Water Journal : Water Journal April 2012
asset management technical features 136 APRIL 2012 water Unreinforced polymers can also be used in contact with brine, for example, within the RO vessels, for pumps and valve components, and many other applications. The selection of unreinforced polymeric and composite materials is usually based on experience, chemical resistance data provided by materials suppliers, or technical literature. Conclusions This paper aimed to present an overview of the challenges posed by selecting materials for the aggressive SWRO brine created by desalination plants. Guidelines for material selection based on a combination of literature and experience presented are summarised below. For reinforced concrete: • Understanding the performance characteristics of different cement binders in this environment; • Measures taken to minimise cracking (including undertaking CIRIA C660 analyses); • Adequate curing (at least seven days' wet curing, but preferably 14 days); • High concentration of Supplementary Cementitious Materials for sulphate resistance; • Provision of a sacrificial layer of concrete to account for sulphate attack (in particular magnesium sulphate); • A recognised modelling approach for the prediction of chloride ingress with adequate modelling parameters (including chloride surface level, chloride diffusion coefficient as measured by an accepted testing method, chloride threshold for corrosion initiation, maturation coefficient and safety factor); • Cover requirements as determined by the modelling (or applicable standards if suitable/available); • Additional protection: coatings, provision for future CP, inhibitors, liners. For metals: • Alloys with a PREN > 40 for super- duplex stainless steel, super-austenitic stainless steel or nickel alloys; • Welding undertaken in accordance with the appropriate codes and standards; • Post-weld treatment, including the removal of weld spatter and surface preparation of welds to remove surface irregularities; • Post-fabrication treatment, including pickling and passivation to ASTM A380. For polymers: • Selection of suitable polymers with established performance; • For UV-exposed components select UV stabilised versions; • Quality detailing around joints and fastenings is a major factor on service life performance. Acknowledgements The authors would like to acknowledge the works of Dr Frank Collins and Dr Marita Berndt. We would like to also thank Miles Dacre and Rob Kilgour for their feedback and comments and Alessandra Mendes for her significant help. The Authors Dr Frédéric Blin (email: Frédéric.Blin@ aecom.com) and Sarah Furman (email: Sarah.Furman@aecom.com) are both Associate Directors with the Strategic Asset Management and Advanced Materials Group at AECOM. References 1 National Geographic, April 2010. 2 Blin F & Furman S: "Durability guidelines for materials in aggressive brine exposures", ACA Paper 032, Corrosion and Prevention 2010, Adelaide, SA. 3 ISO 13823- "General principles on the design of structures for durability", ISO, Switzerland, 2008. 4 "Emerging Trends in Desalination: A Review", November 2008, National Water Commission. 5 AS 5100.5: "Bridge Design. Part 5: Concrete". 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