The Study Of Microzone Electrochemical Behavior And Mechanism Of The Corrosion System TA2/HAl77-2/316L SS In Desalination Plants

As the requirements of processing properties and structural performance,the multi-metal galvanic corrosion composed of TA2,HAl77-2 and 316L SS are widely existed in Low-temperature Multiple-effect desalination equipment.It will induce pitting,hydrogen embrittlement,stress corrosion and other localized corrosion,threatening the safe operation of the device.However,there is rarely reported for multi-metal galvanic corrosion at home and abroad.Therefore,it has has important practical significance to study the corrosion behavior of the coupled syatem TA2/HAl77-2/316L SS in desalination plantsTraditional electrochemical techniques(potentiodynamic polarization curves and electrochemical impedance spectroscopy)is used to study how is the Cl~-concentration and temperature to effect the corrosion behavior of TA2,316L SS and HAl77-2 in this paper.Since traditional electrochemical technique is difficult to characterize the heterogeneous corrosioninformationattheinterfaceofmulti-metalgalvaniccorrosion,micro-electrochemical techniques(local electrochemical impedance spectroscopy)is used to study how is the Cl~-concentration,temperature and relative position to effect the galvanic corrosion behavior of TA2/316L SS/HAl77-2.Conclusions are as follows:(1)With the increasing of Cl~-concentration,the corrosion rate of HAl77-2 and 316L SS increased first and then decreased;with the increasing of temperature of the solution,the corrosion of HAl77-2 and 316L SS accelerated.With the increasing of Cl~-concentration,the corrosion rate of TA2 increased gradually;with the increasing of temperature,the corrosion rate of TA2 decreased first and then increased.(2)In the coupled system,HAl77-2 always worked as anode and TA2 always worked as cathode.Most of the 316L SS worked as cathode and others worked as anode.With the increasing of Cl~-concentration,corrosion rate of anode increased first and then decreased;with the increasing of temperature,the corrosion rate of anode gradually increased.When HAl77-2 was in the middle of the electrode,corrosion is the most serious since the current passing was easy.And,the anode current at the interface of two metals was higher than that away from the interface.So,the anodic corrosion at the interface of the two metals is worse than non-interface.The corrosion of anode HAl77-2 exhibited significant non-uniformity,the ipmedence distribution on surface was very uneven.This said that significant localized corrosion occurred on the anode metal.