Methyl chloride Corrosivity vs. Alloys
Methyl chloride Corrosivity vs. Alloys
(OP)
I need to select alloys to resist small concentrations of methyl chloride (a.k.a. chloromethane) in a planned vapour recovery system. Some condensed moisture is also likely. What is the temperature limit for 2205 duplex in this service?





RE: Methyl chloride Corrosivity vs. Alloys
RE: Methyl chloride Corrosivity vs. Alloys
RE: Methyl chloride Corrosivity vs. Alloys
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if there is moisture i think you've to select another alloy.. these guidelines from NIDI can give u some good advice:
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Corrosion & Rust Prevention Control
RE: Methyl chloride Corrosivity vs. Alloys
Later the mixture (which also contains inert hydrocarbons) will see temperatures as high as 90°C.
RE: Methyl chloride Corrosivity vs. Alloys
I would actually expect the worst pitting conditions at the highest temp that the mixture is still damp. When you get hotter then SCC is the driving concern.
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Plymouth Tube
RE: Methyl chloride Corrosivity vs. Alloys
Is superferritic a viable option for the lower temp. range? I suspect poor impact properties will be a show-stopper though.
RE: Methyl chloride Corrosivity vs. Alloys
RE: Methyl chloride Corrosivity vs. Alloys
I know where 317LMN is, and 904L will be more than that. So I would estimate at least 6x the 2205 price.
-10C isn't that cold. If the tube walls are thin then a super ferritic may do the trick. (thin wall, cleaner micro, finer grain, lower DBTT)
What about mechanical and thermal shock?
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Plymouth Tube
RE: Methyl chloride Corrosivity vs. Alloys
RE: Methyl chloride Corrosivity vs. Alloys
Since SEA-CURE has a small amount of Ni in it, and slightly lower Cr, it does have a better DBTT.
The welding can be an issue. The key is using as thin wall material as possible and welding with Ni alloy filler.
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Plymouth Tube
RE: Methyl chloride Corrosivity vs. Alloys
RE: Methyl chloride Corrosivity vs. Alloys
The ductility issues are in the HAZ, but the only fillers that work are Ni alloy.
If you need 8"s10 then it looks like you are back to looking at duplex grades.
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Plymouth Tube
RE: Methyl chloride Corrosivity vs. Alloys
RE: Methyl chloride Corrosivity vs. Alloys