| With China's "The Belt and Road Initiatives","science and technology development of the ocean" and other major strategic projects implementation,China's demand for corrosion resistant copper alloys is more and more urgent.Taking the corrosion resistant copper alloy for marine engineering as an example,the annual demand is about 400 thousand tons,and the annual output value is about RMB 35 billion yuan.At the same time,the complex and changeable ocean conditions make the service condition of the corrosion resistant copper alloy increasingly harsh,the safety and reliability of the key components is higher and higher,and the corrosion resistance of the alloy is put forward higher requirements.However,the current research and application of traditional brass,B10,B30 and other corrosion-resistant copper alloy can not meet the requirements of the use of high-end areas.Therefore,on the basis of the traditional Cu-Ni corrosion resistant copper alloy,the design and development of a new type of high corrosion resistant copper alloy and its corrosion resistance mechanism were studied.It is of great significance for the basic theory research and engineering application of corrosion resistant copper alloy used in marine engineering.In this paper,a new Cu-Ni-Al corrosion resistant copper alloy was prepared by adding microalloying elements such as Al,Fe,Mn and RE on the basis of the traditional Cu-Ni corrosion resistant copper alloy.The effect of seawater immersion time on the corrosion rate and corrosion morphology of the alloy was studied by static artificial seawater immersion test,and the intrinsic relationship between the addition amount of rare earth and the corrosion resistance was revealed.The electrochemical properties of the alloy were studied by means of electrochemical test.The influence of the amount of rare earth on the electrochemical behavior of the alloy was investigated.The effect of scouring speed and time on the corrosion rate and corrosion morphology of the alloy was studied by seawater scouring test,and the mechanism of the erosion behavior of the alloy was revealed.The conclusions are as follows:1.The corrosion rate of the Cu-Ni-Al alloy and the addition of 0.014% RE and0.035% RE Cu-Ni-Al alloy under immersion conditions were as follows: In the early stage,the corrosion rate of the alloy is larger.With the soaking time prolonged,the alloy surface passivation film began to form and gradually improve,then alloycorrosion rate decreased and tends to be stable.Under the condition of soaking,the corrosion rate decreases with the addition of rare earth.The corrosion rate of Cu-Ni-Al alloy with 0.014% RE and 0.035% RE at 168 h was 26% and 29% lower than that of Cu-Ni-Al alloy.The best corrosion resistance of Cu-Ni-Al alloy added with 0.035%RE.2.The electrochemical behavior of the Cu-Ni-Al alloy and the addition of0.014% RE and 0.035% RE Cu-Ni-Al alloy were the same.At the beginning of immersion,the resistive impedance spectra began to appear at 12 h,and the surface of the alloy began to form a passivation film.As the immersion time was prolonged,the radius of the resist was increased and the three alloys were stable at 168 h,The alloy surface passivation film is dissolved and generated in the dynamic balance.Under the condition of soaking,the electrochemical performance of the alloy increases with the addition of rare earth,and the corrosion current density of the alloy decreases.The corrosion current density of Cu-Ni-Al alloy with 0.035% RE is 2.179×10-6 A·cm-2,which is lower than that of Cu-Ni-Al alloy and the addition of 0.014% RE Cu-Ni-Al alloy decreased by 24.2% and 24.1%.3.In the flowing seawater,the corrosion rate of Cu-Ni-Al alloy and Cu-Ni-Al alloy with 0.014% RE and 0.035% RE at the same flow rate are as follows: At the initial stage,the corrosion rate of alloy is higher,and the corrosion rate of alloy decreases and tends to be stable with the scouring time.The passivation film of alloy surface is improved and the performance is improved.The corrosion rate of Cu-Ni-Al alloy with 0.014% RE and 0.035% RE was different under different flow rate conditions.The corrosion rate of the alloy decreases rapidly from 12 h to 24 h at 1.5m/s,and the surface of the alloy is more stable.During the period of 24 h to 96 h,the corrosion rate of the alloy increases with the increase of the flow rate,and the passivation film on the alloy surface is susceptible to seawater impact.After erosion for 96 h,the corrosion rate of the alloy tends to be stable,and the surface of the alloy has reached a stable state.4.In the flow of seawater,with the rare earth added alloy corrosion resistance improved.Under the condition of 1.5 m/s and the flow rate of 3 m/s,the corrosion rate of the alloy is not significant,but the properties of the alloy film with rare earth addition are better,and the corrosion rate of the alloy decreases rapidly.At the 5 m/s flow rate,the corrosion rate of the alloy is relatively small at the beginning.With the extension of time,the corrosion rate of the alloy with the addition of rare earth is lower,the performance of the passive film is better,and the corrosion resistance is improved.The corrosion rate of Cu-Ni-Al alloy with 0.035% RE was 0.1488 g·m-2·h-1,and the corrosion rate was 43% lower than that of Cu-Ni-Al alloy. |
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