Joe, I've been there.

I'm guessing that you don't see the problem if you "only" go through the
perox. sulf. microetch (if you do, we'll try a different approach).  If the
problem can be localized to the cleaner tank it is probably one of two
possibilities.  (1) The cleaner your using to remove the chromate probably
has surfactants (wetters).  I've found that the surfactants can transfer from
rollers or squeegee roller onto the layers.  To fix this you have to use a
chromate remover/cleaner that has no surfactants.
(2) I've also seen problems, more commonly, found with not turning over the
cleaner often enough.  This leads to a build-up of oils that the cleaner has
removed from the layers.  If the problem is going away when you clean the
tank with caustic, it's because the caustic is removing the build-up.  If
this is the case, "Feed & Bleed" the cleaner at a more rapid rate, so that it
can carry the dirt & oil away.

I would add that using squeegee and roller materials that are closed pore
will be less likely to absorb and transfer.

Start by localizing the problem.  

Good luck!

If you'd like additional information you can contact me here or direct at
[log in to unmask]

Scott Griggs
Applications Engineer
RBP Chemical Corp.

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