During the manufacture of heat exchanger, the welding of tube plate and row tube is generally done by manual arc welding. There are different degrees of defects in the weld shape, such as depression, pores, slag inclusion, etc., and also with the uneven distribution of weld stress. In the meantime, there will be corrosion leakage due to the medium contact reaction and other reasons. In addition, the complexity of the metal structure will also affect the corrosion morphology. Corrosion with a large depth concentrated on individual small spots on the metal surface is called pitting corrosion, or pitting corrosion. There will be severe crevice corrosion in the crevices and covered parts of the metal surface. Therefore, the corrosion of the weld between the tube plate and row tube is mainly pitting and crevice corrosion.
There are many solutions to the above corrosion problems in actual production:
1.On the surface of the heat exchanger in contact with corrosive fluid medium, a layer of metal or alloy with strong corrosion resistance shall be covered by a certain method to isolate the corrosive medium from direct contacting with the surface of base material, such as lining with stainless steel.
2.Metal spraying, electroplating, brush electroplating and other insulation medium.
3.Improving the corrosion environment of the medium, such as adding a certain amount of inhibitor into the water.
4.Protecting the corroded parts, for example, use Solay carbon nano-polymer material for plugging repair.
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