Aluminum Pot/oxidation layer is myth?

Everywhere I read in this forum it seems to say that you should never use an abrasive like steel wool on an aluminum pot and that you need to have an oxidized layer on your pot before brewing with it? But, if you search google, and other cooking/cleaning boards steel wool seems to be recommended method for cleaning aluminum cookware. I know people claim that it will leave a metallic taste in your beer but I haven't experienced it. I scrubbed the hell out of my pot with steel wool, (this was before I had heard that I shouldn't) and it polished up really nice. Almost a mirror finish. I figured it would be easier to clean in the future this way. Anyway, I didn't do anything to "season" the pot before brewing other than a quick wash with dish soap to make sure there were no metal flakes left behind and I think the beer turned out fine. I don't taste any metallic flavors at all. In fact, it might be my best IPA yet.

So seriously, where did the idea come from?

Aluminum has a protective oxidation layer, but it reforms as soon as it's removed. As in, almost instantly.

And most people aren't cooking beer with an acidic pH, who post on cookware cleaning sites.

Would you scrub an old cast iron pan with steel wool to remove the decades (or centuries) of carbon buildup?? Just to get it 'nice and shiny'?

I would also NOT use something like steel wool to clean an aluminum pot. For one thing, chances are you left some steel particles behind, no matter how well you rinsed and wiped it.

I would also trust the advise given on a home brewing site, about using an aluminum pot for brewing beer, long before some cooking/cleaning site. Would you trust advise given on an off-roading site when it came to selecting, installing, and using, high end home electronics?

strongest thing i ever used when i brewed in aluminum was a green scrub pad and water, since i cleaned it right after use. when ready to brew again, i'd scrub it again, then iodophor it.

This seems like a lot more of what has been posted many times before. Opinions with no real facts or data to back it up. I'm not saying I know everything because I read a couple other websites or anything. I'm far from an expert on cleaning or brewing. I'm just offering up the idea that it might not be that big of a deal.

Golddiggie said:

I would also trust the advise given on a home brewing site, about using an aluminum pot for brewing beer, long before some cooking/cleaning site. Would you trust advise given on an off-roading site when it came to selecting, installing, and using, high end home electronics?

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I absolutely agree, and do trust most of the advice I've gotten from this board. But technically what we are talking about here is not really brewing. It's the cleaning and care of an aluminum pot. And maybe there are other people out there who know more about that than we do.

lumpher said:

strongest thing i ever used when i brewed in aluminum was a green scrub pad and water, since i cleaned it right after use. when ready to brew again, i'd scrub it again, then iodophor it.

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Why would you iodophor it? You do boil your wort, correct?

malkore said:

And most people aren't cooking beer with an acidic pH, who post on cookware cleaning sites.

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I would think cooking a large pot of chili or something like that would be pretty acidic.

de5m0mike said:

I absolutely agree, and do trust most of the advice I've gotten from this board. But technically what we are talking about here is not really brewing. It's the cleaning and care of an aluminum pot. And maybe there are other people out there who know more about that than we do.

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For as long as I can remember, it's always been best practice to NOT cook acidic foods in un-cured aluminum pots. Just like it's not a good idea to cover acidic foods in aluminum foil if you're going to bake them in the oven (people often add a layer of plastic wrap between the foil and food).

Think about this for a few moments... An aluminum oxide [protective] coating is formed on the inside of the pot by simply boiling water in it. Said protective coating removes the risk, potential, real, or imagined, of anything negative happening from the equation. It also makes it easier to clean. Cleaning off the coating takes much more effort, and time, than simply leaving it there.

You can clean your pots as you wish, saying you get great brews out of it all you like. I think you'll be a very lonely minority in this method. The way I see it, it would be like sand blasting your car every time you wanted to clean it, then getting it repainted. Sure, it will look great, but the cost (time and materials) make it a poor idea (being kind here)...

Also, for cleaning, since this does impact BREWING, this site has better advice. If a science site said to clean your dishes with hydrochloric acid, to get them REALLY clean, would you?

Palmer says it's important and that dude's a metallurgist. I'm going with him.

Honestly what are you doing in your brew pot to warrant such cleaning measures? It takes me all of a minute with a soapy sponge and hot water to get the few hops stuck to the bottom and the break that is baked onto the sides... A quick rinse and it's like new, no scrubbing needed at all.

Golddiggie said:

If a science site said to clean your dishes with hydrochloric acid, to get them REALLY clean, would you?

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Yes. Assuming that the scientists were the expert on the topic, and that they were giving me the best advice they could, based on what they knew. Then yes, I probably would take their advice. Now of course you are giving an outrageous example and I wouldn't expect a scientist to actually say that.

El_Exorcisto said:

Honestly what are you doing in your brew pot to warrant such cleaning measures? It takes me all of a minute with a soapy sponge and hot water to get the few hops stuck to the bottom and the break that is baked onto the sides... A quick rinse and it's like new, no scrubbing needed at all.

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I'm not talking about doing it every time. I bought my pot off craigs list and it was pretty nasty when I got it. I was actually just trying to make it easier to clean in the future by buffing out a nice shiny finish.

g-love said:

Palmer says it's important and that dude's a metallurgist. I'm going with him.

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If that is true, then that is by far the most convincing argument yet. In all of the previous threads on this topic that I had read on HBT, I hadn't seen a comment from an expert (metallurgist) on the topic.

It's true. Check out appendix G in How To Brew. He talks about it there

Anymore, I'm not so sure I buy the aluminum / oxide layer 'thing'.

I have a friend who uses an aluminum stock pot to brew with. I remember having a few of his brews about a year after I started brewing. I didn't know anything about ss vs aluminum but, I remember being taken aback when I found out he used an non-polished aluminum stock pot to brew in. His beers were great!

So, maybe there are other considerations that need to be taken by people who say they get a metallic taste in their beers. My friends aluminum stock pot is non polished aluminum. The surface of it almost seems rough. It has what appear to be microscopic groves all over it. He brews on a stove top, essentially heating the entire bottom of his brewpot all at once. A nice wide area of distribution of heat. It would be different if he were using a turkey fryer propane cooker. Using mine for example, he would get a LOT of concentrated heat directed via flame in a 7 or 8 inch ring in the center of the bottom of his pot. Being that his pot is non polished with those groves, I would think that he would run a greater chance of a metallic taste coming from his pot, literally. I'm not a metallurgist nor a chemist but, wouldn't the expansion of those microscopic groves raise the risk of leaching?

I feel like I am rambling a bit so, think of it this way. You can do this the next time you go camping... I remember being in boy scouts years ago and somebody showing us this. If you take a styrofoam cup filled with water, you can put it in the fire, just over the coals and that cup will take a very long time to melt, if it does at all. However, if you take a styrofoam cup filled with water and apply a flame from a pocket lighter to it, you'll melt right through it. This is what I am trying to convey...

That being said, I would think the people that are LEAST likely to experience this metallic taste would be those using built in heat elements, where there is no 'direct' heat being applied to any surface of the pot. Instead the pot is heated by the water that is inside of it.

Now, I'm curious... lol I'll have to give him a call and see if he'll let me borrow his pot for a weekend. I use an ss pot personally. It would be fun to throw an expensive smash recipe together and see if I can pull off a metallic taste with his pot...

g-love said:

It's true. Check out appendix G in How To Brew. He talks about it there

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Well, I just so happened to have picked up a copy of "How To Brew" today and this is exactly right. Appendix G talks about "Brewing metallurgy" and Aluminum is the first metal discussed.

Once aluminum has taken a seasoning you can pretty much cook whatever you want. It is a new pot that will give you trouble. Restaurants cook many things far more acidic than wort without issue. I too encourage people to read Palmer's information on the subject.

Golddiggie said:

I would also trust the advise given on a home brewing site, about using an aluminum pot for brewing beer, long before some cooking/cleaning site. Would you trust advise given on an off-roading site when it came to selecting, installing, and using, high end home electronics?

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I think we all know what you are trying to say but this analogy is not at all accurate for what is being discussed.

jiggs_casey said:

He brews on a stove top, essentially heating the entire bottom of his brewpot all at once. A nice wide area of distribution of heat. It would be different if he were using a turkey fryer propane cooker. Using mine for example, he would get a LOT of concentrated heat directed via flame in a 7 or 8 inch ring in the center of the bottom of his pot.

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Actually, depending on the propane burner, there would be more distibution of heat from the flame wrapping rather than the limited size of the electric burner under his pot. Either way the point is kind of moot since Aluminum is an excellent distributor of heat and does not tend to develop hot spots.

Cpt_Kirks nailed it. The oxide layer returns very fast after it has been removed. If you take a chunk of aluminum and scrub it with something like a wire brush the brush will kind of slide along the alum. at first. After a few strokes the oxide layer is removed and you will feel the brush really digging into the soft metal. Leave it alone for 15-20min and try again. You will feel that the oxide layer has re-formed.

I bought a big 20 gal alum. pot cheap on craigslist...the thing was old and pretty beat up. I spent about an hour using brillo pads and even some sandpaper, scrubbies, bkf, just about everything I had I threw at it, rinsed it real good and it looks pretty decent, or a hell of a lot better...do I think the steel wool will affect the pot, hell no! As far as the oxidation thing, I agree, the pot oxidizes on its own in the air, and certainly by the second batch it will be well seasoned. I think it is doubtfull one would notice a difference in their first batch...no huge deal either way!

Kriznac said:

Cpt_Kirks nailed it. The oxide layer returns very fast after it has been removed. If you take a chunk of aluminum and scrub it with something like a wire brush the brush will kind of slide along the alum. at first. After a few strokes the oxide layer is removed and you will feel the brush really digging into the soft metal. Leave it alone for 15-20min and try again. You will feel that the oxide layer has re-formed.

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I checked out a few books on Google Books about metallurgy and one said that the oxide layer reforms instantly. I'd call that Myth Busted.

http://books.google.com/books?id=Wb...&resnum=1&ved=0CDkQ6AEwAA#v=onepage&q&f=false

In the first part of this podcast, John Palmer talks about using an aluminum pot and the build up of the oxide layer on aluminum.

http://www.basicbrewing.com/radio/mp3/bbr01-19-06.mp3

de5m0mike said:

I checked out a few books on Google Books about metallurgy and one said that the oxide layer reforms instantly. I'd call that Myth Busted.

http://books.google.com/books?id=Wb...&resnum=1&ved=0CDkQ6AEwAA#v=onepage&q&f=false

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been reading a lot about aluminum pots and still seem a little confused about it

firstly, i still haven't cleaned mine (i know mistake) but I would like to scrub the crusty wort out without damaging the oxide layer -

but no one ever bothered to respond to this post.

Is the myth busted? It seems like it with no responses, but yet I'm still reading about being careful to leave the dark layer intact, and to boil a new pot before use.

Opivy said:

been reading a lot about aluminum pots and still seem a little confused about it

firstly, i still haven't cleaned mine (i know mistake) but I would like to scrub the crusty wort out without damaging the oxide layer -

but no one ever bothered to respond to this post.

Is the myth busted? It seems like it with no responses, but yet I'm still reading about being careful to leave the dark layer intact, and to boil a new pot before use.

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If you are currently making good beer with no off tastes, just keep doing whatever you have been doing since it seems to work.

Me personally, I just use my hand to scrub my pot. If I get a burnt spot on the bottom and have to scrub it off, I will just boil some water in it before using it. If I remember correctly (it's been a while) I have noticed that after scrubbing an aluminum pot. The first time I boil water in it, the pot will have flakes floating in the water.

ive been using an aluminum pot for full boils for the past year. ive never used more thain the soft side of a sponge and some dish soap to clean it. after the first batch using it, it was already well seasoned. every brew came out just dandy. i got a new one from wall mart for $25 a month ago and de flowered it with an irish red ale. i just washed it by hand and went into the brew full tilt. that brew (witch i finished last week) also came out exellent. no metal taste, no oxidation. furthermore the next batch after my irish red ale i brewed in a ss pot. could not find any difference in taste. drinking it right now actually. although the ss pot looks pretty spiffy compared to the aluminum one.

just my input here, but to say there are flavor differences between brewing in aluminum or stainles steel would be splitting hairs. i think someone debating this would be more suseptable to phsycing themselves out and thingking they are tasting something they really arent.

i will say i think it might be possible fo someone to get aluminum, or steel, or any metal to leech into any liquid or food that they cook in that vessel via improper cleaning or care tequniques. i think aluminum might catch the most crap because it is a softer metal thain any other used to cook in.

Palmer, a metallurgist and home brewer, ought to be enough to settle the question for reasonable people open to information, barring any significant information to the contrary. I haven't seen any good information that refutes that metallurgist/home brewer, so I'm going with that. Anyone have any, other than anecdotal?

I just re-read what Palmer had to say about Aluminum in the Metallurgy appendix of how to brew and all he says on the topic is "Don't scrub it" and "Don't use bleach".

I too will trust the suggestions of a Metallurgist homebrewer...however, I've read some pretty interesting extrapolations of these suggestions on HBT, such as:

1. Put your Aluminum pot in a hot oven for 1,2, 3 hours to build up the passive oxide coat.

2. Boil water in your Aluminum pot for an hour to build up the passive oxide coat.

I'm not sure where these came from, but I'm thinking these are pretty much unnecessary and should be put into the "Myth" category, until an expert tells me otherwise. Aluminum will oxidize just fine at normal atmospheric conditions.

Just my 0.02

broadbill said:

I just re-read what Palmer had to say about Aluminum in the Metallurgy appendix of how to brew and all he says on the topic is "Don't scrub it" and "Don't use bleach".

I too will trust the suggestions of a Metallurgist homebrewer...however, I've read some pretty interesting extrapolations of these suggestions on HBT, such as:

1. Put your Aluminum pot in a hot oven for 1,2, 3 hours to build up the passive oxide coat.

2. Boil water in your Aluminum pot for an hour to build up the passive oxide coat.

I'm not sure where these came from, but I'm thinking these are pretty much unnecessary and should be put into the "Myth" category, until an expert tells me otherwise. Aluminum will oxidize just fine at normal atmospheric conditions.

Just my 0.02

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I don't suppose the world will end if you don't do anything to actively promote the oxide layer, and I fully expect that your aluminum will develop one. The OP, though, was looking for information illuminating the question of whether the oxide layer is a myth. Sounds like you weigh in as a "no".

Pilgarlic said:

The OP, though, was looking for information illuminating the question of whether the oxide layer is a myth. Sounds like you weigh in as a "no".

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I suppose the way I asked the question at the beginning may have been confusing or even a little misleading. To clarify, I don't doubt the fact that there is a real oxide layer that builds up on, and protects aluminum. I was really more getting at weather or not we as brewers have to worry about it.

As to whether we need to worry about it I'd give a resounding no. That having been said I never scrub my aluminum kettle. It's UGLY inside and I don't care.

I think......
........I'll drink a beer

de5m0mike said:

Yes. Assuming that the scientists were the expert on the topic, and that they were giving me the best advice they could, based on what they knew. Then yes, I probably would take their advice. Now of course you are giving an outrageous example and I wouldn't expect a scientist to actually say that.

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Beautiful reply. Dito on that.


As for the main issue, you might not have run into an issue with your brew without that oxidized layer (heavy one, not the quick return you get from instantaneous air contact). You might NEVER run into issues depending upon the pH of your water and brews. However, it probably does indeed cause issues for others.

I scrub my pot pretty thoroughly every time, and sometimes use a metal dish scrubber. Not steel wool mind you, but still pretty strong scrubbing. I would say it is good to steel wool a pot when you first get it to make sure it is good and clean, and then not go there again.

I did boil water in my new pot from Home Depot and it made a nice dark layer.

I only ask because it's been over 2 weeks and I still haven't cleaned the pot. (it's got some nice crusty dried stuff inside of it)

and i would hate to waste that much propane boiling another 7 gallons in it.

Research article titled "A simple pre-treatment of aluminium cookware to minimize aluminium transfer to food" from the journal titled: Food and Chemical Toxicology Volume 47, Issue 3, March 2009, Pages 571–577

Results show: "the pre-treatment at 94 °C, which decreases the amount of dissolved aluminium by a factor from 20 to about 60, while the pre-treatment in cold water is ineffective.

This protection of the foil by the pre-treatment is kept during leaching at higher temperature (100 °C)."
and
"The most important feature from Fig. 2 is the drastic hindrance of dissolution by the pre-treatment in near-boiling water. The rate of dissolution of aluminium changes from 5.5 mg m−2 min−1 for no or cold water pre-treatment to 0.13 mg m−2 min−1 for a near-boiling water pre-treatment of 300 min"

Conclusion
We studied the corrosion of alimentary aluminium foils by an aqueous solution of citric acid, simulating the conditions of cooking acidic ingredients as tomato sauce, lemon juice…

Pitting corrosion was detected and can be favored by the presence of precipitates of a secondary phase Al4.01MnSi0.74. The pre-treatment of the foils in boiling (or near boiling) water strongly modifies the passivation layer, giving rise to the growth of a wallpaper of boehmite needles. During a subsequent cooking simulation, this layer inhibits the formation of pits and the main modification is the crystallisation of bayerite.

Our results indicate that for reducing the leachability of aluminium from aluminium cookware into foods and per consequence, also to decrease the daily aluminium intake during the preparation of food, we must boil water in aluminium kitchen utensils (such as pots, pans, and coffee percolators and others) used for cooking the food. Per consequence, the daily aluminium intake will decrease.

The pre-treatment of aluminium utensils for a certain time is very important to protect the public health.

In conclusion, we recommend a change in foods and beverages cooking practices. This could also apply to storage materials.

Hope this helps add some facts to the importance of this practice.
Keep Brewing. Safety First. Fun is a close second.