Stuck aluminium seat post in steel frame

[KneesUp]

If I go down the caustic soda route I take it the paint around the top of the seat post will be damaged so we’re talking respray?
Don’t want to spend loads on it so don’t really want to start splashing out.

Just buy a pot of enamel from the hobby shop to touch it up then?

 

[Illaveago]

This is my Claud Butler which had a seized post. Even after drilling and bolting a long piece of angle iron to it as the seat clamp part started turning it would not budge. I used caustic soda as mentioned above but protected the frame lower down with plastic sheet. I let it soak for 15 minutes and washed it off.
I placed the frame on my lawn bracing the frame with my feet and pulled hard on the bar. It started to move back and forth and eventually came out.
As you can see the paint is fine.

 

[gazza_d]

I see someone has already recommended The Seatpost Man. He's very good but with carriage it cost me just over £100 to have a sawn off stuck alloy post removed from a Moulton frameset. It's a question of how valuable the frame is to you

 

[Ajax Bay]

If you can't twist it, most unlikely you can 'pull' it.
Here's a 2016 discussion on how to get a stuck seatpost out:
https://www.cyclechat.net/threads/p...tpost-sticking-in-a-steel-frame.174232/

Aluminium seatposts regularly get stuck in all sorts of frames, especially if they are greased.
The mechanism by which this happens is galvanic corrosion. that produces hard aluminum salts which you can see as a white substance with the consistency of salt. The oxide molecule is many times larger than the parent aluminium molecule and thus swells the seatpost to a point where it is stuck. It is very, very common, even with carbon frames or aluminium frames with carbon posts.

A seatpost has a so-called dynamic joint holding it in place. In other words, just the top end at the frame is secured, the insides can and do wiggle around inside the oversized seat tube. This happens as you ride. Water enters by dripping down the seatpost and moving via capillary action (and even gravity once it is past the clamp). There the water gets massaged into the grease to form an emulsion. Emulsions are great at protecting water from evaporation and thus holds the water in place so that it can react with the aluminium.

By not greasing the post you deny the water an emulsifier and it dries out relatively quicker than when there is grease present. However, it will still get stuck and should therefore be removed periodically. Once it is really stuck, it requires hacksaw surgery to remove it, no chemical can undo the damage in there.

Yup, spraying stuff on doesn't work. You can try the caustic soda bomb (I'm still wincing and feel little itchy splotches on my face and hands) or all the stuff you can read about on the internet ranging from Coke to organic lime juice, nothing works. Keep this recipe for when you decide to take the plunge:

1) Get a new seatpost now. Look out for an attractive bargain, buy it and store it.
2) Saw the existing post off 25mm above the frame collar.
3) Remove the hacksaw blade from the saw frame and wrap a cloth around one end. Keep beer on hand and swallow some patience. This is not quick.
4) Have a nice small torch handy.
5) Saw vertically through the remainder of the post stuck inside the frame. The idea is to saw a slot right through the post wall along the length of the post. You will score the frame but be patient, look frequently and adjust your aim as needed.
6) Once you are right through (you'll notice a different colour come through as you nick the frame, take a sip of beer.
7) Now take a pair of standard pliers or one of those hinged pliers (not longnose, you will destroy it) and grip the seat post stubby right next to the slot and wind the post up inwards. By that I mean you open it like an old fashioned sardine can.
8) As soon as the tube bends inwards, pressure is immediately relieved and it will come out in one piece. This seems surprising to most people but remember, it is stuck not through adhesion but through swelling. There is no bond between post and frame.
9) Clean as described above and fit your new post using copper compound or similar.
10) Promise yourself you will remove and check it every six months.

The latter 'recipe' might be difficult to execute because the OP has sawn the (jagged) seat post off with only a few mm protruding.

 

[Illaveago]

I have just seen what Gunk does to a cheap aluminium container when stored for a week. It destroyed it ! I was wondering if it could be used in a similar way. It might take a while though.

 

[Gravity Aided]

I have just seen what Gunk does to a cheap aluminium container when stored for a week. It destroyed it ! I was wondering if it could be used in a similar way. It might take a while though.

It all takes a while. Patience is the main requirement in all this.