CS Methanol Storage Tank corrosion rates
3

Question

CS Methanol Storage Tank corrosion rates

Justice100 (Chemical)

(OP)

28 Apr 21 11:15

Hi,

We are looking at using CS for a methanol storage tank and injection system at and oil and gas site. I see either CS or SS316 is suggested from various sources (e.g. ISO 21457, M-001 etc). Is it possible to calculate a corrosion rate for using CS? I have done some searching but can only find a rate of <0.02" per year (http://www.methanol.org/wp-content/uploads/2016/06...), based on this number the tank could fail in 7 years.

Also, the issue of SCC in CS with methanol, the following link suggests the methanol should have a concentration of <99% to prevent SCC - https://www.stepchangeinsafety.net/alerts-moments/...

Could anyone suggest a further reference that backs this up?

**guest0821** (visitor) · Answer 1 · 2021-04-28 14:03:13

Methanol in CS is playing with fire in terms of stress corrosion cracking risk. SCC doesn't have a 'rate', it is all or nothing. Then after you've built the perfect container, you then must closely control the contents in perpetuity.

Experts, not interweb references are what you are looking for.

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

EdStainless (Materials) · Answer 2 · 2021-04-28 15:28:21

To suppress SCC in Methanol with CS takes something like 1-2% water content. (M-100 is 1-1.5% water)
If you can't allow that or control it then SS is the right way to go.
304L and 316L have been used if there is NO detectable Cl (ppb levels).
Using 2205 duplex should be an attractive option, its higher strength allows for a lighter tank and the increased corrosion resistance makes it more durable. Many reports show that replacing 316L with 2205 in tanks does not increase cost if the tanks are properly designed.

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P.E. Metallurgy, consulting work welcomed

Mussha (Mechanical) · Answer 3 · 2021-05-05 12:47:11

Methanol storage tank can be constructed using CS with higher grade and provided CA 3mm. Additionally internal coating/painting with CP system to be consider if CS plate used. If cost allow for SS then CA=0 and no need for internal paint/coat.

Justice100 (Chemical) · Answer 4 · 2021-05-06 19:03:34

Thanks all for responding.

SKMoshin - is there a reference for that information? Happy to purchase the reference, I just can't find anything with the detail you describe.

**guest0821** (visitor) · Answer 5 · 2021-05-06 23:59:13

Handbooks for construction of vessels for chemicals like this have been published.
Google is your friend.

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

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CS Methanol Storage Tank corrosion rates
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