Screws in Aluminium Oxide "Glue"? 1

[BeeThree]

I have a job removing {mainly 5-6mm) Mild Steel Screws out of Aluminium Extrusion which has become corroded around them.
What`s the best way to remove them in little time.

 

[kenvlach]

I would
1) soak in a nitric acid solution ('deoxidizer') to remove the products of corrosion that are jamming the threads,
2) remove all the screws,
3) disassemble the extrusion from what it's attached to*,
3) clean the extrusion in the nitric acid solution,
4) anodize, [if can't anodize, then chromate chemfilm]
5) Reassemble with Al or Ti screws (or chromated galvanized)
6) If didn't anodize, paint.

*If the extrusion is attached to other Al, I would clean and anodize (or chemfilm) those parts also.