Corrosion on a ductile iron pipe - Water tests

[Hercules28]

Dear all,

I have this ductile iron pipe (see pic) that after a few months in service it corroded severily on one end. The pipe was mechanically attached to another pipe with a mechanical joint also made of Ductile iron. So no obvious galvanic cell.

However due to the nature of the mechanical joint there is the possibility of crevice corrosion.
The medium that flows through is pond water...really dirty (looks black)... and obviously corrosive.

They are using Zn anodes in various areas to tame it down.

I want to suggest that they do some field test to the water to examine the pH.

What else should I be looking for in the water analysis? factors that may cause corrosion?

Thanks

 

[Hercules28]

pic2

 

[Hercules28]

pic3

 

[CoryPad]

You should look for chloride ion concentration, and the presence of any microbes that can influence corrosion (MIC, lots of information available).

 

[btrueblood]

Sulfur content too?

 

[rconner]

Image ...6828 does not look like any "ductile iron pipe" I have ever seen, and I also can't make out any sort of lining (though I guess the material could well be iron). The ends of this piece are also not a conventional "mechanical joint" (at least as normally described in the industry). Frankly, I have no idea what this fitting is!
Was this piece buried or exposed, and where did whatever sorts of end gaskets seat, somehow on or in each end? Are there any pictures, drawings, joint cross-sections or sketches of how this item was connected in the piping system, and also how/where were anodes affixed to the piping?
While "corrosion" of any sort of reasonably cathodically protected iron after a "few months" sounds even more strange than the original inquiry, I guess some sort of stray currents could cause accelerated attack, or gasket leaks and high velocity/turbulent swirls particularly near the end of a pipe or fitting could pick up abrasive particles and erode iron? If corrosion is due to the "water", one would think most metal area would be affected?

 

[mrfailure]

If the mechanical join between the two pipes was properly tightened, would you really expect crevice corrosion?

 

[bimr]

"Pond water" is not commonly corrosive. MIC will not occur in just a few months either. "Stray currents" are usually proposed when one has no idea what is causing the corrosion.

Look for chloride ion concentration, hydrogen sulfide, and acids. Exactly what is the pond water?

Perhaps you should have used a non-metallic pipe.