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coating for caustic storage tanks/pipes

coating for caustic storage tanks/pipes

coating for caustic storage tanks/pipes

(OP)

Hello all,

Just a quick one I feel. I'm designing a caustic scrubber and I would some info on suitable coatings that's typically used to protect metals any other materials against caustic corrosion.

Thanking you in advance..

RE: coating for caustic storage tanks/pipes

Forget about coatings (except for painting the exterior), only use compatible materials. Visit some scrubbers.  You will see white deposits evrywhere -- caustic wicks through valve stems, up tank walls, from pipes, etc.  It absorbs CO2 from air, then dries and becomes abrasive. Make everything so it can be hosed down periodically.
 
I have seen caustic scrubbers with up to 60 HP fans and every one was PVC or FRP for body and tanks. PVC pumps, piping, valves and nozzles. Except, cast iron drive pumps for really large units.

In the metal finishing business, mild steel tanks are used for hot caustic solutions. I think the traditional reason for not using sheet steel for scrubbers was that the caustic would eat through the paint, and when cleaned, rust. Maybe a contributing factor is that commercial caustic soda contains pretty much (0.5% NaCl). However, with better paints nowadays, a good epoxy paint should work.

304 SS is usually used for fasteners. Expensive stuff like Ti works great, too.

Don't even think about using non-ferrous Al, Cu, Mg, Zn or alloys thereof (including galvanize) anywhere. Massive corrosion.

If you don't have a good corrosion book, all of the pump manufacturers have chemical compatability charts.  There is a decent one in the back of the Grainger catalog, and Harrington Plastics has one on-line but with less data: http://www.harringtonplastics.com/

RE: coating for caustic storage tanks/pipes

nuig,

There is information on material selection for caustic systems on the following:

www.hghouston.com/naoh_gph.html
www.hghouston.com/x/20.html

www.corrosionsource.com/technicallibrary/nidi/literature/literature9.htm

www.eng-tips.com/gviewthread.cfm/lev2/7/lev3/37/pid/135/qid/23683

Let us know how you make out......

Please post again with information of your final decision..

MJC


www.tipmaster.com/includes/refinfo.cfm?w=450&h=350')

RE: coating for caustic storage tanks/pipes

To obtain literature from the CorrosionSource link above requires a paid subscription.  You can get NiDI papers on corrosion for free by going directly to the source:
http://www.nidi.org/index.cfm/ci_id/6648/la_id/1.htm

RE: coating for caustic storage tanks/pipes

(OP)
Dear all,

FRP is my prefered option for tankage and storage. PVC for pipes.

Thanks for all the really helpful links.
 

RE: coating for caustic storage tanks/pipes

nuig,
What convinced you to use FRP/PVC? Any technical data from vendors/manufacturers to support your decision that is available for others to reference?

Thanks

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