Failure of Micron Cartridge Filter Components in a Seawater Reverse Osmosis Plant

摘要

The pit on the surface of the bottom cap, the presence of thick deposits of corrosion products at the threading of the bottom cap and the stud, the bottom face of the top flange and the CD-ring slot, and the threading of embedded nuts and hexagonal head bolts are indicative of local attack brought about by crevice corrosion. The following factors significantly aggravated the crevice corrosion failure of MCF components: large concentrations of halides in the seawater, a lower pH range from the addition of concentrated H_2SO_4, and a highly oxidizing environment from chlorination to reduce biofouling. The presence of a significant concentration of bromide in the seawater might have contributed to lowering the CPT, thus initiating an early attack. The Mo and Cr contents of the material were slightly lower than the specified composition of type 904L SS. This might be partially responsible for their poor resistance to crevice corrosion. Based on service experiences from many SWRO plants, it maybe inferred that type 904L SS is not the right material for the construction of a MCF.