary Standards for Drinking Water GB 5749-2006" limits;the electrochemical polarization curve and AC impedance test show that the rapid corrosion of the three stainless steels occurred in the first 30 days and enters the stable corrosion period after 60 days;the corrosion resistance of the three materials From high to low,they are 316 L,304L,and 304;the scanning electron micrograpH shows that the surface of stainless steel is still relatively smooth,with only slight local corrosion;X-ray energy spectrum analysis shows that the surface of stainless steel is covered by biological structure,and the surface of the stainless steel is covered by heterotropHic bacteria.Counting method,the density of bacteria attached to the surface is 304,304 L,316L from high to low;(2)The influence of iron bacteria on the corrosion of stainless steel: Set up a control experiment with bacteria addition and aseptic group.It can be seen from the scanning electron microscope that a large number of iron bacteria are attached to the surface of the coupon of the bacteria-added group;the corrosion rate of the bacteria-added group gradually increases with the increase of the immersion time,and the corrosion rate of the aseptic group increases in the first 10 days.Afterwards,it gradually stabilizes;the presence of iron bacteria promotes the negative shift of the corrosion potential,increases the corrosion current,reduces the AC impedance polarization resistance,and accelerates the corrosion of stainless steel;316L is the least affected by the corrosion of iron bacteria,304 L is in the middle,and 304 is the largest.(3)The influence of residual chlorine concentration on the corrosion of stainless steel:Add sodium hypochlorite solution to the tap water after sterilization to control the residual chlorine concentration of 0.2 mg/L,0.5 mg/L,1.0 mg/L,2.0 mg/L,4.0 mg/L.Due to the attenuation effect of residual chlorine,Maintain the residual chlorine concentration and replace the soaking water every 24 hours.The corrosion changes of the three stainless steels in the residual chlorine solution of various concentrations are similar.The corrosion generally shows a trend of speeding up first and finally stabilizing.The corrosion rate of the three stainless steels becomes faster as the concentration of residual chlorine increases.Observed under a metallurgical microscope at 400 times magnification,there are pits on the surface of each group of stainless steel coupons,and pitting corrosion occurs;with the increase of the residual chlorine concentration,the number and depth of the pits also increase.Aggravating.