Internal Rust

[quixoticgeek]

Just swapped seat posts on my steel framed bike. When I took the old one out, I noticed a lot of gunk on the old post:



It smelt like grease, but it's nowhere near the same colour as the blue grease I used when I installed the seat post. Should I be worried? Is this the frame rusting inside?

J

[Brucey]

it is not unusual to find some corrosion marking on the seat post. You need to pull the seat post, clean and regrease (*) it every year or so; more often than that if you ride without mudguards and/or in the rain much.


(*) 'ordinary grease' varies somewhat.  Some greases work OK on seat pins, most don't.   If you want the best anti-corrosion performance you need to do two things


1) use copper-ease on the frame and
2) make sure that there isn't water inside the frame.


The latter is non-trivial; water gets into most frames with A-head headsets through the headset, far too easily for my liking. If it doesn't drain out it sits and festers; you get condensation inside the seat tube and this can set off such severe corrosion that I have seen seat tubes crack through flush with the base of the seat post.


It is well worth making sure that either water never gets into the frame or that if it does, it drains out. Rustproofing inside the frame is a good idea too.

cheers

[bludger]

This has been weighing on my mind for a while too. I'm minded to take the seatpost off and give the inside a good going over with GT85. Just haven't got round to it yet.

[hubner]

I think it's usual to get black marks and gunk on aluminium seatpins but brown would mean there is rust.

On a bike without mudguards which is ridden on wet roads, the back of the seatpin and seat tube is going get a continuous spray of water. Some of that water will get inside the seat tube, and there is a good chance that there is water inside the bottom bracket shell unless it can drain out through cutouts/holes.

[mzjo]

That rusty colour is coming off the inside of your steel seat tube and soaking into the grease (this is your Vagabond, right?). Bearing in mind that you are in Amsterdam, commuting and riding audax et al in all weathers I think this is probably par for the course. Having seen how things can rust even in garages not too far from the sea (in Liverpool and quite far inland in Brittany) I would guess the solution is as Brucey says. Copperslip seems to resist better than ordinary grease and I would guess that you need to pull the seatpin out at least a couple of times a year to check and regrease if necessary (where I just grease and leave well alone unless I need to remove the pin for other reasons; my riding conditions are diametrically opposed to yours!)

[mcshroom]

Can't add any more to the explanation, but I also get the same with my Dawes Horizon. I also live by the sea, and decided it was a bit of light rust from the inside of the seat tube.

I just grease with normal lithium grease when I remember and live with it.

[giropaul]

I don’t know why frame makers don’t treat the insides of steel frames with Framesaver or similar. I’ve seen numerous frames rot through from inside, usually the chain stays at the bracket end, some frames only a few years old and regularly looked after.

[yoav]

Waxoyl - easier to do with an unbuilt frame but a good spray down each of the tubes helps prevent rust.

[rogerzilla]

Also make sure the slot in the seat tube is filled with grease.  This is where most water gets in.  A drain hole in the bottom of the BB shell isn't a bad idea.  You can tap it for an M6 bolt if you don't want water to be able to get *in* that way - just take the bolt out after a wet ride.

[Jurek]

Also make sure the slot in the seat tube is filled with grease.  This is where most water gets in.  A drain hole in the bottom of the BB shell isn't a bad idea.  You can tap it for an M6 bolt if you don't want water to be able to get *in* that way - just take the bolt out after a wet ride.

The No1 thing ringing at the back of my head is to protect the frame with a rust inhibitor, internally (as per Yoav's post), from the outset.
Anything else amounts to repairs.

[rogerzilla]

Dynax S50 is my favourite.  Comes with a long thin spray lance that will even go into top tubes through the (usual) blowhole inside the seat cluster.