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Author: Subject: Help identifying some corrosion
Daveinar
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[*] posted on 3-9-2012 at 16:16
Help identifying some corrosion


Hello all,
I've been lurking for a while now and finally registered and have a question.
I am putting some things together for a small lab. It's been quite a while since college and grad school and I haven't' been using Chemistry in a long time so it's not brand new but I've forgotten a lot!
In any event, I purchased a variac on ebay and its base was quite corroded.
Good news is that ist was only about $45 delivered! 7.5A 0-140V

Here is a picture.

corrodedtransformer by daveinar, on Flickr

My question is what do you think the corrosion could be? I am guessing the housing is aluminum and that the crystals growing on it are AlCl3 based on color and the fact that it easily washed off in hot water.
Does anyone have any other ideas? I didn't save any of it but would like to think it is fairly harmless. :) After a couple of days after washing some small white crystals are again growing on the housing. These are soluable in water but not cyclohexane (electronics cleaner)
Do you think I am right as to what it is? Any other thoughts? thanks, David
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elementcollector1
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[*] posted on 3-9-2012 at 19:46


Aluminum oxide? Chloride? Those are the two most likely options.



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condennnsa
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[*] posted on 5-9-2012 at 00:25


aluminum objects will often corrode rapidly if stored in contact with a less reactive metal like iron or copper. This is the same principle as the sacrificial aluminum or magnesium anodes which are used to protect steel structures commonly. For the same purpose it is used for example to protect the steel rebar in reinforced concrete, provided that in such cases paint is not a viable option for protection.
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marko
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[*] posted on 5-9-2012 at 21:54


How does it look inside? I'm thinking $45 was too much...
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Daveinar
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[*] posted on 6-9-2012 at 16:42


Perfectly clena on the inside. I had to wash the whole thing out but the coils on the transformer were clean. The fuse, switch and mains connections were pretty fuzzy but it all washed off with water and I hosed it down with iso-Hexane and it's clean and works now from 0V-140V.
All in all, not too unhappy with it if I don't poison myself :)

dr
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BromicAcid
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[*] posted on 6-9-2012 at 17:09


You never know what those things have sat in. Perhaps it came into contact with a mercury salt somewhere along the line? Just a smidgin maybe? Clean it well with scrubbing and dillute base, wash with ethanol, blow dry and immediately clear-coat the metal or paint it with rustoleum and be done with it.



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