Corrosion performance of selected stainless steels brine from reverse osmosis desalination plants

The corrosion performances of some commercial stainless steel alloys in the brine reject solution from a reverse osmosis sea water desalination plant was studied in terms of their pitting susceptibilities (investigated under aerated conditions at ambient temperature using a cyclic polarisation technique) and crevice corrosion resistances (evaluated in the plant over a 3 month exposure period using multiple crevice test assemblies). The alloys used were four austenitic steels. UNSS31603, UNSS31703, UNS N08904, UNS S31254, aferritic steel UNS S44635, and a duplex steel UNS S32550. Cyclic polarisation studies show that the pitting or breakdown potentials for S31603 and S31703 occurred at more active values than for N08904, S31254, S44635, and S32550 alloys, and indicated a reduced resistance pitting corrosion. The multiple crevice tests show that the alloys S31603, S31703, and N08904 do suffer crevice corrosion in the brine reject solution at ambient temperature, while the S44635, S32550, and S31254 alloys showed considerably higher crevice corrosion resistance.