Super Stainless Steel Welded Tubing Solutions: An Alternative To Titanium Welded Tubing For Seawater-Cooled Heat Exchangers?

Thanks to its outstanding resistance to general and localized corrosion attack properties, Titanium has been successfully established as the commonly used material for seawater-cooled heat exchanger tubing, be it for power plants’ surface condensers, thermal desalination plants’ heat exchangers or heat exchangers used in the chemical and petrochemical processing industry. In the current material market context in which Titanium price has increased significantly, engineering companies and end-users have shown an increasing interest for more cost-effective alternative solutions using what are called super alloys which are highly alloyed stainless steels showing a far better corrosion resistance than conventional stainless steels. In addition to Titanium, this paper will focus on six different super stainless steel alloys which may be considered alternative solutions to Titanium for seawater-cooled applications: UNS S31254, N08367 and S34565 super austenitic alloys, UNS S44735 and UNS S44660 super-ferritic alloys, and S32750 super-duplex alloy. Taking power plants’ condensers as an example, the paper reviews both mechanical and corrosion properties for ranking the seven different materials. Both standardized ASTM and electrochemical tests in artificial seawater have been carried out on welded tubes in order to rank the different grade materials according to their pitting and crevice corrosion resistance.