With the expanding of central heating scale in city

the temperature of circulating water in primary heating network has raised from 95 ℃ to 130 ℃. With the temperature increasing

pitting corrosion becomes more serious on stainless steel heat exchange plate. Thus

investigating the critical conditions for pitting corrosion of stainless steel in this case is instructional for establishing the water quality criterion of circulating water. In this work

the characters of water quality of circulating water in heating network from a heating supply company in Ningxia was analyzed firstly. Then

electrochemical tests and simulated experiments were conducted to clarify the critical conditions for pitting corrosion of 316L and 317L. The results indicates that

the p H value of the water is 8.3～ 8.4 and the ratio of mass concentration of SO_4~(2–) to Cl~- is greater than or equal to 1. In the environment at 130 ℃ with this characters

the critical mass concentration of Cl~- for pitting corrosion of 316L is 15.44～21.45 mg/L

and the critical concentration of Cl~- for pitting corrosion of 317L is 42.90～53.62 mg/L. Therefore

the mass concentration of Cl~- needs to be controlled below 15 mg/L in the heating network with 316 L heat exchange plant and below 40 mg/L in the heating network with 317L heat exchange plant.