A pH of -0- is "VERY" Acidic, it is So Acidic in fact, that if you got any of it on cotton clothes, that it would eat holes all in it, probably eat it all up and make it Disappear completely!
Fertilizer which has it's pH dropped to 3.5 pH by addition of Sulfuric Acid will eat holes in your clothes!
I know, because I have handled it before and done mixing of fertilizer ingredients!