And when only for educational purposes or personal curiosity that is a great idea.
BUT, for certification purposes I don't believe it is acceptable. I'd have to look closer at some of the guidelines for macro-etching but seems like the acids are established as to strengths and variety. Could be mistaken, don't do enough of it and already have my procedure established. Anyway, any of those established as ATF's would need to make sure of what was required.
He Is In Control, Have a Great Day, Brent