Can Armoutex remove a seized stem before powder coating?

Had the exact same issue with my frame this week.

Cut the stem right above the headset and then stuck the inverted fork inside a vase filled with a mixture of caustic soda and water.

Thanks - What to put it in was vexing me. A vase is perfect. I'm now 48 hours into dissolving (maybe my mixture is not as rich as yours). I've changed the solution twice and will do it again in the morning.

It's definitely eating away at the aluminium. I'm wondering if I need to wait until it's completely disolved it or does there come a point when the aly becomes fragile and it can be either broken or knocked away from the inside of the tube?