The plate heat exchanger is a partitioned heat exchanger composed of a certain number of plates, gaskets and frame plates. Plate heat exchangers have the advantages of high heat transfer efficiency, small footprint, flexible heat exchange, and convenient cleaning. They have been widely used in metallurgy, mining, petroleum, chemical, electric power, medicine, and food industries. However, the plate heat exchanger will also be corroded during use, so why does it cause the corrosion of the plate heat exchanger?
(1) Corrosion at temperature is a chemical reaction. When the temperature increases by 10°C, the corrosion rate increases by about 1 to 3 times. Generally, the lower the pH value, the greater the corrosion of the metal.
(2) Harmful impurities include chloride ions, sulfide ions, cyanide ions, and ammonia ions. These impurities can cause severe corrosion in some cases.
(3) The influence of medium concentration. For example, in hydrochloric acid, the greater the concentration, the more serious the corrosion. Carbon steel and stainless steel corrode most severely in sulfuric acid with a concentration of about 50%, but when the concentration increases above 60%, the corrosion decreases sharply.
(4) In the assembled plate heat exchanger, a gap is formed between the edge of the plate sealing groove and the deformed sealing gasket, which provides an environmental condition for crevice corrosion. Because the gap is small, the active shape of the fluid medium in this area can only be laminar flow or even dead zone.
(5) The gasket groove in the corrugated plate is a severely deformed area in the entire plate, and there must be many restricted stresses. After the plate heat exchanger is clamped, the compression deformation of the gasket exerts a great pre-tightening effect on the plate sealing groove area.
(6) The appearance of accumulation and aggregation occurs in the crevice area. This situation is more severe when the plate heat exchanger is switched on and off.