Quick question... though this particular experiment took place more than a year ago.
I masked
this Al enclosure using laser printer transfer and
> after testing a quick etch (permanent marker as resist) on the back of the cap, which I deemed fine, I used the following technique:
- scrubbed the surface with (plastic) abrasive sponge: needed for transfer;
- after trying my best to remove the paper fibers after transfer, I dabbed the surface with FeCl
3 using a sponge, replenishing the reactant constantly.
- even after the time that would be sufficient for etching a PCB I did not observe any significant bevel, but the exposed surface looked like rust, even after a thorough rinse with water.
- sanded the surface with fine sandpaper (1000-ish) and some days after oiled it after I noticed rust forming again. It hasn't rusted thus far.
So this is what turned out: looks to me less like an etch and more like penetration of Fe atoms maybe?

I may have taken that picture enthusiastically before oiling.
What was the question? I've seen deep etches through simple immersion in FeCl
3, and the sponge technique is supposed to be more aggressive, so what gives?! Not that I'm complaining, I like the way it turned out, but I'd like to understand the process for the sake of consistency.