Bad idea? Carbon steel and 304 stainless?

[Hercules28]

Is it a bad idea to connect carbon steel and stainless pipe?


Room temperatures and mainly water.

I saw in a galvanic series chart that the difference in potential is about .4 and obviously the Carbon steel will get sacrificed.
Any coating that I could use between them?

 

[moltenmetal]

Treated water? Deoxygenated? Then it's likely OK.

Untreated, oxygenated water? Water with high total dissolved solids or low pH? It might be a risk.

Make the connection with galvanic isolation (galvanic unions etc.) if possible and you can take the risk out of it. Just don't connect them through the structure or with a ground wire etc. or you've defeated the usefulness of the galvanic union.

 

[metengr]

No mention of surface area of the carbon or stainless steel, which is an important variable, so no accurate response can be provided. As with any galvanic couple, surface area of the material behaving as an anode should be larger in comparison to the cathodic material.

 

[Metalguy]

Coat the cathode (304) near the junction.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[EdStainless]

Guy's comment is the answer, coat the SS. Coat the threads, the end, and the ID back about 20 time the pipe diameter.

Actually the galvanic series that you saw is in seawater. In water with low conductivity it is less of an issue. With Lake Michigan water you would not need to do anything.

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Plymouth Tube

 

[dik]

Lake Michigan water provides a coating?

Just curious...

Dik

 

[EdStainless]

No, clean fresh water has such low conductivity that galvanic corrosion is very slow and gradual.

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Plymouth Tube