Galvanic Corrosion

[Xeros]

Hi,

I have an air cooled heat exchanger with stainless steel tube and carbon steel tubesheet. And Joint is expansion type.

In this case,
Could galvanic corrosion occur?

I think that there is no problem because tubesheet surface is larger than tube surface.

However, Some body said Tube surface is larger than tube sheet surface.

My question is there any possibility for galvanic corrosion between SS tube with CS tube sheet?

if possible, what is the solution?

Thanks a lot.

 

[0707]

My answer is yes. Depending on the service temperature of your air cooler one possibility is to line your tube sheet with a composite corrosion barrier such as Belzona or similar coating.

regards

Luis marques

 

[Xeros]

Thanks, 0707

I think SS tube surface (cathode) is very small because it is header side.

If this is shell & tube Heat Exchanger and shell side, SS tube surface is larger than CS tube sheet surface.

However, this case is simmilar with channel side on shell & tube Heat Exchanger. anode (CS tube sheet) is larger than cathode (SS tube).

This is my opinion.

How about your opinion?

 

[strider6]

Xeros

In my opinion there are two important points:

-If you are concerned with internal corrosion, what is the fluid inside the tube? the possibility of galvanic corrosion is a function of the fluid conductivity.

-If you want to paint to protect the Carbon Steel you've to paint both areas or at least the cathodic area and not the anode. If you paint only the anode, carbon steel, and there is a defect you'll have a very small anode vs a very big cathode areas, stainless steel, with very high corrosion rate.

Strider

http://www.corrosionist.com

 

[EdStainless]

Yes you may have galvanic corrosion. It will depend on the conductivity of your fluid. If the fluid is not highly conductive and it is not very corrosive then you may not have any issues.
The standard practice is to coat the tube sheet and water box, then install sacrificial anodes.

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