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Old 10-13-2004, 05:08 PM   #1
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White grains appear on old aluminum

Hi, I have a Presto pressure cooker from about 1952 that I believe is aluminum. I've had it for over a year, and use it all the time as a pot, only once as a pressure cooker. I hand wash it with liquid dish soap, but when I go to use it next, I find it covered with a coarse white powder-like substance. This has only been happening for a few weeks. If the pot is sitting in a skillet, there is a ring of it there, too. Nothing else in the cabinet has this. Has anyone else had this problem? Could it be the aluminum breaking down? Is it still safe to use, and will it still hold a seal if I use it as a pressure cooker? Thanks in advance for any help.

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Old 10-13-2004, 10:13 PM   #2
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Sounds like either a soap residue or minerals in the water, or it could be a combination of both. Kind of hard to blindly guess which. Does the white powder come all the way up the inside of the pot or just to the level you normally have the cooking liquid?.

Have you changed your dish washing liquid - or if you're using the same brand has it changed since you started noticing this problem; is it a different color, "New and Improved forumla", etc. ??? Of course, the hardness of your water could have changed which would affect how well it rinses off the soap ... but you should also notice more water spots on hand washed and air dried glasses. If you can take a dry towel and wipe out most of the powder - it's probably soap residue.

If a dry towel doesn't get rid of all the powder - wipe it with a damp paper towel, wipe it dry with a dry kitchen towel and check it again when it is totally air dried. If it still has some white residue then it's probably minerals in your water. You can get rid of this by first washing the pot and giving it a quick dry with a kitchen or paper towel - then wipe it out good with a paper towel and white vinegar - then wash it with soap and water again so you don't have acid reacting with the aluminum.

I have a lot of minerals in my water and have a lot of problems with this ... not as bad with stainless steel as aluminum - but I still have the problem any time I boil anything in water.
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Old 10-13-2004, 10:34 PM   #3
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Thanks for your reply. As for the soap, it has happened in the dishwasher, and washing by hand. I have used the 2 detergents for a long time. I hand washed and dried it today, and just checked. There is a small amount of the powder. I will check tomorrow to see if it gets worse overnight. It isn't a water line, because it covers the entire inside and outside of the pot (except handle, which isn't metal), including the grooves around the top edge that seals with the lid. The only thing that has changed is my water. I just moved into a house with a well, but we have a water purification system. The only problem with that is only the cold water goes through it. It filters out minerals well, but it's hard to wash with cold water. Would minerals in the water only affect aluminum? It doesn't happen with my stainless steel pans, or anything else. Only that one pot.
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Old 10-14-2004, 07:44 AM   #4
 
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The white residue will happen every time in the dishwasher. Don't ask me why, but it will!

Handwash your pot with the vinegar, and I bet you will have no more trouble.
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Old 10-14-2004, 06:54 PM   #5
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I think the white stuff is aluminum oxide. Aluminum rust.
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Old 10-14-2004, 07:25 PM   #6
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Quote:
Originally Posted by Psiguyy
I think the white stuff is aluminum oxide. Aluminum rust.
Psiguyy, you are so aptly named. And, no, I'm not joking.
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Old 10-14-2004, 09:11 PM   #7
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I thought about it being an oxidation problem too Psiguyy - except aluminum oxide is generally a very fine powder - like talc - not a coarse powder like Cygnus was reporting.

Anyway, Cygnus - why not email Presto and ask them about it? You can email them at: http://www.gopresto.com/information/feedback.php

Let us know what they have to say.
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Old 10-14-2004, 10:43 PM   #8
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I think it's the same thing. I'm wondering if the pot was wet or was stored in a damp area. I've also seen it form if there is some kind of salt left in contact with the aluminum. The salt tends to absorb water from the atmosphere and the water corrodes the aluminum. It also tends to form where there's an imperfection in the aluminum, such as cracks or pits. Cracks and pits are the last place to dry and by nature, more aluminum is exposed to the air.

Some kinds of corrosion actually protects several metals. Aluminum is one of them. The oxide forms and actually protects the aluminum to a degree. Anodized aluminum is a form of "rust" that does a better then average job of protecting the base metal. When there's an imprefection, such as a pit or crack, the oxide tends to grow into crystals from the points instead of spreading out in a smooth layer that's a few molecules thick. The smooth layer of oxide keeps air and moisture from attacking the aluminum. The imperfections keeps the aluminum exposed to air for a longer period of time. The oxide keeps forming and for lack of a better word, it sprouts out from where these imperfections are.

The older the aluminum pot, the more damaged it gets and the more chance of this white powder forming.

I would take extra time in cleaning these old pots using a brush or scouring pad that will get into the imperfections and I would make sure they are absolutely dry before putting them away.
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Old 11-08-2004, 07:57 PM   #9
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Aluminum and white stuff

Found this thread as I was desperately trying to find out what this awful white stuff is. I first saw it on a old aluminum pressure cooker, too. But now it is all over a brand new Bialetti stovetop espresso machine. In both cases, the white powder forms not as a film, but in very discrete "mounds". They look like hundreds of tiny anthills. I thought it was organic, like some kind of fungus.
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Old 11-08-2004, 08:56 PM   #10
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That's easy homerobert - those are mineral depoits. Soak the affected gizmo in a mixture of vinegar and water (1:10) should do it. Or, if the pimples are small - just wipe the thing-a-ma-jig with a paper towel saturated in vinegar .. when clean ... rinse in hot tawer.
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