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syam nibhanupudi
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Subject: AZ92A
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Hello everyone,
i am working on a az92a alloy part. i am curious to know experiences of u guys on this alloy for conversion coatings. i am following ams-3171 - c type VIII. my problem is the smut im accumulating in either phosphoric or chromic-nitric-hf step. can u guys tell me abt a good deoxdiser. i tried looking for commercial ones but i cudnt find. any advise or info is surely appreciated.
thanks alot
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| 28-Dec-2009 20:55 |
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Ilya Ostrovsky
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You can remove the smut by immersion in ARDROX 6376. I suggest to use the same solution as the main cleaner. The process has sequence: 6376 -> deoxidizer -> 6376 -> conversion coating.
I would suggest you also to use Gardobond X4707 or Gardobond X4729 instead of old conversion coating.
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| 08-Jan-2010 11:19 |
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syam nibhanupudi
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u said deoxidizer in the sequence what would be that? i need to follow ams3171 so i have to acid pickle which is a pain but would ardox remove the smut?
thanks
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| 08-Jan-2010 20:49 |
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syam nibhanupudi
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also i have a quick question on a good coating stripper that wudnt hurt the base substrate, may it be hexvalent or trivalnt coatings to be stripped off. any info is appreciated. im on the edge of time here. so some one plz give me heads up
thanks
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| 08-Jan-2010 20:52 |
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Ilya Ostrovsky
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Ardrox 6376 usually removes smut after acidic deoxidizers on magnesium cast alloys. By the way, the product is approved in aerospace industry as cleaner for magnesium alloys, including AZ92.
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| 08-Jan-2010 20:57 |
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Ilya Ostrovsky
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Most of old Dow processes (one of them you are using) can be removed in hot solution of soda caustic - 50-100 g/l.
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| 08-Jan-2010 21:01 |
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Ilya Ostrovsky
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In your case, acid pickle is deoxidizer.
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| 08-Jan-2010 21:03 |
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syam nibhanupudi
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that was quite a helpful advise. thanks a lot. i am going to try both of them soon. one more thing, i have looked up in the research community but is there any clear cut correlation btn contact angle data and corrosion inhibition. people refer to the bubble ability to latch on but wud that clearly affect corrosion resistance?
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| 08-Jan-2010 21:12 |
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Ilya Ostrovsky
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Well, I never investigated such as influence. However, as I know AMS-3171 replaced old MIL-3171 and does not have any standard requirement for corrosion resistance.
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| 08-Jan-2010 21:20 |
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syam nibhanupudi
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that was quite a helpful advise. thanks a lot. i am going to try both of them soon. one more thing, i have looked up in the research community but is there any clear cut correlation btn contact angle data and corrosion inhibition. people refer to the bubble ability to latch on but wud that clearly affect corrosion resistance?
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| 09-Jan-2010 00:56 |
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syam nibhanupudi
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i tried using caustic 120g/l at 160F as a stripping chemical on trivalent conversion coating and it didnt work. i also tried repeated sequence in hot caustic and hot chromic acid . didnt find any change. the only change is the green color change more to some kinda oxide color but i can see the coating still. please do advise me on any effective strippers for trivalent coating.
thanks
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| 13-Jan-2010 19:22 |
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Ilya Ostrovsky
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If your parts are gray from soda caustic, it is normal, because hot soda caustic build hydroxide layer on magnesium. Then you can try any slight acidic deoxidizer, f.e Ardrox 1277 the remove hydroxide layer.
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| 18-Jan-2010 12:53 |
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