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RE: I have a question



Luis,

Good question.  It seems to me that before a switch is made to anything, a
determination of product performance specs should be determined.

First, what are your corrosion specs?? 1000 salt spray or???  Humidity??
Second, what are your adhesion/bonding specs: mandrel flexibility, inch
pounds of impact, and basic cross hatch?

Also an important consideration; what is the capability of the existing
equipment?

I think microcrystalline zinc phosphate will yield good results on all of
the above.  Iron phosphate will give up some corrosion resistance, but
adhesion should be good.  I have no experience powder coating or painting
over zinc plate.  I suspect adhesion may be an issue to thoroughly
investigate though.  If the coating does not bond to the substrate, it will
soon come off in sheets.  If adhesion is good, then the zinc plate should be
sacrificial relative to the ferrous metal and perform like galvanize, in
which case the performance should be similar to zinc phosphate.

Most pretreatment/plating chemical suppliers have laboratories to perform
all the above tests. Just treat q-panels or coupons of your own steel, with
each process, powder coat and test.

Hope this helps,

John Sparks
836 Shawnee Trace Court
Cincinnati, OH 45255
(513)232-8877
cincyjs@fuse.net

-----Original Message-----
From: owner-p2tech@great-lakes.net
[mailto:owner-p2tech@great-lakes.net]On Behalf Of Gallardo, Luis CLE
4063
Sent: Friday, September 12, 2003 10:19 AM
To: 'p2tech@GREAT-LAKES.NET'
Subject: I have a question


Listman Note: Please reply directly to this person (or make sure to cc him
on your reply). He's not a member of P2Tech. Thanks! Laura B.

I am specifying a metal plating process to be done prior to powder coating,
I am currently using zinc phosphate before powder coating, I am looking at
changing to iron phosphate and powder coating, but I am really worried about
down grading to a lower environmental resistance so I have chosen to go to
zinc plating and then powder coating.

Well this is the background now here is my question:

Do you think zinc plating and powder coating is better corrosion protection
than zinc phosphate and powder coating?
Do you know where I can find documentation to support this?

Thanks

Luis E. Gallardo
Mechanical Engineer

Rain Bird Corp.
Controls MFG. Division
7590 Britannia Court
San Diego CA 92173

(619) 671 4063
(619) 661 4424


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