Performance of high chromium stainless steels and titanium alloys in Arabian Gulf seawater

Material selection is a major design parameter for constructing new desalination plants. Over the past four decades, materials for desalination have evolved from simple, low-cost metals into special alloys that resist corrosion and erosion. Reverse osmosis (RO) is a newly emerged desalination technology. Experience with seawater RO indicates the need for materials compatible with the Gulf seawater. A study was initiated at the Desalination Research Plant (DRP), Doha in Kuwait to assess the suitability of certain alloys for seawater applications. The electrochemical impedance spectroscopy (EIS) was used to evaluate the corrosion performance of four high chromium stainless steels (316L, 317L, 317 LNMO and 254 SMO) and grade 2 titanium in natural flowing Arabian Gulf seawater. The EIS provided information concerning changes to the interfacial impedance as a function of exposure time for these alloys. The impedance spectra for all the alloys showed slight changes in the low frequency region over the exposure period. The open-circuit potentials (OCPs) of these alloys exhibited slight fluctuations around the initial exposure potential. However, the grade 2 titanium's initial potential was more active, and then gradually shifted towards the noble direction. The results of the EIS analysis and OCP indicated that grade 2 titanium performed better than the four high-chromium stainless-steel alloys. The use of 254 SMO and 317 LNMO would provide better corrosion resistance and better functional capacity than the use of 316L and 317L.