Hello,
A yellow chromate on Al should meet 168 hrs exposure test per Mil-C-5541C
ask your supplier.
IF YOUR SUPPLIER CAN DO THIS THEN GET ANOTHER SUPPLIER THEY ARE BETTER ONES
AVAILABLE. There are also ASTM specs that are available on the
nternet( http://www.ASTM.org  search in the specification section) Also the
Am. Electroplater and Surface Society has a publication on Chromates in you
need it 407-281-6441, "Chromate Conversion Coatings"
Let me know if you need more. We can arrange for a conference call to your
supplier if you need it.
Richard Haynes
-----Original Message-----
From: [log in to unmask] <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Friday, September 04, 1998 2:45 PM
Subject: [TN] Fwd:Alodine washing off


*** TFS Evaluation Copy of module : cc:Mail ***


____________________Forward Header_____________________
Subject:    Alodine washing off
Author: CharlesC
Date:       9/3/98 6:02 PM

We are having a problem on a PCB which has an Aluminum stiffener/ heat sink
bonded on the component side. When we recieve the board the Alodine is quite
dark but after aqueous cleaning the finish lightens enevenly and after three
or
four washings we have what appears to be bare aluminum. The board
manufaturer
tells us that indeed the finsh has come off. This is only happening on one
part
number PCB, the other board from the same manufacturer does not exhibit the
problem. We do try to minimize washings but due to the nature of the assy.
four
washings is about as low as we can go. We use an inline aqueous cleaner our
saponifier contains monoethanolamine, the water is R.O. and the temperature
is
160deg.F

I have the following questions:
1. Has anyone else had this happen.?
2. Does a high PH remove the Alodine?
3. Do you know of any reference sources?
4. Got any other ideas?

Thanks
Charles Caswell
Process Lead, Printed Circuit Board Dept.
Frontier Electronics Systems

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