Ive seen chemical sharpening on files before. But I dont think it would transfer over to a knife in the sense of what we call sharp. The reason it works for a file, to my understanding, is that most of the time the file is "pinned." Pinning is when the teeth on a file are clogged with tiny pins, or metal shavings. When you chemically treat it, the chemical you use eats away at the metal clogging it. For aluminum its especially bad. It'll gall to the surface or weld if you will. "Cleaning" it will help release the bond of the metal clogging it while etching the teeth. So instead of a shiny smooth surface, its now rough again. It'll sort of square up the teeth again to where they cut. Leaving a dull to dark grey surface similar to Ferric chloride on Damascus steels. Im terrible at explaining sciency things. Think of rust on a car. Its jaggged and sharp where it started as a smooth metal body panel. You're forcing a controlled erosion on the steel so no iron oxides form and turn to rust. While corroding your blade edge could make it somewhat sharp by removing material, it would also be bad for the edge too. Forming or turning the edge into oxides making it brittle. Causing faster wear and damage that needs ground out. Files dont thin out to an apex but instead have stepped ridges and or small raised flats with gullets between that grab and remove material so this isn't a problem. If you use hydrochloric acid you will have a bad time as well. You may run into whats called hydrogen embrittlement, where hydrogen is introduced into alloying elements causing extreme brittleness, cracks, and breaks.
Now I could be completely wrong as well and you have stumbled upon the next great sharpening system. This is all based on half cracked research and learnings over time with no real end goal other than to answer a question I had at the time. Id take it with a bucket of salt or at least a few grains.
