I use about 250 cc of Phosphoric to do the same thing and see no
corrosion to the equipment.   BTW.  We got rid of the cotton socks and
no longer see  white fuzzies on the boards (nor green coated fuzzies.) 
They are available from I.S. or in the states from Nationwide Circuit
Products.  We also have an ASI rinse module and dryer as a following step since I don't trust the short I.S. rinses to get all the dirt off.  We
add 
250 cc of CU-56 to the first of three rinses dump it daily.  The staining
problem is   
history.

John Nelson  <[log in to unmask]>
Automata, Sterling, VA

On Tue, 25 Jun 96 17:05:48 EST "rdenier" <[log in to unmask]> writes:
>     To:        D. Stewart
>     From:      Richard Denier  - Facilities / Maintenance Mgr
>     Re:        Sulphuric acid & pumice
>     
>        We have had a Pumiflex in operation at our plant for over 12 
>years 
>     and have experienced the same problem you are having.  I.S. did 
>not 
>     recommend using sulphuric and neither did our other suppliers at 
>the 
>     time. Although it may be a band-aid, it is still practiced here.  
>The 
>     main slurry tank holds approximately 50 litres and in that, we 
>add 9 
>     kg of pumice / 250 ml of sulphuric acid and fill the rest with 
>water.
>     
>     Caution:
>     
>     1.  Make sure that the core material from your brush manufacturer 
>is  
>     a high grade stainless steel, otherwise the acid will eat through 
>the 
>     core.  This will occur within 36 hours of production and may 
>upset 
>     your maintenance staff ( slightly ) when they have to peel the 
>brushes 
>     out of there! 
>     
>     2.  Do not exceed 250 ml of acid, or it will also attack the 
>cotton 
>     socks that cover the pinch rollers.  This will defeat the purpose 
>of 
>     the pinch rollers and cause excessive dragout into your rinse 
>section. 
>     
>        I don't know if this is what you had in mind, but I figured 
>you 
>     should know that your not alone!  We have had good results over 
>the 
>     years with this method.  Please call me if you wish to go into 
>further 
>     detail. ( 416-299-4000 ext#314 )
>     
>     Regards, Richard Denier
>              PC World, Toronto, Canada
>               
>     
>
>
>______________________________ Reply Separator 
>_________________________________
>Subject: sulphuric acid and pumice!
>Author:  donb at PCWORLD
>Date:    6/25/96 3:45 PM
>
>
>    \0
>   TO:         I4235700 IBMMAIL   new address for ipc technet 25.6.96
>     
>   FROM:       DSTEWART EX2       D.Stewart        - Product 
>Development
>Manager.
>     
>   DATE:       25 June 1996
>   SUBJECT:    sulphuric acid and pumice! 
>   REFERENCE:  removal of nitric stains
>     
>    I'm back online again after a 6 month absence due to technical 
>    difficulties - I could read but not write. I am a voice to be 
>heard 
>    again!
>     
>    We have an issue with nitric acid stains on boards after tin lead 
>    strip - the cause is known and relates to processing thin laminate 
>
>    cores through outer layer processing, but that's another story. 
>    Prior to soldermask, we cannot remove these stains by standard 
>    pumice, but we can remove them by passing through the 1% H2So4 
>rinse 
>    on our developer prior to pumice. We are obviously trying to 
>reduce 
>    handling and interference with a different process so we are 
>trying 
>    to find an inline method of removing this stain.
>     
>    Our pumice machine supplier (IS) is not keen on us using sulphuric 
>
>    in the pumice machine, a nearby friendly shop with the same 
>problem 
>    tried citric in the pumice but it turned the boards yellow! so 
>does 
>    anyone out there have the same problem, or another solution?
>     
>    Dougal Stewart
>    Exacta Circuits
>    Scotland
>     
>
>