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kennedyqc (Industrial) (OP)
17 Jul 06 13:24
I have a new customer that requires aluminum alloy 2024 to have an iridite process.  What exactly is iridite?  I have heard several ideas, which is why I am asking.  I want to be sure to completely understand their requirements and expectations.  


Thanks for any help you can provide.
IRstuff (Aerospace)
17 Jul 06 14:54
A websearch reveals all:
http://www.engineersedge.com/iridite.htm

Note that despite what it says about conductivity, REALLY low resistance contacts requires removal of the iridite.

TTFN



kenvlach (Materials)
18 Jul 06 6:16
Iridite is a brand name for chromate-producing product that belongs to MacDermid Inc. Iridite 14-2 is on QPL-81706 for producing both Class 1A & Class 3 chromate coatings on aluminum.  Alodine 1200S is a similar product from Henkel.

For more information, MIL-C-5541E,  MIL-DTL-81706B and the Qualified Products List QPL-81706 are free downloads at ASSIST Quick Search: http://assist.daps.dla.mil/quicksearch/
See also ASTM B449-93(2004), "Standard Specification for Chromates on Aluminum." http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/B449.htm?L+mystore+eesx0956+1153224308

What is the end use of the 2024 parts?

It's increasingly common to get requests for Non-Hexavalent chromium coatings.  A new QPL including non-hex. Cr coatings is several months overdue.  However, there is  ASTM B921-02 "Standard Specification for Non-hexavalent Chromium Conversion Coatings on Aluminum and Aluminum Alloys." http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/B921.htm?E+mystore

Re IRstuff's comment on resistance.  True, but bare aluminum is rapidly oxidized by oxygen and water vapor in the air, so after a while the electrical resistance of mechanical connections increases (unless precautions are taken, such as sealing with EJC).  Ohmic heating and fires may result.  For many military and aircraft surfaces, MIL-C-5541E Class 3 coatings are required to prevent long-term increase of electrical connection resistance.  Of course, for really low resistance long-term, plate with tin or Ni+Au.
IRstuff (Aerospace)
18 Jul 06 11:05
Nou doubt about the desire, but the reality is that I once spent several hours griding off iridite because we couldn't meet electrical bonding requirements.

TTFN



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