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Copper Corrosion

06/16/2010 11:44 AM

Hi everyone, I'm having a problem with the copper conductors on some for the waste water treatment plants I'm responsible for. All the copper in the plants turns black and becomes really brittle, some of the larger surface area busses get large scale flakes built up that look like a pieces of low carbon steel that had been heated up to near melting point and cooled. I thought some of the milder corrosion came from sulfur in the air, but in some of these plants the corrosion will eat through new copper wire in a couple weeks and turn it into a pile of black scale. I'm just an electrician in the far north of Canada and don't have a lot of other resources to call on, I hope someone can help me!

Thanks

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#1

Re: Copper Corrosion

06/16/2010 2:33 PM

If you're having the same issue every couple of weeks I'd think it really worths to try this.

Yahalsit

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#3
In reply to #1

Re: Copper Corrosion

06/16/2010 5:39 PM

Do you get a commission from three rivers gold plating? Sounds like it.

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#2

Re: Copper Corrosion

06/16/2010 4:54 PM

That sounds like evidence of H2SO4 contamination. The first step to a solution is to do more to prevent it from getting to your conductors, i.e. better air flow from the producing sources to direct it away from equipment. Tin plating helps as well, but avoid silver, that makes it worse.

Or as mentioned above, gold plate everything...

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#8
In reply to #2

Re: Copper Corrosion

06/17/2010 11:55 AM

I agree with JRaef. The OP said this is a wastewater treatment plant application. These sites tend to have lots of sulfuric compounds from the bacterial decomposition of wasteproducts. Generally you can smell it!

Unfortunately, the sulfur also reacts with the copper cables, busbars, etc, and even more so with silver-plated components.

In one WWTP where we found the cause of false circuit breaker trips to be flakes of the corrosion falling off busbars across phases, we wirebrushed the busbars and coated them (wherever accessible) with Glyptal insulating enamel. It has high dielectric strength and pretty good chemical resistance to the fumes. Cleared up our tripping problem. The OP may consider doing something like that, as well as improving ventilation of enclosed areas.

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#13
In reply to #2

Re: Copper Corrosion

11/08/2010 5:47 AM

Little Johnny walks to school but now he walks no more, for what he thought was H2O, was H2SO4.

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#4

Re: Copper Corrosion

06/17/2010 6:42 AM

it seems like you have a serious problem of copper corrosion due to atmospheric contamination, is your plant close or near a chemical plant, refinery? one of the more aggressive contaminant is h2s, and as you can see in this paper also waste water plant are considered as potentially very corrosive:

http://nepp.nasa.gov/whisker/reference/tech_papers/chudnovsky2002-paper-silver-corrosion-whiskers.pdf

S

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#5

Re: Copper Corrosion

06/17/2010 8:25 AM

When were these plants built? Were they renovated recently? This sounds like copper sulfide formation, and I'm wondering if it could be coming from drywall. As many as 300,000 homes and businesses were built with Chinese drywall in recent years (including my own, unfortunately) and have experienced this type of copper corrosion with varying degrees of severity.

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#6

Re: Copper Corrosion

06/17/2010 8:29 AM

You might consider placing as much of your wiring as possible in plastic or metal tubes and ventilating the tubes with fresh air. Then only the wiring exposed to your corrosive elements will require periodic replacement.

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#7

Re: Copper Corrosion

06/17/2010 9:40 AM

It seems you have some chloride contamination in your area or plant. I paste an extract of some report that may assist.

The first step in the electrochemical corrosion of copper and copper alloys is the production of cuprous ions. These, in turn, combine with the chloride in the sea water to form cuprous chloride as a major component of the corrosion layer:

Cu -e >> Cu+

Cu+ + Cl- >> CuCl

Cuprous chlorides are very unstable mineral compounds. When cupreous objects that contain cuprous chlorides are recovered and exposed to air, they inevitably continue to corrode chemically by a process in which cuprous chlorides in the presence of moisture and oxygen are hydrolyzed to form hydrochloric acid and basic cupric chloride (Oddy and Hughes 1970:188):

4CuCl + 4H2O + O2 >> CuCl2 ยท 3Cu(OH)2 + 2HCl

The hydrochloric acid in turn attacks the uncorroded metal to form more cuprous chloride:

2Cu + 2HCl >> 2CuCl + H2

The reactions continue until no metal remains

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#9

Re: Copper Corrosion

06/17/2010 4:32 PM

Hi,

above-mentioned chloride or sulphate corrosion: no, both produce green to blue-green products.

Likely: Hydrogen-sulphide or sulfur in waste (converted to hydrogen-sulphide by bacteria) will produce black copper-sulfide.

Possible cure: oxygen or ozone production to quickly oxidise the sulphide to first sulfite and then sulfate. Either enough air introduced by bubbling or forced ozone may be working.

Other possible cure: change the conductors to aluminum, maybe slightly anodised.

Or graphite conductors.

Search and ask the copper supplier for sulphide corrosion of copper and how to avoid.

Have success

RHABE

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#10
In reply to #9

Re: Copper Corrosion

06/17/2010 4:41 PM

Are you saying that aluminum is not affected by H2S? I'm living in an H2S atmosphere due to tainted drywall, and all of the copper in my receptacles is black. Could I change them out for aluminum to avoid the corrosion?

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#11

Re: Copper Corrosion

06/18/2010 11:51 AM

thanks for everyones input, There are H2S monitors in the plants and I rarely see them above 10 ppm but they are located in the walkways and halls, mabey i'll put handheld gas meter in some of the problematic panels and try to record max levels. I know that 10 ppm is the maximum daily exsposre limit and 100 ppm is the "immediately dangerous to life and health" level, does anyone know what concentration of h2S I would be looking at for this type of corrosion?

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#12
In reply to #11

Re: Copper Corrosion

06/21/2010 8:49 AM

In houses with Chinese drywall, levels are far, far below what would set off an H2S monitor, yet the copper becomes coated with black corrosion, eating away enough metal to destroy AC coils in less than a year, and causing other appliance failures at irregular intervals.

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Anonymous Poster (1); crusader911 (3); JRaef (1); jvrj (1); Leonf (1); lyn (1); nathanmue (1); PeterT (1); RHABE (1); strider6 (1); welderman (1)

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