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galvanic corrosion on cable guides ? suggestions? vintage MTB content

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galvanic corrosion on cable guides ? suggestions? vintage MTB content

Old 05-31-22, 07:25 PM
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DMC707 
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galvanic corrosion on cable guides ? suggestions? vintage MTB content

Dont have a better pic because i am still at work, --- but its time for me to do some maintenance on one of the wall hangers that is showing problems literally due to just sitting

Top tube cable guides (on the sides of the top tube here- are aluminum, and the cable housing ferrules are steel ------- you guessed it - galvanic corrosion

Hoping somebody has an easy suggestion like the old "just pour some coca cola on it " - like we used to do to battery terminals --- but i'm guessing its probably not going to be quite that easy. Was just going to re-string the cables so the machine can sit quietly for another 10 years ----- JK - it might get ridden if i a ever make it out to a Yeti Tribe gathering or something

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Old 05-31-22, 07:38 PM
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I guess there's two issues going on here, one being cleaning up the corrosion and the other being what to do to prevent it from happening again.

I don't know if they are readily available, but aluminum ferrules would fix the problem going forward. And then there's stainless steel, which is much less reactive with aluminum. I'd probably still want to coat them with some clear nail polish or something, but they'd probably be OK without. I've seen plastic Ferrules on some older shifters but I have no idea if they are an option.

If it were me the first thing I'd try on the corrosion is naval jelly. I honestly can't tell much from the photos but unless there is severe pitting I'd go with that to begin with.

Not sure that helps much but those are my thoughts.

That is a wonderful bike, very cool indeed!
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Old 05-31-22, 08:07 PM
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Originally Posted by TugaDude View Post
And then there's stainless steel, which is much less reactive with aluminum.
Isn't stainless much more reactive with aluminum?
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Old 05-31-22, 08:12 PM
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Plastic ferrules for the win, once you get the current ones out.
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Old 05-31-22, 08:34 PM
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Originally Posted by wrk101 View Post
Plastic ferrules for the win, once you get the current ones out.

shifter cable ferrules already are !
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Old 05-31-22, 08:49 PM
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Originally Posted by TugaDude View Post
I guess there's two issues going on here, one being cleaning up the corrosion and the other being what to do to prevent it from happening again.

I don't know if they are readily available, but aluminum ferrules would fix the problem going forward. And then there's stainless steel, which is much less reactive with aluminum. I'd probably still want to coat them with some clear nail polish or something, but they'd probably be OK without. I've seen plastic Ferrules on some older shifters but I have no idea if they are an option.

If it were me the first thing I'd try on the corrosion is naval jelly. I honestly can't tell much from the photos but unless there is severe pitting I'd go with that to begin with.

Not sure that helps much but those are my thoughts.

That is a wonderful bike, very cool indeed!
thanks for the tips

Despite its relatively clean appearance, that rig has a lot of abusive miles on it -- I just never thought that much about it until i was moving it around one day (its on display in my theatre room with the rest of my C&V machinery) and noticed the cables looking bad.

Bike was literally rode hard and put away wet, as i probably just hosed it off at the car wash before i put it in my attic. A couple years back i guess i felt sorry for it and brought it into the display area --- but those ferrules are right in line with where it gets rained on with sweat, combined with my less than optimal storage and handling.

Back in about 2001 i got my first full suspension rig and didnt give much thought to hardtails after that. But now that i have some time i thought to myself i need to rectify the wrongs --- and hitting something with a feather duster occasionally is not the same as maintenance
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Old 05-31-22, 09:33 PM
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Originally Posted by PatTheSlat View Post
Isn't stainless much more reactive with aluminum?
Depends on the stainless. There are two types. I'm not going to search them out but they are not hard to find. One is austen-something, the
other marten-something. The common marine 316 and 304 are one. Close to aluminum and have been used with aluminum on masts, etc on sailboats for at least 70 years. The other type is bad news. (The other I believe also affects compasses and can be picked up with a magnet which the good marine ones do not and cannot.)

And the cheap fix that will probably work (and certainly won't hurt) - try greasing the metal contacts liberally with marine grease. Enough should shield the metals from water and break the circuit. $8-10 at your local car parts store will buy you a lifetime's worth.
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Old 06-01-22, 03:27 AM
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A light coat of Vaseline (Petroleum Jelly) will help prevent that kind of corrosion.
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Old 06-01-22, 06:13 AM
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Originally Posted by PatTheSlat View Post
Isn't stainless much more reactive with aluminum?

Not from what I read. Maybe it is the chromium content?

Last edited by TugaDude; 06-01-22 at 07:08 AM.
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Old 06-01-22, 07:13 AM
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FWIW, here's some information I found. The best practice is undoubtedly to separate the two metals, but they can be used together depending upon circumstances.The most common solution to prevent galvanic corrosion is to select metals that are close together in the galvanic series. Separating the metals that are incompatible reduces the risk of these cells deteriorating. According to the levels of galvanic corrosion, stainless steel that comes into contact with materials such as copper is less likely to be a risk than when it is in contact with aluminum.

Although aluminum reacts negatively to stainless steel, large surface areas of aluminum to stainless steel can be acceptable depending on local environmental conditions. Severe corrosion is likely to take place in a marine environment. However, there are methods that can be used to reduce this effect. A good way to reduce corrosion is to use an isolating coating or paint on the aluminum and the steel to isolate them electrically. Insulating washers are also effective in isolating the two dissimilar materials and creating a relatively safe surface area.

Along with corrosion, discoloration of stainless steel may occur when combined with aluminum. This is also called ‘tea staining’. Discoloration can be prevented by the use of insulation and regular maintenance. Passivation can also be used to create the passive film on the fastener for better corrosion resistance.
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