Hello all, I am working on electrochemical machining of aluminium alloy. But neutral electrolytes enhances the passivization. So, I am currently looking for a way to prevent passivization of alumium to machining the alloy correctly. Do you have any idea what kind of electrolyte should I use for this situation? Thank you.
Dear Gülnur, Al is a tricky material, indeed passive layers grow rapidly, and oxide free Al is hardly possible ... What about a solution similar to what is used for electropolishing? Those are typically organic liquids ... Good luck, Dirk
Yes, aluminum is generally passivated in neutral electrolytes but with alkaline electrolytes of pH higher than 8.5, aluminum loses its passivity and the protective oxide layer will form soluble aluminum hydroxide species as in the following overall reaction:
2Al(s) + 6H2O + 2OH- = 2[Al (OH)4]-(aq) + 3H2(g)
Also, there is sign in literatures that AC can be preferred over DC as power supply for the electrochemical process in preventing surface passivation of aluminum. This trend needs little future experimentation on the electrochemical machining process you working on.
Best regards
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