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Discussion Starter #1
The brake pushrod on the 650e that I have continues to rust, causing me to disassemble it,wire strip it, repaint it ever 3 yrs or so.

Someone should make this part in stainless steel.

43530-mc7-006
 

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Stainless steel is generally a weaker steel. Titanium is primarily cost related.

A thought to consider. Instead of "wire stripping" it. Use a chemical to convert the iron oxide into a paintable surface, then prime and paint. Many rust conversion products on the market.
 

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Another consideration: The master cylinder is an aluminum alloy and stainless and aluminum don't play well together (look up galvanic corrosion).

What kind of paint are you using? I haven't painted a brake push rod (the one on my '83 GL1100 is still well protected by its original zinc plating) but I've had pretty good results with epoxy appliance enamel on some of the smaller parts on my bikes.
But painting the threads would make it harder to adjust so I would think about re-plating it.
 

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Discussion Starter #4
My understanding is that regular steel and aluminum are the problem and stainless is a solution.

Note that in cargo trailers, they typically rust around the wheel wells where the wheel well frame and aluminum meet. A solution to this common problem us an insulator pad beteen them or powder coating the steel.

I had some por-15 leftover that I used this time. Well see how that works. It has rust conversion properties built in


I don't think that there is so much pressure on the brake rod so that a stainless alloy of one type or another wouldn't work
 

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Discussion Starter #5
I think the problem is related twater collecting it the boot and salt water at that. The parts that rust are under the boot and more the steel rather than aluminum, plus there no galvanic action due to no electricity flowthrough. So it's just metallurgic reaction if any.


There was some light pitting on the bottom ringoring the piston but it cleaned up with some 660 w/d. The piston is I think steel.
 

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Discussion Starter #6
I see where high carbon alloys of stainless are problems for aluminum also.

Zinc plated seems recommended.
 

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Galvanic corrosion is caused by dissimilar metals and an electrolyte such as water (salt water is more effective) forming a cell that causes small amounts of current to flow. Read this and study the chart Aftermarket small peices?

How is water getting into the boot? The boot is there to keep water out. Perhaps you need to replace it....

BTW: I believe the piston is either aluminum alloy or zinc alloy.
 

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Discussion Starter #8 (Edited)
The bottom and sides of the piston cup rusted with a dark brown rust,. not white. Could be aluminum alloy though.

I've replaced boot twice or thrice over the years. I'll try to seal it better with a grommet and pack it with grease. The boot doesn't fit tight around the rod like a seal.

sorry for the poor picture.
 

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