Ah! Been there, done that. You have to take out your screws more often.

Lubrication is the key, get yourself some Tef-Gel and never worry about that every again. www.whitworths.com.au/tef-gel-corrosion-eleminator-anti-seize-lubricant-10g

Honestly, the exact same thing happend to me before. I've tried everything including drilling the screws out myself and the only way I found to do a clean job was to cut the mast and re-thread it. I lost about 8-10cm of mast height but I got to keep using it.

Drilling them out requires some high-end precision machinery, I've tried finding places that could do that professionally but the height of the mast made it impossible to fit in the machinery.

Also, aluminum masts are quite cheap, so you might be able to get a new one without spending that much.

Good luck

Christian

Turn it into a 70cm mast

I removed a similar bolt that was stuck using candlewax, a pair of mole grips and a hot air gun.

The standard thread penetration oils had all failed and I'd tried hacksawing a cut into the bolt which didn't work (might do now that I have an electric impact driver?) but the candlewax surprisingly worked. Took about 30 minutes all in - heat the remaining bolt part red hot to make it expand, then dab the candle onto it to cool it down and fill the thread with wax. Do it again and again and then get the mole grips on it (when you get really bored) to try and turn it. Do it a load more when it inevitably fails to turn and be surprised after about 30 minutes when it gets loose.

Its cheap if nothing else.

Here's some dude doing the same thing on an engine block:

Great tips guys. Thanks!