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FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/10/2010 5:22 AM

Hello,

I have a tank of material SS 304, and I want to store acidic solution in it. SS 304 is not good for storing acidic solution, as it gets degraded with time.

So would coating it with FRP, will help me in doing that.

Chemical is used for removing rust from from different components.

Pl suggest.

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#1

Re: FRP coating on SS 304 tanks to prevent acidic reaction

09/10/2010 6:25 AM

Start by accessing the Cole Palmer materials compatibility database, and go from there. Don't forget to state which acid, what strength, and at what temperature!

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#2

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/10/2010 10:42 PM

I think your best option is to use a flame-spray applied teflon coating. It works much like a plasma application tool.

The ground PTFE is fed into an air blast chamber that then goes to a high temperature flame, which will "melt" the teflon enough for it to coat the surfaces. The application is much like a paints spray in that you build up layers slowly- the melted PTFE cools relatively quickly behind the spraying, so- as you work you way around the tank, by the time you get back to your starting point, the previous coating has fully set up and is ready for the next layer to be applied.

Net result is a totally smooth, seamless, relatively inert surface that can withstand up to 650F contact temperatures.

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#3

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/10/2010 10:48 PM

In the oil biz, our acidizing pumps are 316 SS housings with viton rubber liners. the acids we use are Hydrochloric, and Hydrofluoric for the most part with some sulfuric acid.

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#4

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/10/2010 11:16 PM

FRP would be very difficult to apply 100% at the necessary thickness around fixtures of the storage tank such as man-ways, sight glasses, pipe connections, inlets, outlets, agitator shafts etc. If the liquid were to get between the FRP and the St. Stl. it would attack the st. stl. and you probably wouldn't be aware of the degradation.

Once this same problem with a sailboat with a steel centerboard that had a FRP coating on it. Dragging the centerboard on the bottom broke the FRP at the rear-lower corner and the steel rusted. Didn't know this until I was having difficulty raising it because the rust and the steel and the FRP were now thicker than the opening of the centerboard trunk.

Check the compatibility charts should be your first step.

Once you check the easiest and least costly methods then look into the more costly and difficult methods if necessary.

How would you test the coating to make sure there is complete and adequate coverage of the liner?

Good Luck, Old SALT

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#5

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/11/2010 7:11 AM

What is the composition/concentration of the acidic solution? I seem to recall phosphoric acid was used for rust treatment, so it could be this. In which case FRP should be OK.

However, I agree with energygod and old salt, FRP might be difficult to apply, and a thermal spray of something like PFA or FEP should be able to handle most acids, and might be the easiest to apply thoroughly. I used to know of a brush-on coating that was used even in centrifugal pumps for Hydrochloric and Sulphuric acids, but I can't remember what it was called.

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#7
In reply to #5

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/11/2010 10:43 AM

SHIV STEEL IMPEX. was established in 2005. We are one of the leading manufacturers, exporters & suppliers of Stainless Steel,304,304L,310,310S,316,316L,321,410,430, Carbon Steel, Alloy Steel, Copper, Brass, Aluminium Monel, Inconel, ,Hastalloy, Lead in the shape of Pipes, Tubes, Rods, Sheets, Plates, Wires, Angles, Coils, Strips and the entire range ofS.S. Pipe Fittings&M.S.Pipe Fittings such as BW / SW / Screwed / Forges & Compression Type with Ferrules such as Elbows, Tees, Reducers, Stub ends, Flanges, Unions, Caps, Nipples, Couplings, Elbowlets, Weldolets, Nuts, Bolts, Studs, Washers, Valves & Gaskets etc. ,

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#6

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/11/2010 7:47 AM

Thanks to all for the suggestions.

I would check out for the PFE and FEP process.

It would be very helpful if anybody can tell me after coating of how to check it, say it FRP or any other coating.

To update more, my maximum temperature for the chemcial would be 50 deg C, and there is just a dipping process in the tank to remove the rust from a particular component, say for 20-25 min.

About chemical, I read it somewhere,that if I add citrus base in the acidic chemical, then it would not affect SS 304 much, at the requirement that I have for the chemical's conditions.

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#8

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/12/2010 6:42 AM

Would it be better to change it for a plastic tank?

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#9

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/13/2010 7:45 AM

FRP and fluoropolymers may be solutions (although you need to check the resin choice against the specific acid you are talking about - and if you have any reasonable probability that solvents will get in this tank, be very careful on what you choose). If you are not worried so much about durability (you're dipping things in there - will there be a chance of them scratching/rubbing the lining?), you may not need the FR part of FRP - there are many thin film vinyl ester and epoxy coatings that might work, depending again on your chemical environment.

If durability is a major concern, I would probably steer you away from the fluropolymers and anything less than ~80 thousandths thick, and I think you ought to strongly consider a sheet rubber lining - if there won't be any solvents in there (e.g. can be a problem to ppm levels if the wrong solvent, depending on which rubber), sheet rubber can be a good choice.

Whatever way you go, surface prep is the key to long term performance of your lining! Good luck!

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#10

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/13/2010 10:34 AM

Coating the tanks might be a short term solution but you have to keep the coating on there, it will wear off.

I would suggest you start changing your tanks out with tanks made from 316 SS.

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#11
In reply to #10

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/13/2010 10:42 AM

Depending on what the acid is, 316ss might not be good enough (in fact, if it were nitric acid it would be worse). If he is changing tanks it would be better, as PWSlack suggests, to change it for plastic (PVDF?) or FRP.

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#12
In reply to #11

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/13/2010 11:06 AM

I"m not familiar with PVDF and you're more of an authority on this than I am. What I see is chetan is wanting to use equipment that he already has to avoid costs and I think he's going to need to make the investment to get the proper equipment in place, unless this plan to store the acid is a temporary one time thing. It sounds to me like the plastic tanks would be much cheaper than SS.

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#13
In reply to #12

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/13/2010 11:36 AM

Yes, you are quite right, and plastic/FRP should be much cheaper. Looking back over this, if it were just a storage tank then a coating or lining would be fine, but with components being dipped in the tank, there is a risk of coatings being chipped or scratched, so investment in new plastic tanks might be the best bet.

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#14
In reply to #13

Re: FRP Coating on SS 304 Tanks to Prevent Acidic Reaction

09/13/2010 11:46 AM

Since he already has a tank, the least expensive option is probably to line it. If you were buying new, I'd be very surprised if solid PVDF construction would be cost competitive with lined carbon steel. Unfortunately, he hasn't even given enough details on the acid type to do more than hand wave about materials anyway...

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Anonymous Poster (1); chetan11 (1); energygod (1); Holzfeller (3); Janissaries (2); jgjengr (2); old salt (1); PWSlack (2); Rorschach (1)

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