Inconel 625 vs ASTM A182 F55
Inconel 625 vs ASTM A182 F55
(OP)
Which alloy of these two has the higher corrosion resistance? Inconel 625 or ASTM A182 F55??
I understand, A182 is supper duplex alloy, meanwhile Inconel 625 is high alloy steel.
I understand, A182 is supper duplex alloy, meanwhile Inconel 625 is high alloy steel.





RE: Inconel 625 vs ASTM A182 F55
In almost every case the answer would be 625, but a C type alloy would even be better for most applications.
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P.E. Metallurgy, Plymouth Tube
RE: Inconel 625 vs ASTM A182 F55
RE: Inconel 625 vs ASTM A182 F55
The corrosion resistance is relative term, depending on media, operating conditions( pressure, temperature) and many more factors.
Attached are some information on both the alloys extracted from manufacturers data sheets& are worth looking at.
With respect to O&G(Production)environment by an large alloy 625 has better corrosion resistances,due to higher CPT, CCT, PREN values.
However there's is a huge difference in cost between F55 and 625 alloys.
F55 alloys on the other hand are quite versatile, with the reported applications in Offshore O&G, Downstream Applications, e.g. Refining& Petrochemical, chemical environments.
What is the intended service conditions for these alloys? Selection of the best alloy would influenced by many of the factors stated above.
Thanks.
Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299
RE: Inconel 625 vs ASTM A182 F55
It has high strength, great resistance to aqueous corrosion, but can be difficult to weld (and the welds may have inferior properties).
625 has good strength up to 1400F and good toughness down to LN temps, and it welds well.
The cost between a superduplex, 625, and a C alloy (622, 686, 59) is not that great.
So pick carefully, there is no answer that is always correct
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P.E. Metallurgy, Plymouth Tube
RE: Inconel 625 vs ASTM A182 F55
Actually my question is related to a mechanical seal installed on a multi stage water injection pump (Aquifer water).
it failed many times and the internal of the mechanical seal found heavily corroded. all the wet parts are ASTM A182F55.
the other pumps in the same facility/same application are equipped with Inconel 625 mechanical seal internals, this seal is working fine. so I am doubting the ASTM A182 F55 is not suitable for our application (corrosive environment).
the discharge pressure of this pump is 290 barg and seal pressure is 100 barg.
TSS is 20 mg/L.
RE: Inconel 625 vs ASTM A182 F55
You may be up against the critical crevice corrosion temp for the duplex.
We used to only use 622 for seals in high Cl waters (anything no fresh).
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P.E. Metallurgy, Plymouth Tube
RE: Inconel 625 vs ASTM A182 F55
RE: Inconel 625 vs ASTM A182 F55
I will try to get some photos for the corroded parts.
Yes Oxygen ingress is possible.
RE: Inconel 625 vs ASTM A182 F55
The working temperature is fluctuating between 72C to 85C.
Nickypaliwal,
could not arrange any photos due to legal issues, however the corrosion is almost a decay and metal loss. not only pitting.
Gents,
is it possible to have galvanic effect between super duplex and inconel625???? I have discovered that pump shaft is inconel625 meanwhile mechanical seal wet material is super duplex!!
Thanks
RE: Inconel 625 vs ASTM A182 F55
What pH range do you see?
I would move to a Ni alloy, and something better than 625.
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P.E. Metallurgy, Plymouth Tube
RE: Inconel 625 vs ASTM A182 F55
Note that copper based alloys are not good in H2S service so should check before using it.
RE: Inconel 625 vs ASTM A182 F55
On the other hand, there may be some problem with the seal system heat removal operation, producing high temps on the contact surfaces in the seal.
RE: Inconel 625 vs ASTM A182 F55
I am not very much aware of these materials in sea water service. Can you please advise and share your experience for use of alloy 625 in sea water ? Thanks in advance.
RE: Inconel 625 vs ASTM A182 F55
there is no sea water. the pumped fluid is aquifer water( with CL content). the seal barrier fluid is potable water.
RE: Inconel 625 vs ASTM A182 F55
RE: Inconel 625 vs ASTM A182 F55
In general crevice corrosion will start at temperatures 20-40C lower than pitting.
All of these alloys rely on chrome to form the passive film that protects them (Mo and N make the film stronger and more self repairing).
The tighter the crevice the worse the conditions.
In the crevice you get oxygen depletion, so it is harder for the passive oxide film to be maintained.
You also get the concentration of corrosion products, one of which is hydrogen ions.
The result is dropping pH in the crevice.
In Fe bearing alloys (stainless and some Ni-Fe grades) we do corrosion testing in ferric chloride because it resembles what forms inside an active pit or crevice. The solution is high in Cl, and has a pH <1.
This is what happens in a crevice.
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P.E. Metallurgy, Plymouth Tube
RE: Inconel 625 vs ASTM A182 F55
No info provided on seal system configuration. With what little I know, low chloride deoxygenated potable water should work okay for pressurised plan 53 with superduplex materials on the seal, since the aquifer water cannot migrate into the seal chamber.
Where is the 80degC experienced - seal supply or seal return fluid ?
RE: Inconel 625 vs ASTM A182 F55
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Inconel 625 vs ASTM A182 F55
RE: Inconel 625 vs ASTM A182 F55
RE: Inconel 625 vs ASTM A182 F55
If you don't need strength at elevated temp then 625 offers less corrosion resistance and the pricing should be similar.
You said that you have general corrosion, I hope that this is actually widespread pitting.
If you actually have general corrosion you need to find out what is being used to clean or flush this system.
General corrosion is almost impossible to have in these alloys.
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P.E. Metallurgy, Plymouth Tube
RE: Inconel 625 vs ASTM A182 F55
If you want an opinion on 625 performance in seawater, it's in plentiful supply in the literature. Here are a couple of examples:
JS Lee, et al, UNS N06625: A Current Review Of The Literature, Materials Performance, September 2006, pp 36-40
F Martin, et al, Crevice Corrosion Of Alloy 625 In Natural Seawater, Corrosion, Vol 59, (6), 2003, pp 498-504
H Alves, et al, NACE Corrosion 2007, Paper 07215
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Inconel 625 vs ASTM A182 F55
80C is the temperature of the pumped fluid. this will be the same as the seal chamber pressure at both sides (thanks to balance line).
I have seen the temperature trend for one month back. all the time this pump was running at 83C. I would say based in the other replies. super duplex is not the correct selection for this temperature??
RE: Inconel 625 vs ASTM A182 F55
You are right the corrosion is more at the interface wet parts, however as per your theory the 625 should be the first to go (higher potential) am I right??
RE: Inconel 625 vs ASTM A182 F55
RE: Inconel 625 vs ASTM A182 F55
Or perhaps the pumping ring in the pump isnt running as it should - is this a VFD operated pump, with operating speed too low to enable adequate recirculation of the seal fluid with the internal pumping ring ?
RE: Inconel 625 vs ASTM A182 F55
Why is that?? why would alloy 55 go first?
RE: Inconel 625 vs ASTM A182 F55
83 is the pumped fluid temperature NOT the barrier fluid temperature.
RE: Inconel 625 vs ASTM A182 F55
RE: Inconel 625 vs ASTM A182 F55
RE: Inconel 625 vs ASTM A182 F55
Considering how often I have seen 625 suffer crevice corrosion in high chloride waters strongly suggest a higher performance alloy.
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P.E. Metallurgy, Plymouth Tube
RE: Inconel 625 vs ASTM A182 F55
RE: Inconel 625 vs ASTM A182 F55
Regards, Wil Taylor
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RE: Inconel 625 vs ASTM A182 F55
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P.E. Metallurgy, Plymouth Tube