Seawater is one of the most unforgiving services we supply into. A cooling, firewater or ballast system runs chloride-laden water past pump internals, valve trim and pipework for years at a time, often with periods of stagnation that invite crevice corrosion. The grade has to clear a PREN above 40 to survive sustained immersion, and it helps if it resists fouling and starts reliably after a spell idle.
For the wetted structure - pump casings and shafts, valve bodies and trim, pipework and closures - super duplex stainless steel is the default. Ferralium® 255, Alloy 32760 and Alloy 32750 all sit above a PREN of 40 with high strength, machined from solid bar or cut from plate.
Where the duty is corrosion rather than load, the copper alloy Hiduron® 130 is specified for seawater valves and connectors. It offers excellent resistance to seawater, high resistance to crevice corrosion, good anti-fouling behaviour and very low magnetic permeability.
Duplex 2205 covers general pressure duty at a PREN of around 34, and Alloy 316L is limited to sheltered, intermittent exposure. Where the water carries acid, the nickel alloys 625 and 825 take over.
Alloy 32760 is equivalent to UNS S32760, also known as Zeron 100®, a trademark of Rolled Alloys. Alloy 32750 is equivalent to UNS S32750, also known as SAF 2507®, a trademark of Alleima. Ferralium® 255 is the Langley Alloys trade name for UNS S32550. Hiduron® 130 is equivalent to UNS C72400 and meets DIN 2.1504 and DTD 900/4805. Alloy 625 and Alloy 825 are equivalent to UNS N06625 and N08825, sold elsewhere as Inconel® 625 and Incoloy® 825, trademarks of Special Metals. Send us the size and we will confirm from current stock.