Attachment by marine organisms

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.

Marine organism attachment on various alloys. Photo courtesy of Copper Alloys Ltd.

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.

Exposure Panels prior to immersion. Left to right: Steel, 90-10 sheathed steel, 90-10 copper-nickel. All have anodes attached. Far right: 90-10 copper-nickel without anode. Ex IMI Yorkshire
Exposure Panels prior to immersion. Left to right: Steel, 90-10 sheathed steel, 90-10 copper-nickel. All have anodes attached. Far right: 90-10 copper-nickel without anode. Ex IMI Yorkshire
Panels following a 12-month exposure. Note copper-nickel needs to be free of anodes to minimize attachment. Ex IMI Yorkshire
Panels following a 12-month exposure. Note copper-nickel needs to be free of anodes to minimize attachment. Ex IMI Yorkshire

The freely-exposed copper-nickel remains clear apart from biofilms whereas the panels with cathodic protection show attachment similar to that of steel.

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