and I'd equally counsel against rubbing it on your piles too.
It depends on the metals you're using it on. If you want to screw alu into alu, then use copper compound. The copper does two things, it provides a sacrificial anode to prevent galvanic corrosion and, copper has a low shear strength which helps other metals slide against each other under high pressure.
Often, grease promotes galvanic corrosion and in some cases where the grease is massaged in the presence of water, it forms an emulsion that's deadly for some parts like seatposts and quill stems.
You are of course right. On alu, another compound would be better. Copper still gives you the other benefit of low shear and easy removal.Whilst not disputing it's the right stuff for the job, the "sacrificial anode" point sounds wrong, aluminium is far more electropositive (reactive in lay terms) than copper - so whatever benefit the copper has, it won't be that surely
You are of course right. On alu, another compound would be better. Copper still gives you the other benefit of low shear and easy removal.
No. We are not trying to prevent galling. Galling is localized melting of a surface in a friction situation, such as a bolt in a nut under high tension. There is no friction present in the situation we're trying to prevent. We are trying to prevent oxidization. On the face of it, most grease would prevent oxidization but in reality most greases promote it in this particular situation. What happens here is through the pumping action of the stem or seatpost, water enters the interface and emulsifies with the grease. This emulsion promotes oxidation, not prevent it. The copper compounds seems to not emulsify as readily. This is not a feature you'll find printed on the label, because the compound is designed to a) produce a sacrificial anode (between certain metals) as @Profpointy pointed out and b) to provide a low shear layer between two high-shear strength metals such as steel on steel and c) to remain active under very high temperatures.most grease will work with alu to alu as you are trying to prevent the alu Galling . it also hs the added benefit of preventing oxidisation of the 2 faces and that binding .
No. We are not trying to prevent galling. Galling is localized melting of a surface in a friction situation, such as a bolt in a nut under high tension. There is no friction present in the situation we're trying to prevent. We are trying to prevent oxidization. On the face of it, most grease would prevent oxidization but in reality most greases promote it in this particular situation. What happens here is through the pumping action of the stem or seatpost, water enters the interface and emulsifies with the grease. This emulsion promotes oxidation, not prevent it. The copper compounds seems to not emulsify as readily. This is not a feature you'll find printed on the label, because the compound is designed to a) produce a sacrificial anode (between certain metals) as @Profpointy pointed out and b) to provide a low shear layer between two high-shear strength metals such as steel on steel and c) to remain active under very high temperatures.
On bicycles we are only interested in the low-shear and low emulsification properties. Grease offers none of those.
a thread got slavered with copperslip - but it was all steel to steel - . . . - I have seen cases where it was applied to steel/aluminium and left for a considerable time in the ground with the effect that both parts showed considerable corrosion
So for an aluminium alloy seat post in a steel frame, if not copper slip (which is what I use), what's the recommendation?On alu, another compound would be better. Copper still gives you the other benefit of low shear and easy removal.
Keep on doing what you're doing. The galvanic corrosion issue is not an issue with alu on alu interfaces. Things like carbon on aluminium are more problematic but then the industry has created a solution specifically for that - carbon assembly paste. The sacrificial anode bit is relevant on other metals and I should not have mentioned it in this specific case.So for an aluminium alloy seat post in a steel frame, if not copper slip (which is what I use), what's the recommendation?