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Lotion reacts with pennies, turning green

flarn2006
in Chemistry

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I have a bottle of lotion on my nightstand (don't ask) along with some pennies. Occasionally, some of the lotion spills on the pennies, and the lotion turns green. I assume some chemical in the lotion is reacting with the copper plating in the pennies, due to the characteristic color, but I'm curious as to exactly which reaction is taking place. Below are the ingredients to the lotion I have:

 

INGREDIENTS: Water, Petroleum, Glycerin, Stearic Acid, Glycol Stearate, Dimethicone, Colloidal Oatmeal, Cetyl Alcohol, Glyceryl Stearate, Magnesium Aluminum Silicate, Carbomer, Stearamide AMP, Ethylene Brassylate, Triethanolamine, Disodium EDTA, DMDM Hydantoin, Iodopropynyl Butylcarbamate, Titanium Dioxide (CI 77891).

The major reaction is probably

2Cu + O2 + 2 H2O --> 2 Cu(OH)2

The water doesn't evaporate because of the glycerine and other stuff so the reaction of copper with water and air gets a chance to work better than usual.

The triethanolamine in particular , and the others to a lesser extent, might also react to for, complexes or salts.

On the whole the reaction will be a rather complicated mess.

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