For the best economic material selection, there are so many other factos in operating condition, metallurgy, maintenance, etc. Please find the following references; References; 1. API RP 932-B, Design, Materials, Fabrication, Operation, and Inspection Guidelines for Corrosion Control in Hydroprocessing Reactor Effluent Air Cooler (REAC) Systems, 2004 2. API Technical Publication 938-C, Additional Guidance on Materials and Fabrication Practice to Achieve Good Corrosion Resistance, 2004 3. A.K. Singh, et al, Duplex Stainless Steels-Stainless Steel World, TWI Paper 16, 1994 4. Ulf Kivis%E4kk, et al, Duplex Stainless Steels-Stainless Steel World, p379-391, 2000 5. R.L. Piehl, Survey: Air Cooler Corrosion, Hydrocarbon Processing, p169-170, July 1975 and Survey of Corrosion in Hydrocracker Effluent Air Coolers, Materials Performance, Vol 15 (1), January 1976, pp 15-20 6. E.F. Ehmke, Air Cooler Corrosion, Hydrocarbon Processing, p172-175, July 1975 7. B.N. Greene, Materials of Construction, p149-151, Chemical Engineering, Oct.1998 8. C.A. Shargay, et al., Corrosion in Hydroprocessing Units, NACE, 1996 9. A. Shingh, et al., Corrosion of Reactor Effluent Air Coolers, Corrosion Paper #97490, NACE, 1997 10. J. Turner, Design of Hydroprocessing Effluent Water Wash Systems, Corrosion Paper #98593, NACE, 1998 11. C.A. Shargay, et al., Ammonium Salt Corrosion in Hydrotreating Unit Stripper Column Overhead System, Corrosion Paper #99392, NACE, 1999 12. C.A. Shargay, et al., Design Considerations to Minimize Ammonium Chloride Corrosion in Hydrotreater Reactors, Corrosion Paper #01543, NACE, 2001 13. N. Sakai, et al., Hydrogen Absorption in Wet NH4HS Environment, Corrosion Paper #00681, NACE, 2000 14. H. Iwawaki, et al., Hydrogen Absorption in Non-Acidic H2S Environment, Corrosion Paper #96602, NACE, 1996 15. G.W. Wilks, et al., Unusual Aspects of Corrosion Failures in Refinery Hydrotreater Units, Corrosion Paper #00702, NACE, 2000 16. C.A. Shargay, et al., Cost Comparison of Materials Options for Hydroprocessing Effluent Equipment and Piping, Corrosion Paper #96600, NACE, 1996 17. P.R. Petersen, et al., Impact of Ammonia Chloride Salt Deposition of Refinery Operations., Corrosion Paper #01540, NACE, 2001 18. B.E. Hopkinson, et al., Material Upgrading History of An HDS Complex, Corrosion Paper #96599, NACE, 1996 19. J. Gutzeit, Effect of Organic Chloride Contamination of crude Oil on Refinery Corrosion, Corrosion Paper #00694, NACE, 2000 20. A. Bagdasarian, Crude Unit Corrosion and Corrosion Control, Corrosion Paper #96615, NACE, 1996 21. API STD 661, 2001 22. Olof Forsen, et al, Localized Corrosion of Stainless Steels in Ammonium Chloride Solutions, Materials Performance, p59-64, May 1997 23. Materials Considerations/ Concerns and Corrosion Control, American Company Manual, 1998 24. The Role of Duplex Stainless Steels in Oil Refinery Heat Exchanger Applications, Sandvik Steel, 1997 25. The Role of Duplex Stainless Steels in Petrochemical Heat Exchanger Applications, Sandvik Steel, 1997 26. 2004 NPRA (National Petrochemical and Refiners Association)Technology Q & A Answer Book, 2004 27. Corrosion/2003 Minutes, NACE Task 205X, 2003 28. A.J. Bagdasarian, et al., Chloride SCC of ASS in Hydroprocessing Units, Corrosion Paper #97501, NACE, 1997 29. James Turrner, Design of Hydroprocessing Effluent Water Wash Systems, Corrosion Paper #98593, NACE, 1998 30. R.R. Williamson, Chloride Corrosion and Fouling in Naphtha Hydrotreating Units, UOP, AlChE Spring National Meeting, Orlando, Florida, Mar. 18-20, 1990 31. D.G. Damin and J. D. McCoy, Prevention of Corrosion in Hydrodesulfurizer Air Coolers and Condensers, Materials Performance, Vol 17 (12), December 1978, pp 23-26 (see also Corrosion Paper # 78131, NACE, 1978). 32. B.V. Johnson, H.J. Choi, and A.S. Green, Effects of Liquid Wall Shear Stress on CO2 Corrosion of X-52 C-Steel in Simulated Oilfield Production Environments", Corrosion Paper #91573, NACE, 1991 33. C. Scherrer, M. Durrieu, and G. Jarno, "Distillate and Resid Hydroprocessing: Coping with High Concentrations of Ammonium Bisulfide in the Process Water", Materials Performance, Vol 19 (11), November 1980, pp 25-31 (see also Corrosion Paper # 79027, NACE, 1979). 34. http://www.corrosionsource.com/CS2000/session03/paper0301/paper0301.htm 35. API RP 571 Damage Mechanisms Affecting Fixed Equipment in the Refining Industry, 2003 thomaseun@shaw.ca (for more discussion)