It depends on the inhibitor.
Talk to your supplier.
In many cases even if there is carryover it will not be effective.
Many inhibitors have a rather narrow range of use (temp, pH, TDS, ...) and it may not be suitable.
Some have virtually no carryover, while some are more volatile and will carryover a lot.

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P.E. Metallurgy, consulting work welcomed

I would agree with that.

I think it is best to assume the CI will not carry over and actually do any good. If its in the vapour phase, why would it then deposit itself on the pipe surface?

CI effectiveness overall is a different subject and there are many publications and reports which look at this, and about as many thoughts on the number to use as there are corrosion engineers in my experience....

Only be long experience of a system can you really discover the effectiveness of the particular CI you are using on your particular system.

Vendors really do know their substance though so that's usually the first place to look.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

That is one factor that differentiates inhibitors , vapor phase, water phase, oil phase, and "sticks to steel in any phase". As answered , talk to vendors as a start. Look up National Association of Corrosion Engineers ( Houston) ; they have many references available.

Is the question really: "can carryover be relied upon to provide satisfactory corrosion control to downstream carbon steel piping?"

To which the answer would be: "how lucky do you feel?"

Selecting and deploying the inhibitor for the equipment upstream of the separator is a hard enough job in its own right. Add in the business of separation and fluid dynamics, and it all gets out of hand rather quickly.

When dealing with chemical suppliers always remember: their principal aim is to sell chemicals, not operate the production facility

Instead of "inhibitor effectiveness" try to think in terms of "inhibitor availability" within the framework of production assurance, reliability, and maintenance concepts.

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.