Your choice for rust stains.

[Truckcab79]

Have a pressure washing and patio resto job booked. Grey Kandla sandstone as far as I can tell. 3 or 4 slabs with heavy rust staining from steel pots.

Seen lots online using Oxalic acid, Muriatic acid, white vinegar and various commercial products using the acids as a base. Difficulty I’m finding is that on the YouTube vids they all seem pretty much 100% effective so I’m undecided on which approach to go with.

Needs to be effective first and foremost and quick secondly as although I’ll probably be there for 2-3 days I can’t really use something that needs to soak for days and days as it’ll interfere with the re-pointing work.

Any real world experience appreciated.

Thanks in advance.

 

[RickyG]

ive used oxalyic with good results make it like a paste smear over the stain, sit for 10 mins then work it in with a stiff nylon tyre brush took a couple of goes and that was where a wheelbarrow had been left in a few places around the patio this was on the lightest cream porcelain ive seen in a garden

 

[Truckcab79]

ive used oxalyic with good results make it like a paste smear over the stain, sit for 10 mins then work it in with a stiff nylon tyre brush took a couple of goes and that was where a wheelbarrow had been left in a few places around the patio this was on the lightest cream porcelain ive seen in a garden

Great. Think I’ll go with that. Oxalic was my first thought as that’s all I’d read about until today. Might make it less ‘pasty’ though as I need it to soak into the stone I think. Sandstone will be a lot more porous than porcelain. I’ve got some offcuts from previous jobs. Think I’ll make up a couple of test pieces. Don’t really want to be experimenting on the clients patio if I can avoid it.

Is there a particular strength to look for or is it all much of a muchness in powdered form?

 

[RickyG]

Great. Think I’ll go with that. Oxalic was my first thought as that’s all I’d read about until today. Might make it less ‘pasty’ though as I need it to soak into the stone I think. Sandstone will be a lot more porous than porcelain. I’ve got some offcuts from previous jobs. Think I’ll make up a couple of test pieces. Don’t really want to be experimenting on the clients patio if I can avoid it.

Is there a particular strength to look for or is it all much of a muchness in powdered form?

By the looks of it it’s the muchness cos I m looking at the pack of powder there’s no mention of strength just loads of chemistry molecule jargon, I got mine from a firm called “minerals water” up in Doncaster, I originally bought it for some stains on my ipe deck so I’ve had it a while doesn’t seem to have gone off like hypo would of

 

[RickyG]

By the looks of it it’s the muchness cos I m looking at the pack of powder there’s no mention of strength just loads of chemistry molecule jargon, I got mine from a firm called “minerals water” up in Doncaster, I originally bought it for some stains on my ipe deck so I’ve had it a while doesn’t seem to have gone off like hypo would of

Also it goes back to powder form once it dries out just in case the custy mentions white stains they just brush away

 

[Pjj]

We use oxalic acid but in liquid form and just dampen the area then brush in in leave for 10 muinits light scrub with a stiff brush and repeat as needed, to be honest on some stains there is still shadowing depending how long they have been there .

 

[Truckcab79]

We use oxalic acid but in liquid form and just dampen the area then brush in in leave for 10 muinits light scrub with a stiff brush and repeat as needed, to be honest on some stains there is still shadowing depending how long they have been there .

Cheers. Not expecting to get rid of them entirely to be honest. Just hoping to
Improve them. They’re pretty extensive on a few slabs.

Presumably liquid form is just the same as diluting the crystals?

 

[Truckcab79]

By the looks of it it’s the muchness cos I m looking at the pack of powder there’s no mention of strength just loads of chemistry molecule jargon, I got mine from a firm called “minerals water” up in Doncaster, I originally bought it for some stains on my ipe deck so I’ve had it a while doesn’t seem to have gone off like hypo would of

Cheers. As it happens AG Woodcare who I use for other stuff, sell crystals at 99%+ pure and I need to order from them for another project so will probably just pick up a 5kg tub of crystals to try.

 

[Pjj]

Cheers. Not expecting to get rid of them entirely to be honest. Just hoping to
Improve them. They’re pretty extensive on a few slabs.

Presumably liquid form is just the same as diluting the crystals?

The stuff we use is pre mixed ready to use

 

[Truckcab79]

The stuff we use is pre mixed ready to use

Any idea what % or do you have a link?

Many thanks

 

[Pjj]

Any idea what % or do you have a link?

Many thanks

This is what we use it’s from Bonnymans, it is ready to use , much easier than mixing up the crystals although it’s dearer

 

[Truckcab79]

Great. Many thanks.

 

[Pjj]

This is the crystal form of it

 

[tench0771]

Rust x pro workers very well but it gets rid of the rust but you can still see we’re it was if that makes sense

 

[Truckcab79]

Rust x pro workers very well but it gets rid of the rust but you can still see we’re it was if that makes sense

Have ordered some of the Bonnymans crystals. Think client will be more than happy with any reduction in the staining to be honest.

 

[RickyG]

Have ordered some of the Bonnymans crystals. Think client will be more than happy with any reduction in the staining to be honest.

funny stuff that sandstone i laid a large patio about 5 crates few month later had some brown marks starting to show the customer was going dinlow we even had a rep from the stone importer come and have a look says it was the iron oxide in the stone as its natural it can occur, but as time went on it cleared and looked stunning the customer got right into cleaning it so much he ended up starting a pressure washing business and his niche now is doing tennis courts

 

[Truckcab79]

funny stuff that sandstone i laid a large patio about 5 crates few month later had some brown marks starting to show the customer was going dinlow we even had a rep from the stone importer come and have a look says it was the iron oxide in the stone as its natural it can occur, but as time went on it cleared and looked stunning the customer got right into cleaning it so much he ended up starting a pressure washing business and his niche now is doing tennis courts

Unusual for it to appear later. It’s normally a product of using brick acid to wash down after laying. The grey Kandla is particularly prone. I do use it as to be honest there’s nothing else that cleans up as well but use a hand spray to apply it very locally and wash down immediately. I think even if it happens it always fades eventually but not easy to convince the client of that as you walk out the door with their money. Takes years to fade too if its bad.

 

[Truckcab79]

This is the last one I laid before the weather turned last year. Good thing is you get paid to lay them then paid to clean them ?

 

[Truckcab79]

Didn’t think this job was doing to happen. We refurbished the clients gravel driveway. New edging stones, new gravel etc. Never chase estimates up as I can barely keep up with what I have to be honest, and hadn’t heard back from them formally.

I did order the Oxalic from Bonnymans in the end. Long story short it took weeks to arrive thanks to parcelforce delays, refusing to leave it in a safe place and then losing it entirely. Bonnymans lovely ladies sorted it but I was without it for about 3 weeks or so after ordering.

Anyway - Job now booked. Clean and re-point so it looks like I’ll be trying it out after all. Will report back with pics. ?

 

[Truckcab79]

Just for a laugh this was their first delivery attempt. ?‍

…and don’t moan about my driveway. Too busy doing other peoples. ?

 

[Truckcab79]

Finally got to the ‘rust’ job. I’d had a play with the Oxalic acid at home on a rust spot in concrete. Seems to work pretty well. Was expecting some impressive ‘fizzing action’ like brick acid but was disappointed to see that it just sits there working. ?

Job had multiple heavy rust spots on sandstone and for the worst ones I made a paste of the acid crystals as I soon found that dissolving in water it seems to become saturated at a relatively low concentration. The rest were sprayed with a ‘strong’ solution.

Pleased to say it did the trick. 90% gone. Oddly the worst really heavy ones disappeared entirely. Some of the less bad ones disappeared less. Overall though very pleased as is client. Couple of pics. Not sure these are the same stones to be honest but an indication of some of the worst starting points and the best results.

And a couple of the patio overall. Pleased with the result. Will be repointing it tomorrow.

Thanks all.