Galvanic corrosion: zinc vs copper anti-seize. Any reasons not to use zinc anti-seize between aluminum and stainless steel?

[anga]

Galvanic series - Wikipedia

en.m.wikipedia.org

Zinc is less noble than aluminium while aluminum is less noble than copper.
Zinc < aluminum < copper < stainless steel

Joint between aluminum and stainless steel. Protection against galvanic corrosion.
Ambient temperature.

When copper anti-seize is used in above joint, copper doesn't protect aluminum but protects stainless steel..
When zinc anti-seize is used in above joint, zinc protects aluminum and stainless steel.

Are my conclusions correct? Any reasons not to use zinc anti-seize between aluminum and stainless steel?

 

[930.engineering]

That's why I no longer use any copper anti-seize but 'Berner Antiseize-Paste' instead:

That's what Porsche recommends and what I use for almost 20 years:

Berner Antiseize-Paste (white-silver, up to 1400°C/2550°F)


View attachment 79146

MSDS says both aluminum and zink.
.

 

[atikovi]

Been using this for years. Not the easiest to find locally nor cheap.

 

[anga]

Helpful if you can specify the different metals involved and reasons behind your choice of anti-seize.

 

[Jetronic]

I've foubnd that copper anti-seize works just fine with steel bolts in or through aluminium casings. Never once had any corrosion to deal with in 2. yearsof wrenching. Mounting dry is just asking for disaster though.

But iI strongly prefer a non-drying lubricant, rather than a paste.

 

[paulo57509]

I would think that regardless of Anodic Index, galvanic corrosion will not occur without an electrolyte being present (auto fasteners aren't typically submerged in salt water, etc.). What ever petroleum "carrier" that the anti-seize uses would provide some kind of protection from electrolyte intrusion.

 

[jonlandrum]

I would think that regardless of Anodic Index, galvanic corrosion will not occur without an electrolyte being present (auto fasteners aren't typically submerged in salt water, etc.). What ever petroleum "carrier" that the anti-seize uses would provide some kind of protection from electrolyte intrusion.

Then why do aluminum/steel joints show galvanic corrosion in a building situation? The only water they're exposed to (unless the building is constructed near an ocean) is rain water. Are there wind-borne electrolytes that can dissolve in rain water?

 

[kschachn]

Then why do aluminum/steel joints show galvanic corrosion in a building situation? The only water they're exposed to (unless the building is constructed near an ocean) is rain water. Are there wind-borne electrolytes that can dissolve in rain water?

Rainwater will initiate corrosion all day long due to mixed sulfur oxides in the air and atmospheric carbon dioxide. Both can make it acidic. Even without rainwater an aluminum/steel joint can corrode if there is a current path, which there always is. There’s always a little moisture everywhere.

 

[JHZR2]

Can we get back to my query?

This is a good and valid query, and one that I’ve thought about without good answers.

Take for example, spark plugs where people use copper anti seize. I guess the saving Grace there is that there’s no real chance of any moisture. Because otherwise it would seem that the copper-aluminum interactions would be very bad.

Then again, many anti seize products use copper and aluminum in them. So perhaps the angle is actually to allow for the reaction products of those to serve ultimately as an interred boundary layer, lubricated with graphite, since beyond some point all chemical species will be “consumed” (think battery with finite ions).

My perspective is that Zinc is a better option for steel to aluminum, especially where it is prone to being very wet. Certain screws made of steel into an aluminum head, without a lot of torque? Ok I’ll use the usual stuff. Wheels to hubs, stuff like that? I have zinc petrolatum.

 

[anga]

@JHZR2
Appreciate the comprehensive response.
Surprisingly copper anti-seize seems to be more in use than zinc anti-seize in bicycles, given the exposure to weather.

 

[JHZR2]

@JHZR2
Appreciate the comprehensive response.
Surprisingly copper anti-seize seems to be more in use than zinc anti-seize in bicycles, given the exposure to weather.

I’m surprised that copper is. I’d get the standard silver stuff. Usually the copper version is higher heat tolerant, which is pretty irrelevant to a bicycle…

 

[Jetronic]

I undid the caliper bolts on my old car last week. They're steel bolts through an aluminium caliper in an aluminium hub. I used copper anti-seize 7 or so years ago on them. There was no corrosion, no seizing, the grease hadn't dried either, pretty much how I left it 7 years ago.

 

[JHZR2]

I undid the caliper bolts on my old car last week. They're steel bolts through an aluminium caliper in an aluminium hub. I used copper anti-seize 7 or so years ago on them. There was no corrosion, no seizing, the grease hadn't dried either, pretty much how I left it 7 years ago.

Well it’s the matter if that Cu/Al interaction that intrigues all of us. If yours still had grease and particles, it must not have gotten very hot or wet… Obviously a good thing in terms of design and avoiding corrosion. But makes another unknown in terms of what happens with this combo elsewhere…. If anything…

 

[Jetronic]

I track this car, it's got Brembo HP2000 pads for this reason. We also get salted roads in winter. Winters which are more wet than white. Typically we get rain every other day, thoough lately our summers are very dry and hot.

The most appealing trait of the specific copper grease I use is that it never dries out. Another nice thing is that it doesn't swell rubber.

 

[StarCaller]

The most appealing trait of the specific copper grease I use is that it never dries out. Another nice thing is that it doesn't swell rubber.

which specific grease would that be?

 

[Jetronic]

Something made locally:

PATE DE CUIVRE 500 GR

one jar lasted me years and I used it daily as a mech. The one I have now just for personal use will outlive me.

I didn't say what it was as it's not convenient to get in the US anyway.

 

[Kestas]

The most appealing trait of the specific copper grease I use is that it never dries out. Another nice thing is that it doesn't swell rubber.

It's not the copper that would swell rubber, its the carrier fluid.
Are you suggesting other antiseize formulations swell rubber?

 

[Jetronic]

I know it's the carrier fluid. But yes I have seen it.