Leakage Causes of Nickel Tube Used in Caustic Soda Falling Film Evaporator

The causes of leakage of falling film nickel tubes of caustic soda evaporator in a chemical plant were studied by means of optical microscope, scanning electron microscope and electron probe. The results showed that the main causes of leakage were chemical corrosion caused by oxygen from the decomposition of NaClO₃ impurity in the raw lye, and erosion and wear caused by uneven distribution of lye liquid film.