Reasons NOT to use anything but F9 BARC for removing rust, fertilizer and orange battery acid stains on your concrete:

https://www.facebook.com/media/set/?…1&notif_t=like

These were all take on ONE STREET where I live- in only 10 minutes of walking.

Aside from the permanent damage, there are ways for a professional to "fix" this that would look decent. If you come across this, run your surface cleaner over it a few times in at least two different directions. This will help even out the surface damage. If you have BARC, apply it and it will even out the color damage.