Corrosion behavior of austenitic stainless steel in refinery wastewater ozone treatment system

Abstract

Ozone catalytic oxidation technology is widely applied in the field of wastewater treatment of refining and chemical industries. However, there are some corrosion problems in the ozone treatment system during the long period operation, especially in austenitic stainless steel equipment and pipelines. In order to investigate the corrosion characteristics of stainless steel equipment and pipeline under ozone-containing wastewater, electrochemical test and simulated immersion test were used to systematically study the corrosion behavior of 316L stainless steel in refinery wastewater ozone treatment system, and the corrosion mechanism of stainless steel under the combined action of ozone and Cl- was speculated. The results showed that the pitting susceptibility of 316L stainless steel was improved and corrosion resistance was reduced in the wastewater, originating from the increase of temperature and ozone concentration, the deviation of pH value from neutrality, the increase of Cl- concentration and the decrease of SO42- concentration. Welding materials had the highest pitting susceptibility in the heat-affected zone. The synergistic corrosion of ozone and Cl- in chlorine-containing wastewater increased the pitting susceptibility and crevice corrosion susceptibility of 316L, and accelerated the occurrence of metal pitting. Compared with 304L and 316L, 317L showed better pitting corrosion resistance.

Keywords

• refinery wastewater
• 316l
• corrosion behavior
• ozone
• synergistic corrosion