| The series of Al-Zn-Sn anodes materials have gradually become a hotspot for its high theoretical capacities, high driving potential, high current efficiency, abundance resource and low cost. But as the engineering application anode material needs not only high electrochemical performance, but also needs relatively uniform corrosion morphology to increase the material working life and further reduce the cost. So the research of Al-Zn-Sn anode by adding activation elements Ga, can not only improve alloy electrochemical performance but also enhance the corrosion uniformity, however, there were no mature theory can explain the reason of the pefect corrosion performance of the Al-Zn-Sn-Ga alloy.The Al-Zn-Sn-Ga alloy is taken as research object. At first, this article research the effect of Ga on the electrochemical performance of Al-Zn-Sn Alloy, then the influence of organization on electric performance is investigated by solution heat treatment. The current efficiency, operating potential and open circuit potential of alloys were examined in simulated seawater. the electrochemical properties of aluminum alloy was examined with polarization and electrochemical impedance methods, in3.5%NaCl solution. The micro structure of the alloy was observed and analyzed by the scanning electronic microscope (SEM), X-ray energy dispersive analysis (EDAX) and the transmission electron microscope (TEM). What’s more, The samples were immersed in3.5%NaCl solution with different time instead of the Dynamic corrosion process for mechanism analysis. Based on the primary principle, calculated and explained the alloy corrosion pits formation mechanism by using the Material Studio software, then using electrochemical, chemical and diffusion principle discussed the relationship between Al-Zn-Sn-Ga alloy development tendency and morphology of corrosion pits. More clearly describes the corrosion mechanism of Al-Zn-Sn-Ga alloy.The results show that:In the Al-Zn-Sn-Ga alloy, the precipitate phases were Al0.7iZn0.29. Then the second phases will dissolved firstly due to its high Fermi energy (negative corrosion potential) and formed corrosion pits. But those pits which in Al-Zn-Sn-Ga alloy, can not spread deeply because of the reason of "autocatalytic effect ", In the range from0cm to10-4cm, the change of pH value in corrosion pits is minimal. This depth value determines the pits whether can continue to longitudinal expansion. At this time, the Al-Ga amalgam with more negative potential formed by "dissolve-sediment-dissolve" mechanism, which can provide the horizontal driving force and increase diffuse alleyway of ion, finally reduce the pH value of corrosion pits and result in wide-shallow corrosion morphology. In the case of the as-cast sample, it caused the irregular ravined intergranular corrosion morphology, which the corrosion rate of the second phase and the grain boundary was larger than that of the matrix by the result of segregation. In the quenching sample, the solution process makes the element Zn and Sn elements which are gathered in the second phase and grain boundary, dissolved into the aluminum matrix again, the composition segregation phenomenon nearly disappeared, so the transverse corrosion rate was omnidirectional characteristic, that resulted in the regularly circular corrosion pits. |
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