Abstract
The corrosion behavior of duplex stainless steels in open seawaters of Kingdom of Saudi Arabia at two different locations namely, Arabian Gulf at east coast and Red Sea at west coast has been studied in order to find out suitable alloys for seawater handling system particularly pumps in desalination plants as the conventional materials like austenitic stainless steel 316 (UNS 31600), iron and copper base alloys failed unexpectedly during early years of operation. Ten duplex stainless steels were immersed in raw and chlorinated seawaters for a period extending 365 to 470 days. Additionally, superaustenitic, austenitic SS 316L (UNS S31600) and austenitic cast-iron were studied for comparison purposes. The corrosion rates and crevice corrosion behavior of the alloys were determined from mass loss data and by determining rate of crevice corrosion occurrence, "R", respectively. The pitting corrosion was studied by macroscopic examination and pit depth determination.
The results of the studies show that super duplex steels are most resistant to general and localized corrosion attack. Superaustenitic has nearly the same resistance as that of super duplex steels. In general, forged alloys have much higher corrosion rates than cast duplex steels. Alloys having PREN greater than 38 have extremely low corrosion rates. Presence of copper and tungsten appears to increase the corrosion resistance of duplex steels appreciably.
