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Pickle acid tank rib coating

Hello
I have several 1800 gallon tanks that contain 25% nitric acid and 3% hydrofluoric acid which are used to pickle metal tubes at temps up to 100 F. The tanks are currently stainless with a cooling jacket. I also have two ribs in the tanks used to roll 2000 lbs of product tubes for mixing. The ribs are a resin coated fiberglass over stainless steel. The ribs get banged around a bit and only last 3-4 months before the coating is torn apart. I am looking for something else to coat the ribs and possibly the tank. ETFE and a CPVC derivative has been suggested by vendors. Would these work? The ribs need a little bit of friction so the tubes roll and not slide. Thanks.

Ann Lincoln
metal producer - Ogden, UT, USA
2005

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2005

Hi Ann,

You mentioned CPVC and fluorocarbons ... ah, but like nearly all thermoplastics, their coefficient of friction is very low and you'd get slipping, not rolling as you want. Maybe the 'rib' design could be changed?

Also, those materials cost much more to buy and to fabricate than good ole ordinary uPVC.

Please consider a dual laminate, i.e., PVC internally but bonded externally with frp.

Not knowing your 'roll' set-up, I first thought of using HDPE which is very impact resistant (mines use it for slurries) and which, I believe, one can still buy it, the sheet, I mean, with a fibre backing suitable for fibreglassing. Then you could easily add 'ribs' to them when they wear out.... by welding, of course.

But stick with the common plastics such as PVC or Pe ... PVC is fine to l40 and as a dual laminate much higher, Pe is OK, I think, to at least l00 F.

You'd have a problem with a cooling jacket due to low heat transfer using plastics .... consider a PVDF heat exchanger, tubular construction... but if that is likely to get banged up, have the tank made with a recess for it so that the tubes don't bang into it.

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).