Sacrificial Anodes on C/S Exchanger 2

[Saucerito]

I generally see sacrificial anodes used in exchangers to protect against galvanic corrosion between two dissimilar metals. Are they ever used in 100% C/S construction? If not, why not? Is upgrading the metallurgy generally a better long term solution? The galvanic cell created to corrode the sacrificial anode should work the same as with two metals.

 

[TD2K]

Galvanic corrosion (GC) occurs between two dissimilar metals. If you are using CS throughout the exchanger, there is no galvanic corrosion (depending on the grades of CS used, there could be very low levels of GC theoretically but not enough to be a problem.

That doesn't mean there can't be other forms of corrosion occurring in an all CS exchanger, they just won't be galvani.

 

[EdStainless]

Yes they are, in special cases, but generally if a CS requires CP in order to survive then it wasn't the correct material of construction in the first place.

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P.E. Metallurgy, Plymouth Tube

 

[Saucerito]

TD2K,

I wasn't concerned about galvanic corrosion in the all carbon steel construction, but rather, the use of sacrificial anodes to help it survive normal pitting corrosion from water.

EdStainless,

It makes sense that CS isn't the correct material of construction, but what is the disadvantage of using anodes besides inspection PMs?

 

[EdStainless]

The list is long, anode number and placement, current shielding (physical design), limited current throw (no protection down tubes), anode damage, reliability of PM, .....
And CP won't work where high velocities are an issues (HX tube entrance and exit).

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P.E. Metallurgy, Plymouth Tube

 

[Saucerito]

Thanks EdStainless