[ray l]

Hi all

One of my customers has brown marks like rust marks on concrete slab path

She says they appeared after a feed and weed was put on the grass.

Would pressure washing take this off or is there a chemical needed.

Thanks in advance
Ray

[BDCS]

Hello, I have come across these marks myself and although jet washing will improove them you will need some brick acid to remove them

[Roger Oakley]

Ray,
Oxalic Acid will get rid of the stains, but you would have to do the whole area not spot clean them, Oxalic works as a brighter as well so you would have a bright/white area where  the Oxalic has been applied. Easy to use, but you would need PPE with this one. Don't try any bleach as you will set the stain and make it even harder to remove. If you don't like the sound of oxalic acid you could try phosphoric acid, you'll find this in some Aluminium cleaners/degreasers.

[steve k]

some moss killers have ferrous sulphate as the active ingredient which is iron...causes rust stains on hard surfaces.
Do not use acid on York flags...causes horrendous white/orange stains which you will not remove.

[Roger Oakley]

Do not use acid on York flags...causes horrendous white/orange stains which you will not remove.

And don't use an acid on Indian Sandstone either, you'll get same results horrible orange stains that won't shift, as you will have marked the stones. The advice I gave earlier was for concrete only Ray.

[Jet Cleanse Ltd]

Hi,

What weedkiller would you use on block paving after cleaning or does this staining not happen on paving?
Thanks

[steve k]

one without Ferrous sulphate in it. It will cause rust staining on block paving.
Use a weedkiller suitable for paths. This has been developed as a direct need for non-staining weedkillers on hard landscaping.

[Jet Cleanse Ltd]

thanks steve

[BDCS]

I use glypohren

[Ged]

roundup ( glyphosphate)applied 2 weeks ahead of clean. systemic action kills roots so weeds don't return. doesn't stain,  non poisonous to pets and people. if you use a lot it is available as a concentrate from chemical suppliers.

ged