Frozen handlebar stem

I bought a 1982 Hirame Model 48 SUMA bicycle frame a couple of years ago on e-bay, which came complete with a frozen handlebar stem. Hirame were made by Kuwahara, from Osaka, Japan and imported into the UK in the early 1980s, by the now defunct bicycle business Evian (G.B). The frame had been used as a winter bike, judging from the nature of the corrosion and all the gear tunnel braze ons and rear gear hanger had been removed from the frame. It was no longer in the original paint. My frame is not from a top of the range machine built with Ishiwata tubing. It was my intention to restore the bike to as near original as possible, with all Japanese parts. The frame originally had full chrome forks and rear dropouts. The difficulty was how to remove the original alloy stem which was stuck in the frame due to galvanic corrosion? I intended to try and save the stem if possible. It would be easy to cut the stem and melt the seized part out of the steerer tube with a gas torch. I had done this in the past and read of various methods on web forums, of how to remove the stem, but all involved the destruction of the alloy stem. I preferred to try a different method. Making sure that the expander bolt assembly was in the stem and tightened up, I up-ended the frame and hung it over a drip tray. I then poured a product called Plus-Gas, down the steerer tube, leaving a small reservoir above the expander bolt and left the frame for three weeks, refilling from the drip tray as required, adding some new liquid each time. Once the liquid had finally drained out of the steerer tube, I then righted the frame and inserted a front wheel into the forks. I then released the stem expander bolt and inserted a used, salvaged, long steel riser MTB handlebar into the stem to try and turn the stem.

It gave easily and with a little effort, levered out of the frame. There was much evidence of galvanic corrosion, especially in the slot at the back of the stem above the shaped expander nut.

I cleaned the alloy with a brass brush before using a metal polish. There was a linear crack spreading horizontally, each side of the circular hole at the top of the slot designed to prevent cracking!

I would guess the damage maybe occurred when someone tried to remove the stem, whilst it was welded in through corrosion, prior to the frame being sold. I am disappointed that the stem is not safe to re-use, but it was worth the effort to try and remove it in a non destructive fashion.  I have learned something along the way.   I don't know if this method will work in every case, but I will certainly try it again in the first instance, to try to remove a stem without damage, before resorting to a more destructive method of removal as a fall back position.