What kind of paint is used in copper bus bars

[SeanB]

Cheapest will be paint, followed price wise with powder coating, both of which will adhere well to properly prepared copper surfaces. Connection areas best to use a dielectric grease to exclude air and moisture. You can use a plain dielectric grease, very common in things like outdoor communications in connections all over, or even a thin film of the copper containing ones, as it uses the same base grease. Your connections really should use belleville washers, to provide a consistent clamping force, not a shake proof washer, as the copper will slowly flow over time, and the belleville washer keeps a constant tension on the joint. Steel bolts and nylock nuts work well to keep the 2 parts together, as the fastener hardware should not carry current, only the flat surfaces of the copper alone.

[T3sl4co1l]

Hm, looks like copper doesn't flow much at all, at reasonable pressures.  Neat:
https://nvlpubs.nist.gov/nistpubs/jres/47/jresv47n4p272_A1b.pdf

Bus bars are generally going to be half or full hard, I think?  So they should be quite strong, supporting loads in the 20ksi (138MPa) range without appreciable movement.  Under a bolted joint, high points in the surface may crush down, improving the connection; the joint overall shouldn't creep much, and certainly won't creep (over any meaningful time scale, by the looks of it) enough to relieve pressure on it.  I'm certainly not going to say a superior type of washer is bad, not at all; rather, it looks like it merely isn't necessary.   So, you can go for preventing rotation (lock washer) over maintaining tension, it would seem.

The corresponding figures for pure aluminum look to be significantly lower (can confirm, I've bent a thick bar of the stuff by hand, it's like hard shiny putty), even at room temperature (the one paper doesn't even show over 110°F); combined with the propensity for oxidation, an abundance of caution is well deserved with aluminum!


Speaking of hardware types, you can still go for a bronze bolt if you like, of course; this may even be required at high frequencies.  Even if this doesn't affect resistance much, the matching tempco may prove helpful.

Mind, I don't know what actual standards are for using these; like I said at the top -- check your local code!

Tim

[trobbins]

I'm with SeanB.  Even vaseline has been used for > 10kA joints.  One aspect to keep in mind is periodic maintenance of such joints, to identify micro-arcing and tracking if the current density is relatively high, and also to confirm voltage drop across a joint is not increasing.

[Ground_Loop]

I've done many industrial power distribution installations in salt air environments and where bussbar is used it is either bare or silver plated.  Never had a problem.

[EPAIII]

I have seen a lot of copper bus bars in use and very, very few of them were painted. Other means were usually used to protect they from corrosion, like an air tight enclosure.

But if you are going to paint them, you should be a lot more concerned with the mechanical and chemical properties than with any electrical considerations. In your case, that means a paint that will have strong adhesion and resistance to the elements they will be exposed to that are presently causing the corrosion. And, almost any covering over the surface will prevent corrosion.

One tip: it would be a lot better to put the paint ON the bus bars instead of IN them.

[Terry Bites]

Give them a clean with abrasive paper, then alcohol or acetone then Hammerite.
Tip, thinners for hammerite and similar paints are way over priced. Acetone/ White spirit (mineral spirits) 50:50 works a treat.