Corrosion And Protection Of Carbon Steel And Welding Module Of Carbon Steel And Stainless Steel In High-temperture Aqueous LiBr Solution

Lithium bromide absorption pump has been applied widely in recent years,since it has many excellent characteristics,such as high thermal efficiency,wide heat sources,low energy consumption.However,as an aggressive medium,Lithium bromide solution may cause serious corrosion under the high-temperature condition.This has limited its development.It was studied in this thesis that the corrosion and protection of carbon steel and welding module of carbon steel and stainless steel in high-temperture aqueous LiBr solution.Research has been done for the passivate effect of the potassium dichromate solution for the carbon steel by electrochemical measurements in the normal temperature and atmosphere pressure condition.The results indicate that the passivating effects of the different -concentration potassium dichromate solution for the carbon steel are different,and when its concentration is between 15～30g/L,it showed a better result.And when there is a little nitric acid in the potassium dichromate solution,the passivating effect will be better,but the suitable concentration is correlated with the concentration of the potassium dichromate.The corrosion mechanism of the carbon steel in the high-temperature lithium bromide solution with and without silicon dioxide is studied by some physical detection technologies, such as SEM and XRD,and the corrosion of the passivated carbon steel was studied.The results indicate that the uniform corrosion is observed on the surface of the carbon steel in high-temperature lithium bromide solution containing silicon dioxide,and on the surface of carbon steel there is an incomplete film containing crystal Fe₃Si.And for passivated carbon steel by the potassium dichromate solution the film containing chromite(FeCr₂O₄) is made on the surface,and the corrosion is inhibited effectively.And the better the effect of the passivated solution is,the better the inhibition effect for the carbon steel is.The corrosion of the carbon steel and stainless steel welding module was tested experimentally in 55%LiBr/H₂O solution at 200℃.Various approaches using anti-corrosion and film forming agents were employed to protect the corrosion.The microstructures of the different parts of the welding module were studied by optical microscope.The results indicated the corrosion can not be restrained completely either adding natrium molydbate alone or silicon dioxide alone,but when there were both natrium molydbate and silicon dioxide in the solution, it showed a better result.And then,the natrium molydbate is above 0.3g/L,the silicon dioxide is below 0.7g/L.The electrochemical text system was designed,and it can be a better tool for the electrochemical text at high temperture.