Copper corrosion 2

[55413826481]

How do I reduce corrosion on silver plated copper bars?
I have face problems on bars mounted on the coast area!

 

[BarryMartin]

I am surprised to hear that you have a problem. I'd consider first, the thickness and porosity of the silver deposit. You should be able to obtain an essentially pore-free deposit with adequate thickness.

An alternative to consider for less money is nickel. Depending on current densities, it might be a cheaper alternative, although silver, properly applied, should provide better (i.e., lower contact resistance) performance over time.

I can be contacted at martin.sifco@verizon.net.

 

[Himself]

Bill Merrins:
Additional information is required.
Is the silver plate for conductive purposes or for corrosion protection and appearance?
If the silver is for conductance what conductance level would be required for the application?
There are various coatings that can resolve either application.
I can be contacted at: Billmerrins@hotmail.com

 

[kenvlach]

The silver plating can be chromated for tarnish resistance; see QQ-S-365D, Grade A. Chromate is the only protective finish permitted under this spec., non-conductive coatings are prohibited.
MacDermid and maybe Henkel produce chromates specifically for silver.
An answer elsewhere(

http://www.finishing.com/185/80.html),

states that the chromates used on aluminum (e.g., Alodine 1200S, Iridite 14-2) also work on silver. It should be easy to find a jobshop that does 'chemfilm' on aluminum and has tanks to handle busbar, etc.

As are Barry & Bill, I am curious about the quality of the silver plate that comes on copper busbar.

 

[hacksaw]

Silver plate corrosion is common problem in coastal (high humidity) areas especially where H2S/SO2 is present.

Be sure all of the conduits and duct banks are properly sealed to keep humid air out.

There are wipe on corrsion inhibitors if you want to use them, but the best thing is to keep the bus bars warm and dry. That may entail temperature/humidity control.

Good luck

 

[kenvlach]

If your corrosion is dark, it's probably silver sulfide or sulfate as per hacksaw. If white, then silver chloride. I doubt that silver oxide or hydroxide is significant without S or Cl or heat.

I suggest using aluminum conductor*.
I use bare aluminum busbar in coastal area next to air-agitated sulfuric acid anodizing tanks, with humidity to 100% due to heated tanks nearby, plus dust from neighboring farms. Just sweep the bars clean every few months.

*With electrical joint compound (Alcoa #2) properly applied, and about 1000 psi contact pressure for bolted busbar connections. Left original oxide on the extruded bars intact (except for connections).

BarryMartin: Have EN (electroless nickel) plated some Al bar, but only above process tank for electrical contact with parts racks. Some day, might brushplate some gold on.

hacksaw: Re 'duct banks are properly sealed,' 'warm and dry,' 'temperature/humidity control.' Sounds like you work for NASA or at least a prime!

 

[hacksaw]

kenvlach,

nasa not hardly, it was in a pulp mill on the florida coast.

we had serious sulfide corrosion of copper busbars. Only after the DCS cards started failing (same cause), was the seriousness of the problem realized at the upper levels.

 

[qorw]

Would anyone know what method is best to protect copper busbars at the coast and in particular at a Waste Water Treatment Works where there is a lot of Hydrogen Sylphide?

We are debating the use of copper with heat shrink, copper with S6 solder/tin, copper with electroplated tinning (15micron), copper with silvering paint.

Which is most effective (The IEC standards dont seem to address this)

 

[EdStainless]

If you know that sulfide will be an issue I would not use Cu, not even with Ni plating. Unless you can put it in an enclosed and purged bus duct you will be fighting a loosing battle. Use Al and oversize the bus to keep it cool.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[vshaw]

I have silver coated (copper) busbars in an assembly plant, which is no where near the sea. Busbars have tarnished, whilst the manufacturer claims that there is no concern. Will discoloration of busbar affect its performance or have any hazards?