Since stainless steel is particularly sensitive to chloride ions, corrosion will occur once it comes into contact. Most heat exchangers use water or steam as the heat exchange medium. Many units use tap water as a medium to save costs, and many plate stainless steel heat exchangers corrode under certain pressure and chloride ions. To solve or reduce the occurrence of such accidents, we first need to clearly understand the causes of such corrosion, the type of corrosion and specific preventive measures.
We started from two aspects to improve the anti-corrosion performance, one is to improve the manufacturing quality, and the other is to try to avoid or control the contact of chloride ions with the shell.The heat exchanger made of 316 stainless steel, although the chloride ion content in the use environment (water) is high, but no corrosion has been found in the inspection.Therefore, stainless steel with better pitting corrosion resistance should be selected as the shell material, such as 316 or 316L.Since 2% Mo is added to 18-8 stainless steel, its corrosion resistance is greatly increased.When welding, try to use argon arc welding instead of arc welding. On the basis of ensuring the fusion quality of the weld, the welding process parameters should be strictly controlled, and the method of small line energy and multi-pass welding should be adopted to avoid local overheating of the weld. To control the contact between chloride ion and shell, isolation method is mainly adopted. At present, China mainly uses non-metallic anti-corrosion coatings for isolation. Raw paint and epoxy paint are commonly used in pressure vessels. Due to the strong adhesion of these non-metallic materials, the toughness of the paint film, wear resistance, temperature resistance, and low cost, it is not only easy to use, but also can greatly improve the performance of the plate stainless steel heat exchanger.