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Post by pathwinder14 on Sept 17, 2012 6:04:00 GMT -7
So I purchased 3 stainless steel canteen nesting cups for US style canteens.
They have a dull grey coating on them. Does anyone know what this is?
Thanks
-path
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Post by mud on Sept 17, 2012 12:03:03 GMT -7
You sure they are stainless? My aluminum ones had that and a little sos pad tttok it right off.
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Post by cowgirlup on Sept 17, 2012 16:35:38 GMT -7
I haven't seen stainless with any type of coating. Put a magnet to it and see if it sticks.
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Post by wtrfwlr on Sept 17, 2012 16:44:29 GMT -7
Cowgirl is right, if it's Aluminum or Stainless the magnet wont stick. Unless it is a real low grade Stainless...correct me if I'm wrong on the SS cwi555.
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Post by pathwinder14 on Sept 18, 2012 4:06:28 GMT -7
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Post by Cwi555 on Sept 18, 2012 4:50:23 GMT -7
Cowgirl is right, if it's Aluminum or Stainless the magnet wont stick. Unless it is a real low grade Stainless...correct me if I'm wrong on the SS cwi555. Magnets will stick to many grades of stainless. Especially high nickel 400 series. Ferrite (iron), Nickel, and cobalt are considered ferromagnetic materials in that they exhibit a strong attraction to magnetic fields and are able to retain a magnetic field after interaction with an external magnetic field. Paramagnetic materials (stainless 300 series/biomagnetism/magnesium, molybdenum etc) are slightly attracted to magnetic fields, but do not retain the magnetic field after the fact. Diamagnetic materials are slightly repealed by a magnetic field and the material does not retain any field after the fact. Most of the periodic table is diamagnetic. Examples are gold, copper, silver etc. All ferromagnetic materials contain what is known as magnetic domains. This is when the atomic dipoles are coupled together in a preferential direction. 300 series stainless, and some 400 series stainless are predominantly iron. Up to ~85 percent iron in some cases. What makes them stainless is a thin layer of chromium oxide on the surface, therefore, they are not 'stainless', but rather stain resistant. (stain being analogous to oxidation). Those magnetic domains do not line up properly in 300 series due to the mixture of diamagetic and paramagnetic materials in their chemistry. However, and especially with 304 'stainless' too much heat can cook off some of the chromium in it preventing the formation of the chromium passivation layer which will then allow the ferrite content to 'rust' or the creation of ferro-oxides. Now as to the OP, if they are not new, they could have been subject to heat leaving a slight oxidation problem. If they are new, it is most likely they were not properly cleaned post pickling. (chemical processing to stabilize the stainless). Suggest you get a bottle of lemon juice and keep them coated in it for 3 days. You can also use Coolaid non sweetened mix but reduce the water content by half and just let it sit for 5 days in that mix. If it is something left over from the processing, that should clear it up. The attached picture displays the resulting color changes from loss of purge during welding. The varying shades increasing in darkness represent increased levels of chromium carbides and how sensitive stainless is to excessive heat. Attachments:
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Post by pathwinder14 on Sept 18, 2012 5:21:43 GMT -7
You can also use Coolaid non sweetened mix but reduce the water content by half and just let it sit for 5 days in that mix. If it is something left over from the processing, that should clear it up. I presume color/flavor does not matter? Being stainless it should not stain it. What about sanding? If I use 220 grit it should come off. If it is not residue from the mold/casting process and is in fact some sort of minor heat related oxidation, will successive periods in the campfire cause it to re-heat oxidize in the future? Do I want to remove it? |
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Post by Cwi555 on Sept 18, 2012 5:48:51 GMT -7
You can also use Coolaid non sweetened mix but reduce the water content by half and just let it sit for 5 days in that mix. If it is something left over from the processing, that should clear it up. I presume color/flavor does not matter? Being stainless it should not stain it. What about sanding? If I use 220 grit it should come off. If it is not residue from the mold/casting process and is in fact some sort of minor heat related oxidation, will successive periods in the campfire cause it to re-heat oxidize in the future? Do I want to remove it? If it was not properly treated at the factory, no amount of sandpaper will help it. The grey color that you describe leads me to believe that is the most likely case. Try the lemon juice treatment. (citric acid), or the coolaid one (absorbic acid). See if that doesn't take care of it. Or you could just leave it alone. I do know that if it's actually aluminum (which most of those are) the dull grey should come off with a copper brillo pad. |
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Post by pathwinder14 on Sept 18, 2012 6:09:26 GMT -7
If it was not properly treated at the factory, no amount of sandpaper will help it. The grey color that you describe leads me to believe that is the most likely case. Try the lemon juice treatment. (citric acid), or the coolaid one (absorbic acid). See if that doesn't take care of it. Or you could just leave it alone. I do know that if it's actually aluminum (which most of those are) the dull grey should come off with a copper brillo pad. It is slightly magnetic. Is aluminum magnetic in any way? I scratched at the surface and scratching does remove it. I'll try one with sandpaper and another with cool aid. I'll let you know what happens. Thanks for the help. |
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Post by Cwi555 on Sept 18, 2012 19:02:59 GMT -7
If it was not properly treated at the factory, no amount of sandpaper will help it. The grey color that you describe leads me to believe that is the most likely case. Try the lemon juice treatment. (citric acid), or the coolaid one (absorbic acid). See if that doesn't take care of it. Or you could just leave it alone. I do know that if it's actually aluminum (which most of those are) the dull grey should come off with a copper brillo pad. It is slightly magnetic. Is aluminum magnetic in any way? I scratched at the surface and scratching does remove it. I'll try one with sandpaper and another with cool aid. I'll let you know what happens. Thanks for the help. Aluminum is diamagnetic. You've eliminated the possibility of it being aluminum. You've also proven its either poorly treated 300 series or a low grade 200 series stainless. Either way, the best way to clean it up is chemically. You may also try lemon juice soaked in a scotch brite pad. |
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Post by pathwinder14 on Sept 19, 2012 4:07:54 GMT -7
It is slightly magnetic. Is aluminum magnetic in any way? I scratched at the surface and scratching does remove it. I'll try one with sandpaper and another with cool aid. I'll let you know what happens. Thanks for the help. Aluminum is diamagnetic. You've eliminated the possibility of it being aluminum. You've also proven its either poorly treated 300 series or a low grade 200 series stainless. Either way, the best way to clean it up is chemically. You may also try lemon juice soaked in a scotch brite pad. I also noticed that after handling it, my fingerprints are all over it. Could that be from the oils in my skin? Do you know of anyone in the St. Louis area that could do an analysis of the outer material? I have built up a small pile from sanding one of the cups. |
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Post by Cwi555 on Sept 19, 2012 17:32:46 GMT -7
Aluminum is diamagnetic. You've eliminated the possibility of it being aluminum. You've also proven its either poorly treated 300 series or a low grade 200 series stainless. Either way, the best way to clean it up is chemically. You may also try lemon juice soaked in a scotch brite pad. I also noticed that after handling it, my fingerprints are all over it. Could that be from the oils in my skin? Do you know of anyone in the St. Louis area that could do an analysis of the outer material? I have built up a small pile from sanding one of the cups. It would not be worth it. Most of the people with the capability charge a minimum of 200 and thats if you bring it to them and they use a niton xray diffraction unit. It goes up exponentially from there. For what your after, it would run ~1,000 to 7,500 depending on the detail. The sanding won't work if the metal is not properly pickled as mentioned before. |
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Post by thywar on Sept 19, 2012 18:41:52 GMT -7
Pathwinder, I'm not nearly as smart or knowledgeable as CWI but I CAN solve your problem and without a lot of expense or time.. Take those cups to the sink, rinse them out (wash them if you feel so moved), fill them with water, drink the water and if it doesn't taste like crap then pack em up and use them.. if HOWEVER they do taste like crap, throw them in the trash, chalk it up to experience and buy a real stainless steel cup.. for a lot more money.  Like the U.S. Government, I'm just here to help. No, No Please.. no thanks necessary |
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Post by pathwinder14 on Sept 20, 2012 3:37:01 GMT -7
It would not be worth it. Most of the people with the capability charge a minimum of 200 and thats if you bring it to them and they use a niton xray diffraction unit. It goes up exponentially from there. For what your after, it would run ~1,000 to 7,500 depending on the detail. The sanding won't work if the metal is not properly pickled as mentioned before. You sir are a wealth of knowledge. Thank you for all your help. ... chalk it up to experience and buy a real stainless steel cup.. for a lot more money. Like the U.S. Government, I'm just here to help. No, No Please.. no thanks necessary  You're plenty smart. Pragmatic is the most useful approach. It's just now more of a curiosity for me. |
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Post by pathwinder14 on Oct 3, 2012 8:47:11 GMT -7
Well I have sanded each of them down and soaked them in lemon juice. I figured I'd over-kill teh process. Better safe than poisoned. |
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Like the U.S. Government, I'm just here to help. No, No Please.. no thanks necessary
You're plenty smart. Pragmatic is the most useful approach. It's just now more of a curiosity for me.