How do Aqueous corrosion and high temperature oxidation/sulfidation differ?

[YungPlantEng]

Trying to understand approximations for corrosion mechanisms impacting a quench tower nozzle that supplies water to so2 to cool it down.

I don’t want to get into details but from common texts I can’t really understand if a specific corrosion type is known to more impact the spray nozzle.

The metallurgist who studied the sample assumed sulfidation based on the sulfate samples existing, but my understanding is salts are a primary component of most sulfidation mechanisms, and no salts/carbon was found in the sample study or are expected to exist in our process.

I’m not really sure if I can make an assumption of “wetted surface” and say high temperature oxidation / sulfidation mechanisms aren’t relevant/aqueous mechanisms dominate the reaction.

And if we can make that assumption could we potentially move to a metal/coating more focused for its erosion protection / aqueous acid protection characteristics without needing to consider the system as high temperature?

Currently use c276 for this process and component lifetime improvement would be very beneficial. There is very little literature specific to this process and a lot of idiosyncrasies that I won’t cover here so apologize for the question if it’s elementary - don’t come from a corrosion background.

Thanks for any help! I can supply more info as needed but obviously IP purposes can make that difficult

 

[Dhurjati Sen]

Consult API RP 572.

ASME Handbook on Corrosion (Volume 13) could be your last resort.

DHURJATI SEN
Kolkata, India

 

[Chumpes]

even not getting into details, temperature remains an important parameter...

HT corrosion mechanisms does not initiate below 200°C


Another important parameter is the actual metallurgy... carbon steel ?

SO2 + H2O can be very corrosive (acid dew point corrosion, wet acid corrosion, etc.)

 

[EdStainless]

In aqueous corrosion the electrolyte is water soluble/based.
At high temp the electrolyte tends to be molten salts and such.

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P.E. Metallurgy, consulting work welcomed

 

[YungPlantEng]

So sulfidation would be the equivalent of high temperature corrosion in the absence of salt contaminants? Ah I wish I remembered my heat transfer courses well enough to figure out whether I should expect condensation and aqueous corrosion on the nozzle in aqueous service

 

[EdStainless]

One of the problems is knowing what actually condenses first.
Some acids will condense at 250F or so.
And sulfur compounds will condense over a wide temp range, and they cause corrosion issues when the temp goes back up.
There is an excellent book on high temp oxidation and sulfidation, but I'm not home to give you the title.

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P.E. Metallurgy, consulting work welcomed

 

[YungPlantEng]

I would imagine our dry side is only subject to dew point corrosion during transients where the flue gas flow stops and resulting convection of wet side into dry side creates acid dew point corrosion. Would love to see some good resources on it

 

[EdStainless]

High Temperature Corrosion of Engineering Alloys
G. Lai
pub ASM
ISBN 0-87170-411-0

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P.E. Metallurgy, consulting work welcomed

 

[Rubje]

To add onto what others have said, alloy C-276 is relatively corrosion resistant to aqueous corrosion, but not to high temperature oxidation or sulfidation. What you are describing can actually be high temperature oxidation so this is important.

Alloys like 625, 725, C-22, C-2000, or titanium may be better options for this application but a more thorough analysis is needed.