Corrosion Behavior Of C71500 Copper-nickel Alloy In Static And Flowing Seawater

With the increasing attention to the exploitation and utilization of marine resources,the requirements for the corrosion resistance of marine equipment materials are getting higher and higher.Sea water pipeline is an important part of ships and other marine equipment.Due to the harsh environmental conditions of its service,corrosion problems have always been prominent.Among them,the erosion-corrosion of flowing seawater significantly accelerates the failure rate of pipeline materials,which is one of the main causes of various failures of the seawater pipeline system.Copper-nickel alloy has good mechanical processability,corrosion resistance and anti-fouling performance of marine organisms.It is widely used in the field of marine engineering,especially in the application of seawater pipelines.C71500 copper-nickel alloy is used as a typical seawater pipeline material.There have been relevant reports on applications in the field of offshore engineering abroad,but they have not been used in my country.With the development of China's Marine strategic development,the need for new Marine metal materials is increasingly urgent.To further expand the series of metal materials in the field of marine engineering in my country.It is necessary to carry out the import,research and imitation of new copper-nickel alloy materials,and finally realize localization.The most urgent task is to study the corrosive behavior of new copper-nickel alloy materials in seawater environment while carrying out the related research and development work of new copper-nickel alloy materials.This thesis is aimed at the future application needs of C71500 copper-nickel alloy in the field of marine engineering in my country.The corrosion behavior of the alloy in static and flowing seawater environment has been systematically studied.The main research contents and results are as follows:1.In order to meet the needs of relevant tests for alloy materials in the flowing seawater environment,the seawater folw and corrosion experimental equipment was developed by ourselves,which realized the quantitative control of seawater velocity and temperature,solved the test problem of seawater scour with high velocity,and provided technical support for the development of relevant experimental work in this thesis.2.The corrosion behavior of C71500 copper-nickel alloy in static seawater was studied.The results of EIS,ECN and SEM tests showed that the film formation process of C71500 copper-nickel alloy surface corrosion product film in seawater could be divided into four stages:film growth,film rupture,film regeneration,and film stabilization and densification.After 480 hours of corrosion in static seawater,a double layer of corrosion product film was formed on the surface of the material.To further investigate the relationship between corrosion resistance and surface corrosion products,XPS was used to study the composition of compounds in the two-layer corrosion product film after 720 hours.Results showed that in the double layer corrosion product film and the inner membrane formed more dense Cu₂O and MnO₂ reservoirs and adhere to the substrate surface,cut off from the water of the sea from the outer layer of the porous membrane into the material base,seawater corrosion of the material,the material had good corrosion resistance,membrane layer was relatively dense,the protection of matrix performance was better also.3.The corrosion behavior of C71500 copper-nickel alloy in moving seawater was studied.The results of the EIS,ECN and SEM test showed that 4m/s was the critical flow velocity of C71500 copper-nickel alloy.In order to further study the relationship between corrosion products on the surface of the material and seawater flow rate,XPS was used to analyze the surface corrosion product film.The results showed that Fe³⁺could be converted to Fe³⁺at a high flow rate,and the MnO/Mn2O3 in the corrosion product gradually changed into a more stable MnO₂ with the increase of flow rate,which further improved the corrosion resistance of the copper-nickel alloy surface film.Moreover,the formation of Cu₂O on the surface of C71500 copper-nickel alloy at a high flow rate improved the corrosion resistance.The above research showed that Cu₂O and MnO₂ in the corrosion product film of C71500 copper-nickel alloy played a key role in the corrosion resistance of the alloy in static and flowing seawater environments.