[drive surgeon]

need to remove rust from concrete grey flags. cold water wont shift it alone.  will chlorine shift it?

[Aquakleen Restoration Services]

Try brick acid mate it works for me and its v cheap

[drive surgeon]

i have got brick acid. did not think that would shift it? do you use it neat? what method do you use?

[Aquakleen Restoration Services]

Yeah neat mate. I did a job a few weeks ago. Rust on paving stone. Put brick acid on neat, agitated with scrubbing brush then blasted off with pressure washer. Worked for me.

[BDCS]

Acid should remove rust but won't remove fertiliser - they look the same

[Phild]

Have a look on the carpet cleaners section and you will see rust removers mentioned somewhere for removing the stains caused by furniture feet when stood on wet carpets. It does work as I've done it myself alternatively the "brick acid" you need is a phosphoric acid based one not hydrochloric. It's nasty stuff so be very careful.