ab s t r ac tSeawater desalination infrastructures require a careful material selection with high corrosion resistance. The high seawater temperatures in warm regions, where many desalination plants are developed, must be clearly considered regarding the corrosion of materials. To comply with the operational characteristics of seawater reverse osmosis (SWRO) process (high pressure, high chloride content and dissolved oxygen content at saturation values), the conventional material selection was stainless steel with sufficient pitting resistant equivalent number. However, many cases of corrosion failures of stainless steel in SWRO desalination units have been reported. In most cases the cause of the failures was attributed to the use of not enough alloyed grades. However, high alloy stainless steels are also susceptible to crevice and pitting corrosion in seawater. The operational corrosion risk will highly depend on the stainless steel composition, on the metallurgy (i.e. cast or wrought), on the service conditions, and on the geometrical configuration of the confined zones in contact with seawater. The present paper reviews the corrosion performance of metallic materials used for SWRO desalination plants. It focuses on the corrosion behaviour of several stainless steel grades. Recent corrosion failures of stainless steel pumps used in SWRO desalination plant in the Mediterranean Sea are also discussed.
Several high alloys are candidate materials for the severe corrosive environment of reverse osmosis desalination plants. In the present study, the crevice corrosion performance of duplex, superduplex, superaustenitic stainless steels, and nickel-based alloy was investigated in natural and chlorinated seawater, at different temperatures. Several crevice configurations were evaluated including flanges assembled with gaskets, bolts mounted with nuts to plates, and the standard CREVCORR-type crevice formers. It was thus possible to illustrate the effect of crevice configuration on the corrosion behavior of the different alloys. The crevice geometry was confirmed to be of major importance in terms of risk for initiating crevice corrosion. In natural seawater (i.e. not chlorinated), the most severe temperature was 30˚C, due to high biological activity and high corrosion kinetics. Chlorination at 0.5 ppm increased the risk of localized corrosion but decreased the corrosion propagation rates. In chlorinated seawater, crevice corrosion risk significantly increased with temperature for all tested alloys. For each of the tested configurations, the superaustenitic stainless steel UNS S31266 showed better crevice corrosion resistance than superaustenitic UNS S31254 and S34565, superduplex S32750, and also nickel-based alloy N06625. The present results are part of a three-year Joint Industry Program supported by end-users, engineering companies, and material producers.
To comply with the demanding operational conditions of seawater reverse osmosis (SWRO) process, both in terms of corrosion resistance and mechanical properties, the conventional metallic material selection was often stainless steel for seawater and brines handling units (e.g. pumps, valves and piping). However, many cases of corrosion failures of stainless steel in SWRO desalination units have been reported often attributed to un-adapted stainless steel grade selection and/or to the particular aggressive conditions in "warm" regions where many recent desalination plants are built (high ambient temperature, severe biofouling, etc.). The operational corrosion risk will actually highly depend on the material composition, on the metallurgy (i.e. cast or wrought), on the service conditions and on the geometrical configuration of the concerned units in contact with seawater. Considering all these parameters, a proper material selection should avoid corrosion issue. For existing corrosion, cathodic protection (CP) may be an efficient solution to stop or to control the propagation of the degradation. However, the CP for materials used in SWRO desalination plants and in its specific operational conditions (i.e. high pressure, velocity and confinements) is not well documented; as a result, an adapted CP design is not always possible from existing data. The present paper reviews some corrosion cases of stainless steel and copper-based alloys in SWRO desalination plants. Solutions to manage existing corrosion of metallic materials in SWRO plants are discussed and focus is done on CP of stainless steel elements. Some results of an ongoing investigation about the CP for the specific operational conditions of SWRO desalination plant are presented and discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.