Why did the salt on the skin of my turkey react with the aluminum foil it was touching?

Question

I sprinkled salt on my turkey skin and left it to dry out over night. It was covered with aluminum foil. The next morning the aluminum foil had holes ‘burnt’ in it and the turkey skin turned silver at the spots where the salt crystals had touched the aluminum foil. Was my turkey poisoned with aluminum at this point? I did not eat it to find out.

Answer 1

If you don't mind, I'll start with a more colloquial and hopfully not to lengthy explanation:

Precious metals, such gold, do not corrode under "household conditions", others, such as iron or aluminium do. Rusting of iron is a typical example. Here, the corroded surface often is very porous and the corrosion carries on until the whole piece of metal is turned to rust (oxidized).

In the case of aluminium, the initial corrosive layer is very tight and serves as a protection for the rest of the aluminium foil. Such a very thin and transparent protection layer often is artificially applied. The item are sold as Eloxal (= electrolytically oxidized aluminium).

Now comes the table salt, which is sodium chloride ($\ce{NaCl}$). Sodium chloride is hygroscopic, it "attracts" the water and that's why you sprinkled it on the turkey. It is also very soluble in water. When it dissolves, sodium $\ce{Na+}$ and chloride $\ce{Cl-}$ ions are formed.

The chloride ions attach and move into the protective oxide layer of the aluminium foil and finally induce the corrosion of the aluminium metal. Aluminium ions are released to the water (= the wet surface of the turkey).

For a more scientific, in-depth explanation of this corrosive processes known as pitting, you might want to have a look at this article or this review.

Was my turkey poisoned with aluminum at this point?

There seem to be some crazy myths concerning the "toxicity" of aluminium (ions), often spread by opponents of immunization and other quacks.

Fact is that

• a healthy human body is capable to excrete aluminium ions though the kidneys
• the British Alzheimer Society does not see any convincing relation between the uptake of aluminium and Alzheimer's Disease
• the cancer information service of the dkfz (Deutsches Krebsforschungszentrum, German Cancer Research Centre) refutes the aluminium induced breast cancer myth
• many antacids do contain aluminium hydroxide as one ingredient. The effect of "poisoning" is not known.

In summary:

1. Yes, aluminium ions were released to the wet surface of the turkey.
2. There's no reason to assume that the turkey is "poisoned".

Answer 2

You asked:

Was my turkey poisoned with aluminum at this point?

I don't know. But I do know that it's not recommended for you to combine salty foods and aluminum foil in the future.

In Germany, the Federal Institute for Risk Assessment (BfR) wrote an article named "FAQs about aluminium in food and products intended for consumers". I shall quote a bunch from that article; the discussion of aluminum and salt is at the very end of my post.

What health risks does aluminium absorption pose?

Any assessment of the hazardous potential of aluminium focuses is on its effects on the nervous system and the fact that it is toxic to reproduction (effects on fertility and unborn life) as well as the effects of aluminium on bone development.

When aluminium is ingested with food, its acute toxicity is low. ... But even in healthy individuals, the light metal accumulates in the body in the course of a lifetime, especially in the lungs and the skeletal system.

...

What quantities of aluminium can be absorbed ... without any health risks?

For oral intake from food, the European Food Safety Authority (EFSA) has derived a tolerable weekly intake (TWI) of 1 milligramme (mg) of aluminium per kilogramme of bodyweight.

Finally, later in their article, they touch upon mixing aluminum with salty foods:

Why can aluminium be transferred to food from packaging or tableware?

Aluminium is soluble under the influence of acids or salt. For this reason, packaging and containers used for food such as beverage cans, yoghurt cup lids and aluminium containers for fruit juice are coated on the inside to prevent transfer of aluminium ions to the food or drink.

Aluminium from tin foil can be transferred to foods containing acid and salt. For this reason, the BfR recommends that acidic and salty foods are not wrapped in aluminium foil.

Answer 3

You might want to look at what happened to people involved in the mass Aluminium Sulphate poisoning event in Camelford, UK. http://www.bbc.co.uk/news/uk-england-cornwall-17367243 Alzheimer's-like death and illness.