Study On Electrochemical Performance Of Magnesium Alloy Anodes In Qinghai-Tibetan Plateau Frozen Soil

The groundsill between Geermu and Lhasa of Qinghai - Tibet railway had been frozen for many years,adopting Hot-Pipe to strengthen frozen soil in order to avoid the frozen soil of groundsill sink cause by frozen soil melting.Using magnesium alloy as cathodic protection materials due to carbon steel of outer Hot-Pipe was easy to suffer corrosion.Electrochemical performance of magnesium anodes in Qinghai-Tibetan plateau frozen soil was studied.Electrochemical performance of four magnesium alloy anodes in simulated Qinghai-Tibetan plateau low temperature soil at -4℃ and 4℃ has been studied by polarization curves, electrochemical impedance and current efficiency tests in this paper. The results showed that magnesium alloy anodes presented active dissolution state in low temperature Qinghai-Tibetan plateau frozen soil,and the sequence of dissolution activation and reaction activation from high to low was MGAZ63B, MGAZ31B, MGMIC and pure magnesium. Addition of Mn, Al and Zn elements could increase natural electrode potential of magnesium alloy, and increase the current efficiency through formation of weak cathodic effect intermetallic compound between Mn, Al, Zn and impurity elements. Among the four anodes, natural electrode potential of MGAZ31B was the highest, and current efficiency of MGAZ63B was also the highest, the steady current density MGAZ63B was the biggest after magnesium alloy anodes coupling with cathode at -850mVcsE-Electrochemical performance of MGAZ63B is the best,and it suit sacrificial anode in Qinghai-Tibetan plateau frozen soil.The dissolution reaction of magnesium alloy were endothermic reaction at -4℃ and 4℃, reaction balance constant would largen and reaction velocity would quicken with temperature raising, dissolution activation,current efficiency and current density of magnesium alloy anodes in Qinghai-Tibetan plateau frozen soil at 4℃ were higher to thatof at-4℃.The surface of magnesium alloy anodes had been done physical test after corrosion potential test.using SEM to observe surface,using EDXA to analyse content and using XRD to confirm structure after corosion.The result of test showed that corrosion at 4℃ were serverer to that of at -4 ℃, the main offspring of corrosion was Mg (OH) 2-...