# Metal soap?

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heres a question Ide just Love an answer to!

the other day I bought one of the blocks of "Soap" made from stainless steel, its supossed to remove the smell of Garlic from your fingers after cutting it up, just by washing your hands with it in plain water.

I thought yeah Right! more Gimic spoof Science garbage.

it was only 50p so I bought it, Ive just tried it and even deliberately rubbed garlic on my hands, IT WORKED!!!!

and yet normal soap hardly shifts it?

anyone know WHY/HOW?

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Nope.

Where did you get it?

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from a local cancer charity shop, they had a basket full of them, but Ive seen them in stores selling for about a fiver!

figured it was worth the 50p to experiment, and I had enough left after all the books I bought.

if they still have any, do yo want me get you one?

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No it's ok - I just found out the steel alloys react with the acids that cause the smell, which means you can use any steel implement!

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Does it dissolve like soap?

 Ah ok, that's less intersting.

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No it's ok - I just found out the steel alloys react with the acids that cause the smell, which means you can use any steel implement!

Hmmm... this then begs the question as to whether Im doing myself a diservice using a stainless steel Wok?

could perhaps the foods taste much more "potent" using something teflon coated or in a Glass pan?

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Does it dissolve like soap?

Over millions of years, I suppose so

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Over millions of years, I suppose so

Well if its solid steal I think it would completely oxidize in a few hundred?

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Wouldn't the oxide layer on the outside protect the chewy goodness on the inside?

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Whether steel oxidises will depend alot on how wet it is.

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Wouldn't the oxide layer on the outside protect the chewy goodness on the inside?

I dunno. I wouldnt think so because if youre constanty rubing it on yourself then it would break up the layer of oxide.

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I might be thinking of aluminium. It's been a while since I did metals chemistry.

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I can just picture that soap-on-a-rope being used as a weapon in prison showers.

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Wouldn't the oxide layer on the outside protect the chewy goodness on the inside?
mmMMmmm stainless arghglarghhh
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Yeah aluminium. The dull white appearance is the aluminium oxide.

The oxide layer on steel in the rust, which doesn't really look like it does much to protect the underlying layers.

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• 3 months later...

Update:

dont bother unles you have to, Ive found that rubbing your fingers on the Chrome plated tap nozzel works just as well as the metal block!

I only know this because I misplaced the "soap" and couldnt find it, and thus fifured the taps would do just as well, they DO! ))

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Hmmm... this then begs the question as to whether Im doing myself a diservice using a stainless steel Wok?

could perhaps the foods taste much more "potent" using something teflon coated or in a Glass pan?

Teflon could be dangerous. I heard somewhere that poorly made teflon pans can chip, and teflon gets in your food, and you don't want that in you system. However, cast iron is good. It adds some iron to your diet.

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Hi.

The reason that stainless steels are corrosion resistant, even though

they consist mainly of iron, is because they contain a minimum of 12%

chromium, usually along with some other metals.

Ordinary iron and steel alloys rust quickly because atomic iron is much

smaller than oxides formed by interacting with atmospheric oxygen and/or

oxygen dissolved in water. The oxides formed during rusting create a loose

layer that flakes away, exposing fresh metal to the corrosion.

Chromium, along with other metals ( such as nickel ), are added to

stainless steel alloys to help improve physical propeties and corrosion

resistance. The chromium in the stainless steel combines with oxygen,

forming a very thin passive film of chromium-containing oxides.

The sizes of chromium atoms and their oxides are similar, so they bind

together on the surface of the metal, producing a thin oxide layer only

a few atoms thick. If the surface is rubbed or damaged and the passive

film is broken in air or water, more chromium oxides will immediately form

and recover the exposed metal substrate surface, protecting it from

further oxidative corrosion. Note that the oxide film is not physically

strong, it just forms rapidly, and weakly adheres to the alloy, thus

protecting the metal below from further corrosion. It can be disrupted

and displaced easily by abrasion, so many common stainless steels aren't

suitable for corrosive situations where the surface is continually swept,

and special alloys, with other elements are used..

The passive film requires oxygen to self-repair, so stainless steels can

have poor corrosion resistance in situations where there is limited oxygen

or other elements or species will compete with the oxygen. The smelly

active sulphur species in garlic and onions; the volatile selenides in

garlic, cabagge, and broccili; and also the chlorides in salty water will

all attack and destroy the passive film of most stainless steels more

quickly than the film can be repaired in a low oxygen environment.

Some of the smelly compounds will bind to your hands ( onto proteins,

lipids etc ) and will become non-volatile ( non-smelly ), but the number

of binding sites is limited, hence any excess of smellies results in

smelly hands.

By binding to the metals in the stainless steel bar, the unbound smelly

compounds on the surface your hands are transformed into non-volatile

( and thus non-smelly) compounds and complexes on the surface of the

stainless. The new surface layer, which is weakly adhering and fragile,

will be continuously abraded off by the active rubbing of the bar and

replaced by oxides using oxygen from air or water.

For many stainless steel items, especially those in contact with chemicals

or water, passivating metal finishing processes are applied ( such as

treatment with nitric acid ) when fabrication is complete. This ensures

they start life with a good, thick layer of oxide. Otherwise corrosion

may start in any crevices, scratches, or heat-affected areas ( welding ),

and unprotective deposits ( eg smutty black sulphur layers ) may form in

low oxygen environments, such as water.

(by Bruce Hamilton)

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I guess this plays into it somehow. My dad told me about this when I was young - I haven't heard it discussed recently.

When he would machine stainless, and then handle the finished part - it would corrode where he touched it. He was told that he had too much acid in his body - people who had this problem would take a very small amount of milk of magnesia daily - not enough to cause any severe gastrointestinal eruptions.

Any chemists want to speculate on why that works?

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