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SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon
2

SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

(OP)
We are in search of best suitable material for following condition as of now we have SS304 for which we are getting Cl-SCC in piping.
1. Max operating temperature is 90 degC.& process fluid is Benzene (45,123 kg)+ AlCl3 (800 kg)+ C14-C18 Olefin (20,922 kg)+ 32% HCl (10 kg)+ CaO (714 kg)+Filter Aid (1000 kg).
2. Only Chlorine content w. r. t. 32% HCl is around 45.4 ppm.
3. 32% HCl aqueous solution (10 kg) as a whole in the total reaction mixture corresponds to 146 ppm i.e. aqueous chlorine.
4. Max operating pressure is ~4 kg/cm2g

RE: SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

So it is hot, acidic, and has Cl present?
How much more resistance do you need?
Is there any other corrosion than CSCC?
Normally the next step up in CSCC resistance from a 300SS is to move to 2205.
It is not immune but it does have significant resistance to CSCC.
2205 is also significantly stronger which allows people to redesign systems and use thinner walls.
Using less metal can offset a large part of the cost difference.
The next step up from there is a very large one to things like Ni alloys.

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P.E. Metallurgy, consulting work welcomed

RE: SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

No half measures here, go directly to one of the elite C alloys.
Alloy 59 and Hastelloy C-22 are my preferred options in this class.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

I'm with EdStainless- sounds like a solid duplex like 2205 should do the job. I don't see the need for Hastelloy though if you can afford it, it would be pretty bomb-proof.

RE: SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

Considering the cost involved, I suggest you ask the NiDI experts.
Pay them a few bucks if necessary, because you want to build this one time only.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

You need to go back and check some actual fluid analysis. The acid and Cl only matter in the water, their fraction of the total is not relevant.
Get an actual Cl and pH on the water fraction.
I have seen systems where I was told that they were 100ppm Cl, but it was only 0.5% water and the Cl was based on the total. The result is that the water phase was 20,000ppm Cl.

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P.E. Metallurgy, consulting work welcomed

RE: SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

EdStainless gets a star for that point. This could be mostly organics and the aqueous phase could basically be partially neutralized concentrated hydrochloric acid...in which case ironic metallurgist's recommendation of alloy C would be spot on.

RE: SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

EdS,

You have described the situation inside oil storage tanks. The small fraction of denser water absorbs all the chemical nasties and carries them down to the floor where they have their way with the steel.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

(OP)
Thanks EdStainless,
Is there any other corrosion than CSCC? NO
Normally the next step up in CSCC resistance from a 300SS is to move to 2205. 2205 also not immune to Cl-SCC. so i need to think.
Using less metal can offset a large part of the cost difference. How we go for any Non metallic coating like BELZONA something.
The next step up from there is a very large one to things like Ni alloys. For Ni Alloys we are exploring option for change MOC to Monal/ Alloy-B-2/ Alloy-625 but you know all need too much money.
For lab analysis i will reply you after getting proper feedback.

Thanks again for all feedback.

RE: SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

If you go for a coating then you need a CSCC resistant substrate, because there will be holes in the coating. So people generally move to very thick carbon steel pipe, and hope that their inspection can find local defects and pitting before it goes through the wall.
There is a lot of data out there on 2205. Maybe you could install a couple of test spools and get some real plant experience.
If you are looking at alloys both Monel and B-2 are designed for very specific service. I would go with IronicM suggestion and stick with C-22, 59, 686. the price will be the same and you will get broad corrosion resistance.

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P.E. Metallurgy, consulting work welcomed

RE: SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

(OP)
The feedback i got from NiDI:
{
Depending on the required life of the piping and the economic incentive
upgrading to an alloy such as Alloy 20Cb-3 (N08020), Alloy 825 (N08825), 6%
Mo austenitic (S31254) or one of the duplex alloys, 2205 (S31803) or 2507
(S32750). Any of these alloys will have a higher threshold temperature/chloride
concentration for chloride SCC than the existing Type 304.
}
FYI,

RE: SS304 getting Cl-SCC in 0.03% aqueous HCl+AlCl3+CaO+hydrocarbon

The key work is 'higher threshold', none of those alloys are immune to CSCC.
You need to search and find out how resistant they are, in numbers.
And you need to know what your real water phase composition is.
Then maybe you can narrow it down.

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P.E. Metallurgy, consulting work welcomed

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