Passivation of copper-nickel alloy conduits for marine use

A passivation test method comprising:

• situating a first copper-nickel alloy conduit in a tank;
• effecting a continuous flow of a first passivation solution through said tank for a first duration, said tank containing said first copper-nickel alloy conduit, said first passivation solution consisting essentially of seawater, said first copper-nickel alloy conduit characterized by a first conduit length, a first inside conduit surface, and a first outside conduit surface, said continuous flow of said first passivation solution being effected wherein:
• said first copper-nickel alloy conduit is immersed in the flowing said first passivation solution;
• the flowing said first passivation solution is contiguous, along said first conduit length, with respect to said first inside conduit surface and said first outside conduit surface;
• a first passivation film forms, along said first conduit length, on said first inside conduit surface and said first outside conduit surface, said first passivation film characterized by a first corrosion resistance and including copper oxide;
• situating a second copper-nickel alloy conduit in said tank;
• effecting a continuous flow of a second passivation solution through said tank for a second duration, said tank containing said second copper-nickel alloy conduit, said second passivation solution consisting essentially of seawater and 0.5 mM nickel hydroxide, said second copper-nickel alloy conduit characterized by a second conduit length, a second inside conduit surface, and a second outside conduit surface, said continuous flow of said second passivation solution being effected wherein:
• said second copper-nickel alloy conduit is immersed in the flowing said second passivation solution;
• the flowing said second passivation solution is contiguous, along said second conduit length, with respect to said second inside conduit surface and said second outside conduit surface;
• a second passivation film forms, along said second conduit length, on said second inside conduit surface and said second outside conduit surface, said second passivation film characterized by a second corrosion resistance and consisting essentially of nickel hydroxide, nickel oxide, and copper oxide;
• wherein said second duration is less than said first duration, and wherein said second corrosion resistance is greater than said first corrosion resistance.