Copper-Nickel, Seawater Applications

[brian eiland]

I've always had an interest in this subject since my days with submarines, and the building of those two fishing trawler hulls of copper-nickle for work down off the extremely hi-fouling coast of South America. Just happned across this:

Neptune's Daughters: Copper-Nickel Creates Two Dream-team Alloys for Seawater Applications

http://www.copper.org/innovations/20...daughters.html

...a few excerpts....
Sitting comfortably at atomic number 29 in the Periodic Table, the element Copper is a friendly, outgoing sort of person, getting on superbly well with both of her nearest neighbors. In the company of the equally friendly and multitalented Zinc, for example, at atomic number 30, copper sallies forth on myriad expeditions, creating the vital and prolific range of commercial brass alloys, for which there are in excess of seventy international specifications.

But it is with the element Nickel, at atomic number 28, that copper has a really special affinity. The elegant simplicity of their mutual relationship results in the uniquely performing, two copper-rich nickel alloys, CuNi 90/10 and 70/30 (percentages by weight). These two alloys are both so compatible with the exacting marine environment of seawater, that they could truly be regarded as the “daughters” of Father Neptune.

Atoms Form the DNA:

What the Textbook Says:
....Father Neptune’s two pure-bred ‘daughters’, of impeccable lineage, are therefore, Cu90/Ni10 and Cu70/Ni30, the two perfect alloys for marine applications.

What They Do for Sailors:
The two main copper-nickel alloys have their major applications in marine environments, due to a unique display of two chief properties: corrosion and bio-fouling resistance.

Copper and nickel come together in alloys for pipes, fittings and components used for contact with one of the most corrosive environments on earth, the world’s seas and oceans, with their various compositions, temperatures and biological idiosyncrasies.

Several very successful exercises have also been conducted over recent years with entire ships’ hulls being either fabricated from copper-nickel, or clad with sheets or small platelets. This is seen as an important future market both for leisure and commercial vessels.

What Textbooks Don't Tell You:
Both daughters grow protective skins
The copper-nickel alloys intriguingly perform a strange and miraculous act of bio-metallurgical epidermy. Starting immediately on contact with seawater, they grow a complex, oxide-based “skin” of the order of 4x103 Angstroms thick (human hair is approximately 200 times this thickness).

This bio-metallurgically complex skin uses a combination of electrochemical and microphysical characteristics unique to the biology of the sea to create a quasi-living surface which in a gentle, ecologically protective manner, dissuades the attachment of both micro and macro biofouling, and enables any attached macroorganisms such as molluscs to be sloughed away in a soft slurry, leaving the metallic copper oxide film intact to continue its protection of the underlying alloy.

Such an effect is not seen to this degree in any other metallic or alloy system, and it is this very property that gives Neptune’s daughters their unique and entrancing character. As they taunt and play with the sea, they react with it in this enigmatic way.

Birth of CuNi Seamless Pipe:

The Submariners:

Exciting Lives:
Every day, in every marine application, the unique characteristics of copper-nickel alloys interact with the waters of the sea, which have become the natural habitat of Neptune’s two daughters, as they support the navy and the marine industries in their endeavors: offshore platforms tapping into remote energy sources; active service with the world’s navies in the defense of nations; acting as a conduit for billions of gallons of seawater daily, worldwide; preventing biofouling on critical structures without damaging the environment.

A respect for the sea is what every sailor soon learns. Once cultivated, it often becomes a reciprocal situation. The mutual compatibility of copper-nickel alloys and the marine environment exemplifies this admirably.

One can imagine Father Neptune looking on at the achievements of his two daughters with considerable pride, and allowing himself a big smile.

[brian eiland]

from that same website, http://www.copper.org/innovations/20...eathing_gg.htm

Copper Hull Sheathing Foils Barnacles

...some history...
Data collected from the use of copper-nickel alloy hulls on the Copper Mariner and the many vessels that followed established that the alloys are highly effective in preventing biofouling of the hull. (The vessel remained essentially free from fouling for the first 11 years of service, despite the vessel's use in fouling-prone tropical waters.) The copper-nickel hull resulted in lower maintenance costs, lower fuel costs (due to lack of drag), and a net cost saving over the life of the vessel, even when the high cost of fabricating the copper-nickel hull was taken into account.

[Ike]

copper-nickel is the commonest material used for piping on ships. I would think though that it would be very expensive to build an entire hull of it.

[jehardiman]

There are some problems with 90/10 and 70/30 CuNi, the largest is concerned with other fittings. Both will eat them up. Then there is the anode problem, most will not work around them. I have had extensive experience with both 90/10 and 70/30...they both require deep pockets and need to be monitored constantly. Painted steel is cheaper in most applications.

[Hunter25]

This material has been used as a hull shell and it is a fine metal to use. It's heavy and quite costly, but can pay for itself in maintenance reductions for the non fouling hull. Fuel savings on a constantly clean hull can make it worth the initial cost. About the same strength as marine aluminum, but 530 pounds a cubic foot, ouch. Herreshoff designed a substantial yacht (AC defender I think) that had dissimilar metals issues and wasted away pretty quickly, but they had limited understanding of these problems in the 1880's.

[jehardiman]

Originally Posted by Hunter25

It's heavy and quite costly, but can pay for itself in maintenance reductions for the non fouling hull. Fuel savings on a constantly clean hull can make it worth the initial cost.

Not true, Cu-Ni will foul if left in stagnat water. Velocities must be ~ 3 ft/sec for it to be non-fouling and less than 15 ft/sec to prevent stripping of the passivation. This is why it is good for seawater pipe. See the following site.

http://www.copper.org/applications/marine/1-toc.html

[duluthboats]

I would add that it is very hard on machining tools making an expensive material a much more expensive finished part. Use of any metal in a salt water setting should be designed in as part of system not individual components. I remember seeing valves with like new gates and seats, but the stems and bodies were corroded away.