Noalox for copper to aluminum wire joints
Noalox for copper to aluminum wire joints
(OP)
Apparently this material is zinc powder in a polymer grease binder which is commonly used in copper to aluminum wire joints. Apparently the idea is to put a film of the compound on the aluminum part, then wire brush the part or wire to remove the aluminum oxide, leaving the grease to prevent the reformation of the oxide. Then, after the joint is made up, the grease binder keeps moisture and oxygen out of the joint.
I'm a little suspicious about the usefulness of the zinc. Zinc is modestly up the galvanic series from aluminum, so I guess the hope is that it will protect the aluminum in the same way as cold galvanizing paint protects steel. But those paints must be over 70 wt% zinc so the zinc particles are in electrical contact with one another to work, from what I've read, and the MSDS says Noalox is about 20% zinc.
As someone who feels he's at least fairly knowledgeable about galvanic corrosion, this has me legitimately puzzled. The corrosion products of both Zn and Al are nonconductive. Is the Noalox doing anything? And if you use enough to act as a real physical water and air barrier, the stuff is combustible- so it must be kept to a thin film only to be safe. Will that likely do any good?
As I have some posts on LiFePO4 batteries to bolt with copper straps and lugs which will see currents short term as high as 500A, and be used in a damp (not wet) location, I'm wondering about the advisability of using this stuff versus a non combustible non conductive grease used only on the exterior surface of the joint post assembly. Bolts, just to add a little more galvanic action, are 18/8 garden variety stainless steel.
I'm a little suspicious about the usefulness of the zinc. Zinc is modestly up the galvanic series from aluminum, so I guess the hope is that it will protect the aluminum in the same way as cold galvanizing paint protects steel. But those paints must be over 70 wt% zinc so the zinc particles are in electrical contact with one another to work, from what I've read, and the MSDS says Noalox is about 20% zinc.
As someone who feels he's at least fairly knowledgeable about galvanic corrosion, this has me legitimately puzzled. The corrosion products of both Zn and Al are nonconductive. Is the Noalox doing anything? And if you use enough to act as a real physical water and air barrier, the stuff is combustible- so it must be kept to a thin film only to be safe. Will that likely do any good?
As I have some posts on LiFePO4 batteries to bolt with copper straps and lugs which will see currents short term as high as 500A, and be used in a damp (not wet) location, I'm wondering about the advisability of using this stuff versus a non combustible non conductive grease used only on the exterior surface of the joint post assembly. Bolts, just to add a little more galvanic action, are 18/8 garden variety stainless steel.





RE: Noalox for copper to aluminum wire joints
RE: Noalox for copper to aluminum wire joints
The product claims from the vendor (Ideal Inc.) indicate that it is conductive enough to provide meaningful filament to filament conduction in multistrand conductors at connection points, reducing the temperature of the junctions, i.e. some people are using it on finestrand copper conductors before crimping a lug or ferrule onto them. I've noted that their official literature (at least what I can find) makes no claims about its suitability for use on Al to copper transitions, though it is widely used and indeed inspectors look for it as an indication of good/knowledgeable workmanship in such transitions.
Your guess is about the same as mine- that the zinc may do something but probably not much, and the grease is doing most of the heavy lifting in this product. But I'm interested to hear from others what they think.
RE: Noalox for copper to aluminum wire joints
However, the real way to do this is to put together a bunch of connections with and without the grease, put them in a slightly harsh environment and see what happens.
RE: Noalox for copper to aluminum wire joints
As I understand it, zinc oxide and similar pigments used as corrosion inhibitors work for steel parts because they are basic and raise pH to a level where steel is more passive. Aluminium is less passive in basic conditions, and I am not sure how well zinc, aluminium and copper would work when coupled. I agree with you regarding the proper testing method.
RE: Noalox for copper to aluminum wire joints
RE: Noalox for copper to aluminum wire joints
As for improving the conductivity of contact by filling the gap with conductive particles, I think that is plain wrong. Zinc particles squeezed in the contact area between two current carrying conductors would raise the contact resistance, not lower it.
RE: Noalox for copper to aluminum wire joints
I am sorry, which part of your system is Al?
Are you sure that the Al will carry the current?
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Plymouth Tube
RE: Noalox for copper to aluminum wire joints
The part that is aluminum is the positive post on a LiFePO4 battery, and yes it's good for the current- if it isn't corroded! The geometry is a flat faced cylindrical stub at the top of the cell with a female threaded hole in the centre of the flat face, to which a lug or strap is bolted using an 18/8 bolt. The - post is identical dimension but solid copper. The vendor doesn't specify so I'm asking my supplier whether the Al post is solid Al or plated/coated with something already. It looks like solid uncoated Al to my untrained eye, and filing a shallow notch in one post near the threaded hole indicates that the material is the same colour through its thickness.
The posts will be accessible for inspection but a bear to clean up and re-torque if they get corroded in service.
RE: Noalox for copper to aluminum wire joints
RE: Noalox for copper to aluminum wire joints
As pointed out, positive to negative anode/cathode cable side differences may be important on DC circuits, but AC is going to oscillate each cycle.
Surrounding chemicals and temperature, tightness of the actual clamp, etc.
And, of course, basic care in assembly of the circuit: A company and foreman and crew who have decided they need to use a connection grease are going to be more interested in protecting that circuit and will be usually taking more care of each assembly (proper torques, cleanliness of the contacts, length of the contacts, using proper screws and bolts and crimping "because" (as a symptom of their interest and care), they have chosen to add grease! So, over time, their connections are going to be better anyway.
A sloppy crew in a "don't care" facility (or a cheap assembly area not supervised) are going to get bad connections (on average) regardless of what grease they (don't) choose to use.
A commercial products "test" about corrosion on a connections grease is going to be testing the connections, right? So, again, it will likely be a "self-selected" test - The advertising department will not want to "test" bad or poorly-fit up and tightened connections.
RE: Noalox for copper to aluminum wire joints
We never made Cu to Al joints, when we needed a transition we used explosively bonded transition pieces.
When we made Cu-Cu we always silver plated them.
With Al-Al we always used a paste product similar to yours.
The long term problem that we had was keeping joints tight.
We tried many things but were never fully satisfied.
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Plymouth Tube
RE: Noalox for copper to aluminum wire joints
Nordlock washers have been recommended to me by one of the EV guys, and my supplier of various EV parts says that these connections coming loose is a periodic worry for him too. Some people use Bellevilles on the connections.
RE: Noalox for copper to aluminum wire joints
We found that the washers got hot enough to relax at times.
We used Si Bronze bolts for the AL joints also, it was as close as we could get in thermal expansion.
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Plymouth Tube