Galvanic Corrosion 1

[heylj]

I have project that is showing signs of what appears to be galvanic corrosion on the domestic water lines. The water source is well water. The corrosion is showing up at water heater connections and at flanged connections. That is where we would expect to see it, but the interesting condition is that we did specify and have installed di-electric couplings.

Has anyone else run into this type of corrosion condition?

Our first guess is grounding and we do have the water line grounded but it might be possible that the hot water line, since it is isolated by the di-electric, did not get bonded to the ground wire lead? Any other thoughts or conditions that may cause this?

Any specific products that anyone has used that work better than others?

 

[ChasBean1]

Id be interested to know the salinity of the well water. I don't think dissimilar metals need to be in direct contact for oxidation of one and reduction of the other, so long as the salinity of the electrolyte is sufficiently high. Dielectrics generally separate the two dissimilar metals but don't provide a sacrificial anode. Water stagnation can also add to the electrolytic properties of the water as impurities aren't flushed away in a moving stream.

Interesting you note the corrosion on flanges - are there two dissimilar metals at the flange? It makes me wonder if this is a hard water issue or corrosion from chloride or other ionic impurities versus a galvanic corrosion issue...

The cure could be water filtration/softening or use of sacrificial anodes. I'm not in the business of purchasing and installing, but if you're pretty sure this is galvanic corrosion, see if there's a replacment for the simple dielectric fittings with similar fittings containing some sort of sacrifical metal inside (not one that acts as a pressure barrier, but a solid fitting that may be lined with zinc) - check google.com or any search engine and search for 'sacrificial anode'.

No concrete answer today, but I hope some of this helps. -CB