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Letter 33052
Restoring damaged pickled finish to 304
stainless steel [No. Carolina]
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Hi,
I work for a company that manufactures stainless steel products
for waste water treatment appications. All of our machines are made
with 304 stainless steel and finished with a pickling method, which
produces a sort of matte or dull finish. Our parent company is in
Germany and we are located here in the USA. At times, we transport
these machines on a flatbed, covered with a plastic tarp. While this
does keep the machine dry from the elements, it causes the finish to
look blotchy and dark from where the tarp would beat and flap against
it. We could not find any cleaning solution that would remove the
dark spots.
I would like to know it there is a method or solution of some sort
the you know of, that we could use to remove these dark spots from
the affected areas and restore the finish back to the original
pickled or dull finish without ruining the existing finish?
Any information would be much appreciated.
Thank You,
Dave Fuller
- Huntersville, NC, USA
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It sounds like you may have more things going on here. What is the
pickling chemistry? (Do not use HCl.)
IF it is only a physical effect caused by flapping of the tarp
covering the units it seems logical to change the type of tarp used
to be something that is less "abrasive" to the finish. Is there any
possibility that moisture is in contact with the units under the tarp
and the tarp is chemically attacking the surface? If it is black it
does not sound like a physical effect.
Once the "dark" blotches are there it is probably necessary to
re-pickle or grit blast the units to get the matte finish even again.
January 23, 2006
Dear Sir,
I hope that you talk about the stain made by the physical beating of
the ss304 material by the tarpaulin used for covering it. You can
swab with Chromic/sulphuric mixture and rinse it before putting to
use. You can try to coat by a thin of colourless polymer film
(lacquer film)which will make a hard film on curing to keep the
surface intact. Of course you should see the cost aspect on this
method. But you can always try to use different material for the tarp
and avoid these stains.
Ramaswami Sundar
- Al-Khobar, Saudi Arabia
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