The image below shows an exposure rack following a 22-month immersion trial at Levington Marina, UK. It indicates the marine organism attachment on various alloys, including 70-30 copper-nickel and Cu-30Ni-Cr alloys.
Lowest levels of attachment are observed when copper-nickel alloys are free from galvanic coupling to less noble alloys and cathodic protection, as shown by the following images, taken from exposure trials in Langstone Harbour, UK, before and after 12 months of immersion.
90-10 Copper-Nickel Exposure panels before and after 12 month exposure, Langstone Harbour, UK.