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Painting on fireproofed steel

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Soojin,

Historically concrete fireproofed pipe racks in petrochemical plants have
been bare uncoated steel.  The idea being that the concrete's low pH and
thickness (1 to 2 inches) would prevent corrosion and money could be saved
by not painting.  This is probably still valid in dry arid areas but I did
some retro fit work in a 25 year old plant in Venezuela and after we
removed the concrete fireproofing we saw holes in the webs you could put
your fist through.  The culprit in this case was sea water spray.
Personally I would recommend sand blasting and at least a prime coat.

Thomas Hunt, S.E.
Duke/Fluor Daniel

----- Forwarded by Tom Hunt/DFD on 01/09/01 08:44 AM -----
                                                                                                                   
                    Soojin Hur                                                                                     
                    <sjhur@hdec.c        To:     SEAOC <seaint(--nospam--at)seaint.org>                                         
                    o.kr>                cc:                                                                       
                                         Subject:     Painting on fireproofed steel                                
                    01/08/01                                                                                       
                    06:05 PM                                                                                       
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                    seaint                                                                                         
                                                                                                                   
                                                                                                                   




I am designing pipe rack steel structure, which are to be fireproofed by
cement based material (like vermiculite) as 2 hrs rating to UL1709.

And the project spec. calls for applying painting system of primer + 1st
& 2nd coating of epoxy paint + top coating of polyurethane paint to
steel structure.

Here I have a doubt. Shall I apply the same painting system to
fireproofed steel, or just apply only primer to it considering the
contribution of fireproofing material to enhancement of the corrosion
protection ?

Thanks in advance for any help or advice in advance.