1. Use metal and non-metal materials resistant to media corrosion. Take effective anti-corrosion measures (1) Anti-corrosion coating on the contact surface of the heat exchanger and the corrosive medium, covered with a corrosion-resistant coating protective layer, the coating should have good corrosion resistance, impermeability and better Adhesion and flexibility. For the water cooling system, the inside of the tube is cleaned and pre-film treated.
(2) Common methods of metal protective layer are lining, composite board (tube), metal spraying, metal surfacing and so on.
(3) Electrochemical protection Cathodic protection is too high and is generally not used. The anode protection is an anode protection heat exchanger connected to an external power source, and the metal surface is protected by a natural passivation film.
(4) Anti-stress corrosion measures 1 The expansion joint structure, the larger the expansion rate, the greater the residual stress, the higher the electrode potential in the corrosive medium, the greater the corrosion tendency. In the same corrosive medium, compared with the welded structure, the expansion joint structure, especially when the expansion ratio is large when the joint is expanded, the stress corrosion is more likely to occur, so that the expansion joint is ensured under the condition of ensuring the expansion strength and the sealing property. The pressure should not be too high to control the residual stress after expansion, and reduce the possibility of stress corrosion. If necessary, the connection form of the heat exchange tube and the tube sheet can be changed, for example, the strength expansion joint and the slightly expanded structure are used instead of the original expansion joint structure, which reduces the residual stress of the structure and prevents welding only. The possibility of crevice corrosion is to reduce the residual stress of the structure by changing the connection form of the heat exchange tube and the tube sheet, which is effective and feasible for preventing stress corrosion cracking of the heat exchanger.
2 The depth of the expansion tube should reach the bottom of the tube sheet to eliminate all gaps.
3 In the heat exchanger under the strong stress corrosion medium, the tube sheet should be subjected to stress relief treatment.
4 Eliminate the concentration conditions of chloride ions, such as the use of internal hole welding to eliminate the gap between the tube head.
(2) Common methods of metal protective layer are lining, composite board (tube), metal spraying, metal surfacing and so on.
(3) Electrochemical protection Cathodic protection is too high and is generally not used. The anode protection is an anode protection heat exchanger connected to an external power source, and the metal surface is protected by a natural passivation film.
(4) Anti-stress corrosion measures 1 The expansion joint structure, the larger the expansion rate, the greater the residual stress, the higher the electrode potential in the corrosive medium, the greater the corrosion tendency. In the same corrosive medium, compared with the welded structure, the expansion joint structure, especially when the expansion ratio is large when the joint is expanded, the stress corrosion is more likely to occur, so that the expansion joint is ensured under the condition of ensuring the expansion strength and the sealing property. The pressure should not be too high to control the residual stress after expansion, and reduce the possibility of stress corrosion. If necessary, the connection form of the heat exchange tube and the tube sheet can be changed, for example, the strength expansion joint and the slightly expanded structure are used instead of the original expansion joint structure, which reduces the residual stress of the structure and prevents welding only. The possibility of crevice corrosion is to reduce the residual stress of the structure by changing the connection form of the heat exchange tube and the tube sheet, which is effective and feasible for preventing stress corrosion cracking of the heat exchanger.
2 The depth of the expansion tube should reach the bottom of the tube sheet to eliminate all gaps.
3 In the heat exchanger under the strong stress corrosion medium, the tube sheet should be subjected to stress relief treatment.
4 Eliminate the concentration conditions of chloride ions, such as the use of internal hole welding to eliminate the gap between the tube head.
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