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MessierScott
sage


Reged: 06/18/07

repair of slightly rusty iron meteorites new
      #5807471 - 04/18/13 06:51 PM

OK, sorry if this has been asked before, but a search didn't get me much. A search for "rust" brought up every thread, and a search for "rusty" brought up only two. Weird!

OK, so I have several iron meteorites that I've had for several years. A couple of them are starting to show a little surface rust.

I typically rub a little light lubricating oil on them all many once a year. And they get a lot of handling by people at outreach events, so they get a lot of human oils on them as well.

One of the meteorites that I bought was sprayed by its previous owner with a clear coating, but all that did was seal any moisture in, and now large chips of that are flaking off.

So I figured that I just do a little scrubbing with a little wire brush on the ones now showing a bit of rust and just lube them up again.

But is there anything else I should be doing?

Thanks!


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lee14
super member


Reged: 12/19/09

Re: repair of slightly rusty iron meteorites new [Re: MessierScott]
      #5808742 - 04/19/13 02:06 PM

Almost all irons will rust naturally with exposure to the atmosphere, and oil can effectively seal that out and slow the process. As you said, water alone will not cause rust, but it is a catalyst in the oxidation reaction. Practically though, water also contains dissolved oxygen, so rust can proceed due to trapped moisture even if the surface has been coated with oil. Normal rust is best minimized by removing any loose flakes, heating the specimen, and then applying oil. The best oil I've found is gun oil, specifically G-96 brand, commonly available online from sporting goods outlets.

The second variety of surface degradation through rusting involves lawrencite, formed by the presence of chlorine, producing ferrous chloride, which through a series of reactions produces hydrochloric acid, which again serves to accelerate the corrosion process. The chlorine is due to terrestrial contamination, and if the lawrencite reaction is indeed occurring, you will generally see small yellow-green droplets of liquid collecting on the surface. To prevent further degradation, the chlorine can be removed by a variety of chemical processes. Many dealers consider these proprietary, but effective ones can be found by an internet search. An appropriate solution will be one that allows the chlorine to combine with another element (such as sodium) which can then be removed from the specimen by washing. The use of anhydrous alcohol is often recommended for this, but is really unnecessary, since the alcohol will readily absorb moisture from the atmosphere anyway. It is perfectly acceptable to use distilled water for washing after the chlorine is neutralized, and again, mild heating is employed to dry the specimen, applying the oil coating as soon as the piece is cool enough. Never use tap water in any step of rust mitigation because it always contains chlorine.

Lee

Edited by lee14 (04/19/13 02:12 PM)


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Dick Lipke
professor emeritus
*****

Reged: 02/20/07

Loc: Marine City,Mich.
Re: repair of slightly rusty iron meteorites [Re: lee14]
      #5812906 - 04/21/13 11:56 AM

www.paleobond.com/Meteorite_Info.html

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