Copper Nickel Seawater Corrosion Resistance and Antifouling

This review describes the behaviour of the C70600 and C71500 copper nickel alloy, which were developed for and have been used extensively in seawater applications for over half a century. It provides an assessment of the corrosion resistant characteristic and also the inherent biofouling resistance of the alloys with the aim of learning from past experiences and ensuring good commissioning and operational practices for future use.

Copper-nickel alloys were developed specifically for seawater service over five decades ago, initially for condensers and piping systems. Their overall suitability has since been confirmed by continuing use in these and other marine applications. The alloys are currently used in sizeable quantities for offshore, power, and desalination industries and also continue to be used by many Navies and in merchant shipping.

Although developed for seawater corrosion resistance, it was soon recognised that the alloys also had inherent resistance to macrofouling. This properties has been advantageous in avoiding or reducing the necessity for biocide dosing in condensers and seawater systems, and in reducing drag forces and cleaning regimes on offshore platforms and boat hulls.

Even as established alloys, knowledge of copper-nickel alloys evolves further as new applications arise, appreciation of corrosion analysis and monitoring progresses, manufacturing techniques change and engineers new to the product provide different perspectives. Occasionally, the lessons learned in earlier times are lost and previously solved problems re-occur.

This review is aimed at providing a current understanding of both the corrosion and biofouling properties of the more common copper-nickel alloys through established and new data, exposure trials and service experience. Good commissioning or initial start-up and operation practices are also reviewed to enable optimum performance in service.

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