Ace Hardware, many paint stores, Lowes, and some others sell Muriatic acid at 31.45%
The remaining percentage is comprised of inert ingredients or so it says.
What and how inert the ingredients are is what I'd like to know.
And I would say that a definition of corrosive depends as much on the material to be (or not to be) corroded as it does on the corroding (or not corroding as it were) substance.