Study on corrosion perforation behavior of copper nickel alloy pipe during service in marine environment

A CuNi90/10 copper nickel alloy seawater pipeline experienced premature perforation and leakage during service in the marine environment. The reasons of perforation and leakage of CuNi90/10 copper nickel alloy pipe in seawater pipelines were studied through macroscopic morphology, chemical composition, metallographic structure, microscopic morphology, and en-ergy spectrum analysis, the influencing factors and key points for anti-corrosion and leakage prevention were analyzed. The results show that the chemical composition, hardness, and grain size of the CuNi90/10 copper nickel alloy pipe with perforation leakage meet the standard re-quirements, and the composition, microstructure distribution in the perforation leakage and nearby areas are uniform. CuNi90/10 copper nickel alloy pipe undergoes erosion-corrosion and perforation near the straight pipe section (approximately 10 mm from the weld toe) on the inner arch side of the elbow. The high flow rate of the seawater on the inner arch side of the elbow generates significant shear stress on the alloy pipe wall; solid particles such as sediment in the seawater impact the alloy pipe wall, causing damage to the passivation film and local plastic deformation; and due to the protrusion of the weld joint near the elbow, the local micro-turbulence of the seawater is generated; Under the combined action of erosion and corrosion, premature perforation and leakage of the copper nickel alloy pipe are caused. In order to avoid premature perforation leakage of the copper nickel alloy during service in the marine environ-ment, safety technical operating procedures should be strictly followed during use, such as controlling fluid flow rate, maintaining seawater flow in the early stages of the service to form a protective film, and reducing the content of solid particles (such as sediment) in the fluid, etc.