Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations MintJulep on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Connecting duplex, monel and aluminum / bronze in seawater service
- Thread starter samoht
- Start date
EdStainless
Materials
I am concerned about the AlBrz and dealloying. The duplex/monel should be fine.
Just remember a 22% Cr duplex will not fully resist cevice corrosion in seawater.
= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.
Just remember a 22% Cr duplex will not fully resist cevice corrosion in seawater.
= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.
At 45 deg C, your client may be replacing the vessel a little earlier than planned.
Steve Jones
Materials & Corrosion Engineer
Steve Jones
Materials & Corrosion Engineer
- Thread starter
- #5
mshimko,
Since there is a chance for galvanic corrosion, would you recommend using a non-conducting material in the gasket i.e. rubber?
Sjones,
What is your main concern at this temperature? FYI customer plans to use some kind of corrosion inhibitor (chemicals) there is also a 3mmm corrosion allowance on the vessel. Oxygen level at normal operation will be approx 300ppm. Design life is 25years.
Since there is a chance for galvanic corrosion, would you recommend using a non-conducting material in the gasket i.e. rubber?
Sjones,
What is your main concern at this temperature? FYI customer plans to use some kind of corrosion inhibitor (chemicals) there is also a 3mmm corrosion allowance on the vessel. Oxygen level at normal operation will be approx 300ppm. Design life is 25years.
If you can reliably electrically isolate the bronze vale, at EVERY connection, and verify same using impedance measurements, then its an option to consider.
WHat I would recommend, (but maybe not practical at this point in time) would be to install a duplex stub about 12 incges long off the vessel, then connect the valve, This would at least provide an equal ratio.
WHat I would recommend, (but maybe not practical at this point in time) would be to install a duplex stub about 12 incges long off the vessel, then connect the valve, This would at least provide an equal ratio.
A 3mm corrosion allowance on a duplex stainless steel vessel plus the use of inhibitor - somebody is having a laugh. The PREN of 22Cr duplex is not sufficient to withstand seawater at 45 deg C. A 40 minimum PREN is required taking it straight to 25Cr. Why pay for a duplex vessel and then pay again for corrosion allowance and chemical corrosion control?
Steve Jones
Materials & Corrosion Engineer
Steve Jones
Materials & Corrosion Engineer
- Thread starter
- #9
I suppose the client knows best eh?
Steve Jones
Materials & Corrosion Engineer
Steve Jones
Materials & Corrosion Engineer
I saw an article a few years back in NACE Materials Performance. The point was one of the primary aspects of being a corrosion engineer is SALES. Sales in that we need to convince someone (typically the boss or the customer) that it may be smart to spend more money now and avoid a corrosion problem later, as corrosion is almost always a probem "tomorrow" rathr than "today".
When dealing with cutomers, I'd just just suggest that you (a) answer the mail; that is, provide the answer to the question the curtomer asks, but then (b) provide the answer to the question he didn't ask.
It may not help as often as we would like, but I've seen customers change course based on this type of feedback (most recently just 2 weeks ago, in fact). Occasionally I even submit responses to solicitations that essentially suggests (in nice terms, of course) the customer is asking the wrong question.
When dealing with cutomers, I'd just just suggest that you (a) answer the mail; that is, provide the answer to the question the curtomer asks, but then (b) provide the answer to the question he didn't ask.
It may not help as often as we would like, but I've seen customers change course based on this type of feedback (most recently just 2 weeks ago, in fact). Occasionally I even submit responses to solicitations that essentially suggests (in nice terms, of course) the customer is asking the wrong question.
EdStainless
Materials
The other thing to remember is that there is no such thing as a corrosion allowance in stainless steel exposed to a chloride environment. Since the failures will be localized, either crevice or pitting attack, the time to penetration is limited by corrosion initiation. Once it starts it will penetrate the full wall quickly, adding metal will have little effect.
= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.
= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.
- Status
Similar threads
- Locked
- Question
