Research On Effect Of Electrolytic Treatment On Corrosion Behavior Of Industrial Circulating Water

The stability of industrial circulating cooling water system is an important prerequisite for the normal operation of industrial production.As the microbial breeding problem has a relatively large impact on water quality and it is difficult to control from the root,which is regarded as the biggest challenge in industrial circulating water treatment.As for electrochemical water treatment technology,researchers generally concentrate on how to improve the descaling efficiency under unit energy consumption but few studies are conducted on the collateral anticorrosion and sterilization effect of electrolysis.In view of the oxygen absorption corrosion and microbial corrosion problem in the industrial circulating cooling water,the effects of electrolytic descaling process on the corrosion and microorganisms of industrial circulating water were systematically studied.The synergistic sterilization effect of weak electrolysis process and low concentration residual chlorine bactericide is proposed,and the multi-factor combination sterilization mechanism of weak electrolysis process is revealed.The main research contents are as follows:Firstly,carbon steel,copper and stainless steel were used as working electrodes to explore the effect of electrolysis on the corrosivity of sterile simulated industrial circulating water.The results of Tafel polarization curve test show that the I_corrof carbon steel and copper increases from 17.562μA/cm²and 0.848μA/cm²to 63.483μA/cm²and 9.711μA/cm²respectively,and the pitting corrosion breakdown potential of stainless steel decreases from903.25 m V to 448.34 m V,indicating that electrolysis can enhance the corrosivity of water.The main reason is that the dissolved oxygen in water increases due to anodic oxygen evolution during electrolysis.This problem can be solved by the oxygen release process of cooling tower in practical industrial application.Electrolysis can make the corrosion inhibitors used in the experiment have different degrees of failure.However,the failure of HPMA and sodium aluminate is small,0.35%and 0.45%respectively,which can be considered to be used in conjunction to solve the corrosion problem of the industrial circulating water system in the electrolytic process.Secondly,the sterilization effect of electrolysis on heterotrophic bacteria,sulfate-reducing bacteria and iron bacteria in simulated industrial circulating water was explored.The results show that the effect of continuous electrolysis was better than that of periodic electrolysis on inhibiting bacterial reproduction under the condition of ensuring the descaling rate of 25.74 g/（m²h）.Although the two electrolytic manners can slow down the propagation speed of bacteria,they still cannot effectively control the bacterial proliferation.It is found that weak electrolysis process and low concentration residual chlorine bactericide can produce excellent synergistic bactericidal effect.Continuous electrolysis and periodic electrolysis only need to supplement 0.1 mg/L and 0.2 mg/L residual chlorine bactericide respectively,to achieve the effect of 0.7 mg/L residual chlorine bactericide.In this synergistic sterilization process,electrolysis was the dominant factor and bactericide was the secondary factor.The dominant factor is that residual chlorine and H₂O₂oxidants can be produced in situ for sterilization during weak electrolysis process.Then,the decrease of COD and Fe²⁺,and the local over-alkali and over-acid environments formed in the vicinity of cathode and anode can assist in inhibiting the normal reproduction of bacteria.Furthermore,the electric field force between anode and cathode can push the bacteria to move to the electrode surface quickly,making the sterilization process more rapid and efficient.Finally,electrolytic sterilization experiments were carried out on the actual industrial circulating water collected from the site.The results show that electrolysis can effectively slow down the subsequent reproduction rate of heterotrophic bacteria,sulfate reducing bacteria and iron bacteria.The amount of biological slime on the coupons decreases from0.117 g·cm^-2to 0.038 g·cm^-2after electrolysis.The corrosion rate of carbon steel coupons decreases from 0.613 mm·a^-1to 0.325 mm·a^-1.Electrolysis can effectively inhibit the process microbial corrosion.