Deposition Behavior Of Corrosion Products In Inner Cooling Water System Of Hvdc Converter Valve

Converter valve plays a key role in HVDC transmission project.The safe operation of converter module is also the premise to ensure the efficient operation of converter valve.Through the analysis of valve fault since 2000,the frequency of inner cooling water system is very high,and the main fault in cold water is due to the corrosion to a certain extent,moreover corrosion products will be deposited in the voltage sharing electrodes,pipe joints and other parts,causing damage to the seal,water plugging water leakage phenomenon.In order to solve the problem of converter valve system caused by corrosion products of internal cooling water system,we need to further explore the causes of corrosion and the deposition rules of corrosion products.In order to explore the corrosion mechanism of inner cooling water system and the deposition rule of corrosion products,the corrosion process of aluminum radiator and the deposition process of corrosion products in the inner cooling water were simulated in the laboratory stage.Based on the corrosion mechanism of the aluminum radiator in the inner cooling water system,the corrosion product contains aluminum oxide colloid.By measuring the relationship between the colloidal Zeta potential and the pH value of solution,we get the zero charge point(pH_pzc)of the colloid.The results show that the zero charge point(pH_pzc)of the colloid in the corrosion product may be the oxide colloid of two kinds of aluminum in 8⁹ and 5⁶.By measuring the Mott-Schottky curve of the metal at different test frequencies,the Mott-Schottky curve of the aluminum electrode and the stainless steel electrode is measured at the optimum frequency,and then the respective zero charge potential(E_pzc)is obtained.The results show that the zero charge potential(E_pzc)of the aluminum electrode is-0.973 V,and the zero charge potential(E_pzc)of the stainless steel electrode is-2.057V.Through the experiment of corrosion electrode deposition,the deposition of aluminum colloids on the electrode of aluminum corrosion product was studied by adjusting the different deposition time and the action voltage.Then deposition of the products deposited on the electrode was measured by the aluminum reagent spectrophotometric method.The results show that the deposition of negative electrode on the platinum electrode is greater than that of the positive electrode when the voltage is 2V.When the voltage is 1V,the positive deposition of stainless steel electrode is greater than that of negative electrode,and the deposition of 2cm on the electrode interval is greater than the amount of aluminum deposited at the interval of1cm.