Sciencemadness Discussion Board

Encouraging an naturally occurring electrochemical

AJKOER - 4-4-2013 at 10:36

Per this reference (see full paper at http://www.jim.or.jp/journal/e/pdf3/50/06/1433.pdf ). , the following corrosion reaction naturally takes place:

Al = [Al]3+ + 3 e as the anodic reaction.

and

2Et-OH + 2 e = 2 [Et-O]- + H2 as the cathodic reaction.

Anhydrous AlCl3 is added to the 99.5% Ethanol (Et-OH) to serve as the electrolyte.

My questions are if one added an external current, would the indicated reactions proceed more rapidly?

A more complex question is as a significant amount of water interferes with the chemical reaction (more precisely the reaction between Aluminum and Ethanol), would a new electrochemical reaction take place removing the water so that the above reaction could proceed in any event?

Thanks for any input.

Fantasma4500 - 4-4-2013 at 11:32

probably not the answer youre looking for, but i mean to understand that ethanol doesnt react with aluminium or aluminium oxide (or well not very much)
i got some high conc. ethanol standing around from accidental destillation so to say, and i filled in aluminium foil (as methanol which was the impurity i wanted gone) because aluminium foil have a layer of aluminium oxide on it, which methanol happens to react with going into H2O and CO2
but ethanol is a base, so as aluminium metal already reacts very slowly with water it would be plausible there would also be a reaction with ethanol and aluminium..

Metacelsus - 4-4-2013 at 11:36

As to adding a current, I doubt the conductivity of ethanol (even with a few % water) is great enough for any appreciable current to flow. You could try it, I guess, with aluminum as the anode.

DraconicAcid - 4-4-2013 at 11:54

Quote: Originally posted by Antiswat  

but ethanol is a base, so as aluminium metal already reacts very slowly with water it would be plausible there would also be a reaction with ethanol and aluminium..

Don't be fooled by the OH at the end of EtOH or CH3CH2OH- ethanol is less basic than water. In the proposed reaction, ethanol is acting as an acid with a reactive metal (just like reactive metals react with water, and less reactive metals react with, say, hydrochloric acid).

This may be sped up with a current, but as Cheddite says, ethanol's a very poor conductor of electricity (unless you've got a lot of aluminum chloride in there). You might make the aluminum more reactive by making an amalgam with mercury or gallium.

AJKOER - 4-4-2013 at 12:33

Draconic Acid:

Usually a small amount of water (just a couple of percent) stops the normal chemical reaction between the alcohol and Aluminum (true for Aluminum/Methanol as well). Note,the reference paper I supplied indicates that heating the alcohol pushes the normal chemical (or is it the normal electrochemical) reaction.

So, if unwanted H2O is present, would a electrochemical breakdown of the water in the Al/AlCl3/Ethanol cell occur with current? In other words, is it your opinion that a current could eventually make the cited reaction proceed upon decomposition of the H2O?

[Edited on 4-4-2013 by AJKOER]

DraconicAcid - 4-4-2013 at 13:01

If unwanted water is present in the solution, it may react with the aluminum chloride, or it may react at the aluminum to passivate the metal (coating it with aluminum hydroxide). Destroying it electrochemically might work. It might be easier just to add more aluminum chloride.

AJKOER - 4-4-2013 at 17:34

Quote: Originally posted by DraconicAcid  
If unwanted water is present in the solution, it may react with the aluminum chloride, or it may react at the aluminum to passivate the metal (coating it with aluminum hydroxide). Destroying it electrochemically might work. It might be easier just to add more aluminum chloride.


Yes, adding the aluminum chloride would be easier if one has the anhydrous AlCl3 and not the hydrate.