During the use of the stainless steel plate heat exchanger, the parts near the water will be severely corroded and fail. After analysis, the corrosion failure of the heat exchanger that occurs when the operating temperature is high will mainly occur cracks, and the main corrosion failure form of the heat exchanger that operates at a low temperature is pitting corrosion.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.In order to save costs, many units use tap water as a medium.Under certain pressure and chloride ion, many stainless steel plate heat exchangers have corroded.To improve the anti-corrosion performance, we can start from two aspects, 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.
By comparison, it is found that the heat exchanger is made of 316 stainless steel. Although the chloride ion content in the environment (water) is high, 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, the isolation method is mainly adopted. China mainly uses non-metallic anti-corrosion coatings for isolation. Raw paint and epoxy resin are commonly used in pressure vessels.Because these non-metallic materials have strong adhesion, the paint film is tough, wear-resistant, and temperature-resistant, and the cost is low. Therefore, it is not only easy to use, but also can greatly improve the performance of the stainless steel plate heat exchanger.