Water Well Corrosion 1

[bimr]

The carbon steel bolts have corroded away on this 1,100 feet deep municipal water well. The well has been in service for 2 years.

The deeper column pipes have black staining.

I suspect that this is due to hydrogen sulfide. The bolts disintegrate in your hand and there is a faint odor of sulfide.

Has anyone seen this type of corrosion and the cause?

 

[bimr]

Attached is the water analysis.

 

[rconner]

Are the flanges etc. that appear to be bolted together also basically plain "carbon steel"?

 

[bimr]

The piping is painted carbon steel. This is the column piping that is screwed together.

The flanges are the pump stages and are bolted together.

 

[rustbuster]

Upgrade your fasteners, coated, stainless, etc.

 

[EdStainless]

Maybe the best would be to go to Monel. These are available as high end marine hardware and will hold up well, without some of the issues of SS bolting.
Is the pump ductile iron or Ni-Resist?
How does your pump shaft look?

The painted pipe has partially protected it, allowing the bolts to suffer full exposure.

I have seen large carbon steel anodes bolted to such pumps to provide some sacrificial protection.

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Plymouth Tube

 

[bimr]

As of todayo, the pump has not been disassembled. I understand that the pump bowls are cast iron.

I will update when the pump is taked apart.

 

[rconner]

While I guess you haven't really said that the degree of corrosive attack is worse or more problematic on the bolts, that is an inference. While I’m not going to profess specific expertise in that downhole environment, and along with this I guess there may be other factors perhaps of interest that are not provided e.g. pH, conductivity, temperature, presence of carbon dioxide etc., a lay look at the dissolved solids you have tells me you might have at least a pretty good “electrolyte” (if not some funky stray current or sulfurous/ic acid or bug stuff going on!) I agree bare or uncoated carbon steel bolts (and maybe particularly with inherent differentially high stress, crevices, or any sort of undesirable galvanic relationships that might be involved) probably would not be the first choice of most experts for such an immersion environment. With regard to general or first principles, and further link references you might be interested in, see prior threads e.g. like at

http://www.eng-tips.com/viewthread.cfm?qid=177785

. Have a good weekend.

 

[blacksmith37]

If corrosion is bad enough to warrent new pipe, a improvement could be 13% Cr (at a cost less astonishing than monel,etc). API tubing (up to 4") is reasonably available, thread and coupled (get the cheapest thread you can find for this application). API casing comes in larger diameters ,but availability is problematic.
And oil production submersible pumps will offer some alloy availabilty if you want new pumps.

 

[EdStainless]

At this point the bolts are the concern.
I doubt that the piping will be very bad.
I do worry about the pump internals.

Normally I would say that this kind of attack requires air exposure, which should be zero at 1,100' in a well.
Makes me suspect MIC.

I do worry about the condition of the pump internals.
Let's wait and see.

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Plymouth Tube

 

[bimr]

The pump bowls are actually a porcelain coated cast iron.

 

[TVP]

I tend to agree with Ed that a nickel alloy like Monel (Alloy 400, UNS N04400) is attractive for this type of application, since it has excellent resistance to aqueous corrosion, sulfuric acid, and MIC. However, it is not very strong (YS ~ 275 MPa, ASTM F 468M), so the tightening torque/preload may need to be reduced relative to a higher strength steel fastener. There are higher strength, corrosion resistant alloys available, but they will have much higher cost, reduced availability, etc.

 

[bimr]

We have come to the conclusion that the corrosion of the carbon steel bolts was caused by hydrogen sulfide produced by sulfate reducing bacteria that must have been present in the well.

No other well component was observed to be corroded.

The well column pipe was stained black, most likely from iron sulfide.

 

[ione]

Have you any possibility of inspect concrete elements in the well. The microbial sulphur metabolism could also affect concrete