Hah! Back when I had braces I used to wrap tin foil around the wires when my mouth was really sore, like when I got new wires. I didn’t know why it helped soothe the pain, but I suppose it’s because it generated a bit of an electric charge. Cool! Try it sometime, those of you who suffer through the horrors of orthodontal correction!
My question is, why isn’t my ketchup dissolving my aluminum foil? It’s been over 24 hours now since I started this “test”. How long is this supposed to take?
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Why does ketchup dissolve aluminum foil? (25-Jun-1982)
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If you use a glass dish or a coated metal pan, it won’t work. The pan must be bare metal, and the aluminum foil must be in electrical contact. The corrosion occurs because a shorted battery is formed. Search google for keywords “lasagna cell.”
Cecil errs. Yes, the effect is electrochemical, but it involves two metals and an electric current. The metal baking pan and the aluminum foil supply the two metals. Physics teachers know this as the “Lasagna Cell” effect. (Yes, it works with lasagna, not just meatloaf.) You need a salty electrolyte between the two metal plates. Wadded paper wet with saltwater probably works too. The two metals plus the salty food form a battery. Since the two metals are touching together, the battery is shorted out and electric current is maximum.
To prevent the aluminum from corroding, just stop the electric current. Use a pyrex (glass) baking dish. Or you can insulate the edges of the metal pan so the alumium foil doesn’t make electrical contact. Or you can use an alumium baking pan. If both metals are the same, no battery is formed.
If you want to do some mad science experiments involving meatloaf, try the following. You need a double-ended alligator clip wire (Radio Shack has them) and a sheet of insulator such as plastic wrap or wax paper.
Use a bare metal baking pan (not the non-stick coated kind) and make a meatloaf. When cool, wrap the entire meatloaf pan with plastic wrap or wax paper. Cut a big hole in the wrap to expose the top of the meatloaf, but make sure the edges of the metal pan remain covered with the wrap. Now put the foil on top. Make sure the foil doesn’t touch the metal pan directly (the plastic wrap stays between the foil and the metal pan and breaks any electrical contact.) Stick the whole thing in the fridge for a day. What happens? Nada. The meatloaf ketchup doesn’t corrode the aluminum. Wait several days. Still no corrosion.
Next, clip one alligator cliplead to the edge of the metal pan (make a hole in the plastic wrap so the teeth grip the metal) and clip the other alligator clip to the aluminum foil. Wait another day and you’ll find many corrosion spots all over the foil. The wire has “shorted out” your battery. It generates a small current (typically under a milliamp), and the chemical reactions convert the alumium metal into alumium ions (and metallic mush.)
It seems to work better if the alumium only touches the wet food in small spots (such as the high points of a lasagna, as opposed to the whole wet surface of castup-coated meatloaf.) I imagine that the food has too many ohms (not enough salt), which limits the maximum battery current, so if the current is forced through small spots, the chemical action is concentrated in those spots.
erm, although aluminium is high up in the reactivity series, it readily reacts with the oxygen in the air to for a layer of relatively inactive Al2O3 (aluminium oxide) on the surface, hence making it to all intents and purposes inactive.
get a block of aluminium and scratch it, you will see (for a few seconds) it is shiney then dulls as it forms a new layer assuming you carry this out in a atmosphere that has oxygen present.
If ketchup ate threw it, I would take the foil back to the shop
Is the food safe to eat after this experiment?
Why would you want to? It’s icky gray. And I wonder if it tastes very good.
Icky gray food never stopped anybody from eating at McDonalds. 
Keith
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