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Help needed - "rust" on a JAH-055 OC L4-5 or?

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#1 ZielkeNightsky

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Posted 04 January 2014 - 05:30 PM

Hi

A few years ago I bought a beautiful slice of Jiddat al Harasis 055 (OC L4-5). The specimen was perfect last year.

My annual review of the collection showed that my JAH 055 slice, is now in very poor condition. I certainly looks like rust, but I think there's more to it.

So the question for the experts. What is happening and can I restore and stop this?

The problem
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under the microscope - low power
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The Glory Days
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#2 lee14

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Posted 04 January 2014 - 09:09 PM

I'm not familiar with this particular meteorite, but this is a clear case of what used to be known as 'lawrencite disease'. The globules of moisture on the surface are a clear indicator of chlorine contamination. The iron in the specimen has formed ferric chloride, which is absorbing water from the atmosphere to produce, among other things, hydrochloric acid which is accelerating the formation of rust. I would expect the previously discussed methods of removing the chlorine would be effective here as well, but I must admit to never having used the process on a chondrite. The NaOH could possibly react with some of the other minerals that are present. On the other hand, the piece is so degraded that a little experimentaion might be in order. You might try suspending the piece so that only a small portion is immersed in the solution for a few days. If there are no signs of any unwanted reactivity, you could proceed with the treatment as if it were an ordinary iron. Of course you'd have to refinish the surface, but I know you're certainly up to that!

Lee

#3 ZielkeNightsky

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Posted 05 January 2014 - 09:19 AM

Thanks Lee

So this is how lawrencite disease looks like. Well I'm going all in, After cleaning and some sanding to remove the rust and droplets, I've wrapped the slice lightly into alu-foil and dropped it in a jar with distilled water. The jar with the distilled water, alu-foil and slice is then heated in water-bath to almost boiling. Last a teaspoon of sodium carbonate and the process begins.

It will stay there for the next couple of hours, then cleaning and another run and so on.

I'll keep you posted.......

Hopefully my fist and last specimen with lawrencite disease.

In the meantime I'll acquire some more meteorites. I'm expanding in the iron department at the moment. Also looking for a small Almahata Sitta sample with a little crust and a with all the fuss about Katol a few days ago, a small slice of that too. Collecting seems to be a "fever" that can't be cured, only treated for the symptoms by acquiring more sample :lol:

#4 lee14

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Posted 05 January 2014 - 10:35 AM

I've never used that process, I'm very interested to know how effective it is. I'm not sure what function the aluminum plays, but I'm pretty sure the sodium from the carbonate will replace the iron in the ferrous chloride and ferric chloride, where it can be removed with the solution. Good luck!

Lee

#5 rfinney

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Posted 05 January 2014 - 04:30 PM

Lars:

Thanks for this thread - please send updates!

- RF

#6 ZielkeNightsky

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Posted 05 January 2014 - 05:56 PM

Hi

Here's the first update.

The process I used was this:
Galvanic Cleaning

Today the slice was cleaned, sanded a little and dropped in the sodium carbonate solution 3 times for two hours. The cleaning was done cleaning gasoline, alcohol and WD-40 - in that order.

The hot solvent broke the slice at a weak point, but it seems to have removed the problems. But how to determine that? :question:

It will now be stored in "dry box" for the next week or so.

If it continues to look good then I will do a high-gloss polish.

Some pics. after the "galvanic process"
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Larger photos
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