What kind of paint is used in copper bus bars - Page 1
Forum section: electronics / projects

author: drakejest
author_rank: Regular Contributor
timestamp: October 03, 2021, 02:25:54 pm
content: I have some bare copper bus bar that i would like replace because i have grown concerned on how corroded they become because of humidity and salt (yes even inside boxes, ill be replacing the box too so that humidity wont get in easily) . I do not want to tin the entire bus bar but instead paint the majority of it and only tin the one near the contacts.So may i know what kind of paint,primer, or coating is used, always see these like in the image

author: Bud
author_rank: Super Contributor
timestamp: October 03, 2021, 03:04:44 pm
content: You can try Plasti Dip for soft rubberized coating.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 03, 2021, 03:32:06 pm
content: You could use enamel paint such as Rustoleum. I would also suggest using dielectric grease instead of tinning since the solder layer would have to be really thin to not interfere with the clamped connection.

author: drakejest
author_rank: Regular Contributor
timestamp: October 03, 2021, 04:46:12 pm
content: Thats great there seems to be may ways to do it !Im curious how are they done in industrial setting? im sure this is very common in that areaQuote from: NiHaoMike on October 03, 2021, 03:32:06 pmThat is indeed true it will be hard for me to do a uniform layer of TIN.

author: Marco
author_rank: Super Contributor
timestamp: October 03, 2021, 05:03:59 pm
content: If you get it done professionally isn't it cheaper to just tin/silver plate the entire bus bar?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 03, 2021, 05:53:45 pm
content: Have seen copper grease (anti-seize) used for that purpose, not sure how well the particles actually smoosh down and make contact, though. Grease is a good idea for thermal contact. Not sure offhand if dry, clean contacts are better (for which tin plating is perfectly fine, again, as long as it stays clean!).NEC should say something about it, no?Tim

author: drakejest
author_rank: Regular Contributor
timestamp: October 03, 2021, 07:14:31 pm
content: Quote from: Marco on October 03, 2021, 05:03:59 pmI will not get it done professionally as there is no one that can do that withing few hundred KMs. I just want to know how its done professionally to set a baseline on how its done. the closest i can do to professionally done is powder coating, as there is someone that can do that that is close.Quote from: T3sl4co1l on October 03, 2021, 05:53:45 pmIm not an NEC expert , the NEC doesnt even apply to us as we have our own electric code. But most likely how its done by the NEC is pretty much close to ours.To the NEC experts out there the floor is yours

author: PartialDischarge
author_rank: Super Contributor
timestamp: October 03, 2021, 07:49:22 pm
content: And what is the problem with glued heat shrink tubing? Cheap as ..

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: October 03, 2021, 08:02:54 pm
content: I am undecided regarding the tin coating. But any synthetic or linseed-oid based varnish would work too for painting the busbars.While it is a good idea to have an enclosure that keeps moisture and especially salt out, it is of utmost importance to allow any moisture that WILL get in to leave. Depending on your environment, that can mean a breather valve or a trap at the lowest point!

author: drakejest
author_rank: Regular Contributor
timestamp: October 03, 2021, 08:47:41 pm
content: Quote from: MasterTech on October 03, 2021, 07:49:22 pmI cant get them in colors except black. If i can paint it in colors i would prefer that, but yes shrink tubing is my last resort optionQuote from: Neomys Sapiens on October 03, 2021, 08:02:54 pmYes i agree thats why the bus bars still need protection because if i make it airtight, the inside of the box will "sweat" and we dont want that

author: bdunham7
author_rank: Super Contributor
timestamp: October 03, 2021, 09:07:28 pm
content: Is there anyone nearby that can do nickel plating? A nice, thick coat of nickel, then powder coat the non-terminal areas and finally use silicone grease on all the nickel-plated parts that are still exposed. I assume you are near the sea?

author: mansaxel
author_rank: Super Contributor
timestamp: October 03, 2021, 09:32:16 pm
content: I'd be very concerned about the longevity of tinned bus bar connections. Tin cold-forms and "floats" under pressure, and this is why it these days is prohibited to tin stranded cable and then terminate it in a screw terminal.I'd go for some suitable grease to proof the naked bar where it meets lugs or similar, and then where you want colour paint the bar with Rust-O-Leum, Hammerite or one nice paint I've used for external metal, "Brantho-Korrux" from Germany.If you have serious condensation problems, bitumen-based corrosion-prevention paints are available. You probably need to reevaluate things like creepage distance et c. -- mostly depending on voltages present and so on.

author: trobbins
author_rank: Frequent Contributor
timestamp: October 03, 2021, 10:19:44 pm
content: Professionally bright tinned copper busbar is a long term industry standard for harsh environments.Adhesive heatshrink in black can be overlaid in relevant colours at the termination ends - same as for black insulated cable with coloured sleeves at lugged ends (or even at set distances).

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: October 03, 2021, 10:19:58 pm
content: Quote from: bdunham7 on October 03, 2021, 09:07:28 pmI thought about that too but I was not sure if it can be applied to copper directly.Very important consideration: is it possible that a DC component appears on those connections?

author: drakejest
author_rank: Regular Contributor
timestamp: October 04, 2021, 03:30:15 am
content: Quote from: bdunham7 on October 03, 2021, 09:07:28 pmNo, I originally was planning to tin them myself, but i dont think ill be doing that now since for sure it will be uneven. Yes the sea is less than 100 meters.Quote from: Neomys Sapiens on October 03, 2021, 10:19:58 pmThere is but it should be no concern, for remote monitorig , runs on 5v DC and its tapped after the breakers.

author: coppercone2
author_rank: Super Contributor
timestamp: October 04, 2021, 03:54:06 am
content: thats almost certainly going to be powder coated I think. I have seen them in heat shrink too.. thats a very professional solution so long you get heat shrink that is good from a good manufacturer.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 04, 2021, 05:55:18 am
content: Quote from: mansaxel on October 03, 2021, 09:32:16 pmThis is true of soldered connections, especially leaded solder; we're talking about platings, which are too thin to cold-flow. Tin plated wire, and connector mating surfaces, are quite common. The only counterindication, really, is to not mix tin and gold platings, in connectors. (I don't know for sure offhand but I doubt tin and nickel have the same problem.)Quote from: bdunham7 on October 03, 2021, 09:07:28 pmWhich, nickel plating has one edge-case, poor high frequency performance -- it is magnetic. I would recommend against using it in a switching converter, say (10s of kHz up). For anything near mains frequency, this is basically irrelevant.Quote from: drakejest on October 03, 2021, 07:14:31 pmAh, well your location isn't set so I'd just as well assume the most likely, USA. Still, it's at least a starting point; and definitely, look at whatever your local equivalent is.Tim

author: coppercone2
author_rank: Super Contributor
timestamp: October 04, 2021, 06:18:28 am
content: I found this on youtube from a real busbar manufacturer, I think they have some very specific opinions on how to insulate busbars. Yes, its a real companies youtube channel.

author: drakejest
author_rank: Regular Contributor
timestamp: October 04, 2021, 09:01:25 am
content: Quote from: coppercone2 on October 04, 2021, 06:18:28 amWhat am i watching hahaha

author: tszaboo
author_rank: Super Contributor
timestamp: October 04, 2021, 03:21:10 pm
content: Quote from: mansaxel on October 03, 2021, 09:32:16 pmI've seen busbars that were tin coated. They had screw connection on one end, soldered into PCB the other few ends. I never seen any which would be tarnished, or problematic like that. Screws didn't get loose even without shakeproof washer. Probably thousands of them was installed with 24/7 (or close to it) high current DC operation, forced air cooling pushing fresh air on it, not a sealed enclosure. So it is fine, if done properly.

author: bdunham7
author_rank: Super Contributor
timestamp: October 04, 2021, 03:38:54 pm
content: Quote from: tszaboo on October 04, 2021, 03:21:10 pmTinned copper busbars are a standard item in commercial and heavy-duty service panels here, with aluminum used in household-grade panels. There are essentially no issues with them as far as I know. Of course they aren't 'tinned' by some guy with a roll of 60/40 and a torch.

author: bdunham7
author_rank: Super Contributor
timestamp: October 04, 2021, 03:59:53 pm
content: Quote from: T3sl4co1l on October 04, 2021, 05:55:18 amTens of kHz? I thought this was an RF--and I mean GHz--issue? I hadn't contemplated it being a problem at that level. How do ENIG PCBs not have problems?

author: nctnico
author_rank: Super Contributor
timestamp: October 04, 2021, 07:24:00 pm
content: Quote from: MasterTech on October 03, 2021, 07:49:22 pmCan be bought from Ebay for little money indeed. But the problem I see is that moisture can get in and you can't visually inspect the busbars underneath the heatshrink. I would not recommend going this route.

author: PartialDischarge
author_rank: Super Contributor
timestamp: October 04, 2021, 08:30:21 pm
content: Quote from: nctnico on October 04, 2021, 07:24:00 pmNot withgluedheat shrink. My car for example uses it in the crimped ground terminals that go to the chassis to avoid humidity inside the crimp area and the copper cables. It is mostly available in black color, but then a normal colored one can be put over it

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 04, 2021, 08:36:10 pm
content: Quote from: bdunham7 on October 04, 2021, 03:59:53 pmIt's most sensitive at RF, yes. Like a waveguide plated with nickel, and not enough silver over top of it, will absolutely kill the Q. All of the current flow is in the plating.Down in the MHz, the effect on Q will be minor, because the element's impedance is small compared to circuit impedances. But the skin depth will still be significant: at 1MHz, the skin depth in copper is already small at ~70um, but it's over 10 times smaller in nickel -- and a typical plating thickness is around 12um, so that ain't too great!Down at 50kHz, it'll easily penetrate the plating, but heating may still be unusually (even objectionably?) high.A reminder that we mainly use bus bars, in high power converters, because of heat dissipation -- electrical conduction is almost entirely a surface phenomenon, we just use bulk metal parts because they are strong, and effectively carry heat away from that surface.Heh, wouldn't be surprised if the effect is also lessened somewhat, at high currents, due to sheer saturation. The effect of saturation is to locally increase skin depth.As for PCBs, ENIG is only over the pads -- SMOBC means traces are bare copper covered by dielectric, no problem there. The pads are slathered in solder, and current flows up the side, much of the nickel area is shielded by the solder blob on top, or the component lead thereupon.Or in thru holes, the inside is shielded and current flows on the outer surface (the FR-4 side), same idea. So it works out alright for PCBs.Tim

author: SeanB
author_rank: Super Contributor
timestamp: October 05, 2021, 05:30:31 am
content: 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.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 05, 2021, 07:48:32 am
content: Hm, looks like copper doesn't flow much at all, at reasonable pressures. Neat:https://nvlpubs.nist.gov/nistpubs/jres/47/jresv47n4p272_A1b.pdfBus 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

author: trobbins
author_rank: Frequent Contributor
timestamp: October 05, 2021, 08:04:13 am
content: 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.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: October 06, 2021, 01:00:34 am
content: 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.

author: EPAIII
author_rank: Super Contributor
timestamp: October 09, 2021, 09:12:46 am
content: 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.

author: Terry Bites
author_rank: Super Contributor
timestamp: October 10, 2021, 05:25:25 pm
content: 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.