The leakage of heat exchanger is mainly caused by corrosion, a small part of which is due to the defects of heat exchanger modeling and manufacturing process. There are basically two types of tubular corrosion: electrochemical corrosion and chemical corrosion.

During the manufacture of tubular heat exchanger, the welding of tube plate and tube is usually done by manual arc welding. There are some defects in the weld switch, such as depression, air hole, slag inclusion, etc., and the distribution of weld stress is not uniform. In use, the tube sheet is generally in contact with the industrial cooling water, and the impurities, salts, microorganisms and gases in the industrial cooling water will constitute the corrosion of the tube sheet and the weld. This is what we often call electrochemical corrosion. The results show that there are all kinds of ions and dissolved oxygen in industrial water, no matter in fresh water or in sea water. The concentration of chloride ions and dissolved oxygen play an important role in the corrosion shape of metals. In addition, the complexity of metal structure will also affect the corrosion morphology. Therefore, the corrosion of the weld between the tube sheet and the tube is mainly pitting. From the outside, there will be many corrosion products and deposits on the surface of the tube sheet, with pits of different sizes. When seawater is used as medium, galvanic corrosion will occur. Chemical corrosion is the corrosion of medium. When the tube plate of heat exchanger contacts with various chemical medium, it will be corroded by chemical medium. In addition, there is bimetal corrosion between the tube sheet and the tube. Some tubesheets are still in the partial corrosion of corrosive medium for a long time. In particular, the fixed tubesheet heat exchanger has temperature difference stress, and the connection between Tubesheet and heat exchange tube is very easy to leak, which leads to the failure of heat exchanger.