Abstract: According to exemplary practice of the present invention, a passivation solution is circulated in a closed loop so as to laminarly flow on a continual basis through the channels of copper-nickel alloy piping or tubing. The passivation solution consists essentially of seawater (natural and/or artificial) plus 0.5 mM nickel hydroxide additive. The cyclical flow of the passivation solution is administered to the piping/tubing for a selected period of time (e.g., seven days), resulting in growth of a corrosion-resistant film on the inside (channel) surfaces of the piping/tubing. The film thus formed consists essentially of nickel hydroxide, nickel oxide, and copper oxide, and represents a durable and effective anti-corrosive barrier when exposed to seawater.