Pot Went Black

[bradsbrew]

In your pot's case maybe it could apologise to the kettle

:icon_chickcheers:
I was trying to think of a wity pot, kettle, black, line but couldn't so I had another beer.

 

[SpillsMostOfIt]

I don't agree, yet. Napisan and suchlike things contain around 35% sodium percarbonate (at least the stuff that is close to my hand does). I wonder what the other 65% is and have given the manufacturer an email query to see if I can't find out. I reckon my lack of issues are probably due to the contact time, but wouldn't it be cool if...

I got an automated reply, including (weirdly) a link to their MSDS suppository. The stuff I would use if were cheap enough (no colours or flavours) is described here:

http://www.rb-msds.com.au/uploadedFiles/pd...re-v5-31157.pdf

So, like PBW, the Napisan in question contains sodium silicates, thus conforming to Palmer's *cough* good-to-use list *cough*.

I reckon the offending blackness most likely came from the exposure time, but...

 

[QSR]

Napisan ( sodium percarbonate ) comes in at around 10-11 on the pH scale ( meaning it is high on the alkaline side of the pH scale ) Bleach comes in at around 12 BTW. Aluminium is one of many things that does not like to be left in a high alkaline state like this and has caused a chemical reaction with the aluminium because it was left in this state too long - turning it black. What needs to be done ( which you have already done btw ) is to get this pot back to around a neutral pH level ( 7 is neutral - most drinking water is also near 7pH ). But to get it back around 7ph, you need to use an acid solution to get it there. Vinegar is an acid.......so is lemon juice - rubbing it with a sliced lemon will remove the black because you have changed the ph of the pot. Once you have removed all of the black - you need to also remove the lemon juices from the pot - the best way to do this is with boiling water............and...................DON'T DO IT AGAIN !! :lol:

 

[Gulf]

What QSR said... basically (pun intended) you're slowly eating away at the aluminium and oxide layer. You would have been fine if you didn't leave it overnight.

I think the chemistry is something like the following, but the hydroxide ions come from the deprotonation of water by the (sodium) carbonate (to form bicarbonate ions) in the Nappisan:

http://www2.uni-siegen.de/~pci/versuche/english/v44-10.html


Also... check the labels of all the different brands next time you're in the supermarket. You'll find that "coles/home brand" nappy soaker is not only the cheapest, but contains the equal highest percentage of sodium percarbonate.

 

[user 10246]

Wow, thanks for the replies.

@Bribie, that's a classic.

I tried the lemon juice & it seems to do the trick, only did a small batch, will do the rest tomorrow.

I used the Coles brand one in this case.

I guess the rule is not to soak for any periods then.

Cheers
Goldy

 

[Yeastie Beastie]

In my experience with aluminium pots (currently use one) napisan is not the greatest on porous surfaces.
I did it, it went black also.

Don't stress, clean it with normal dishwashing liquid rinse and sanitize if you are worried about infection etc.
I do it this way and have not had any dramas.

My theory, IMO, clean off any scale etc, wash, rinse, sanitize if you wish and use again.

 

[chappo1970]

Give chap Chap a bell. Pretty sure he done the same thing. I use 100% sodium perc to clean my ali kettle but have never leave it soak due to what happened to Chap .

cheers Brad

+1

Ali ain't stainless you need to give it more consideration to the chemicals you use. Gumption + Elbow Grease + Bone Dry + Gentle sustained Heat = New protective oxide layer

 

[Batz]

I can't be f$^cked reading all these answers, just hit it with a Scotch-Brite, I did the exact same thing with my ali pot.
It's no be deal just a bit of rubbing.

Don't let that put you off ali now.

Batz

 

[Ducatiboy stu]

A strong solution of caustic soda will remove the black layer.... h34r:

 

[user 10246]

Won't put me off Ali Batz :chug:

Will sort it out today

Thanks guys
Goldy

 

[SpillsMostOfIt]

What QSR said... basically (pun intended) you're slowly eating away at the aluminium and oxide layer. You would have been fine if you didn't leave it overnight.

I think the chemistry is something like the following, but the hydroxide ions come from the deprotonation of water by the (sodium) carbonate (to form bicarbonate ions) in the Nappisan:

http://www2.uni-siegen.de/~pci/versuche/english/v44-10.html


Also... check the labels of all the different brands next time you're in the supermarket. You'll find that "coles/home brand" nappy soaker is not only the cheapest, but contains the equal highest percentage of sodium percarbonate.

Found this in my travels:

http://books.google.com.au/books?id=Lskj5k...num&f=false

which suggests that sodium silicate is often added to alkaline cleaners to help prevent etching, which explains its presence in Napisan, etc (and also seems to me to reflect what Palmer wrote). There is clearly something going on because (according to wikipedia, at least) sodium silicate is more alkaline than sodium hydroxide.