Cu-Ni-Sn-xSi合金静态腐蚀及冲刷腐蚀行为研究OA

Copper and its alloys have broad application prospects in the fields of ship components,offshore platforms and marine industrial materials due to their excellent corrosion resistance in seawater and resistance to corrosion fatigue.However,due to the complex and harsh service environment in the ocean,copper alloys inevitably undergo corrosion failures during long-term service.High seawater flow rates exert significant mechanical forces on the surface of copper alloys,leading to the detachment of corrosion product layers and promoting further corrosion.Currently,research on the erosion corrosion behavior of copper alloys remains relatively limited.Cu-Ni-Sn alloys offer advantages such as high strength,wear resistance,corrosion resistance and good electrical conductivity,while excessively high Sn contents in copper alloys often leads to a tendency for Sn segregation during the solidification.Microalloying is commonly employed to address this issue.To date,there have been numerous reports on the effects of microalloying on the microstructure and mechanical properties of Cu-Ni-Sn alloys,but research on changes in their corrosion performance still remains limited.This work investigated the static corrosion and erosion corrosion behavior of Cu-Ni-Sn alloys with different Si contents in 3.5wt.%NaCl solution.Two copper alloys,Cu-12Ni-5Sn-0.25Mn-xSi(x=0.3 and 0.7),were fabricated and subject to cold rolling and high-temperature solution treatment.The scanning electron microscopy(SEM)was employed in combination with energy dispersive spectroscopy(EDS)to observe the intermetallic compounds and corrosion morphology.The corrosion behavior was analyzed through electrochemical impedance spectroscopy(EIS)and potentiodynamic polarization(PDP),while the differences in the erosion corrosion behavior of the two alloys in 3.5wt.%NaCl solution at different flow rates were investigated with an erosion corrosion tester.No significant elemental aggregation was observed in the 0.3Si alloy,whereas the excessive Si content in the 0.7Si alloy formed Ni2Si intermetallic compounds with Ni.The 0.7Si alloy exhibited higher hardness(21HV higher)but inferior corrosion resistance in a 3.5wt.%NaCl solution,which was attributed to the micro-galvanic corrosion between the hard precipitates and the matrix,promoting matrix dissolution.Both alloys demonstrated relatively good corrosion resistance in a static NaCl solution due to the formation of an oxide film during prolonged immersion.However,when the copper alloys were exposed to flowing media,no dense oxide layer or widely distributed corrosion products were observed on the surface.The shear stress from the fluid flow disrupted the newly formed oxide layer,re-exposing the matrix to the corrosive medium.As a result,the weight loss of the copper alloys in flowing media was 4-5 times greater than that in static conditions.The 0.7Si alloy exhibited a higher weight loss rate than the 0.3Si alloy after prolonged exposure to low-flow conditions,primarily due to localized micro-galvanic corrosion induced by the precipitates.At high flow velocities,this difference in micro-galvanic corrosion was mitigated,as the high flow rate would promote the penetration of corrosive media into the pits of both alloys,accelerating pit propagation.