The plate heat exchanger is a high-efficiency heat exchanger which is assembled from a series of metal sheets with a certain corrugated shape. A thin rectangular channel is formed between the various sheets, and heat is exchanged through the sheets.With the continuous expansion of the field of use and the advancement of production skills, it has now been widely used in various fields.Therefore, avoiding or slowing the corrosion of the plate heat exchanger is an urgent mission.Discussion and use of anti-corrosion doubts to avoid premature damage to plate heat exchangers and reduce waste of resources caused by corrosion.The corrosion of stainless steel plate heat exchangers mainly refers to the corrosion of the plates. The most common corrosion is divided into pitting corrosion, crevice corrosion, stress corrosion, wear and wear corrosion.
(1) Stainless steel heat transfer plates are mechanically stamped. Inevitably, there must be a certain amount of residual residual stress remaining.With regard to stainless steel sheets containing no molybdenum, the elimination of residual stress on the surface is very difficult or even impossible.
(2) After the plates are assembled, a multi-slit structure is formed, such as a contact between the plates and a bottom of the sealing groove.The gap is simple to form the enrichment of Cl-, and the degree of partial enrichment usually far exceeds the ability of stainless steel itself to resist stress corrosion.
(3) When the dust on the outer surface of the sheet is severely smeared, the corrosive elements (Cl, S) in the medium may be attached to the dirt and enriched in the gap at the bottom of the scale.
(4) The harmful elements in the bottom of the sealing groove are usually separated by the increase in temperature of Cl- in the binder.For example, the neoprene series of adhesives, compacted asbestos (rich in CaCl2), usually under the conditions of water and steam, the separation of Cl- and H+ forms HCl, causing severe stress corrosion at the bottom of the groove.