FYI....If you leave a scratched aluminum Teflon coated pan in soapy water, the Teflon will slowly flake off bit by bit. Soap reacts with aluminum to form atomic hydrogen. Atomic hydrogen is a very small atom that actually moves into the aluminum pan's metallic structure where it eventually meets up with another atom of atomic hydrogen. The resultant molecule that forms when the two atoms meet is what we know as molecular hydrogen (or H2 gas). The hydrogen gas thus formed by the combination of the two atoms greatly increases the size of the molecule such that it can no longer move into the metallic structure. It is the accumulation of this hydrogen gas between the Teflon layer and the aluminum layer that actually lifts the Teflon off of the aluminum pan. This phenomenon is known as "hydrogen blistering". This is a corrosion mechanism that large petroleum refineries must deal with in certain operating equipment.
Bottom line........If you want your Teflon lined aluminum pans to last longer, do not let them soak is soapy water.
The teflon coating will flake off if you do. Iwonder why the pan manufactures don't tell us consumers about this????

Dan

I got that information from my former career dealing with metal corrosion issues in a major petroleum refinery. Hydrogen blistering is one of the corrosion mechanisms of aluminum and iron.

Hydrogen blistering in iron is caused by a chemical reaction usually associated with cyanides in sour (hydrogen sulfide containing) water. Atomic hydrogen forming then converting to molecular hydrogen is what causes the blisters to form.

Aluminum reacts with alkaline materials......soaps, caustics, even wet concrete....... to form atomic hydrogen which subsequently forms hydrogen gas which can blister coated aluminum. Sort of like iron oxidized to rust can flake off paint.

I first learned of this back in 1976. I was the lead chemist in investigating the cause of a minor explosion in an electrical panel box that was located in a remote area completely away from any source of hydrocarbons. When I sampled and tested the gas inside of the electrical box after the incident I found Hydrogen. We had no idea where hydrogen could possibly be coming from. Upon further investigation, it was discovered that new six inch aluminum electrical conduit had been laid for a major expansion project in the refinery and was tied into the electrical box that had exploded. The source of the hydrogen was traced to soap that was used to lubricate the huge electrical wires so that it could be pulled through the aluminum conduit that was encased in concrete and buried underground. The soap was generating combustible hydrogen.

Also, hydrogen was formed in some conduit pipe that had been laid in wet concrete. Wet concrete is alkaline and when aluminum is encased in it, hydrogen gas forms inside of the conduit and carries itself up and into the electrical boxes where there can be a source of ignition. The wet concrete "outside" of the conduit was also generating combustible hydrogen "inside" of the conduit. It does this by the atomic to molecular mechanism cited above.

The concrete would eventually dry and stop producing hydrogen. However, the soap that was inside of the conduit could and would produce hydrogen anytime in the future whenever any water made it way into the conduit. We couldn't take a chance with this type scenario; so, we ripped out all of the aluminum conduit and wires and started over.

It was a very revealing finding which cost our company many millions of dollars to repair. The soap which was used was from a major company (Teflon manufacturer) that had certified that it was OK for aluminum service. Fortunately we were able to identify the problem fairly early in the project and did not delay it too long. Engineering specs changed as a result of this incident and it is now impossible for this to happen again.

One does not forget such an incident and I can't help but apply chemistry to the cooking that I do.

Dan

You probably don't see a problem now because the surface on your Teflon pans have not been scratched to the metal surface because you do not abuse your cookware. Those that use a knife to cut foods in a Teflon coated pan will expose the aluminum layer beneath. Any soaking of the pan in any alkaline soap will cause pit corrosion to occur in the pan around that cut. The resultant hydrogen blistering that forms at that site will slowly but surely flake off additional Teflon coating. How fast this occurs depends on the pH of the soapy solution, the amount of soap used, and how long you let it soak. Once it starts faking, additional soaks speed up the deterioration of the Teflon coating.

Don't cut food in a Teflon coated pan and don't soak too long using soapy water and your pans will last much longer.

I collect cast iron and frequent many flea markets and garage sales in search of new pieces. I often see aluminum cookware that has abused by the previous owner. Many of the old cast aluminum pots have severe pitting in them that obviously was caused by frequent soakings in soapy water. Acidic foods can cause damage too, but soaking in soapy water for extended times causes more damage.

Dan