Landsurfer
Veteran
Duralac Jointing Compound .... all over an aircraft near you now .... it works !!
What To Use To Prevent Galvannic Corrosion On New Quill Stem?
- Thread starter woodbine
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Rusty Nails
We remember
- Location
- Living in the slow lane
Just clean it once a year, or twist it in situ a couple of times a year.
The scores of stuck stems or seatposts I've worked on have all been on the bikes for years without being moved.
Greasing is better, but not the only way.
The scores of stuck stems or seatposts I've worked on have all been on the bikes for years without being moved.
Greasing is better, but not the only way.
fossyant
Ride It Like You Stole It!
- Location
- South Manchester
Or grease it well, and 10 years later, it just comes out when you want it to. 
Rusty Nails
We remember
- Location
- Living in the slow lane
Yebbut remember you will save around 1p on grease in that time. You could put that towards a new bike.Or grease it well, and 10 years later, it just comes out when you want it to.
I didn't question that it happens, I questioned the given reason (galvanic corrosion).
@Rusty Nails has it covered, when you clean the bike, just make sure you move the stem so it doesn't seize.
I've greased mine with lithium grease in the past which also helps prevent moisture ingress, those two together will keep it free.
Galvanic corrosion tends to happen when the parts are left in contact for a long period of time in the presence of moisture, remove one of those and you'll stop seizing from happening.
I've greased mine with lithium grease in the past which also helps prevent moisture ingress, those two together will keep it free.
Galvanic corrosion tends to happen when the parts are left in contact for a long period of time in the presence of moisture, remove one of those and you'll stop seizing from happening.
raleighnut
Legendary Member
- Location
- One of the 'Elite'
I still say that 'petroleum jelly' is better than any grease/antiseize compound as it is inert and waterproof, I'll always use it on stems and seatposts. It isn't a lubricant like grease (which contains a mixture of Soap and Oil) and does not protect threads like 'Copaslip' but it is waterproof
battered
Guru
steel screws in ally parts corrode faster than steel in steel, it's galvanic corrosion as you say. I spent a long time yesterday removing seized steel screws from an aluminium front mech. A horrible job.
That has nothing to do with galvanic corrosion but with the screws non-stainless steel reacting with the gas oxygen which expands its volume and the surrounding aluminium not, leading to seize.
As said: galvanic corrosion causes the least noble metal (the anode in the electrical circuit) to dissolve. The aluminium becomes fine powder, causing the exact opposite: not seizing but loosening.
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raleighnut
Legendary Member
- Location
- One of the 'Elite'
Cobblers, Aluminium Oxide takes up more space than Aluminium metal so the seatpost/stem gets stuck.
battered
Guru
No, it has everything to do with galvanic corrosion. Yes, galvanic corrosion involves oxygen too. Aluminium turning to Al2O3 in steel will NOT loosen the joint. Ask any engineer or mechanic.
Galvanic corrosion is a battery effect. An electrical current due to a potential difference. It thus requires "more" than oxygen, unlike rust-alike general corrosion. Galvanic corrosion DISSOLVES the least noble metal. Ask any engineer or mechanic how removed material near a mechanical joint causes the joint to seize.
It's like claiming that removing the front door of your house makes it harder to get in / out.
Drago
Legendary Member
- Location
- Suburban Poshshire
Moly anti seize is the varisity, but normal grease is fine if you clean and regrease every few years.
Once assembled a fine smear of clear silicone prevents water ingress past the stem and down into the steerer.
Once assembled a fine smear of clear silicone prevents water ingress past the stem and down into the steerer.
battered
Guru
You are mistaken. Aluminium and steel will suffer galvanic corrosion, the Al is oxidised to Al2O3. This is not especially soluble and is of greater mass than the original Al, hence the jamming of steel screws in aluminium components that any engineer or mechanic has observed. I know you won't listen to this, so don't take my word for it. See it for yourself. Take a threaded ally component, degrease it. Degrease a steel fastener of the right size, screw them together. Put this in some salty water, maybe add a bit of bleach too. Free chlorine is great for corrosion of metals. Come back in a month or three and see whether the screw is loose or seized solid. Trust me, it will not be rattling about in the hole. In fact, don't trust me, carry out the experiment.
As I said: you don't understand the potential difference / the battery effect.
This potential difference, in the presence of a conducting medium, allows an electrical current to flow to the anodic material, which corrodes to then DISSOLVE within that conducting medium (named as "electrolyt").
You know what dissolving is? The anodic material desintegrates and mixes up with the electrolyt. As salt in water. Fine particles. Take away the water and you see fine powder.
Now explain me how such fine powder, coming from the jointed surfaces, is gonna seize the joint.
It's the very opposite: the joint get loose.
An example my bike suffered: the smart'o'guys of its production company chosed 2 A2-70 stainless steel to fix the bikes stand on the frame, through an aluminium block, in order to bring the to-mate surfaces parallel to eachother.
After some time, I noticed that those bolts had come loose.
I retensioned them.
They again came loose.
I retensioned them again.
But they kept on coming loose.
Then some day, at a flea market, with me parking my bike a couple dozens times, it became plain ridiculous. The bike fell down several times, with me retensioning the bolts all the time. With tens of minutes inbetween.
Back home, I wanted to know what was going on with that stand.
I took out completely the two bolts, removed the block. The bolts were covered with white dust. On the ground: fine white powder.
Then I started to realize what had happened. Galvanic corrosion that dissolved the aluminium, causing lotsa play.
The holes through the interface block, were enlarged. The thread in the bikes frame, was damaged.
I solved it by replacing the stainless steel bolts with longer non stainless steel bolts, with washers and nuts on the other side.
All greased to avoid corrosion. Not to avoid galvanic corrosion, but to avoid "common" corrosion: RUST.
And no problem since. The bikes stand just stays fixed. It's years ago now.
I informed the production company of the problem. They first asked me what alternative I would use, I proposed non stainless and grease/oil to avoid rust. They said they would take this in account for next productions. I don't know if they did.
So galvanic corrosion, that implies DISSOLVING of joints material, that causes seizure of the joint?
Seizing has a number of possible reasons. One is an inner material that expands more (ex due to oxidation) than the outer material. Abit like frost causes water to crystallize to a bigger volume. Abit like non stainless steel oxidizes to rust that occupies a bigger volume. That is for ex the reason for what they name "concrete rot". If water reaches reinforcement bars, the steel corrodes, expands, and pushes away more concrete, aggraveting/speeding up the process.
Chlorine can even make stainless steels rust. Especially the cheapest / most common grade 304 also named A2. That is even especially prone, more than common steel. Know why stainless doesn't rust? Or why aluminium doesn't rust? Because it DOES rust, BUT, the rust forms a protective layer against further rust. Take away that protective layer, or prevent its formation (case stainless) and it just continues to rust like common steel.
An example: take a so called salt lamp. That is a nice looking block salt, with a lamp in it. People use it as a sphere lamp.
But there is a danger most are unaware of: the salt block has a cold surface. Water from the air condenses on it, salt dissolves in it (so the salt block shrinks over time) and the water-with-salt flows to under the lamp. You get water with salt, possibly near metals, near electrical wiring.
I know someone that had such lamp (hence my example), discovered the water, and wondered where it came from. Person decided to put the lamp in a kitchen stainless steel bowl. Some weeks later, the bowl had holes with ugly brown edges in its bottom. In the end, person was forced to put a glass ashtray under the lamp.
So salty water is an own story. You're mixing up stories and you know it.
