Cupro Nickel

The default seawater alloy. 90% copper with 10% nickel and a controlled iron addition builds a protective cuprous oxide film in seawater, and the inherent copper toxicity stops macrofouling — barnacles and mussels do not settle, so cooling lines stay clean without chlorination. Specified for ship and platform seawater systems, firewater ring mains and condenser tubing where the velocity stays below about 3.5 m/s.

The higher-duty cupro nickel. Tripling the nickel to 30% raises strength, erosion-corrosion resistance and the allowable seawater velocity to around 4.5 m/s, and lifts the service temperature well above 90/10. It is the grade for pump and valve-adjacent piping, hot brine and MSF desalination heat recovery, and any line where turbulence or sand loading would strip the film off 90/10.

The desalination variant of 70/30. Raising iron and manganese to about 2% each stabilises the protective film under high velocity, sand-laden and partly deaerated brine, which is exactly the duty inside MSF evaporator heat recovery and reject sections. Where 70/30 tubes thin at the inlet ends, C71640 holds.