The Electrochemical Performance Of Al-Al Composite Sacrificial Anode Material

The cathodic protection of sacrificial anode has many exceptional merits, and haswidely applied in offshore structure.However, the protective current density needed atthe early stage of cathode protection is about3~5times than the average current density in the whole protection period. There is a problem of the waste of resources andthe protectd cathode load is too large when common sacrificial anode is protecting. Inthe initial period, the protective current that steel structure need is much more than thecurrent in the later,studies have reported the magnesium anode coated aluminum alloysacrificial anode to solve the contradiction. But this composite anode is difficult toprocess, because the magnesium metal has the different melting point and the swellcoefficient with aluminum alloy.Based on the purpose of the current density and sacrificial anode material, thisthesis developed a new kind of A1A1composite sacrificial anode. In the initial perio–d, the activity alloy anodes will provide enough initial currents without oversizing.When the high active alloy anodes are dissolved completely, the currents that the steelstructure needed are deceased to a very level, then the high efficiency anodes begin todissolve and offers long term and steady protection to the steel structure.The electrochemical performance of Al Zn In Ga Sn Bi, Al Mg Ga Sn andAl Mg Ga Sn In sacrificial anodes were studied by using constant testing,4d speededup constant current test, polarization curve, electrochemical impedance spectroscopy(EIS), scanning electron microscopy(SEM). The best formulation of the high activesacrificial anode material were determined. Then the activity alloy anode and substatealloy anode composed, the mixed potential and the polarization characteristic wereresearched. Electrochemical properties of Al activity sacrificial anode and compositesacrificial anodes and were investigated in the simulation field sea. The results of testing indicated that Al Mg Ga Sn In sacrificial anodes couldsignificantly be used as the activity anode part of the composite sacrificial anode.The electrochemical performance of21#sacrificial anode was the best, its openpotential of it was1.413~1.519V （vs. SCE）, the working potential was1.052~1.318V（vs. SCE）, it has the high current efficiency and the betterpolarization performance in seawater. So choose21#anode as the activity anode partof the composite sacrificial anode.The test of21#activity anode in the simulation field sea indicated that it couldhigh current discharge in the initial period, its initial polarization performance wasbetter, its current efficiency was81.8%. The steel plate was protected effectively.The current density became larger with the increase of the area ratio of cathode toanode.The test of composite sacrificial anode in the simulation field sea indicated that itcould high current discharge in the initial period, its initial polarization performancewas better, The steel platecould protected effectively. As the same time, The testindicated that the composite sacrificial anode could be devoleped whose mixedpotential between1.2~1.3V （vs. SCE）by adjusting the type of the area ratio ofactive anode to substrate anode.