Copper Grease On Aluminium?

[ReganAndCarter]

About 10 days ago I changed the antifreeze and thermostat on my 2004 Fiat Scudo van. When put the 3 bolts back that hold the stat cover on I put a smear of copper grease on them. The bolts are steel screwing into aluminium casting.

Yesterday I read online that copper grease should not be put on aluminium as it will cause it to corrode. Is this true? Will I be causing damage? What should I do?

Thanks for any advice.

 

[JohnD]

copper does accelerate corrosion of aluminium. I was advised by an engineering supplier to use Nickel grease, for stainless steel bolts going into aluminium, and bought a small tin of it. You need very little. Dissimilar metals, including steel and aluminium, are supposed to be isolated with grease or other material. Stainless steel is prone to cold welding and seizing, so in my case a lubricant is essential. Lanolin was formerly used.

You can now get ceramic grease, used on brake parts that can get very hot, which I think would also do the job, and it is more widely available than the Nickel grease and is free of metal.

I still think the copper grease is very useful for high-temperature connections like steel manifold nuts onto steel pipes and studs, because even when the grease burns away, it seems to leave a fine powder of copper that prevents the steel seizing.

I met a Lt. Cdr from the Naval dockyard who told me that stainless bolts into alloy decking cause the holes in the deck to corrode, starting on the day the ship was built. This is very tricky because it is much harder to replace a deck than a bolt. The ships are exposed to salt water which accelerates corrosion.

I suppose it would be impractical to try to dismantle and clean out the holes on your car. Maybe you could have a go and apply ceramic grease to leave a film on the bolts. PTFE tape might also work.

I don't know what effect the copper grease will have on your car. I imagine the casting is quite thick and will be free of water, so damage may be slight.

 

[Burnerman]

Well yes in theory the two may react......if you live long enough
Ceramic grease is probably better but I would’nt lose any sleep over it....there’s a marine quality grease called Duralec I think which is even better for salty conditions.
John

 

[JohnD]

p.s.

I just found this online but don't know the author's authority

"Copper is used in some anti-seize formulations to prevent galling in high temperature applications where the organic portion of the grease will be cooked out. It serves NO function at ordinary temperatures (I've done the research both in the lab and field). Second, marine anti-seize products, from the same companies, do NOT contain aluminum or copper. It is well know that even in grease, copper increases galvanic corrosion. Sure, you may no notice, since the effect is small, but copper never helps a marine grease. There is simply no chemistry to support that assertion.

All the OP needs is a good water proof grease. Lewmar Winch Grease, for example, would be an excellent choice, since only a dab is needed."

in my case I have a vehicle which is almost entirely made of aluminium, so corrosion of thin pressed sheet that may be exposed to water and road salt, could be more significant than in your thick casting.

 

[ReganAndCarter]

Thanks for your replies. Sounds like I don't need to be too concerned. I have some aluminium anti-seize. Should I remove each bolt one at a time, clean the thread and hole if I can and put the aluminium a/s on the threads?

 

[magicmushroom666]

If you get some brake cleaner, that is in a spray can, a blast of that will wash out any grease easily, especially stuff just applied.

 

[Keithmac]

I've been fighting removing steel fasteners into aluminium casings for over 20 years now.

All the snapped ones DIDN'T have coppa-slip applied.

We use coppa-slip to prevent the steel fasteners corroding into aluminium and it works very well indeed. I've never seen any evidence of corrosion caused by it.

Normally we say why the fxxk didn't the last bloke in use any when mentioning it at work.

 

[Burnerman]

You wouldn't be talking about exhaust studs, per chance
John

 

[Keithmac]

You wouldn't be talking about exhaust studs, per chance
John

They're the worst!, would rather spend 20 minutes cutting a nut of than trying to pull the stud out.

Cat in hells chance of drilling one out in situ, especially after customer has snapped 3 off before giving up!.

The joys.

 

[Harry Bloomfield]

My heavy alloy wheel tend to stick extremely well to the cast iron hubs. That was until I put a tiny smear of copper grease on, around seven years ago. I have never needed to use it since and never had a problem with wheels sticking.

 

[fixitflav]

but I would’nt lose any sleep over it.

Neither would I. What's wrong with ordinary lithium grease for a bolt thread? Or even silicone grease.

 

[ReganAndCarter]

Neither would I. What's wrong with ordinary lithium grease for a bolt thread? Or even silicone grease.

I cleaned off the copper grease in the end and just put a smear of ordinary Castrol LM on the bolt threads.

 

[JohnD]

I formerly used copper grease a lot, but it now appears that it only has the advantage in hot conditions, such as exhausts, where the oil/grease content burns away.

And it seems that Ceramic grease is now preferred for brake parts, that can also get very hot and are exposed to weather and road salt.