At present, plate heat exchanger plates are usually made of austenitic stainless steel, titanium and titanium alloys, nickel and nickel alloys. The corrosion types of plate heat exchangers for these materials are all-corrosion cracking, pitting corrosion, crevice corrosion, Intergranular corrosion, stress corrosion cracking, corrosion fatigue, hydrogen damage and selective corrosion.(1) There are many media for causing intergranular corrosion of Cr-Ni austenitic stainless steel. Generally, austenitic stainless steel may occur in acidic media such as inorganic acid, organic acid, strong acid and weak alkali salt, and urea methyl ammonium solution. Intergranular corrosion.(2) Non-sensitized intergranular corrosion mainly occurs in HNO3 or concentrated HNO3 medium containing Cr6+(3) Stress corrosion of stainless steel is the most common and most harmful of local corrosion damage of stainless steel. The most common medium causing stress corrosion of various types of stainless steel is atmospheric and industrial water containing Cl- and oxygen, seawater etc.