Expert: Mike Fulcher - 10/4/2007

Question
Mike,

I recently read a U.S. "Science Fair" report on using two Al electrodes (in 10% NaCl electrolyte)in a simple electrochemical cell. The student claims a polarity reversal when loading the cell, happening in the first few seconds after charging!

My electro-chemistry knowledge and the Nernst Equation both indicate this type of cell should produce zero potential (NOT including concentration cells).

Have you knowledge of this strange phenomena. Your opinion would be most valuable, even if your knowledge is "limited".

Thank you

John Parrish B.Sc.(Tech)<---- NOT Chemistry unfortunately!!

PS I would have contacted the original author, except the article came from a 1985 document.

Answer
I have never heard of this, and it doesn't make much sense.  Now, if you applied a voltage across the same cell, you would still see a voltage when the power was removed due to boundary layer formation.  This voltage would decay within a few seconds to zero.  By just hooking up a load (i.e. resistor) I wouldn't expect to see anything.