Critical Conditions for Pitting Corrosion of Stainless Steel Heat Exchange Plate in the Heat Exchange Station of Heat - Supply Network

Abstract

Plate heat exchangers are always employed in the secondary heat exchange station of heat - supply network. If corrosion perforation took place on stainless steel heat exchange plate during its service, it might not only contaminate the circulating water in primary side, but also disturb the steady running of heat exchangers, or even affecting the heat - supply to resident. Thus, investigating the critical conditions for pitting corrosion of heat exchange plate in this case was instructional for establishing the water quality criterion and preventing pitting corrosion. In order to clarify this issue, material chemical analysis, XRD, SEM and electrochemical tests were conducted. Results indicated that the critical concentrations of Cl- for pitting corrosion of 304 stainless steel and 316L stainless steel under 65 ℃ were 125 mg/L and 230 mg/L, respectively. Once the scale layer was formed on the stainless steel surface, local acidification would occur on the surface, and the stainless steel was more prone to pitting corrosion at this time. In order to prevent pitting corrosion of stainless steel heat exchange plate during operation, the concentration of chloride ions in circulating water should be controlled strictly, and meanwhile the methods to prevent scale and reduce the amount of corrosion products in the surface of hear exchange plate should be taken as well.

Keywords

• heat exchange station|stainless steel|secondary side water|pitting corrosion|critical conditions|cl- concentration