An MOC that Can Withstand Corrosion by Hydrofluoric Acid at 100 Degrees C?

I believe acid brick or acid resistant brick is not resistant to HF.

To find a compatible material you are most likely going to have to move away from metals. Graphite will work as will some of the higher temp. fluoropolymers. I happened upon an article about coatings here that may be of interest.

I did come upon this solution... but here's a catch...

Heating and Cooling Provisions have to be provided to the vessel...

So that suggestion of mine went for a toss...

Hi again surajp333,

Have you looked into fluoropolymer lined vessels? I saw a few teflon-lined on line. I just don't know how the bond of the lining to the vessel wall would stand up to the operating temperature.

Just something more to think about.

What's the volume of the reactor?

I found this that may be of interest, but I suspect it is way below the volume you are looking for.

Here is something that may be more in line with what you need:

http://www.engiplas.com/en/c-3-products/

Mike

I m sorry for not mentioning the volume...

That is quite low..

Its a 5.5 kl reactor with a 4 kl manufacturing capacity, this suffices the demand for the product in the market since we get 2 batches in 3 days...

Will check out your suggestion..

Among the metallic choices, this study found Hastelloy C-276 to be the best:

http://www.ornl.gov/~webworks/cppr/y2002/rpt/114718.pdf

Hastelloy C-276 is indeed a good solution... and its availability in India is also not questionable...

But there are two points of concern...

1) The High material costs, fabrication costs... and I guess in this case the shaft of the agitator would also need to have the same MOC... Thats a thorough headache...

The cost in this case in comparison to SS 316 would be almost 10 times.. I understand cribbing in this case would be detrimental but I would have been more confident if I had reasonable data to support my findings... So going to the next point...

2) Last but not the least...

If we closely look at the Brochure of Hastelloy C-276 provided by the OEM, Haynes International:

http://www.haynesintl.com/pdf/h2002.pdf

We can clearly see that even just for HF of Conc. 5 %, the corrosion rate is 10 mils / year ( 0.25 mm / year)... and that is just the average..

So C - 276 cannot be termed a 'Long termed Solution'...

Hi Suraj,

Really tough chemical to handle, you are right! You can try for Monel 400 or Monel K-500 for HF handling. I am not sure about the cost, but it should be equivalent to Hastelloy-C or Inconel, if not less. I have made use of Monel K-500 for mechanical seal parts (which are obviously very thin in cross section, compared to a big storing tank) to seal HF in one of the Petrochemical plants.

Sanjeev

Thanks Sanjeev...

Will take your word for it...

But frankly speaking I have spoken to the vendors manufacturing Vessels of Inconel and Monel... with the the operating conditions of this process... and the answer was a straight no...

The Vendor of Hastelloy C-276 was quite enthusiastic but When I asked for a Bank Guarantee , I have never heard from him since...

There's a coating here http://www.corrocoat.com.au/products.php that claim to be suitable for HF. I'm sure there are other similar sites around.

What are the operating parameters? ie duration at temperature, rate of addition of HF, order of addition of reactants, is it agitated, under pressure, are abrasive solids present? Is the HF consumed in the process? Years ago we tested all the usual culprits for a process which was high nitric + HF and we found the best was Hastelloy G-30. If the process is oxidising I doubt that Monel will work.

Will post the exact operating parameters with the process variables...

The Process is agitated and its an ambient process with HF being consumed in the reaction...

And When you mention abrasive I would say none... but there are chromic acid flakes which are corrosive and is hand in glove with HF in giving us sleepless nights...

I would look into your suggestion of Hastelloy G-30

Thanks

As soon as I hit the submit button I remembered something else. Previous to G-30 we had used PVDF lined vessels which sort of worked but the HF was able to permeate through the polymer and attack the bonding and backing material. If my memory serves me well, the bonding failed, the lining would distort and split at seam welds - perhaps bonding systems have improved since then.

I am no chemical engineer so what I am about to write might be a right load of rubbish. OK?

My initial thought was to use a glass lined vessel but a quick trip to Wikepedia stopped that idea straught away.

The HF is delivered/ stored in probably a plastic container (ok not at 100degC I guess). Have you looked into using a plastic lined vessel for example the same material that the HF is delivered/ stored in? Even if it did need to be replaced every number of years I would think it would be cheaper than replacing a whole vessel.

Sorry if this sounds dumb.

Not dumb at all. Certain types of plastics or synthetic rubbers might be good, but with care about the 100°C. Maybe some type of lining or bladder could be the way to go.

As mentioned by me, Heating and Cooling Provisions have to be provided to the vessel...

So Fluoropolymers and linings dont stand a chance...

In any case HF has the typical characteristic of creeping when linings are involved.. So that option is definitely out..

How is heat applied to the vessel? Jacketed with hot-oil or steam? A lot would depend on what that is. Maybe an alternate method of heating could be devised. A coil submerged in the vessel maybe?

If this is a batch reaction, what is the reaction time? Does it need to be continuously heated for the entire reaction? Knowing these things might help.

Lol wow. When I first read this post I was thinking you said 100 degrees F. You're problem is that you're above the boiling point of HF acid so you'll have all kinds of bad corrosion problems.

My NACE Handbook actually has no recommendations for metals at these conditions. You need to consider a lined vessel. What's your design pressure and is there any way to lower the temperature?

I understand the concern...

Thats why The management and our engineering team are considering to have the product removed...

But that would amount to giving up which I cannot be a part of...

When linings come to the picture what immediately comes to the picture is creep in linings by HF which is a typical characteristic...

Well I understand your difficulty with giving up (sometimes I have the same problem). But if you spend too much time chasing this thing then you're only wasting time that you could be spending on something more productive.

If linings are not an option, then I suggest you contact a metallurgist or materials expert. I would even try to get in touch with the organization NACE. I'm not sure what NACE stands for but all they do is corrosion studies, so if they can't provide you with something then I doubt anyone else can.

Also, check out API 751.

NACE = National Association of Corrosion Engineers. They have extensive data on corrosion rates for a very wide range of metallic and non-metallic materials for a very wide range of fluids.

If it is feasible to apply deposition type coatings (such as Parylene or Titanium Nitride) to the vessel in question this should be a serious consideration. There are a wide range of such coatings, also including fluoropolymers, so there should be something suitable for Hf. I'm sure a coatings specialist would provide good advise.

Sigh...

Hadnt there been a consideration for Heating and Cooling Provision...I would have jumped at Fluoropolymer's coating even after taking into consideration the creep corrosion... more thickness of coating would have served the purpose..

But it is not to be...

Will look out for NACE

Thanks

I don't know much about liners but I do know that FEP Teflon has exceptional resistance to HF acid. I would imagine it would still be good at 100C too because I know that FEP Teflon is good up to about 450F (I had a senior design project on this so forgive me if my numbers are off).

That being said this material is extremely expensive. I pulled up a square plate on McMaster Carr (1 ft x 1 ft x 0.5 inch). That piece is $125.

I am sorry if you have felt this in any of the posts.

I have tried to remain as courteous and humble as possible.

I am just trying to give in my comments on the suggestions because if I would not I guess the topic would be closed without a proper resolution on it... And if there comes out a resolution for the same, I hope it may help anyone facing a similar issue in the coming future...

I really appreciate the ones who are investing their valuable time in this discussion because if that would not have been the case, I would not have thanked them in many of the posts..

If I am giving out any negative vibes...please accept my apologies..

I didn't take any of what you said negative so don't worry about him. He's posting anonymous for a reason.

Although I do appreciate your determination, though, you have really gone about as far as you can go with this topic. You should use CR4 for suggestions and direction. I wouldn't use it for exact answers. I know I wouldn't trust what someone on a website told me without doing my own research.

So, contact some of the experts like NACE and get their advice.

I do understand that...

I am trying to get in touch with their representatives..

Thanks for suffering me all this while..

Be sure to let us know what solution you find. I'm sure you will find one.

You can discount the fluoropolymer coatings then, but you should still be able to consider something like Titanium Nitride or Parylene. It's worth talking to a coatings company.

Thanks...

I did not take both of these in my purview...

Will try to find out more info on these 2...

According to Corrosion Resistance Tables" by Scweitzer, 50% HF, 100C:

Hastelloy is questionable

Good:

Monel,carbon,carbon impregnated resin, Furan Resin, Penton, Halar, ETFE, FEP, TFE

Looks like Teflon (the last three listed) may be your best bet

Have a look at this publication from NIDI:

Corrosion Resistance of Nickel-Containing Alloys in Hydrofluoric Acid, Hydrogen Flouride and Flourine (443)

Presents the corrosion-resistant characteristics of nickel and nickel-containing alloys in hydrofluoric acid, hydrogen fluoride, fluorine and some fluorine-containing compounds, information helpful in selecting materials of construction in plants handling these chemicals. Hydrofluoric acid, hydrogen fluoride and fluorine readily react with many metals to form metallic fluoride films which, in the case of high-nickel alloys, tend to be protective to further reactions. This characteristic makes nickel-containing alloys useful for the handling of fluorine compounds. Reports extensive corrosion data for laboratory and plant exposures, and industrial applications of several nickel-containing alloys.

http://www.nickelinstitute.org/index.cfm/ci_id/15786/la_id/1/ci_doc_id/3128/search_keyword/acid/method/1.html

hope this help

V.

corrosion prevention

Please ignore crass comments from an anonymous poster. You have a genuine problem which you are trying to solve. Whatever candidate materials you come up with, test them all in the actual environment. None of the published information will match your conditions exactly and testing will eliminate the non starters very quickly and may throw up some surprises. I doubt that my earlier suggestion of G-30 will work in your process but it was an unexpected winner in our tests in a nitric / HF system and went on to provide many years service. We did also identify at the testing stage that standard G-30 weld filler was going to be a weak point and Haynes tweaked the composition to come up with an alternative capping filler which had significantly better corrosion resistance. I have also had experience of HF processes using fluoropolymer lined vessels and heating coils - very expensive but they can work in the most aggressive environments. Anyone thinking of going that way needs to be aware that HF permeates readily through thin wall tubing. We used to get corrosion by dilute HF on the water side of the heating circuit. Good luck with your search

On the anonymous poster, I respect his comments because it is his opinion and guess he has his Freedom of Speech...and he did wish me luck...

And he got 2 points off for being off topic..

Right... Creep corroison is a characteristic associated with HF Acid... I have gone through numerous literature mentioning this..

Hastelloy G-30 Works well with Nitric Acid and with a low concentration of HF... I will give you that...

But If I am not wrong, Haynes International does mention in their brochure that in an
HF environment with the conditions in this process, there would be substantial loss of thickness..

I am in the process to get in touch with a Haynes Representative and also with someone from NACE. I am also in discussion with our thoroughly experienced Process Consultant who will give his valuable comments on this one...

Though one thing I am quite surprised about is...

HF has not been considered for deep corrosion studies in the leagues of Hydrohalic Acids... in spite of its unique corroding characteristics like its action on glass... atleast I hardly heard about HF Acid in my academia...

Here I can guess the reason may be because that its included in the category of 'Weak Acids'..

Well.. it will be quite a ride..

Will keep posted on the developments!!!

Cheerio!!

Well.. what do you know???

Our Facility in USA is using Hastelloy G-30 successfully, but in less extreme conditions than ours...

A Friend of mine had suggested SS Duplex and SS Super Duplex... but no one's ready to give free samples...

No Compatibility charts are available from the almighty Google Search too.. Looking to get that from the OEM...

But We are carrying out Corrosion studies now...

NACE India are giving their inputs too....

Hoping for the best... with fingers crossed....

Consider borosilicate glass process vessel and pipework lining. Consider "kalrez" elastomer for joints. Consider graphite for heat exchangers. Check the Cole-Parmer corrosion chart for more guidance.

I am using butyl rubber and it should withstand HF acid at 100 Degrees. It is also quite cheap.