In the production of shell and tube heat exchangers, manual arc welding is generally adopted for the welding of tube sheet and tube column. The weld shape has defects of varying degrees, such as depression, porosity, slag inclusion, etc. The shell and tube are generally in contact with the industrial cooling water in operation, and the impurities, salts, gases, and microorganisms in the industrial cooling water will make corrosion to the sheet and welds, which is often referred to as electrochemical corrosion.

Whether the industrial water is fresh water or sea water, there are various ions and dissolved oxygen included. The concentration changes of chloride ions and oxygen play an important role in the corrosion shape of metals. In addition, the complexity of metal structure will also affect the corrosion morphology.

The corrosion of shell and tube heat exchanger is closely related to the concentration and composition of heat exchange medium. This is chemical corrosion (medium corrosion). The tube sheet of heat exchanger will be corroded by chemical medium when it contacts various chemical media. In addition, certain bimetal corrosion occurs between the tube sheet of the heat exchanger and the heat exchange tube. Therefore, the leakage caused by corrosion is mainly at the joint of the two parts. Shell and tube heat exchanger with ordinary metal is severely corroded in hydrochloric acid and concentrated sulfuric acid, and its service life will be greatly reduced.