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I use a big aluminium pot to boil water. I think the water contains iron because after 4-6 months, the inside of the pot is full of brown stains. The colour is just like ferric. There are lots of circular brown areas (1-4mm diameter) in the pot.

  1. Is this stain caused by the iron in the water? If not, what is the cause?
  2. How can I remove these stains?
  3. Can I do anything to prevent these stains in the future?

Pictures

At the side Stain in real color Stain close up at the bottom of the pot

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Shiplu Mokaddim
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2 Answers2

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If it's rust stains or other kinds of scale build up, CLR will take care of it:

http://www.jelmar.com/CLRbasic.htm

From the pictures (thanks for adding) it looks like sediment from the water (source, pipes, etc) and CLR cleans it easily. Just don't breath the fumes.

Also, you can try commercial coffee pot cleaners such as http://www.urnex.com/ to remove the build up.

Finally, if none of the above is available in your area, try Vinegar first. If that didn't work, wash off and switch to baking soda. you may have to make a paste and let it treat for a while.

There is also this recipe for cleaning rust stains from aluminum pots, though I haven't tried it.

MandoMando
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  • How exactly would an ALUMINIUM pot rust? Even if it was building up aluminium oxide, he wouldn't want to clear it off since it will just reform. Not to mention that aluminium oxide couldn't form under water in the usage conditions he described. – sarge_smith Mar 13 '13 at 17:28
  • @sarge_smith ALUMINIUM corrodes but not like Iron. The rust I'm referring to is external to the pot. As in Iron existing in the [water](http://www.idph.state.il.us/envhealth/factsheets/ironFS.htm), the pipes, or even an overused spatula. In some places the rust can build up in a matter of days. You might have also seen an under-used bathroom where the ceramic looked like it was rusting. Did you ask yourself there how could CERAMIC rust? – MandoMando Mar 13 '13 at 18:00
  • That rust isn't rust, it's scale. It's what's formed by the evaporation of water and the mineral deposits that the process leaves behind. While this gentleman's issue might be scale (I doubt it actually, but anything is possible), it definitely isn't rust. Once again, unlike with many other metals, when aluminium corrodes into aluminium oxide, it forms a dull barrier that protects the aluminium. That's because it remains bonded to the surface until you remove it. It's almost as good a protecter as anodizing. Of course, almost all aluminium cookware sold is anodized so (cont) – sarge_smith Mar 13 '13 at 18:20
  • it's unlikely that's a major issue either. This answer could apply to certain types of cookware (Like unseasoned cast iron), but I would be astonished if it could apply in this particular case. – sarge_smith Mar 13 '13 at 18:22
  • @sarge_smith have a look at the pictures on [this post](http://www.homebrewtalk.com/f36/rust-aluminum-kettle-287890/) and speculate about what you see. – MandoMando Mar 13 '13 at 19:18
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    From Wikipedia: `...a thin surface layer of aluminium oxide that forms when the metal is exposed to air` so the oxide is almost always present and the above answer is NOT about aluminium rust. It's about Iron Oxide staining an Aluminium pot. – MandoMando Mar 13 '13 at 19:28
  • You are wrong. I'm tired of talking about it. Have a great day! – sarge_smith Mar 13 '13 at 20:14
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    I have added some pictures – Shiplu Mokaddim Mar 13 '13 at 21:04
  • I tried Baking soda. It fails. So I think something Acidic might help. I am quite unsure about Vinegar. The bottled Vinegar I bought is already 10% solution. But after some searching I found water and vinegar should be mixed in 2:1 ratio. Should I used 100% vinegar here? If I use 10% vinegar it'd be 3.3%. – Shiplu Mokaddim Mar 15 '13 at 21:42
  • BTW, do you think quicklime could help here? The big problem is local shop keeper dont understand these standard names. and I dont know all the local names these cleaning chemicals – Shiplu Mokaddim Mar 15 '13 at 21:46
  • No sure. Quicklime gives off heat when mixed with water, if you try it, careful not to burn yourself. – MandoMando Mar 15 '13 at 22:51
  • The vinegar ratio is fine. Just heat up the mixture and let it run for a while. You can try lemon/lime juice as well (better smell). Give it lots of time. – MandoMando Mar 15 '13 at 22:55
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It's hard to say what is causing these stains without more information about exactly how you are using the pot. If you are just using it to boil water and nothing else, then the stains could be a result of the minerals in the water in your area. Also, if you are just using the pot for water, do you wash the pot in between uses? Repeated exposure to moisture can cause an oxidation layer to form on the surface of the metal. Cleaning the pan thoroughly between each use should help prevent oxide buildup.

The stains could also be caused by what you are using to clean the pot. Aluminum is a fairly reactive metal; so any acidic compound or residue that gets left on the material for too long is likely to cause a stain. You can read more about how to take care of your aluminum cookware here:

http://www.jesrestaurantequipment.com/jesrestaurantequipmentblog/cleaning-aluminum-cookware/

Hayden Fennell
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