11352 An Assessment of the Biofouling Resistance and Copper Release Rate of 90-10 Copper-Nickel Alloy

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Product Number: 51300-11352-SG

Author: Carol A. Powell, James H. Michel and Harold T. Michels

Publication Date: 2011

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90-10 copper-nickel is one of the few engineering alloys available which offer both high resistance to seawater corrosion and biofouling. The alloy is not immune to microfouling but colonization of macrofouling is much restricted. The mechanism is not fully understood and is thought to be at least partially linked to copper ion release from the complex protective surface film. There may also be an effect of the nature of the surface film itself.

There are no suitable standards available to assess copper release from solid alloys but ASTM* D64421, Standard Test Method for Copper Release Rates of Antifouling Coating Systems in Seawater was developed for coatings. Although coatings are designed to release copper in a totally different way to the behavior of solid metal, 90-10 copper-nickel has been evaluated using the method to assess whether it could be used or modified to provide data which has a relevance to service conditions and experience.

This paper reviews existing knowledge about corrosion rate and biofouling resistance of 90-10 coppernickel and then reports and evaluates test work carried out to ASTM D6442. It is apparent from the results that protective surface film build up on the metal in live sea water is compromised by the test technique and reproducibility is poor. The work does however provide indicators about how a more relevant method could be developed.

Key words: C70600, copper-nickel, copper leaching, ASTM D6442, corrosion, biofouling, surface film, cuprous oxide.