stained path

[speckledjim]

Hoping someone can help.
I have my own lawncare company and a couple of months ago I applied some fertiliser to a customer's lawn. After applying i swept the path/patio as i normally do but unfortunately it got windy later that day and blew some of the fertiliser back onto the path. A couple of days later it rained and as a small part of the fertiliser is iron some of the path (spots) was stained a rusty colour. I have tried removing it with various substances but it hasn't worked. Now the customer wants me to replace the stained areas with new concrete slabs.
Am I liable for this?
Thanks

[Old_Geezer]

No expert so I can only guess that if you made all reasonable effort to avoid the problem, "due diligence" and all that, then it could be construed as something out of your control, and just bad luck for the owner. That said an unhappy customer don't make for good future recommendations/referrals. Might be best to try to come to an agreement anyway.

Have you tried a weak acid in an effort to take off the stained layer ? I suppose it does depend on the existing surface as to whether that would be an option or not.

[Old_Geezer]

That sounds a possibilty to me, or course it depends on how badly the underside is stained ;-)

BTW ought your user name not be 'speckledpath' ?

[HowardKennitby]

Electric drill with wire brush attachment or even an angle-grinder if things are severe?

[buildersmate]

Have you tried a power washer?
The ingredient that caused this is ferrous sulphate - I'd have been inclined to try a neutraliser as well but I guess there is a danger of it spreading back onto the grass and killing it.
This has happened to me as well - I found it much lighter in colour after power-washer treatment, though not completely removed.
Don't like the idea of turning slabs over - utterless useless unless they are those dreadful machine pressed flat concrete ones. And a lot of work to do.

[speckledjim]

The problem is that it is concrete which is porous so it's difficult to remove stains -i've tried power wash, acid etc and they have helped a little bit. I also got a bit on his york stone patio - no problem removing it from that surface.

[missprim]

I asked a similar question to this back in 2008 and this is the answer I got back.
///brick acid will remove the rusty stains that you are talking about.you can get this from most builders merchants ( usually in 5 litre containers ) but make sure you read the instrutions and wear rubber gloves.///

[buildersmate]

Brick acid is 30% w/v hydrochloric acid, Ms Trim, so no mean stuff in terms of acidity. It will normally work, because it converts the ferrous oxide (which is brown and largely insoluble in water) to ferrous chloride (which isn't brown).
However I don't see a way of doing this without killing the adjoining grass.

[missprim]

It's Missprim actually:-) Sorry I couldn't help.

[AlBags]

What a fussy one!

Brick acid you will get at builders merchants. 5L not dear.
You never stated whether these are concrete pre-cast, riven concrete (coloured) natural stone, or whatever.

[speckledjim]

It's precast concrete

[AlBags]

You won't be turning them then.
They have a face side.