Corrosion from AC overhead lines

[Baltoche]

Dear All,

I'm working on corrosion generated on buried infrastructures by overhead distribution lines. If somebody is experienced on this field, could we start a discussion ?

Thanks

 

[LittleInch]

What do you want to know?

This is a well known issue in coated buried pipelines. You either bury some zinc wire and attach it or earth it via a device which lets the AC voltage out, but keeps the DC cathodic protection.

Search "AC induced corrosion".

The attached might help? I've got a few more like that.

You might be better off in the Corrosion Engineering forum. Just report your own post and ask the mods to move it as you can't have two, but a bit more information on what your issue is or what you need to know would help...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

The first step is to actually measure the leakage currents.


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P.E. Metallurgy, consulting work welcomed

 

[LittleInch]

Not really "leakage" though. It's about AC induced voltages, which vary depending on voltage of the OH lines, distances, length being paralleled to the OH line etc.

It is a real thing, but needs specific sized coating defects otherwise there isn't enough current to cause an issue for a big defect, or not enough area for a pinhole defect. You need about 1 sq inch from memory and then it is like someone drilled a hole in your pipe....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

I know that the current is induced, but it doesn't cause corrosion issues until there is leakage.

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P.E. Metallurgy, consulting work welcomed

 

[LittleInch]

There is apparently a "sweet spot" for the size of coating damage and hence current.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

All coatings are permeable, just some more than others.
There are some coatings that if they have a potential across them, they will end up disbonding.
You have to careful about handling this or you can make it worse.

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P.E. Metallurgy, consulting work welcomed