Black stuff on freshly bought steel - healthy?

[CrazyModder]

Some types of steel (warm rolled, I guess) come with a black coating, which is obviously a result of the manufacturing method. As far as I can tell, according to Wikipedia, this is stuff like Hematite or Magnetite (i.e., iron oxides), and it is pretty tough - i.e., not something that will flake off etc., but it sticks where it is and is also a pretty good rust preventer, as long as the piece stays rust-free. As far as I can tell, one way to remove it is by giving it a good long soak in readily available citric acid, although I have not tried it yet and don't know if it is completly "shiny" afterwards (I assume not).

I am currently working on a roasting drum, which obviously does come in contact with food (coffee beans, in my case). I am not too squeamish in this regard, but does anyone know if that black coating is a health problem, or if it is completely harmless? The roast drum (which is freshly bought and looks pretty pristine, i.e., shiny black, not scaley-flakey) will obviously be washed down as best as possible to get rid of any other possible residues. Also, the first few roastings will be thrown away anyways since it is unlikely that the temperature will be gotten to the right point from the get-go (I have experience with other roasters of the kind, this is just the newest generation for me ;) ).

I found explicit sources that say at least Magnetite is non-toxic (medicinal uses), FeO and Fe2O3 are FDA-approved in cosmetics, Fe3O4 is used in medicine, and I never saw any remark anywhere that iron oxides / rust is are unhealthy (no, I do not suggest drinking the PCB etching stuff ). No-non-stick (traditional) iron pans don't pose health problems, rusty barbecue grills have been spotted in the wild, etc. Last but not least, as only the surfaces of the beans are actually in contact with the metal, and then the water is only pressed through the ground stuff, I guess anything that rubs off will be in homeopathic dilution anyways.

Anyone got anything else to add to my thoughts, to keep me a long-lived healthy coffee guzlling mad modder?

[rleete]

That stuff is referred to as scale.  No, it is not harmful.  You need a certain amount of iron in your diet, and that is (mostly) what it is.  I wouldn't go chipping pieces off and easing it, but whatever comes in contact with the beans should not pose any hazard.

I'd be more concerned of loose pieces coming off, getting mixed in with the beans, and ruining the blades of whatever grinder you use.  A good wire brushing should remove any loose scale. 

[CrazyModder]

Yeah, there is no lose scale and it looks pretty clean.

In my experience, after a while, these drums tend to be coated with residues from the roasting process (like iron pans - the beans contain some oils), which seems to keep them from rusting inside. So I don't expect flakes to occur, plus they will be sucked off in a later stage (coffee beans develop lots of small flying flakes of their own, which have to be evacuated anyways). Thanks for mentioning it though, I might inspect the inside of the drum once in a while to be ready if it should happen.

[vtsteam]

If it's objectionable, salt and vinegar will remove it over about 24 hours or so if kept warm and covered. Faster if heated.

[sparky961]

If it's objectionable, salt and vinegar will remove it over about 24 hours or so if kept warm and covered. Faster if heated.

When you're done with it, do you sprinkle it on your fries?

[trevoratxtal]

Look at the ingredients on a bottle of Ironbrew the north country fizzy drink.
I think it is the same as scale.
Trev

[RobWilson]

Look at the ingredients on a bottle of Ironbrew the north country fizzy drink.
I think it is the same as scale.
Trev

 


Rob