| Converter valve is the core equipment of HVDC transmission project.By converting three-phase AC voltage to the DC terminal,the desired DC voltage can be obtained and the power can be controlled.Valve cooling system is an important auxiliary system in HVDC transmission engineering.Its normal operation is the guarantee of efficient operation of water-cooled converter valves.By studying the failure events of valve cooling system in converter station,it is known that the corrosion behavior of aluminium radiator is an important cause of scaling blockage,water leakage,equipment failure and DC blockage.In order to avoid valve cooling system failure caused by corrosion products and ensure the normal operation of converter station,the corrosion mechanism of aluminium radiator need to be deeply explored.In order to study the corrosion mechanism of aluminium alloy radiator in waterway system,different experimental conditions were set to analyze the influencing factors of corrosion behavior of aluminium alloy: the influence of electric field on corrosion behavior,the influence of ion exchange resin powder on corrosion behavior,and the influence of ethylene glycol on corrosion behavior.In order to reveal the corrosion mechanism of aluminium alloy radiator in waterway,electrochemical analysis,weightlessness analysis,Zeta potential analysis and metallographic analysis were used in the experiment,and water quality data such as total aluminium ion content,pH value and conductivity were measured.The experimental results show that in the current field,the increase of voltage and conductivity accelerates the corrosion rate of aluminium alloy,and the corrosion morphology is different according to the location of aluminium alloy in the current field.In the voltage field,the corrosion rate of aluminium alloy increases in the range of 0~300 kV/m,and decreases gradually in the range of 300~500 kV/m.The increase of electrical conductivity has an promoting effect on the corrosion behavior.The influence of ion exchange resin powder on corrosion of aluminium alloy is from a high level to a low level:anion resin powder(Cl type,OH type),mixed powder(Na/Cl type,H/OH type),anode resin powder(Na type,H type),and the corresponding pH range of zero charge potential of colloids in anion resin powder solution and anode resin powder solution is obtained.The addition of ethylene glycol helps to inhibit the corrosion behavior of aluminium alloy,and the best sustained-release effect is obtained when the concentration is above 50% of volume fraction. |
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