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Can copper and aluminum play nice?

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auto.pilot

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#1
Within the next month, I am planning to build a version of the hoglet, as shown in the picture. The plans call for a 4" bronze flywheel. I am very fortunate to have a large local supplier of metal drops and cut-offs. However, they didn't have any bronze. Without thinking I bought copper. questions: are copper and brass similar in weight? Will I need to worry about corrosion of the aluminum at the copper joint?

Bob Pickering Hoglet 0554.JPG
 

joshua43214

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#2
Galvanic corrosion requires an electrolyte solution to occur.
So unless it will be exposed to something like salt water, no corrosion will happen.

Copper masses slightly more than bronze. Once you have flywheel machined, you can weight it and figure out what it should weigh if it was bronze and lighten it. The effect on the engine will be less low end torque and slower throttle response.
 

auto.pilot

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#3
Thank you very much for your excellent and prompt reply.

Jim
 

Dave Paine

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#4
An electrolyte can happen when some chemical combines with moisture in the atmosphere. This happened in my indoor unit of the heat pump - twice. Expensive repairs. I expect some chemical left over from the manufacture of the copper coils, or brazing flux not completely cleaned off. In the case of a heat pump small pinhole leaks result in losing performance.

Clean off the copper well. Should be easier for your parts than my heat pump coil.
 

Ulma Doctor

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#5
as a point of information,
copper can oxidize and take on a brown and then a green patina as it ages, that may not be desireable for a showpiece
 

Wreck™Wreck

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#6
Bronze is an alloy of copper and tin for the most part, alloy C932 is 80-85% copper, so mostly copper.
Aluminum Bronze C954 is 85% copper and 10 0r so % aluminum so is also mostly copper.

Brass is an alloy of mostly copper and zinc. Free machining 360 brass is 60% copper.

All will oxidize in air, there exist many clear coatings to prevent this or just do as people have been doing for thousands of years and polish it once in a while.
 

KBeitz

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#7
Buy a tube of NOALOX oxidation paste Made for alum to copper wires.
 

KBeitz

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#8
........ Double post............
 

whitmore

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#9
Buy a tube of NOALOX oxidation paste Made for alum to copper wires.
That paste inhibits Al oxidation (no-aluminum-oxide :== NOALOX); the oxide would prevent electric current from one metal
to the other. That current is the battery that drives the corrosion, you don't want NOALOX here; you want to anodize
the aluminum, if possible: the oxide layer is chemically inert as well as being an insulator.

Unless it stays wet, the aluminum/copper contact is harmless. Copper will eventually show fingerprints and such,
it would be worth a bit of buffing and a spritz with clear lacquer.
 

KBeitz

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#10
I was told that the stuff keep oxygen off stuff to stop oxidation from happening.
 

Cadillac

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#11
Within the next month, I am planning to build a version of the hoglet, as shown in the picture. The plans call for a 4" bronze flywheel. I am very fortunate to have a large local supplier of metal drops and cut-offs. However, they didn't have any bronze. Without thinking I bought copper. questions: are copper and brass similar in weight? Will I need to worry about corrosion of the aluminum at the copper joint?

View attachment 235265
Are there plans out there for this engine. That’s is awesome:encourage:
 

JPigg55

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#12
The copper will be susceptible to galvanic corrosion if any moisture gets to the interface. The water will act as the electrolyte, but the process can be prevented/reduced as stated.
 

RJSakowski

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#13
I have found automotive clear coat to work well at preventing oxidation and fingerprint stains on all metals. It is more durable than clear lacquer. I have used it on antique iron doorknobs and they show no sign of wear after fifteen years.
 

Latinrascalrg1

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#14
I have found automotive clear coat to work well at preventing oxidation and fingerprint stains on all metals. It is more durable than clear lacquer. I have used it on antique iron doorknobs and they show no sign of wear after fifteen years.
I Agree. I would personally choose a solvent based clear coat over water based if i had the option but If I had Options, Especially for a project like this motor, I would go for a Clear Powder Coat as my Protective layer after Highly Polishing what I wanted to stand out which will give me the most durable Clear coating that will last many many years!
 

whitmore

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#15
I was told that the stuff keep oxygen off stuff to stop oxidation from happening.
Right. But, oxidation in air just replicates anodizing on aluminum; it's corrosion in water that is the target here.
Traces of copper can cause pits in aluminum as part of some wet-chemistry that I don't understand. More
info here: <http://www.totalmateria.com/Article14.htm>
 
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