Aluminium busbar

Use an electrical jointing compound (such as a zinc-based grease). There are plenty around and they both increase joint conductivity and protect surfaces against oxidation.

Try your local electrical wholesaler.

Thanks. How long will that work? I am considering to use aluminium bars instead of copper cables in a apartment building vertical power supply. Bars must last forever.

Look here:

http://materials.globalspec.com/Industrial-Directory/electrical_joint_compound

Also here:

http://www.acasolutions.com/products/compression_accessories/quick_compress_accessories/compounds/Alnox_electrical_joint_compound.html

You might also find this useful.

http://www.usbr.gov/power/data/fist/fist3_3/vol3-3.pdf

Good luck.

Spray the contact points using a tungsten alloy. I have done this in the past with good results.

Spray the contact points using a tungsten alloy. I have done this in the past with good results.

Was this for custom made Aluminium to Aluminium disconnect type switch contacts or was it for actual Aluminium to aluminium bolted busbars?

I cant be sure. It seemed to be a common type application. I don't believe anything we sprayed was custom engineered.

No I mean was your application you worked on tungsten alloy coated Aluminium to Aluminium disconnect type switch contacts (effectively two busbars that move and act as a big switch) or was it actually tungsten alloy coated Aluminium to Aluminium bolted busbars (joining two fixed bus bars togeather)?

As far as I can remember we were coating the Aluminum because of wear the contact points were receiving. I reviewed my notes and found that we also applied this same alloy on copper for the same reason.

I thought it may be for contacts. Coating switch or other similar types of contacts with gold, silver, tungsten or alloys is all well and good because they have to move against each other and potentially also carry make and break currents that can electrically pit and wear contacts down thru inductive and capacitive load arcing) and increase their resistance (potentially overheating the contact surfaces and causing the switch to fail). When bolting two bus bars together it isn't really necessary. A bolted joint that doesn't need to be opened and closed (like a switch) has less surface preparation requirements, so in most situations (including the original poster's one), coating the faces of the busbars being bolted together is an unnecessary expense.

An electrical grease wouldn't be a good idea for a switch because it would quickly be rubbed off by the switching action (in which case you would want plating that doesn't rub off), but in the above application electrical grease is the way to go.

Does the grease prevent oxidation of the Aluminum?

Among other things yes. It also provides a barrier against water and moisture getting into the joint which can degrade the joint over time causing joint failure thru overheating (in certain environments, such as outdoors).

One such product is ALMINOX from ALM Dulmison another comes from Utilux. There are sharp particles within the paste to cut through the Alumina film which forms on the surface. As for using bolted Aluminium bus bar, unless it is done perfectly expect failure sooner rather than later. Welded busbar is another story, the hollow welded busbar in HV switchyards stands up nicely to the elements, is self supporting and low maintenance as well as being compatable with aerial conductors