Stubborn Stain on New Patio

[derekcampbell]

Hi folks, I'm looking for a bit of advice from those in the know. The images attached are of some staining I have on my garden patio, which was only laid a year ago. The stains aren't rust, despite looking like that, as nothing metal has ever covered the area.

I have a Karcher K2 basic pressure washer which is fine for removing dirt as a pressure washer would normally do, however these stains aren't budging. I've tried a couple of things:

- upgrading the pressure washer - figured the higher pressure of the Karcher K4 would help, however it didn't help and was duly returned.
- tried the usual methods, including scrubber, wire handbrush, soap and water etc.

Nothing seems to be doing the trick however. I imagine there's some sort of solution out there that is the answer, but my lack of knowledge around the subject has brought me here for some advice. Does anyone have any ideas?

 

[Pjj]

Are you sure it’s not something in the actual stone ? Could be iron oxide in its natural form and will turn rusty , I think a bit of oxalic acid might help , but @kevinc250 is the expert in this type of thing .

 

[ched999uk]

Have you or a gardener applied any treatments to your lawn like moss killer as most of them have iron in?

 

[scottish cleaning service]

Looks like the centre of the spots has a tiny bit of iron oxide and once the rainwater has touched it, it has formed rust.

 

[derekcampbell]

No, no treatments as it’s actually astro beside. Thanks for the help, will see if oxalic acid does the trick.

 

[Truckcab79]

Normally that’s someone cutting or grinding steel near your patio. The filings rust when wetted. Had any other work done?

 

[derekcampbell]

Normally that’s someone cutting or grinding steel near your patio. The filings rust when wetted. Had any other work done?

It happened not long after it was laid, so quite possibly work when the landscapers were in as the full garden was done at once.

 

[Truckcab79]

Seen it so many times and the fact that it radiates out from a tiny darker speck in the centre makes me more certain. You can try Oxalic acid. Worst case it looks to be mostly that one slab so not the end of the world to replace

 

[WRH]

Try United Stonecare, I've used them for difficult stains on sandstone

 

[derekcampbell]

Hi again folks, tried the Oxalic acid with mixed results. Tried it initially with x6-8 part water, as a few places online suggested this, however didn’t shift it. Tried straight solution from the container, which seemed to lessen the test spot below by around 30%, but still a way off getting rid after multiple go’s. Any other suggestions?

 

[derekcampbell]

Try United Stonecare, I've used them for difficult stains on sandstone

Had a look at their store, what has worked in the past for yourself? The buildersase looks like it fits the description, have you used this solution before?

 

[scottish cleaning service]

I would just gently smooth it down with my battery angle grinder to see if its on the surface.