In the one experience I had using amonia to get stuck aluminum out of a steel tube, it didn't get it out, but the amnonia did discolour the andozing of the aluminum part. I was not happy. Only one experience of course.
Freek Faro Rotterdam in corrosive Netherlands
2007/4/26, Mark Bulgier <Mark@bulgier.net>:
>
> I agree with Dale on the size issue - the stem is not the "wrong size" -
> it's just corroded in place. I agree on the Kroil, but in my experience
> this quite often won't be enough, no matter how long you soak it. Heat
> _may_ help break it loose, but I'm not a big fan of it here, and don't
> do the twisting while it's hot. The thermal expansion coefficient of
> aluminum is much higher than that of steel, so when you heat the
> assembly, the Al expands more than the steel, making the fit even
> tighter. Extreme _cooling_ is more likely to help you break it free,
> because the stem will shrink more than the steerer.
>
> But the key is to dissolve the corrosion "stuff" that's between the
> steerer and stem (mostly aluminum oxide), which is what's locking the
> stem in place. Ammonia is the right stuff for that. See
> http://www.sheldonbrown.com/
> maybe your stem will also be able to say "Free at last! Free at last!
> Thank God almighty, I am free at last!" (Thank you MLK and Sheldon)
>
> Mark Bulgier
> Seattle WA USA
>
>
> Dale wrote:
>
> > << Wouldn't you know it, some jerk apparently hammered the wrong size
> > stem into the steerer tube?>>
> >
> > No, that steerer is the largest "hole" made in that era.
> >
> > Have you used "Kroil"? absolutely great stuff.. but it would
> logically
> > take 3-4 days of applications, soaking, tapping with hard rubber
> > hammer, etc.
> >
> > << The shop owner says a torch, but this qualifies as a special case
> > because the stem is aluminum and so is the pitifull frame. >>
> >
> > The fork steerer, what the stem is really stuck in, is steel...
> > hacksaw the frame away from the fork and steerer. Then use heat on the
> > steerer. Not enough to melt the stem (doh!) but to loosen all the
> gunk.
> > Clamp the fork crown in a big vise, then put some bars in the stem and
> > start twisting and pulling...