This review describes the behaviour of the 90-10 and 70-30 copper-nickel alloys, which were developed for and have been used extensively in seawater applications for over half a century. It provides an assessment of the corrosion resisting characteristics 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. Keywords : copper-nickel, seawater, corrosion, biofouling.