Bubble Bubble Toil and Trouble

Right, let's get back to the sticky issue of my stuck seatpost that was causing such a problem last week,

The weekend was an opportunity to get to grips with it, with some serious chemistry. I was seriously nervous about attacking the bike with sodium hydroxide, which the research all said would dissolve the aluminium seatpost while leaving the steel frame undamaged. Trusting the internet is one thing but, if this had been wrong I was in for a destroyed frame.

I was up early and off to the shops to get caustic soda, gloves and eye protection and to bag a spot outside the flat.

With the caustic soda added to water and heating up nicely there were some false starts as I struggled to keep the mixture inside the seattube, without it running out of the bottom bracket, but eventually I hit on a solution bunging the top of the seatpost and turning the frame over. This meant I had to use a bit of inner tube to funnel the sodium hydroxide into the seattube.

Nervously filling up the tube things started to happen as there was fizzing, some serious heat developing in the frame and smoke and foam starting to spill from the frame.

The reaction creates hydrogen and that started bubbling up in the midst of some grey foam. It was clear that something was happening. This continued with me getting braver with the strength of the solution and adding stronger and stronger sodium hydroxide and getting more and more exciting reactions.

For all my inner-tube protection the paintwork of the frame was clearly suffering, but after a few hours it looked like I might end up with the result I hoped for, and the survival of the frame to be ridden again.

Eventually the reaction seemed to be calming down and so I decided to check the state of the seatpost. Taking the bung out I was pleased to see the aluminium almost entirely eaten away. A quick twist with the molegrips and the remains of the metal was out.

You can see the results here, with the remaining part compared to the broken seatpost part.

What was left was the serious job of rinsing the frame off and cleaning up,and then rebuilding it ready to be ridden to work again.

This remains one of the scariest and most severe bits of bike mechanics I have ever attempted,and one of the most satisfying because of that. There's something exciting about serious chemistry and with the reaction that went on. It's also satisfying to set out to do something and have it work so well. As long as the frame remains intact from now, I'm claiming it as a huge victory.

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