Desalination Plant Pumps: 2507 vs. 904L Erosion-Corrosion Resistance

 

Why super duplex 2507 dominates RO high-pressure pumps?
2507 provides PREN >42 and 550 MPa yield strength for 80-bar service. Its dual-phase structure withstands 45,000 ppm chlorides at 8 m/s flow velocity. Cavitation resistance is 3x higher than 316L due to 300 HV bulk hardness. Cost is 40% lower than nickel alloys.

 

When 904L is specified for brine heater internals?
904L excels in stagnant seawater zones with <0.5 mm/year corrosion rate. High nickel (25%) prevents chloride stress cracking during thermal shocks. Molybdenum (4.5%) resists pitting under silica scale deposits. Required for sulfuric acid cleaning cycles.

 

Minimum 1.8 m/s prevents particulate settlement. Maximum 6.5 m/s for 2507 and 8 m/s for 904L before erosion acceleration. Velocity >10 m/s causes cavitation damage regardless of alloy.

 

Laser-clad Stellite 6 on impeller leading edges. Boronized diffuser surfaces (1,500 HV). Cathodic protection at -950 mV vs. Ag/AgCl reference. Micro-grooved textures reduce turbulence 25%.

 

Monthly UT thickness mapping at erosion hotspots. Vibration analysis detecting impeller imbalance. Quarterly seawater chemistry analysis (chloride/oxygen/sulfide). Ferrite content verification after 10,000 hours.