alternates to 625 inconel cladding 2

[Mous1747]

I have a 2" ball valve will be used in highly corrosive service( hydrochloric acid of high concentration at ambient temperature and below 100 psi)
we won't be able to do inconel 625 cladding because the welding gun can't fully get in all the small areas inside the valve body.

so what are my alternates? duplex stainless steel,super duplex or something else? ofcourse the alternate material needs to be cost effective

 

[EdStainless]

What concentration of HCl?
What is the max temp?
Is there any oxygen or Cl in the system?

I wouldn't trust a weld overlay anyway in HCl.
There are special alloys that are used depending on conditions.

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P.E. Metallurgy, Plymouth Tube

 

[Mous1747]

all the info i was given was as follow
37% HCI w/ 4% H2S
nothing was stated in regard to oxygen or Cl in the system
operating temp is ambient and max pressure is 100 psi

why you wouldn't trust the overlay with HCI ? I found some graphs for 2507 duplex it was acceptable at low temps? quoting special materials will get pretty expensive

 

[EdStainless]

In concentrated acid Ni based alloys are the rule.
Up to about 5% or so I would use superduplex or 6%Mo super austenitic grades.
In strong acid B-2/3 is good, provided that there is no oxygen or oxidizers in the system.
You could also use C276. Alloy BC-1 is supposed to be the best in HCl.
But if you are going with solid parts then 625 is still an option.
Do you think that a high alloy valve is more expensive than a failure?

The reason that I don't like weld overlay is two fold. First you get some Fe dilution from the base metal so you don't really have the full alloy chemistry. And secondly you have a cast structure with segregation while published data is for wrought homogeneous products. In other words YMMV (your mileage may vary), and there is no way to tell how it will preform.

Have you looked at non-metallics?
from MS-3
Phenolic or Furane Resin Composites
These composites comprise phenolic or furane resins with short-staple glass or carbon fiber reinforcement. The phenolic grades are recommended for use to 130°C (265°F) in hydrochloric acid, while furane-based composites can be used to 160°C (320°F). Furane resins have excellent hydrochloric acid resistance over the full range of concentration to the boiling point.


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P.E. Metallurgy, Plymouth Tube

 

[XL83NL]

For a current application which runs at the same (approximate) conditions we use PVC(-U) glued piping components. I believe we have up to 42% HCl. Pressure and temperatures are low (I.e. atmospheric/ambient). Sounds like a similar situation.

 

[moltenmetal]

I'd recommend lined construction- a plug valve like this:

https://www.flowserve.com/en/products/valves/plug-valves/lined-plug-valves/lined-plug-valves-t4e

That assumes that plastic piping isn't an option because of fears of mechanical robustness and the need for safeguarding- but strong acid can also be safely handled in properly designed, constructed and tested thermoplastic piping for sure.

Using a nickel alloy at ambient temperature and only 100 psig pressure is a waste of nickel. Whenever given the choice between corrosion resistance and corrosion immunity, choose the latter.