The Preparation And Study On The Performances Of Aluminum Based Alloy Sacrificial Anodes

Al-Base alloy has been a new kind of sacrificial anode material which has beenrecently developed, with its high driving potential, high theoretical capacities, highcurrent efficiency. But on the surface of Al-Base sacrificial anode, there normallyforms a passive oxide film, due to pure aluminum's active nature and easy to beoxidated. The oxide film will prevent the sacrificial anode from normally dissolvingand decrease the current efficiency. Thus, the reverse potential may accelerate thecorrosion rate of the metal. To solve this problem, the scholars in and out of thecountry often destroy the oxide film to reduce the potential of the surface and promotenormal dissolution of the anode by alloying.Several kinds of Al-Zn-In-Sn system, Al-Zn-In-Si system, Al-Zn-In-Sb systemsacrificial anodes are cast. Their electrochemical performances are tested withconstant current method and microstructures are also observed and analyzed bymetallography microscope, scanning electron microscope and energy spectrumanalysis. Conclusions as follows:1. The electrochemical performances of Al-Zn-In-Sn alloy sacrificial anodescorrelates with the content of Sn. When the content of Sn reaches 0.02%, theelectrochemical performances are the best; and the current efficiency and actualcapacity decreases with the increasing content of Sn .2. The electrochemical performances of Al-Zn-In-Si alloy sacrificial anodes correlateswith the content of Si. Its performances decreases with the increasing content of Si.But proper addition of In can eliminate the disadvantage influences and admits of themore content of Si.3. Sb addition can diminish crystal grain size and increase the quantities ofsegregations at crystal boundary, but its current efficiency is lower. In comparisonwith Sb addition, Sn addition can also diminish crystal grain size, which is benificialto raise the current efficiency, and reduce the quantities of segregations at crystalboundary, but diffusional corrosion of the surface is grave. The cooperated action of iSb and Sn can effectively prevent Si from segregating, enhance the current efficiency.At the same time, anode materials possess preferable surface dissolutioncharacteristics.4. The research of Al-Base sacrificial anode's spouse corrosion behavior in NaClsolution shows that jg increases with the increasing concentration of Cl- and isproportional to the ratio of the cathode and anode working surface areas. Eg increaseswith the increasing concentration of Cl- and shifts to more negative potential valuewith the decreasing ratio of the cathode and anode working surface areas.5. The research of Al-Base sacrificial anode' spot corrosion behavior in NaCl solutionshows that the larger the lagging ring areas is, the worse the ability against spotcorrosion is. On the contrary, this kind of sacrificial anode has better activity ofdissolution.6. The metallography structure and electrochemical performance of Al-Base sacrificialanode are studied. And the results show that the smaller the grain sizes are and thefewer the segregative phases are, the higher the current efficiency is. Theself-corrosion,the drop of the segregative phases and the drop of the grain accountsfor the drop of current efficiency.