Valve disc corrosion - Possibly MIC?

[Hercules28]

Dear all,

Does this look like MIC corrosion? any ideas?
This was closed all the time. Nothing was flowing trough it.
Only at one spot as you can see in pic 1 I see this smooth corroded surface. The medium was water at room temperature.

Herc

 

[Hercules28]

Here is how the matching wall looks like. It has corroded too.
Material isL: ductile iron for the housing and the disc is ductile iron coated with electroless Ni. They don't touch because there is a seal between them.

 

[Hercules28]

And here is how it looks closed. You can see the hole.

 

[Hercules28]

And a cut section.
I am thinking to send it out for a SEM EDX analysis.

 

[metengr]

Based on the last photograph and the concentric rings of oxide streaks, it could be MIC damage. This could have been initally caused by underdeposit corrosion if this valve is closed and contained stagnant water. How clean was the water?

 

[Hercules28]

This was regular stagnant municipal water with no treatment.

 

[Metaljon]

Hard to tell from a photograph that it is MIC or not. Just looks like under-deposit corrosion. Can't see any obvious signs of slime's unless they have all be cleaned off. MIC loves ductile iron in stagnant conditions and causes an accelerate rate of corrosion attack. You would need to do Biological testing if you want to confirm a diagnosis of MIC not just EDS.

 

[bimr]

This appears to be MIC caused by anaerobic bacteria that will reducing the sulfate ion to sulfur. The end result for the bacteria is a sulfuric acid solution. Would also expect some black staining of the pipe. The piping material may be flaking off in layers, but this is hard to see in the pictures.

I witnessed this with a deep well where the carbon steel bolts of a well pump were eaten away in about 2 years.