Galvanic corrosion between carbon steel column and stainless steel pall rings

[daniellouw]

We have a carbon steel (CS) column with carbon steel pall rings. Methane-rich gas is fed at the bottom at about 30 °C and at the top, water containing CO₂, is fed at about 200 °C. The purpose of the column is to saturate the gas with water to reduce the required steam needed to feed into the reactor.
Currently the carbon steel pal rings are prone to corrosion (not the shell). The Fe²⁺ is then transferred from the bottom of the column to another column and precipitates as FeCO₃.
Thus, if the corrosion on the pall rings can be reduced, it will reduce pall ring replacement cost and will reduce FeCO₃ blockages in the other column.
The original design suggested using ceramic pall rings, most probably for this reason.
My question is: is it an option to install stainless steel (SS) pall rings instead? The main concern is galvanic corrosion of the carbon steel column shell and column supports which will be in contact with SS. Is this a serious concern? Some people are of the opinion that the gas will prefer to flow at the wall of the column, thereby keeping the wall fairly dry and therefore will galvanic corrosion not be a serious concern. It also seems that there are other CS columns with SS rings in industry which does not have a galvanic corrosion problem.
Any thoughts will be much appreciated.

 

[Dhurjati Sen]

Dear daniellouw,

It is best to follow the designer and use ceramic pall rings.

However, SS trays, pall rings, chimney trays, packings, etc. are a common feature in CS columns. The CS shell is not affected by Galvanic Corrosion due to the "Area effect"

Regards.

DHURJATI SEN

 

[EdStainless]

You may have accelerated corrosion at localized areas of contact, but overall it should not be a big issue.
Yes, this is likely why they used ceramic and that would be your best option.

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P.E. Metallurgy, Plymouth Tube

 

[racookpe1978]

Do the small localized corroded areas affect your product clarity, purity, or function?

 

[daniellouw]

Thank you so much! This helps.