CLR vs. Muriatic acid to remove hard water scale?

[bradleyheathhays]

Recently acquired a used tank with an unidentified white scale on the sides that I'm trying to remove. Turned the tank on it's front side and soaked the scale for a week with 100% vinegar and it still didn't scrub off. Was given advice to soak a small spot with either CLR or muriatic acid to determine if it was actually water scale, or if it was glass etching for which nothing can be done. Thankfully a small patch soaked with CLR for 2 hours has scrubbed away!...which means what I'm dealing with is probably just water scale.

So, my question is...which should I used to get the rest of this scale off...CLR or muriatic acid? I'm guessing the muriatic, because after rinsing, if the residue shows up in my filled tank water I can just adjust by using pH+ or -.

Thanks

 

[Smitty]

Have you tried using a razor blade to scrape it off...I'm not sure about using those particular chemicals.