Remove rust stains from concrete patio slabs

First, my note on the (suspected) cause of the rust stains, which is said to lie in an iron-containing fertilizer. My response to this: impossible! Reasoning: to oxidize iron-II to iron-III to cause visible rust requires more than the 0.1-0.3% iron in a mineral fertilizer. Presumably, these are iron components that are either in the bedding mortar, but more likely in the substrate (concrete or cement screed). These unavoidable iron-containing components are often found in the aggregate – and are allowed within limits. On the topic of removing the rust streaks: just last week I was able to remove rust stains within a few minutes on the outdoor terrace of a friendly couple using an aqueous oxalic acid solution. Oxalic acid, a solid white powder, is also available cheaply via the internet. Prepare about a 10% solution with warm water (although not everything dissolves) and massage this solution into the "discolored" surface of the tiles with a soft hand-wrist brush in a circular motion. After about 3 minutes, remove this dirty solution with a cloth and rinse the previously treated surface twice with clear water. However, the visual rust situation will not be permanently eliminated as long as the corresponding rust potential still lurks in the substrate. This means: after probably 1 year you will have to repeat the procedure. But I think this option 1 is doable and acceptable. Because the alternative (option 2) is: open the tiled surface at the affected areas, remove the rust particles in the mineral substrate, seal the created breakout area again with a reactive resin mortar, and re-glue the removed tile. I suspect: option 1 is rather more practical? --------------------- Greetings to everyone: KlaRa

Oxalic acid,

The acid component in the removers that can be bought.

The acid content in the removers that you can buy.

With this reply, I am - admittedly - intellectually overwhelmed!
"The acid content (...)" now it has to come WHAT IN. Example: The acid content in .....
But now follows
"The acid content in the removers (...)" The term "removers" is unfortunately not known to me, written in lowercase it seems to be an attribute, thus it does not fit with the word order in the sentence.
Now it continues finally:
"The acid content in the removers that you can buy." Now I am completely overwhelmed with the content perception of the supposed meaning of the sentence.
Can "nordanney" please explain again clearly what is meant with his sentence (as above)?
----------------------------
Regards: KlaRa

That was the cellphone. Entferner must be capitalized. Everything is already there Rost-Entferner Nagellack-Entferner Use.

It is supposed to mean that oxalic acid is also a component of commercially available removers for rust stains on stones. It is of course not in nail polish remover; that was only an example for the word "Entferner".

I quote Einstein: "So simple as possible, but not simpler."

So it can only come from the fertilizer Other possibilities do not exist and it would be way too big of a coincidence

I used the mellerud rust stain remover and it worked but some stains that also look like rust don’t go away and it no longer turns purple so there is no more reaction happening

My question Does anyone of you know a good intensive cleaner for concrete stones that is for everything (not just for algae) We hardly have any algae, if at all

I would need a cleaner that helps the stones against dust, grease, (possibly rust, brown stains) and other deposits?

Application: apply cleaner and work in with a brush and rinse off with water, please without a pressure washer