Study On Corrosion Behavior Of High Magnesium Aluminum Alloy And Its Mechanism In Simulated Flowing Seawater

China,rich in marine resources, has a very superior maritime transport industry, maritime trade is also more frequent with the development of economy, so the ship is regarded as the main maritime transport to play a huge role. Magnesia aluminum alloy replaces steel as the main material of transportation industry because of its excellent physical and mechanical properties.Magnesia aluminum alloy is widely used in the field of marinea, however, it has many defects. Harsh marine environment will cause serious corrosion to metal for a lot of reactive anionic and metal cation.Therefore, how to effectively detect magnesia aluminum alloy of corrosion characteristics and corrosion rate in the marine environment, which makes an effective assessment to the material life and service status. Now, this will have important research significance for the further development and utilization of marine resources.This thesis mainly used the electrochemical polarization curve and electrochemical noise (EN),electrochemical impedance spectroscopy (EIS) to study magnesia aluminum alloy in simulated dynamic electrochemical methods, using scanning electron microscopy (SEM) and energy spectrum (EDS) to observe the magnesia aluminum alloy corrosion morphology observation, drawn the following conclusions:(1) Based on researching electrochemical polarization curve of 5383 aluminum alloy in simulated dynamic water, found that cathodic process was mainly control steps of the magnesia aluminum alloy of corrosion process in simulated dynamic seawate, which is oxygen diffusion control, the magnesia aluminum alloy of corrosion resistant performance overall showed gradually enhanced with the increase of water flow trend, but it relatively different at different stages.(2) Based on researching electrochemical impedance of 5383 aluminum alloy in simulated dynamic water, found that corrosion of magnesia aluminum alloy under different flow rate can be divided into four stages in simulated dynamic water: a) at the primal stage, EIS spectra of high frequency and low frequency appeared two obvious capacitive reactance arc, high frequency region capacitive reactance arc is much greater than the low frequency region, the impedance modulus values decrease gradually, show the corrosive ions in seawater began to attack the oxide film on the surface of the electrode in simulated dynamic water, This is in the midst of the pitting induction period; b) at the second stage,. high frequency capacitive reactance arc obvious shrinkage, low frequency capacitive reactance arc first increases then decreases, the impedance modulus values decreases after the first increase, pitting corrosion occurred, and accompanied by the formation of corrosion products. c) at the transition period, c) corrosion transition, normally only see a capacitive reactance arc, and arc radius is in fluctuation condition, the impedance modulus value is in fluctuation condition, corrosion product film play a protective role to magnesia aluminum alloy matrix with the increase of corrosion time,and corrosion in the metastable state. d) at the later stage,the one and only see a capacitive reactance arc, arc radius showed a trend of increase, but the change of the arc basically remain stable and impedance modulus value basically remain unchanged, corrosion is in a stable state.(3) Based on researching electrochemical noise of 5383 aluminum alloy in simulated dynamic water,under different velocity ,using wavelet analysis way analyzed electrochemical noise signal of magnesia aluminum alloy in simulated dynamic seawater was obtained its EDP spectra ,EDP spectra is a clear indication of the proportion of energy situation from D1 to D8 crystal cell, which reflects the initiation and development of pitting as well as gather and falling off phenomenon of corrosion products on the surface of the electrode, energy distribution magnesia aluminum alloy electrode surface is roughly similar under different velocity. a) at the primal stage, magnesia aluminum alloy electrode surface energy mailly focuses on High class cell D5 - D8, which shows that the seawater erosion sex ion gradually spread to the electrode surface, so as to achieve the activity of electrode surface oxidation film,This is in the midst of the pitting induction period ,b) at the second stage, cell energy mainly concentrats in the low class cell D1 - D4, it belongs to the stage of development of pitting corrosion. c) at the transition period, cell energy mainly concentrats in the High class cell, and energy distribution is higher,it shows that pitting gradually transition to uniform corrosion. d) at the later stage , cell energy mainly concentrats in the High class cell D5-D8, this is the time that producing a large number of metal oxide and hydride accumulat on the anode area stage, thus forming a relative dense corrosion product film film protect magnesia aluminum alloy matrix,the corrosion is from the metastable state transition to a stable state.(4) Magnesia aluminum alloy corrosion morphology EDS analysis shows that the white patches on the surface of the electrode material is mainly Al-Mn, Fe - Si intermetallic compound, corrosion pit element analysis of is the magnesia aluminum alloy substrate after cleaning corrosion pit.